S A L Z B U R G SUPPORTED BY

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1 SUPPORTED BY S A L Z B U R G

2 Preface Preface Asker Jeukendrup The booklet in front of you is the summary of the 6th Sport Nutrition conference. After conferences in Birmingham UK (2x), Indianapolis USA, Munich, Germany and Mallorca Spain these are the conference proceedings of a meeting in Salzburg. This meeting was held during the World Cup Football and therefore the theme of the meeting was Nutrition for team sports. Again several leading scientists shared their insights with a select group of sports nutritionists, sports dietitians, physiologists, coaches and athletes and this time it all took place in the beautiful surroundings of Salzburg in Austria, the birthplace of 18th-century composer Wolfgang Amadeus Mozart. With its beautiful Alpine setting Salzburg was a fantastic and inspiring venue for this conference. The format of these conferences has been highly successful and this is due to the unique formula that was used. In short, we bring together a relatively small audience consisting of leading sports nutrition professionals, a small number of elite speakers, journalists and a few elite athletes and coaches. The carefully selected speakers are not only academically well established but also have a background in sport and not only can deliver an excellent scientific presentation but also have the ability to translate science into something that can be used by athletes. If we combine this with a number of hot topics in sports nutrition, we allow sufficient time to interact we have a basis of some great discussions. We have introduced workshops to further bridge the gap between science and practice. The main theme of this and all previous conferences: translating the often complicated science into a practical message that is of immediate use to an athlete or coach. This aim of this booklet is to provide a short overview of the science and a number of practical guidelines illustrated with figures and tables. These conferences, the summary booklet you have in front of you, the DVDs and a web site with information are an important step in closing the existing gap between the science and the real world. Hopefully they will be helpful to you too. I want to thank Professor Erich Mueller for organising and hosting the 6th Sport Nutrition Conference in Salzburg and Zibi Szlufcik and Daniel Albrecht for all the hard work in putting this together and making it all possible. Also, I would like to express my sincere gratitude to PowerBar and the Nestle Nutrition Institute. Without their help and support the conference and we would not have been able to produce these and other materials. Asker Jeukendrup University of Birmingham 2

3 Welcome to Salzburg to the Sport Nutrition Conference 2010 in Salzburg. The Department of Sport Science at the University of Salzburg will host this Conference. The newly renovated Edmundsburg will be a unique venue for our meeting. It is situa- ted on the roof of the city and within a few minutes walking distance away from the Congress hotel. The city of Salzburg, often called the stage of the world, is famous for its historic and cultural background. Strolling through Salzburg you will find many architectural attractions, a variety of cultural events and a beautiful landscape. Discover the city of Mozart and the Sound of Music. Allow us to tempt you with the magic of Salzburg. We look forward to meeting you in Salzburg. Erich Müller University of Salzburg Content Preface Asker Jeukendrup... 2 Welcome to Salzburg Erich Müller Assessment of training and game load in team sports Magni Mohr Metabolic demands of soccer and nutritional implications Stuart Galloway Overtraining: how to monitor and how to prevent? Asker Jeukendrup New developments in supplement use by athletes Ronald Maughan Buffering agents and their possible role in team sports Trent Stellingwerff Fluid requirements in team sports Susan Shirreffs

4 1 Assessment of training and game load in team sports Magni Mohr University of Copenhagen, Denmark. Introduction Team sports are characterised by a highly intermittent activity pattern with acyclic and unpredictable changes between different types of activities. For example in soccer there are incidents or activity changes throughout a game (9). In most team sports prolonged intermittent work is conjoined with brief high intense exercise sequences and explosive actions, which has marked implications for the physiological response to games and training, as well as the recovery period. Thus, quantifying game and training load is complicated in team sports and must be viewed as a multi-variable phenomenon. The activity pattern and physiological demands in teams sport games and training are closely dependent on the physical capacity of the player, technical abilities, tactical role, playing position, style of playing, the opponent, as well as numerous environmental and internal factors. Thus, there is large individual variation in physical loading and physiological stress in both games and training within a team sport squad even in high standard teams (9,10). These individual differences must be carefully taken into account when monitoring and evaluating game and training load, planning fitness training or tapering regimes and development of nutritional strategies. There is large individual variation in physical loading and physiological stress in both games and training within a team sport squad even in high standard teams Activity pattern in game and training Limited observations have been made on the activity pattern in team sports training, however, extensive informations excist on the movement pattern in games, especially in soccer. These studies on game responses are essential in understanding the specific movement pattern in team sport, since a considerable part of the training in soccer, rugby, basketball etc. is performed as small sided games or as activities mimicing game situations (2,3). Moreover, the most demanding physical training session of a normal week is the game. A top-class male and female soccer player covers around km in total in a game (9,11), which is more than in other team sports (Mohr, unpublished observations). However, total distance covered is a poor measure of physical strain in team sports, since the majority is performed as walking and jogging. Male and female elite players run 2-3 km and km at high intensities (15-35 km/h), respectively. This distance in achieved by completing around and intense runs for the two genders of an average duration of 2-3 s. Figure 1 shows the characteristics of sprints performed by an elite soccer player in a ~8 min period in a game. Most of these all-out runs are short accelerations, but the player is also approaching maximal running speed in few of the sprints. These types of measurements can be very valuable during different types of team sport training drills, when the intense activities should be quantified. Figure 1: The duration and maximal running speed of sprints performed during an intense sequence (500 s or ~8 min) in a competitive soccer game for one representative elite midfield player. Data are collected with the multiple-camera system (9). 4

5 The duration of the runs is likely to be even shorter in team handball, basketball and hockey because of the smaller pitch. In support of this small sided games in soccer (1v1-7v7) have been shown to have a shorter duration of high intense runs (~ s) compared to a normal game (12). Thus, most of the demanding high intense runs in team sports are brief explosive accelerations followed by vigourous decelerations, which adds markedly to the energy demands and stress on the muscle. In contrast to normal running, the intense runs in team sports are also irregular and often sprints, intense runs and explosive direction changes are initiated from unfavorable and awkward positions, which makes them extraordinary demanding. Therefor, it is essential to quantify the team sport specific activities such as amount of high intensity running, sprint characteristics, accelerations, impacts, change of direction, jumps etc. during training and games. Physiological response to game and training A high number of scientific observations have assessed the aerobic loading in team sport games and training by heart rate measurements. It has been demonstrated that the average heart rate in a soccer game is ~85% of HRmax with near maximal values in periods of the game (1). A similar response has been substantiated in other team sports games (5) and during training (7). This shows that the energy demands in team sport are very high and can be estimated to be 70-75% of the maximal oxygen uptake on average based on individual HR-VO2-relations (1). A few studies have measured the oxygen uptake with portable gas analysers during aerobic training in soccer where a HR response of ~85% of HRmax corresponded to ~75% of VO2max (4). The traditional method to quantify the aerobic loading in team sport training is to measure time spent in different heart rate zones (2,3). Figure 2 shows the heart rate response to two 9-day periods (phase 1 and 2) for a National team preparing for the Euro Cup 2004 (2). It is clear that during phase 1 the overall training load is higher than in phase 2, however, the difference is small in the high heart rate zones, indicating that the training intensity was maintained high despite a tapering period prior to the first game of the competition. Figure 2: Heart rate distribution during two 9-day preparation periods (phase 1 and 2) for a European National team before the Euro 2004 (a: beats/min; b: % of HRmax; from Bangsbo et al., (3)). Blood samples have been drawn during soccer games (1,8) and small sided training games (12) and high blood lactate values have been found, indicating that there is a high lactate production in periods of team sport games and training sessions. Blood samples can be used to study the physiological response to a training session, for example to examine whether the glycolytic energy pathway is stimulated in a certain training drill based on blood lactate levels. However, blood lactate measurements can not be used to quantify anaerobic energy contribution, due to a weak and scattered relationship between muscle and blood lactate concentrations during irregular intermittent exercise (2,3,9). Muscle biopsies have been taken during soccer-match play (8) and training (12), which have shown a significant muscle lactate production and phosphocreatine (PCr) degradation. However, a valid method to physiologically assess the anaerobic training load in team sport is currently non-excisting. However, in order to control the training intensity during for example in speed endurance training (6), motion analysis, such as GPS-recordings can be applied to measure accelerations and running speed and express these in relation to maximal values for the individual player. Moreover, different types of training-fatigue indexes can be calculated during certain speed endurance training drills. For example during standardised drill (for example 6 x 30 s of exercise at an intensity of ~90% of maximal effort with 120 s of recovery) a speed endurance fatigue index can be calculated as the relative decline in running speed during the first compared to the final exercise interval. A central player to consider when quantifying the load in a training session is the recovery from that type of training. The exercise mode in intense intermittent sports is energetically demanding and the consumption of muscle glycogen 5

6 is high (1,8,9). A number of studies have shown that after a soccer game muscle glycogen concentrations are still in the range ~ mmol/kg/dw, however, the glycogen content in individual muscle fibres is likely to be markedly lower. This was also shown in a study by Krustrup et al. (8), where nearly half of the fibres were rated as completely or almost emptied of glycogen after a game. This is supported by a progressively increase in plasma FFA and glycerol towards the end of a game (1,8,9). A similar pattern has been shown during a 1 h training session, where a significant number of muscle fibres were very low on glycogen at the end of the session. In addition to being very glycogen consuming, it has been shown that the resysthesis of muscle glycogen is It has been shown that the resysthesis of muscle glycogen is much slower after a team sport game in comparison to prolonged continous running and cycling. It has been shown that the resysthesis of muscle glycogen is It has been shown that the resysthesis of muscle glycogen is much slower after a team sport game in comparison to prolonged continous running and cycling. Individual demands and fitness testing As aforementioned there are large individual variations in work rate between players in a team during games as well as during training, which naturally raises the question to what extent players training load should be prescribed individually. Figure 3 shows the characteristics of all sprints performed in a soccer game by a top-class external midfield player and a central defender, which clearly demonstrates the large differences that excist in physical demands and loading. Thus, the specific game demands must be included in the process of loading players in training. Figure 3: Duration (black circles), speed (black triangles) and distance covered (white circles) in all sprints performed during a game by a external midfielder (left panel) and central defender (right panel; from Mohr; (2)). Fatigue development in team sports or fatigue profiles of the individual player is also highly important to integrate into training. It has been shown that different types of fatigue develop during for example soccer match-play (9,10), and these types of fatigue can be quantified as different types of game-fatigue indexes (9). Another essential component in planning of training is the physical capacity of the player. The Yo-Yo tests have been welldescriped in scientific litterature (Bangsbo et al., 2008), and for example the two different Yo-Yo tests (IR1 and IR2) provide valid information on soccer-specific fatigue-resistance (9). Thus, when setting the targets for individual training load in team sports, the sport specific physical capacity of the player must be taken into account. Summary Team sports have a complicated movement pattern, due to the irregular change between activities and the combination of prolonged intermittent exercise and short-term sequences with high intensity work. These activity characteristics challenge a variaty of physiological systems, which to a large degree are difficult to estimate. The energy demands and stress on the aerobic system can be assessed by heart rate measurements, while the anaerobic and explosive activities can be quantified by a multi-variable movement analysis. These measurements must be related to the impact of the training on the recovery capacity of the players. There are large individual variations in activity pattern, physical demands and capacity in a team, which must affect the prescription of training load. Development of individual work and fatigue profiles in games and training combined with team sport-specific fitness testing are essential tools to perform playerspecific loading in training. 6

7 References Bangsbo, J. (1994). The physiology of soccer with special reference to intense intermittent exercise (book). Copehagen, Denmark. Bangsbo, J., Mohr, M., and Krustrup, P. (2006a). Physical and metabolic demands of training and match-play in the elite football player. J Sport Sci: 24(7): Bangsbo, J., Mohr, M., Poulsen, A., Perez-Gomez, J., and Krustrup, P. (2006b). Training and testing the elite athlete. J Exerc Sci Fit: 4(1): Castagna, C., Belardinelli, R., Impellizzeri, FM., Abt, GA., Coutts, AJ., and D Ottavio, S. (2007). Cardiovascular responses during recreational 5-a side indoor soccer. J Sci Med Sports: 10(2): Gabett, TJ. (2005). Science in rugby league football: a review. J Sport Sci: 23(9): Iaia, FM., Rampinini, E., and Bangsbo, J. (2009). High intensity training in football. Int J Sports Physiol Perform: 4(3): Impellizzeri, FM., Macora, SM., Castagna, C., Reilly, T., Sassi, A., Iaia, FM., and Rampinini, E. (2006). Physiological and performance effects of generic versus specific aerobic training in soccer players. Int J Sports Med: 27 (6): Krustrup, P., Mohr, M., Steensberg, A., Bencke, J., Kjær, M., and Bangsbo, J. (2006). Muscle and blood metabolites during a soccer game: implications for sprint performance. Med Sci Sports Exerc: 38(6): Mohr, M. (2008). Fatigue in soccer with reference to intense intermittent exercise (book). Copenhagen, Denmark. Mohr, M., Krustrup, P., and Bangsbo, J. (2003). Match performance of high-standard soccer players with special reference to development of fatigue. J Sport Sci: 21(7): Mohr, M., Krustrup, P., Andersson, H., Kirkendal, D., and Bangsbo, J. (2008). Match activities of elite women soccer players at different performance levels. J Strenght and Cond Res: 22(2): Randers, MB., Nybo, L., Petersen, J., Christiansen, L., Bendiksen, M., Brito, J., Bangsbo, J., and Krustrup, P. (2010). Activity profile and physiological response to football training for untrained males and females, elderly and youngsters: influence of the number of players. Scand J Med Sci Sports: 2010, Feb. 10 [Epub ahead of print]. 7

8 2 Metabolic demands of soccer and nutritional implications Stuart Galloway University of Stirling, Stirling, Scotland Introduction Soccer is reported to be the most popular sport in the World with an estimated 265 million male and female players worldwide (2006 Big Count, The purpose of this short review is to summarise the metabolic demands of soccer match-play and training, and to provide some detail on the nutritional implications for players. Metabolic demands of soccer match-play and training The demands of soccer match play have been studied extensively in males and have recently been examined in females. Matches are characterised by an overall intensity of play at approximately 75% of maximal oxygen uptake, with short periods of supramaximal effort, interspersed with longer periods of low-intensity activity. This changing nature of the intensity of play continues throughout the match and is variable dependant upon playing position, team set-up and opposition. In females the demands of the game are similar but the intensity of play overall is slightly lower, mainly due to fewer high-intensity efforts (9). During a match, elite male players will typically cover about 10-12km, with intermittent activity intensity (high-intensity for short periods, low-intensity for long periods), and activity type reported to change every 4-6 seconds. Female players cover a similar distance but with more at low-intensity and less at high-intensity, and with similar intervals for changes in activity type. Therefore, footballers are generally required to be good endurance athletes with a reported maximum aerobic capacity of around 60 ml/kg/min in male and 50 ml/kg/min in female players, with low body fat (around 10% for males and 15% for females), and with good speed, agility, and high anaerobic capacity. To achieve this range of physiological attributes requires a focussed training programme which aims to improve aerobic and anaerobic capacities and endurance. In Scotland the training intensity, duration, and frequency vary considerably between soccer clubs with semi-professional women s soccer clubs training 2-3 hours per week, women s national team academy players training for 9 hours per week, professional under 19 males training about 12 hours per week, and professional senior team players training 15 hours per week. Added to this is one match per week for female players and often two matches per week for male U19 and senior players, with one rest/recovery day. Training at the higher end of this spectrum now typically consists of about 6 hours of gym based resistance training per week and roughly 9 hours of on-pitch skills and drills training per week. Much of this training is at low intensity but is interspersed with high intensity interval training in both the gym sessions (sets of squats at high-intensity) and on-pitch sessions (small sided games / intense interval drills). Data from a Scottish premier division youth development programme (n=17 players) demonstrates that on average about 60 minutes of on-pitch training per week was at high intensities (>85% max HR) over a season (Figure 1). This represented around 10-15% of total on-pitch training time at or above lactate threshold. Figure 1. Mean ± SE Scottish Premier League club U19 squad minutes spent with a heart rate above 85% maximum during training over each week of the season. n=17. Others have previously reported that around 145 minutes per week was sustained at high intensities (>90% of max HR) in senior National team players preparing for the World Cup (3). This presumably represented around 15-20% of their total on-pitch training time. 8

9 Given the demands of match-play and the typical training load and intensity distribution sustained by players, it would seem that footballers train in a similar manner to elite endurance athletes (13). Given this similarity it would seem sensible to also recommend that the standard nutritional guidelines for elite endurance athletes should be followed by soccer players. Fatigue profile in soccer Most studies examining fatigue in soccer have observed a reduction in distance covered in the second half of matches and particularly in high-intensity running distances covered in both males and females. There is some good evidence that the overall intensity of play declines in the second half, reflecting ongoing fatigue (5) and that this can impact upon technical performance (12). With match duration of 90 minutes, and the intense short burst nature of play, it is not surprising that glycogen depletion will be a likely factor limiting the sustainability of high intensity runs, and distance that can be covered in the second half of the match. Indeed, Krustrup et al (10) and other authors have observed that muscle glycogen declines by about 50% over the duration of a standard match (from 450 mmol/kg dw to 250 mmol/kg dw). Although this muscle glycogen content does not reflect complete depletion it does become important when considering depletion in all fibre types. Most striking is the fastest fibre types (type IIa and IIx) which before the match show approximately 85% of all fibres being full of glycogen end up with only 20% of fibres full at the end of the match. Overall about 45% of all fibres are almost empty or are completely empty of glycogen at the end of a match. This glycogen depletion could explain the observed reduction in sprint performance between pre-match, half-time and post match time points that are observed. The implications of this glycogen depletion are potentially wider than just impacting upon local muscular fatigue. There could also be an impact of fatigue on maintenance of skill performance, and cognitive function in the latter stages of a match, and these effects would be even greater if extra time was required. Dietary carbohydrate to support training To maintain performance, meet the energy demands of training, maintain and to restore muscle glycogen stores for training and competition, players should aim to consume a high carbohydrate diet (7-12 g/kg/day) from nutrient rich complex carbohydrate food sources. Macronutrient intake analysis in Scottish soccer players reported a mean intake of 4.8 g/kg/day or only 376 g/day of carbohydrate, well below current recommendations. Alcohol intake accounted for <5% of energy intake on average but for some players accounted for as much as 10% of their daily energy intake (~12 MJ/day). The inter-individual variability was a striking feature of this data. Other data on footballers still highlights individual requirements and reveals that the activity energy expenditure during training is in the region of MJ/day suggesting that a total energy intake of around 16 MJ/day is needed to sustain training if energy balance is to be maintained. Whilst it is now recognised that there may be a place for some glycogen depleted training to enhance adaptations in skeletal muscle metabolism, this type of training cannot be sustained on more than one or two occasions per week without having potential effects on recovery or performance over the longer term. Carbohydrate feeding on match-day Given the association between glycogen depletion and fatigue profile in the latter stages of a match, it would seem prudent to ensure that glycogen stores are maximised prior to competition. Adequate intake of carbohydrate during training in the days preceding matches, and inclusion of a high carbohydrate meal consisting of low glycaemic index foods 3-4 hours before a match should make this possible (14). During matches players should aim to consume carbohydrate/fluid to help maintain hydration status and provide substrate to delay fatigue, and maintain skill and cognitive functioning, to minimise performance decrements towards the end of the match. Endurance performance It is now well established that a body fluid deficit >2% of body mass can negatively impact upon endurance performance and sprint performance in team sports. Ensuring that any fluid deficit remains within this range is therefore recommended. Carbohydrate ingested with fluids can improve performance in intermittent high-intensity endurance activity and could help to maintain running capacity late in a match. High-intensity shuttle running capacity after 80 minutes of match related game play in professional soccer players is greater when carbohydrate is ingested compared to ad libitum ingestion of fluid (Figure 2). Thus, consumption of carbohydrate containing beverages in a volume sufficient to supply g/h of carbohydrate can have the dual effect of maintaining hydration status and providing substrate to maximise high-intensity running capacity late in a match. 9

10 Figure 2. High intensity shuttle running capacity following 80 minutes of match play drills in Scottish professional youth footballers when ingesting fluid ad libitum (1-2% mass loss) or when fluid is prescribed to offset sweat losses. N=8. Data are mean (SD). Skill performance Fatigue and hypohydration can also impact upon skill performance but even when hydration status is maintained there is evidence that carbohydrate ingestion helps to maintain skill. Studies examining soccer players with compromised glycogen stores indicate that carbohydrate feeding may help to maintain skill (1, 2). Other studies examining skill in nonfasted athletes also seem to support a beneficial effect on motor skill performance when assessed pre and post fatiguing exercise (4, 6). The application of these findings is somewhat limited by the ecological validity of the skill test protocols used and the nature of the fatigue induced in the testing procedures. More work is needed using notational analysis to examine the impact of carbohydrate feeding on skill performance in soccer. One example of this approach is our recent study on tennis in which skill test performance pre and post a 2 hour match did not decline on the placebo trial, and was thus not surprisingly unaffected by carbohydrate feeding. This suggests that the 2 hour match did not induce sufficient localised fatigue to impact upon unopposed serving and groundstroke skill assessment due to the frequent recovery breaks in play that occur during tennis match-play. However, notational analysis revealed that during the match certain aspects such as serving success and return success improved with carbohydrate feeding over placebo ingestion and this was associated with higher perceived arousal / activation. Cognitive function Some of the improvement in skill performance following carbohydrate ingestion has been attributed to improved cognitive functioning. Studies have demonstrated improved visual reaction times following carbohydrate ingestion and improved arousal / activation which could help to maintain skill performance. These changes are likely to be due to elevated blood glucose concentration with carbohydrate feeding. Indeed, blood glucose elevation is consistently shown to alter brain activity in reward centres and may heighten awareness in athletes. Furthermore, caffeine ingestion has been shown to have at least some effect on skill performance in soccer (7) and although these authors did not measure cognitive function this could also explain their observations. Recently, a study on caffeinated sports drink ingestion in soccer referees demonstrated a reduction in vigilance errors after 30 minutes of fatiguing exercise that could also have implications for players, but this effect could have been due to carbohydrate alone. In summary, carbohydrate feeding on match day should help to maximise performance by delaying the onset of fatigue and maintaining skill performance and cognitive function. The challenge is to ingest sufficient amounts at breaks in play and during half time. Carbohydrate / protein for recovery. Clearly, recovery is also an important aspect to be considered for professional soccer players. Immediate post-match recovery strategy should involve ingestion of g/kg/hr of carbohydrate consumed at frequent intervals in meals or drinks. Longer term recovery strategy should focus on maintaining a high carbohydrate intake to maximise glycogen restoration. Nicholas et al (11) demonstrated improved intermittent running capacity following ingestion of 10 g/kg/day over a 22 hour recovery period. Furthermore, addition of protein to carbohydrate ingested post-exercise has been shown to enhance muscle glycogen restoration (8). 10

11 Conclusions Soccer players have demanding high volume training and match schedules that requires them to focus attention on energy intake and carbohydrate intake in particular. Carbohydrate can not only help to fuel the demands of training but can assist in delaying high-intensity running fatigue, maintaining skill, and sustaining cognitive function during exercise, as well as promoting faster recovery. Some key practical messages from this brief review are highlighted in Table 1. Table 1: Practical messages from this brief review. 1) Soccer is a demanding sport and requires a high volume of training with about 15-20% of this conducted as high intensity interval work. 2) Players should ensure that their energy intake is adequate and that carbohydrate intake meets the demands of training and competition. 3) Players should ensure adequate hydration to minimise hypohydration effects on performance. 4) Carbohydrate supplements should be considered to aid in performance of high-intensity running during the latter stages of training and matches. 5) There is evidence that carbohydrate ingestion may also help to retain skill performance and cognitive function during fatiguing training and matches. 6) Maintaining a high carbohydrate intake in the post-training / post-match period is essential to maximise restoration of muscle glycogen and high intensity intermittent running capacity. 7) Addition of protein to the recovery strategy should enhance glycogen restoration. 8) Individual players require individual nutritional strategies rather than a whole team approach. References 1. Ali et al The influence of carbohydrate-electrolyte ingestion on soccer skill performance Med Sci Sports Ex 39(11): Ali and Williams Carbohydrate ingestion and soccer skill performance during prolonged intermittent exercise J Sports Sci 27(14): Bangsbo et al Physical and metabolic demands of training and match-play in the elite football player J Sports Sci 24(7): Bottoms et al Effects of carbohydrate ingestion on skill maintenance in squash Players Eur J Sport Sci 6(3): Bradley et al High-intensity running in English FA premier league soccer matches J Sports Sci 27(2): Currell et al Carbohydrate ingestion improves performance of a new reliable test of soccer performance Int J Sports Nutr Exerc Metab 19(1): Foskett et al Caffeine enhances cognitive function and skill performance during simulated soccer activity Int J Sports Nutr Ex Metab 19(4): Ivy et al Early post-exercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement J Appl Physiol 93: Krustrup et al Physical demands during an elite female soccer game : importance of training status Med Sci Sports Exerc 37(7): Krustrup et al Muscle and blood metabolites during a socer game : implications for sprint performance Med Sci Sports Exerc 38(6): Nicholas et al Carbohydrate intake and recovery of intermittent running capacity Int J Sport Nutr 7: Rampinini et al Technical performance during soccer matches of the Italian Serie A league: effect of fatigue and competitive level Int J Sports Med 28: Seiler and Kjerland Quantifying training intensity distribution in elite endurance athletes: is there evidence for an optimal distribution? Scand J Med Sci Sports 16: Williams and Serratosa Nutrition on match day J Sports Sci 24(7):

12 3 Overtraining: how to monitor and how to prevent? Asker E Jeukendrup Summary Overtraining is something that is talked about a lot in sport. Sometimes athletes overtrain on purpose for a period of time with the aim to improve their performance in the long term. This is called functional overreaching. It is believed that when such periods are sustained for too long that a long term pathological situation develops referred to as the overtraining syndrome. There are several links between nutrition and overtraining. Well-balanced nutrition in combination with well-timed sports nutrition can help to maintain performance even during periods of hard training. An insufficient or unbalanced diet, on the other hand, may result in deteriorated performance and poor recovery. In a period of overreaching, a high carbohydrate diet has been shown to reduce symptoms of overtraining but it cannot completely prevent it. Early detection of overtraining is crucial and there has been an interest in developing tools and parameters that can be used in the monitoring of training. Amongst the more successful tools are simple measurements such as questionnaires, sleeping heart rate and regular performance measurements (benchmark sessions). Introduction There is considerable debate in the overtraining literature about what overtraining is, how it can be detected, how it can be prevented and how it can be treated. There are many questions and very few answers mostly because of the fact that there is very little research. The area is characterised by more review articles than original work. Many people have an opinion but most information is anecdotal and hardly ever based on well controlled studies (1). Because of this we even questioned whether overtraining really exists (1). Another problem that makes comparing different studies almost impossible is the lack of common and consistent terminology in the study of overtraining. Here, the following definitions will be used. Figure 1: Definitions Overtraining An accumulation of training and/or non-training stress resulting in long-term decrement in performance capacity with or without related physiological and psychological signs and symptoms of overtraining in which restoration of performance capacity may take several weeks or months. Overreaching An accumulation of training and/or non-training stress resulting in short-term decrement in performance capacity with or without related physiological and psychological signs and symptoms of overtraining in which restoration of performance capacity may take from several days to several weeks. The first thing that becomes obvious from these definitions is that overtraining can be caused by a number of factors (stresses) other than training. Secondly, these definitions suggest that the difference between overtraining and overreaching is the amount of time needed for performance restoration, and not the type or duration of training stress or the degree of impairment. The process by which intensified training and/or limited recovery lead to overreaching or overtraining, is often viewed as a continuum (figure 2). On the left-hand or beginning of the continuum is the acute fatigue that occurs as a result of a single training. When single training sessions are applied repeatedly with appropriate recovery, a positive adaptation and improvement in performance generally occurs. However if the balance between training and recovery is inappropriate, a state of overreaching may develop. If intensified training and limited recovery continues the more serious state of overtraining or overtraining syndrome may ensue. 12

13 Physiology Pathophysiology Fatigue Overreaching Overtraining (syndrome) Figure 2: the fatigue-overreaching-overtraining continuum According to this continuum, if athletes undergo periods of intensified training in the absence of appropriate recovery, they may not respond appropriately to the training and progressive fatigue and decreased performance ensues. Once a state of overreaching has occurred one of two outcomes may follow. Firstly, the athlete/coach/sport scientist may recognise the symptoms associated with overreaching and provide appropriate rest and recovery for the athlete. Following this, full recovery may occur and the process of overreaching may have stimulated supercompensation and performance may increase to a level higher than that previously attained. The second possible suggested outcome following overreaching is the progressive development of a state of overtraining. The reduced performance that occurs as a consequence of overreaching may be the stimulus for an increase in training in a bid to improve the diminished performances. Alternatively, the reduced performance may be unrecognised. If high levels of training persist and/or rest and recovery is inadequate, the more serious state of overtraining is thought to develop. Other contributing stressors include frequent competition, monotonous training, psychosocial stressors and heavy travel schedules. Symptoms of overreaching and overtraining are extensive and varied. They are also highly individual and this complicates the issues even more. A selection of commonly reported symptoms can be found in figure 3. Figure 3: A selection of symptoms associated with overreaching and overtraining Reduced performance Washed-out feeling, tired, drained, lack of energy Mild leg soreness, general aches and pains Chronic pain in muscles and joints Insomnia Headaches Decreased immunity (increased number of colds, and sore throats) Decrease in training capacity / intensity Moodiness and irritability Depression Loss of enthusiasm for the sport Decreased appetite Increased incidence of injuries In order to investigate early stages of overtraining we used a model of 7-14 days of intensified training (both intensity and volume). During this training performance is reduced and various symptoms start to develop. It is important to realise that performance is the cardinal symptom of overreaching/overtraining as without this symptom the condition does not exist. Other symptoms include changes in mood state which can be tracked relatively easily with questionnaires such as the Daily Analysis of Life Demands in Athletes (2). Other indicators that may be useful include sleeping heart rate (disturbed sleeping patterns and higher average heart rate), lower submaximal and maximal lactate concentrations and possible a reduction in cortisol response to a standardised exercise bout. Many suggested markers may not be as helpful as sometimes suggested and may simply respond to fatigue rather than overreaching (3). These markers amongst many others include cortisol concentration, cortisol/testosterone ratio and creatine kinase. Muscle glycogen As overreaching is thought to be brought about by high intensity training with limited recovery, it is perceivable that the fatigue and underperformance associated with overtraining is at least partly attributable to a decrease in muscle glycogen levels. Therefore, studies have been performed in a bid to elucidate the role of carbohydrate and dietary intake on performance after intensified training. 13

14 Costill et al. (4) investigated this possibility by examining the effects of 10 days of increased training volume on performance and muscle glycogen levels. Of the 12 swimmers participating in the investigation, 4 were unable to tolerate the increase from 4000 metres/day to 9000 metres/day and were consequently classified as non-responders. The group of non-responders consumed approximately 1000 kcal per day less than their estimated energy requirement and consumed less carbohydrate than the responders (5.3 g/kg/d vs. 8.2 g/kg/d). However, importantly, muscular power, sprint swimming ability and swimming endurance ability were not affected in either the responders, or the non-responders. Costill et al. (4) concluded that the glycogen levels of the non-responders were sufficient to maintain performance, but inadequate for the energy required during training and thus fatigue resulted. These findings directed Snyder et al. (5) to examine performance responses to intensified training with the addition of sufficient dietary carbohydrate, in a bid to determine whether overreaching could still occur in the presence of normal muscle glycogen levels. To ensure sufficient carbohydrate intake, subjects consumed 160g of a liquid carbohydrate in the two hours following exercise. Subjects completed 7 days of normal training, 15 days of intensified training and 6 days of minimal training. Resting muscle glycogen was not significantly different when compared between normal training (531 mmol/kg dry weight) and intensified training (572 mmol/kg dry weight). Subjects were reported to be overreached. However maximal power output during an incremental cycle test was not statistically different after intensified training. Only four of the eight subjects demonstrated both a decline in maximal power output and an increase in responses to questionnaires. Therefore, it appears that in this study only half of the subjects could perhaps be classified as overreached. Since muscle glycogen depletion is a risk factor for the development of overtraining, nutritional strategies should aim at optimising glycogen resynthesis during periods of hard training. Amount and timing of carbohydrates and possibly the coingestion of protein are factors that influence glycogen resynthesis. When carbohydrate supplements are provided immediately post-exercise, and are ingested at regular intervals providing g/kg per hour this generally results in the highest glycogen resynthesis rates over a 4-6 hour period. When carbohydrate supplements are provided immediately post-exercise, and are ingested at regular intervals providing g/kg per hour this generally results in the highest glycogen resynthesis rates over a 4-6 hour period Besides carbohydrate depletion there are other nutritional issues that can increase the risk of developing overtraining. Dehydration and a negative energy balance can increase the stress response (increased catecholamines, cortisol and glucagon, while insulin levels are reduced) which can contribute to the risk of developing overtraining. It is a fine balance because many of these stresses are necessary to obtain the training adaptation necessary for the performance improvements. Glutamine, overtraining and the immune system Prof Eric Newsholme and colleagues suggested that hard training and overtraining result in a decreased glutamine concentration in the blood (8). When the glutamine concentration decreases below a critical level, this could result in immunosuppression. Indeed, plasma glutamine concentration has been reported to be lower in overtrained athletes. In a number of studies drops in plasma glutamine levels have been reported in fatigued or overtrained athletes and these drops have been in the range of 9-40%. On the basis of these thoughts it is often claimed that glutamine supplements would help reduce immunosuppression after strenuous training and could help to fight overtraining. However, it is unclear at present if plasma glutamine is a useful biochemical marker of immune function or overtraining, particularly since most of the body glutamine pool is present in muscle (90%) and not in plasma and because many factors can influence plasma glutamine levels (short term exercise, nutritional status, diet, infection, trauma). Branched chain amino acids In 1987, another hypothesis was launched by Prof. Eric Newsholme in which the amino acid tryptophan was associated with central fatigue (8). Tryptophan is the precursor of 5-hydroxytryptamine (5-HT or serotonin) in the brain. Only about 10% of the plasma tryptophan is in the free form and there is evidence to suggest that only this fraction is available for uptake by the brain; the remainder is bound to plasma albumin, where it shares a binding side with the fatty acids. During exercise, fatty acids are mobilised from adipose tissue, bind to albumin and tryptophan will be disposed from its binding. As a result the free tryptophan concentration in the blood will rise. Simultaneously, the oxidation of the branched chain amino acids (BCAA) leucine, isoleucine and valine in muscle will increase during prolonged exercise. This will lead to a decrease of the concentration of the BCAA in the blood. Since BCAA and tryptophan compete for carriermediated entry into the central nervous system by the large neutral amino acid (LNAA) transporter, the increase in this 14

15 ratio would lead to increased tryptophan transport across the blood- brain barrier. Once taken up in the brain, conversion of tryptophan to 5-HT would occur and lead to a local increase of this neurotransmitter. This increase indeed has been found in certain brain areas in the rat, but it has not been established whether it also occurs in man. Prof. Newsholme and colleagues suggested that overtraining can lead to chronically elevated fatty acids levels and a chronically elevated free tryptophan/bcaa ratio. According to the hypothesis this would lead to increased 5-HT concentrations in the brain and it has been used to explain some of the (central) fatigue symptoms of overtraining. Although the theory was attractive, the overarching conclusion from a number of studies is that BCAA supplementation has no effect on performance and although the effect in overtraining has not been directly studied, the efficacy of BCAA feedings should be questioned. References 1. Halson SL and Jeukendrup AE. Does overtraining exist? An analysis of overreaching and overtraining research. Sports Med 34: , Jeukendrup AE, Hesselink MK, Snyder AC, Kuipers H, and Keizer HA. Physiological changes in male competitive cyclists after two weeks of intensified training. Int J Sports Med 13: , Halson SL, Bridge MW, Meeusen R, Busschaert B, Gleeson M, Jones DA, and Jeukendrup AE. Time course of performance changes and fatigue markers during intensified training in trained cyclists. J Appl Physiol 93: , Costill DL, Flynn MG, Kirwan JP, Houmard JA, Mitchell JB, Thomas R, and Park SH. Effects of repeated days of intensified training on muscle glycogen and swimming performance. Med Sci Sports Exerc 20: , Snyder AC, Jeukendrup AE, Hesselink MK, Kuipers H, and Foster C. A physiological/psychological indicator of over-reaching during intensive training. Int J Sports Med 14: 29-32, Achten J, Halson SL, Moseley L, Rayson MP, Casey A, and Jeukendrup AE. Higher dietary carbohydrate content during intensified running training results in better maintenance of performance and mood state. J Appl Physiol 96: , Halson SL, Lancaster GI, Achten J, Gleeson M, and Jeukendrup AE. Effects of carbohydrate supplementation on performance and carbohydrate oxidation after intensified cycling training. J Appl Physiol 97: , Newsholme EA, Parry-Billings M, McAndrew N, and Budget R. A biochemical mechanism to explain some mechanisms of overtraining. In: Advances in nutrition and topsport, edited by Brouns F. Basel: Karger, 1991, p

16 4 New developments in supplement use by athletes Ronald Maughan Loughborough University, UK The use of dietary supplements continues to be widespread among athletes at all levels of competition, reflecting the pattern in use among the general population. A recent study of 310 male and female athletes competing in the track and field World Championships showed that 83% of males and 89% of females were using one or more dietary supplements (Unpublished data of F Depiesse). The reasons these athletes gave for using supplements were: to aid recovery from training 71% for health 52 % to improve performance 46% to prevent or treat an illness 40% to compensate for a poor diet 29 % These reasons raise some questions. Dietary supplement manufacturers are not permitted to claim that supplements can prevent of treat illness unless there is valid proof of such an effect, and this is invariably absent. If an athlete is concerned about a poor diet, it makes more sense to improve the quality of the diet than to try to compensate for this by the use of supplements. It is important to recognise that there is limited evidence of either safety or efficacy in the case of most dietary supplements. This is in part because any effects on performance are likely to be small, and may be too small to be seen with the standard laboratory tests that are used to assess performance. Hopkins et al (3) estimated that the smallest worthwhile performance effect for an athlete in an individual sport would be about one half of the within-athlete random day-today variation for that performance measure. Many laboratory tests of performance, however, lack the sensitivity necessary to measure this. The difficulties in assessing efficacy are magnified many times when there is a less well-defined endpoint, for example in areas such as wound healing, alleviation of muscle soreness, preservation or stimulation of immune function, and joint health. Even with a very large financial investment, which manufacturers are generally unwilling to make, it is unrealistic to expect clear evidence of efficacy in these areas. It is also increasingly recognised that any population may include some individuals who respond positively to treatment, some who show no effect, and some who respond negatively. In such a mixed population, the scientist may reasonably conclude that, on average, there is no significant effect. The athlete and the coach, however, are concerned with effects on individuals, not effects on populations. New supplements are emerging (eg, β-alanine, nitrate) and new information is emerging on some old supplements (eg carnitine, hydroxycut). New supplements are emerging (eg, β-alanine, nitrate) and new information is emerging on some old supplements (eg carnitine, hydroxycut). The challenge for athletes is to know when the evidence of efficacy and safety is strong enough to warrant use of a supplement. Where there is evidence of harmful effects, as in the case of Hydroxycut (FDA, 2), it is clear that use should cease immediately, but it takes time before the link can be made, and it may be too late to prevent harmful effects. It has been known for many years that performance in events where a substantial metabolic acidosis is induced may be improved by the acute pre-event ingestion of compounds, such as bicarbonate or citrate, that can increase the extracellular buffering capacity. Such events include middle distance running, rowing, and the pursuit in cycling. Increasing the ph and the buffering capacity of the extracellular space promotes the efflux of hydrogen ions from the active muscle cells and so slows the rate of development of intracellular acidosis. The muscle also has intracellular buffers, however, and carnosine, a dipeptide of histidine and β-alanine accounts for a small but significant part of this buffer capacity. The muscle carnosine content can be increased by training and by supplementation with carnosine or β-alanine. There is some, albeit limited evidence for performance enhancement, but β-alanine use by athletes appears to be widespread. Recent studies have reported a substantial reduction in the oxygen cost of exercise following short-term dietary nitrate (NO3-) supplementation, with resulting improvements in performance (1). The total number of studies is small and they involve only a few subjects, but the data look robust and athletes have not awaited further studies. In some of these 16

17 studies, subjects consumed 500 ml per day of nitrate-rich beetroot juice, rather than a nitrate supplement per se. Further studies are sure to follow rapidly and will either confirm or refute these findings. Carnitine has a long history of use as a dietary supplement, with claims that it can promote fat oxidation which can lead to enhanced fat loss and to improvements in endurance exercise performance. The evidence, however, has been mixed at best, although there is a strong underpinning rationale: carnitine plays an essential role in the transport of fatty acids across the mitochondrial membrane for oxidation. It has been argued, however, that supplementation with carnitine is not effective in increasing the muscle carnitine content, without which there would be no effect. Recent data have confirmed this, but have also shown that administration of insulin along with carnitine supplements can result in an increase in the muscle total carnitine content (via insulin-mediated stimulation of muscle carnitine transport) and that this may indeed increase fat oxidation and reduce muscle glycogen utilisation in endurance exercise (7). Although insulin use is prohibited under WADA regulations, this will not deter some athletes form using this approach. Others will seek to induce elevations of insulin by ingesting large amounts of high glycaemic-index carbohydrates. As new information emerges athletes must revise their practices, while continuing to carry out cost-benefit analyses for all supplements used. In most cases there is insufficient evidence to be sure of efficacy or safety of these products. Although new legislation is being applied to supplement manufacture and distribution, the possibility of contamination with harmful or prohibited substances, including anabolic androgenic steroids, stimulants and prescription appetite suppressants, appears to remain a significant risk. The US Government Accountability Office (8) has released a report on herbal dietary supplements showing that most of the herbal dietary supplements tested contained trace amounts of heavy metal contaminants, and some supplement sellers made illegal claims that their products can cure cancer and other diseases. The levels of heavy metals - including mercury, cadmium and arsenic - did not exceed the levels considered dangerous, but remain a concern nonetheless: 16 of the 40 supplements tested contained pesticide residues that appeared to exceed legal limits. Nine of these 40 products made apparently illegal health claims, including a product containing ginkgo biloba that was labelled as a treatment for Alzheimer s disease and a product containing ginseng labelled as a treatment to prevent diabetes and cancer. For athletes, the problem of contamination with WADA-prohibited substances remains. For athletes, the problem of contamination with WADA-prohibited substances remains, and there are frequent reports of contamination with androgenic anabolic steroids, stimulants and other prescription medications. A significant number of herbal weight loss products have been found to contain appetite suppressants that have potentially harmful sideeffects a swell as being prohibited in sport. Similar problems are being reported in products aimed primarily at nonathletes. Various schemes at identifying high risk supplements and offering some quality assurance are beginning to emerge and may provide some degree of reassurance to athletes. References and further reading 1. Bailey SJ, J Fulford, A Vanhatalo, PG Winyard, JR Blackwell, FJ DiMenna, DP Wilkerson, N Benjamin, AM Jones. (2010) Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans. J Appl Physiol (In the Press) 2. FDA (2009) Warning on Hydroxycut Products. Published at: 3. Hopkins WG, JA Hawley, LM Burke (1999) Design and analysis of research on sport performance enhancement. Medicine & Science in Sports & Exercise, 31, Krishnan PV, ZZ Feng, SC Gordon (2009) Prolonged intrahepatic cholestasis and renal failure secondary to anabolic androgenic steroid-enriched dietary supplements. J Clin Gastroenterol 43, Maughan RJ (2005) Contamination of dietary supplements and positive drugs tests in sport. J Sports Sci 23, Maughan RJ, F Depiesse, H Geyer (2007) The use of dietary supplements by athletes. J Sports Sci 25, S103-S Stephens FB, D Constantin-Teodosiu, PL Greenhaff (2007) New insights concerning the role of carnitine in the regulation of fuel metabolism in skeletal muscle. J Physiol 581, US Government Accountability Office (2010) Herbal dietary supplements. Assessed at: 9. Watson P, C Judkins, E Houghton, C Russell, RJ Maughan (2009) Supplement contamination: detection of nandrolone metabolites in urine after administration of small doses of a nandrolone precursor. Med Sci Sports Exerc 41,

18 5 Buffering agents and their possible role in team sports Trent Stellingwerff Nestlé Research Center, Switzerland Anaerobic metabolism (or glycolysis) provides the majority of energy for high-intensity sports, including the energy required for the important sudden bursts of speed needed in many team sports. However, these situations of high intensity energy requirements come at a cost, as metabolic acidosis results via increased hydrogen ion (H+) accumulation in conjunction with lactate (La-) production. Intense exercise can cause significant decreases in muscle ph (resting values of ~7.0 to ~6.5 post-exhaustion). This drop in muscular ph (not the lactate formation!) has been shown to negatively affect metabolic processes, including: limiting the re-synthesis of phospho-creatine (PCr), inhibition of glycolysis and the muscle contraction processes itself, which all cause fatigue and decreased performance (5). Accordingly, a higher buffering capacity in humans has been directly associated with improved performance, from long sprints to high-intensity exercise (8). A buffer has the ability to retain a nearly constant ph when either a small amount of an acid or base is added to a solution. Therefore, the enhancement of both intra- and extra-muscular buffering of H+ should lead to an increase in performance where metabolic acidosis is a limiting factor. During high-intensity exercise, with increased H+ production (which causes a decrease in ph), many different innate metabolic processes and physio-chemical properties contribute to total buffering capacity in attempts to maintain intramuscular ph (Figure 1). Muscle histidine (essential amino acid) and the breakdown of PCr provide nearly ~60% of the total natural buffering capacity of the muscle, while bicarbonate and other processes provide the remaining ~40% of buffering (5). Accordingly, there are several nutritional supplements that anaerobic athletes can potentially utilise to augment buffering capacity, and potentially performance: 1) the prolonged supplementation of ß-alanine to increase muscle carnosine contents and possibly phospho-creatine supplementation, which both could enhance intra-cellular (inside muscle) buffering, and 2) the acute supplementation of sodium bicarbonate (NaHCO3) or citrate can be utilised to enhance extra-cellular (outside muscle) buffering. As of 2010, all of these substances are not on the World Anti-Doping Agencies (WADA) prohibited substances list. Figure 1. The relative contribution of metabolic process and physio-chemical properties to total buffering capacity during intense exercise. Figure adapted from (5). Intra-cellular Buffering: Creatine and Carnosine (β-alanine) Creatine supplementation to potentially augment buffering Phospho-creatine is most well known as a high-energy phosphate donor for ATP regeneration during exercise. During exercise, the creatine kinase (CK) reaction allows for the breakdown of phospho-creatine (PCr) and adenosine triphosphate (ADP) to create more adenosine triphosphate (ATP- energy ) and creatine (Cr). In this process, hydrogen ion (H + ) is also utilized and buffered: CK H + + PCr + ADP Cr + ATP 18

19 Therefore, PCr breakdown during exercise can also act as a principle metabolic buffer in the muscle, accounting for ~30% of total muscle buffering capacity (Figure 1; (5)). Phospho-creatine breakdown can act as a principle metabolic buffer in the muscle, accounting for ~ 30% of total musicle buffering capacity. Skeletal muscle contains approximately mmol/kg dry muscle weight of creatine (~60% is stored in the form of phospho-creatine), and can be increased 15 to 20% with the oral administration of creatine, depending on initial muscle creatine stores. There are two ways to do this, depending on how quickly you want your muscle creatine augmented (Table 1): 1) Loading phase of ~20g/day for 5 days (taken in 4x5g doses spread throughout the day) followed by a maintenance phase of ~2-3 g per day 2) ~3-5g per day for ~30 days Some individuals experience water retention with creatine intake, as many studies show a 1-3% BW increase with supplementation. When examining the scientific data creatine supplementation does not appear to have much effect in single sprints. Instead, increased PCr stores via supplementation have the most benefits in sports featuring repeated sprints and in studies with a power phase lasting ~ 1 to 4min in duration (1). It is difficult to isolate the metabolic mechanism responsible for these performance benefits, as creatine could either be acting as a high-energy phosphate donor for ATP regeneration or a metabolic buffer, or both. However, it is estimated that a 10-20% increase in muscle creatine could increase muscle buffering capacity by ~3% (5). More studies are needed examining PCr s role as a metabolic buffer, and given the 1-3% increase in body-weight (BW) associated with creatine supplementation, whether divergent performance results are found in weight dependent (e.g. running) and less weight-dependent (rowing, cycling) events. Β-alanine supplementation to increase muscle carnosine, buffering and performance Carnosine (β-alanyl-l-histidine) is a cytoplasmic dipeptide found at high concentrations in skeletal muscle, and in particular type II (fast twitch) muscle (for review see: (2)). Already since the 1930 s, carnosine has been described as a potent intra-muscular buffer due to its nitrogen containing side imidazole ring, which can directly accept and buffer H+ ions. The contribution of normal muscle carnosine levels to total intracellular muscle buffering capacity has been suggested to reach ~6 to 7% (Figure 1). However, when increased via β-alanine supplementation can reach ~15% (4). Prof. Roger Harris was the first to show increases in muscle carnosine with prolonged β-alanine supplementation (4). All studies that have followed have shown a significant increase in muscle carnosine content utilising ~3 to 6g β-alanine/ day over 4wks (Table 1; (2)). On average, this has lead to a significant ~40% increase in muscle carnosine. Even 1.6g β-alanine/day can lead to a ~30% increase in muscle carnosine in 8wks of supplementation (10). The washout of augmented skeletal muscle carnosine after the termination of β-alanine supplementation is very slow, with an estimated washout time of ~14 to 15 weeks after a ~50% increase in muscle carnosine (10). 19

20 Table 1. Overview of intra- and extra-cellular buffers, and their recommended dosing protocol, side effects and potential performance benefits. Horizontal arrow indicates no difference in performance. Arrow(s) up indicate a performance benefit, and arrow down a potential performance decrement. Supplement Creatine to increase muscle phospho-creatine stores β-alanine to increase muscle carnosine stores Sodium bicarbonate (NaHCO3) Recommended Dosing Protocol Low Dose: 3-5 g / day for 31 days or High Dose: 20g / day (taken as 4 x 5g/doses) for 5 days High Dose: 3 to 6 g / day for 31 days or Loading Dose: 3.2 g / day for 31 days, followed by 1.6g / day 31 days ~300mg/kg BW (~20g) in ~1L of water taken 1 to 3 hrs prior to event Body Weight Side Effects Gain? Intra-Cellular Buffers ~1 to 3% BW gain with ~80% as water weight No ~1 to 2% increase in BW Body weight gain & possible increased muscle cramping in very elite speed/power athletes utilizing a high-dose creatine loading regime Pure β-alanine: mild paraesthesia (minor pins and needles, skin vasodilation, flushing, over ~ 60 to 120 min). This is prevented with slow-release β-alanine. Extra-cellular Buffers NaHCO3 can cause significant GI upset (e.g. stomach upset, diarrhoea) in ~50% of individuals Type of sport or event single sprint (< 15 sec) repeated sprints intense exercise ~ 1-5 min prolonged exercise (> 10 min) single sprint (< 15 sec) prolonged exercise followed by 30 sec sprint ~1 to 6 min of intense exercise neuromuscular fatigue/ isokinetic contractions circuit training / weight room training prolonged exercise (> 10 min) single sprint (< 60 sec) repeated sprints intense exercise ~ 1-5 min prolonged exercise (> 10 min) Performance Benefit? Sodium citrate same as NaHCO3 same as NaHCO3 same as NaHCO3 slightly effective, but several studies have shown less effective than NaHCO3 Several well-done studies have shown that prolonged β-alanine supplementation can result in significant anaerobic performance benefits (for review see: (2)). The studies not demonstrating positive performance effects are most likely due to either inadequate β-alanine dosing protocols, studies not using well-trained and motived subjects, being under-powered and/or inappropriately designed performance tests. Taken together, the emerging data is starting to reveal that when subjects consume ~3 to 6g β-alanine/day over 4 to 8 weeks (for a total β-alanine intake of >120g) this will result in an increase of muscle carnosine of about 40 to 50%, and this will lead to positive anaerobic performance outcomes. At this point, whether prolonged β-alanine supplementation can also lead to significantly enhanced weight training, or sprint (<15 sec) and endurance (>20min) performance, remains to be further established. Several well-done studies have shown that prolonged β-alanine supplementation can result in significant anaerobic performance benefits 20

21 Paraesthesia symptoms with β-alanine supplementation When β-alanine is supplemented at levels greater than 800 mg/dose it results in mild paraesthesia in most subjects (paraesthesia: minor pins and needles, skin vasodilation, flushing, over ~ 60 to 120 min). Given this, most studies have implemented small repeated daily doses of 800mg doses, to circumvent and minimise paraesthesia symptoms. Recently a commercialised slow release tablet of β-alanine has been produced and demonstrated that a 1.6 g dose resulted in a blunting of the peak plasma curve and none of the subjects reported any paraesthesia symptoms (11). Other than acute paraesthesia, no other side effects (including no changes in BW) have been demonstrated with β-alanine supplementation. Extra-Cellular Buffering: Sodium bicarbonate and Citrate During intense anaerobic exercise situations, intra-cellular buffering (primarily histidine, PCr and carnosine) can become overwhelmed, and is insufficient to buffer the excess of hydrogen ions, resulting in muscle metabolic acidosis. Accordingly lactate (La - ) and hydrogen (H + ) can be transported out of the muscle via transporters to the extra-cellular space (blood). Hydrogen ions are transported against a concentration gradient, therefore any mechanism to increase the rate of H+ release from the muscle will help maintain muscle ph and delay fatigue during intense exercise. One such mechanism is the blood bicarbonate pool (HCO 3- ), which combines with the H + to form carbonic acid (H 2 CO 3 ), which immediately dissociates to from carbon dioxide (CO 2 ) and water (H 2 O): Na + - HCO 3 + H + + La - H 2 CO 3 + NaLa H 2 O + CO 2 (sodium bicarbonate) (carbonic acid) (water) (carbon dioxide) It has been shown since the 1930 s that the supplementation of sodium bicarbonate (NaHCO 3- ) or sodium citrate can lead to increased plasma bicarbonate (HCO 3- ), and increased muscle buffering through improving the rate of H+ release from active skeletal muscle. However, the findings of whether NaHCO 3 - supplementation can significantly delay fatigue and improve performance have been mixed, and may depend on the mode of exercise testing, and BW considerations (Table 2; (7)). Acute sodium bicarbonate or citrate supplementation The normal protocol of increase blood bicarbonate, and improving the bloods buffering capacity, is through the large - (~300mg/kg BW; ~20g) acute supplementation of either NaHCO 3 or sodium citrate in solution (~1 liter) in the 1 to 3 - hrs prior to an anaerobic based competition (Table 1). A meta-analysis on the performance effects of NaHCO 3 found that on average supplementation resulted in a performance effect that was 0.44 standard deviations better than the control trial, with most studies featured relatively untrained subjects (6). An improvement of 0.44 of the SD would result in a modest ~0.8 second improvement over a ~1 min 45 sec race, which for world-class athletes is within a worthwhile range of improvement. Recent publications since 2000 support this meta-analysis and appear to more clearly show a performance benefit albeit in laboratory settings, and have also shown benefits in swimming, judo and repeated sprint performance. Therefore, with the ideal dosing regime (~300mg/kg BW; ~20g), there appears to be a small, but significant, effect of NaHCO3 to improve intense exercise performance in situations lasting from ~1 to 5min or during repeated sprints, with less pronounced effects on single sprints (<50 sec) or longer exercise duration (>5 min). However, there is a high degree of individual tolerance and variability, as NaHCO3 can cause significant GI upset (e.g. stomach upset, diarrhoea) in ~50% of individuals ((7) and personal experience/communication). Discrepancies in performance enhancement with bicarbonate loading There are several reasons for the discrepancies in the literature regarding whether NaHCO3 can improve performance. The main reason is that some of these studies did not use either an optimal performance test (too long or too short) or bicarbonate dose, or were drastically under-powdered. Sodium citrate also appears to result in lower buffering and performance effects as compared to sodium bincarbonate supplementation (12). Furthermore, in the studies that have monitored BW, it appears that both sodium bicarbonate and citrate cause a small ~1 to 2% increase in water-retention and BW. This small increase would have more of negative impact on performance in tests that are weight dependent (running) vs. less weight dependent (cycling, rowing). Therefore, athletes and coaches need to thoroughly experiment with NaHCO3 in practice and low key competitions to ascertain individual water retention, BW gains and GI effects, before implementation into major targeted championships. Chronic sodium bicarbonate supplementation A recent study has also found favourable results of chronic (several days) of NaHCO3 supplementation (3). This study utilized a daily dose of ~500mg/kg BW; ~35 to 40g) taken continually over 5 days (split up into 4 daily doses), without having to take an acute dose prior to exercise to minimize potential GI issues. The proposed mechanism of action with chrodaily 21

22 dosing of NaHCO3 is that the body is able to store the [HCO3-] surplus over the 5-day dosing period, for potentially up to 2 days post-supplementation. In this study, Douroudos et al. (3) found a 12% improvement in the average power output during cycling Wingate testing. Notwithstanding these promising results, this study did not use a standard cross-over design, nor did they report any BW data (personal experience has also shown increased BW with chronic NaHCO3 loading). Therefore, more research is needed to show performance efficacy for chronic NaHCO3 ingestion protocols in elite athletes, and to better elucidate the dosing and time-course effects between the cessation of dosing and exercise performance testing, and potential impact on body-weight. Combination of intra- and extra-muscular buffering Given that intra- and extra-muscular buffering use different mechanisms to buffer H+ during intense exercise, it could be hypothesized that an additive effect on buffering, and performance, could be found with chronic β-alanine supplementation to raise muscle carnosine coupled with acute pre-exercise NaHCO3 supplementation. Indeed, this was found in a very recently presented abstract, in which cycling performance at 110% of maximum power (CCT110%) for total work done was most improved with a combined buffering approach (9). After initial pre-supplementation CCT110% performance tests, subjects were randomized into 2 groups (β-alanine vs. placebo). After prolonged supplementation of either β-alanine or placebo, two CCT110% tests were preformed again, with and without acute NaHCO3 supplementation. In this study, they found a ~11% performance improvement compared to pre-supplementation with just β-alanine. However, impressively, subjects realized a ~18% improvement in performance when prolonged β-alanine supplementation was combined with acute NaHCO3 supplementation (9). The pros and cons of supplement use There are many pros and cons that need to be considered with the use of any supplement. Table 2 below highlights some practical advice that athletes, coaches and practitioners need to consider when evaluating the use of a new supplement. Table 2. General practical recommendations for the use of any new supplement. Items to consider with supplement use in athletes Supplements do not compensate for poor food choices. Some supplements may benefit performance, but athletes are cautioned against the use of these products without first conducting an individual risk-benefit analysis (2007 IAAF Consensus Statement). Only consider supplement(s) if the athlete has already nearly maximized progress and quality in training, everyday wholesome nutrition, sleep, and proactive recovery approaches and healthcare support. Get advice on supplements from several reputable sources, and cross-reference that advice with published papers/ reviews - do your homework! Only a handful of supplements have strong scientific support for ergogenic benefit, there is a moderate list with emerging potential, and even a longer list with no proven benefits. Many supplements will add no further benefit over what a wholesome well-balanced diet will provide, except extra expenses. A previous study has shown that ~15% of supplements (out of 634 supplements tested) contained WADA prohibited substances. Only obtain supplements from reputable sources and/or check with: Certified Saef Company or Informed Choice Company or NSF Company or Global Drug Reference Online for companies that batch test supplements for quality and purity. Athletes may improve performance on supplements due to either: 1) direct ergogenic (performance-enhancing) effect or 2) placebo effect or 3) allowance of a higher training load or 4) all of the above. Understand the physiology and metabolism behind the supplement, and therefore, whether it is relevant for a certain type of athlete. Periodize the supplement in accordance to the individual athletes training and competition schedule. Know the specific efficacious dosing regime and protocol, and stick to it. Pilot test any new supplement very early in the competitive or training season (during the less important time of the year). Try to collect as much data from both the athlete and coach (give them a log) during this period (e.g. body comp, physiological testing, competition testing, psychological outcomes, side-effects etc.) to ascertain whether the individual athlete is having a positive, neutral or negative impact from the supplement. If pilot testing was positive, periodize supplement into more major competition and training camp situations. 22

23 References 1. Burke L. Practical Sports Nutrition. Champaign, IL: Human Kinetics, 2007, p Derave W, Everaert I, Beeckman S, and Baguet A. Muscle carnosine metabolism and beta-alanine supplementation in relation to exercise and training. Sports Med 40: , Douroudos, II, Fatouros IG, Gourgoulis V, Jamurtas AZ, Tsitsios T, Hatzinikolaou A, Margonis K, Mavromatidis K, and Taxildaris K. Dose-related effects of prolonged NaHCO3 ingestion during high-intensity exercise. Med Sci Sports Exerc 38: , Harris RC, Tallon MJ, Dunnett M, Boobis L, Coakley J, Kim HJ, Fallowfield JL, Hill CA, Sale C, and Wise JA. The absorption of orally supplied beta-alanine and its effect on muscle carnosine synthesis in human vastus lateralis. Amino Acids 30: , Hultman E, and Sahlin K. Acid-base balance during exercise. Exerc Sport Sci Rev 8: , Matson LG, and Tran ZV. Effects of sodium bicarbonate ingestion on anaerobic performance: a meta-analytic review. Int J Sport Nutr 3: 2-28, McNaughton LR. Bicarbonate and citrate. In: Nutrition in Sport, edited by Maughan RJ. Oxford: Blackwell, 2000, p Parkhouse WS, and McKenzie DC. Possible contribution of skeletal muscle buffers to enhanced anaerobic performance: a brief review. Med Sci Sports Exerc 16: , Sale C, Saunders B, Hudson S, Sunderland CD, Wise JA, and Harris RC. Effect of beta-alanine supplementation, with and without sodium bicarbonate, on high-intensity cycling capacity. In: American College of Sports Medicine. Baltimore, Maryland: Stellingwerff T, Anwander H, Egger A, Buehler T, Kreis R, Boesch C, and Decombaz J. The effect of two β-alanine dosing protocols on muscle carnosine synthesis and washout. In: American College of Sports Medicine. Baltimore, Maryland: Stellingwerff T, Beaumont M, Vuichouid J, Bouisset F, Oguey-Araymon S, Blondel-Lubrano A, and Decombaz J. Plasma and symptom kinetics associated with slow-release beta-alanine. unpublished observations- data to be submitted to journal in Van Montfoort MC, Van Dieren L, Hopkins WG, and Shearman JP. Effects of ingestion of bicarbonate, citrate, lactate, and chloride on sprint running. Med Sci Sports Exerc 36: ,

24 6 Fluid requirements in team sports Susan Shirreffs Loughborough University UK Introduction Many team sports such as football, rugby, basketball and hockey are stop-start in nature and consist of prolonged periods of exercise with repeated intermittent high-intensity bursts interspersed with lower intensity exercise. Successful performance in these sports involves fatigue resistance, but also relies on cognitive function for decision making as well as proper execution of complex skills. This makes assessment of sport performance challenging to study. However, a number of protocols have been developed which have attempted, amongst other things, to investigate the effect hydration status may have on aspects of sports performance (eg 1,8). In many of the studies undertaken in this area, the protocol used involves allowing dehydration to develop on one trial and preventing it on another by provision of drinks. However, the drink provided has frequently been a sports drink so therefore, influence of carbohydrate or other components in the drink on the outcomes measured cannot always be distinguished from any effects due to prevention of dehydration. McGregor and colleagues (11) have reported that fluid replacement with flavoured water, sufficient to limit body mass loss to 1.4% prevented a reduction in soccer skill performance in comparison to performance when body mass was reduced by 2.5%. More recently, Edwards et al (4) investigated the influence of hydration status on the movement patters in football using the Yo-Yo intermittent recovery test (8). This evaluates an individual s ability to repeatedly perform intense exercise, typical of that undertaken in football. Body mass reductions of 2.4% and 2.1% resulted in 13% and 15% reductions in Yo-Yo test performance in comparison to a trial when drinking resulted in a body mass reduction of only 0.7%. Baker and colleagues (1) determined the effect of up to 4% dehydration on basketball performance by allowing or withholding drinks during exercise in the heat prior to performing a sequence of basketball drills designed to simulate a fastpaced game. They reported that performance during all timed and shooting drills declined progressively as dehydration increased from 0 to 4% body mass loss and the performance decrement reached statistical significance at 2% body mass loss for combined timed and shooting drills. This information on the effects of alterations in hydration status on performance in team sports or on aspects of team sports performance, together with knowledge of the effects of sweat loss in endurance (3) and sprint, power, highintensity endurance (6) activities, suggests that the effects of sweating will be similar to effects in these e other activities. Therefore, it is frequently generalised that a body mass reduction equivalent to 2% should be the acceptable limit of sweat losses. However, it must be remembered that this is an average and some people may be negatively affected with much smaller body mass losses and others may be able to cope with this body mass loss without an impact on performance. Some people may be negatively affected with much smaller body mass losses and others may be able to cope with this body mass loss without an impact on performance Methods of assessing water and electrolyte loss in team sports Methods of assessing water loss It is common practice to use body mass changes as an index of body water content changes and thus of changes in hydration status. This is based on the assumption that 1kg of mass loss is equal to 1 litre of sweat loss. Any fluid intake and urine or faecal loss need to be accounted for and appropriate corrections made and the dehydration level can then be calculated as the reduction below the baseline body weight. The sweating rate is calculated as the change in body weight (with appropriate corrections) during the exercise period. Potential sources of error in using body mass change to quantify sweat loss include loss of water and therefore mass from the respiratory tract and mass loss due to substrate oxidation. Although individually these losses may be small, their overall effects are not insignificant in many exercise situations. The decision whether or not to correct for substrate oxidation and respiratory water loss is usually determined by the relative magnitude of the different avenues of mass loss, the precision required in the expression of the data and the purpose for which it is being determined. Indeed, respiratory water loss and metabolic water produced are generally of similar magnitude and approximately cancel each other minimising the need for correction. 24

25 Methods of assessing electrolyte loss A wide range of values for all of the major sweat electrolytes has been reported in the literature, reflecting variations between individuals, differences due to the experimental conditions and differences due to the collection methods. Sweat composition has been investigated using a variety of collection methods. The two main methods used involve collection of sweat from a specific body region using some form of enclosing bag, capsule or absorptive patch, or a variation on the whole body-washdown technique. There are regional variations in sweat composition so when regional collection is used collection from both trunk and limb regions are recommended. Also, regional sweat collection procedures typically provide higher sweat electrolyte concentrations than from the whole body-washdown technique. In most of the whole body sweat collection methods, total sweat loss is calculated from the change in body mass and the body and any clothes worn washed after exercise with distilled water and the electrolyte content of that water measured. Alternatively, subjects have worn a close-fitting plastic bag or have exercised within a large plastic bag which makes a small room around. Clearly, some of these procedures are more suited to laboratory research with others being able to be used easily in the field. The majority of published data from team sport players has been obtained using regional collections from absorbent patches that collect sweat. Whilst this is not a particularly difficult technique, clubs and players wanting to investigate their sweat electrolyte losses are likely to need specialised help to do so (2). Besides providing approximate sweat electrolyte losses, this approach, at a minimum, identifies those athletes with electrolyte rich ( salty ) sweat and who need to pay particular attention to electrolyte replacement. When it is not possible to determine electrolyte losses in this way, it may be possible to subjectively identify players with very high salt losses. That is, they may complain of the very salty taste of sweat in their mouth or that they have eye irritation when salt gets in their eyes or salt stains may be visible on clothing worn during training or matches. Water and electrolyte losses in team sports In recent years there have been several published papers reporting the results of in-the-field hydration monitoring, sweat collection and subsequent estimation of sweat water and electrolyte losses in team sport players. Most of these have been in adult males (eg 5,9,10,12,13,14) but similar data has also been published for child and adolescent teams sport players (eg 15) and also in adult female players (eg 7,14). Some of this data is from training sessions and some from games and matches. When pre-training or pre-game/match hydration status has been assessed it has typically been done by assessment of urine specific gravity or osmolality. Most research has suggested that the majority of players appeared to start training in a euhydrated state, with a urine osmolality less than about 700 mosmol/kg or a specific gravity less than However, the data does suggest that some players appear to start training and/or matches hypohydrated and only in some research have these players gone on to consume more fluid during the training and/or match than their euhydrated team-mates. When mean values for sweat volume losses are considered they detract from the considerable variation in both sweating response and drinking behaviour between players as illustrated in Figure 1 which shows data for three different football teams taking part in their club s 90min training sessions. This variation, however, does not appear to be due to any difference in body size between players. Therefore, other factors like activity rate (metabolic rate), heat acclimatisation status and genetic differences probably contribute to this large variability. Figure 1. Estimated sweat body mass loss (% dehydration ) from 3 football teams training for 90min. Each circular symbol represents a different player and the triangle represents the mean within each club. 25

26 The sweat sodium concentrations measured in team sport players generally fall within the normal range reported in the literature of around mmol/l. However, as for the sweat volume losses, the mean values detract from the considerable variation in sweat sodium concentration and sodium losses between players. As shown in Figure 2, there are examples of players losing about 5 times as much sodium as others. Figure 2. Estimated sweat salt loss from 10 football teams training in a variety of environmental conditions for approximately 90min. Each symbol represents a different player. In conclusion, therefore, both the volume of sweat lost and the amount of sodium lost with it is highly variable in players doing the exact same exercise at the exact same time. Summary and practical recommendations From knowledge of the effects of water and electrolyte loss on athletes undertaking other forms of activity together with limited data on team sport players, it seems prudent to recommend that players consider the benefits of limiting their body mass loss due to water loss during both training sessions and matches to less than about 2%. However, the activity pattern in many tem sports may make this recommendation difficult for some players in many situations, in which case careful consideration must be given to providing drinks that are palatable and encourage drinking. During matches and training sessions some players will lose considerable quantities of electrolytes particularly sodium and may need to replace these during the match or training session. If sodium-containing beverages do not suffice, players may want to consume small amounts of salted snacks between periods of play to replace salt losses and stimulate drinking. Finally, the inter-individual variation between players in the same team taking part in the same training session or game/match is so great that players must be treated as individuals with regard to their water and electrolyte needs. Some specific recommendations are summarised in Table 1. The inter-individual variation between players in the same team taking part in the same training session or game/match is so great that players must be treated as individuals Table 1: Some practical recommendations to establish water and electrolyte needs in team sports and some practical recommendations regarding water and electrolyte consumption. Monitoring fluid / electrolyte status in players: Treat each player is as an individual. Measure body mass changes during training and games/matches as a player education tool. o Educate players on their likely individual sweat losses during training and games/matches. If feasible, monitor each player individually (in varying environmental conditions) in training and in game/ match-play to assess electrolyte losses. o Or identify salty sweaters by taste, eye irritation, salt stains on clothing to identify possible problem players. 26

27 Water and electrolyte intake: To ensure adequate hydration during training or matches assess hydration status prior to events. If hypohydration is present or predicted, players should consume some fluid (eg water, sports drink or other soft drink) a number of hours before the start. Water required by the body will be retained and excess will be excreted as urine over the intervening period. Consume plain water at this time only if some solid food is consumed with it; this will provide electrolytes, and in particular sodium to retain the consumed water. When appropriate, ensure each player has suitable drinks available during training and games/matches. During training and games/matches, limit body mass loss (due to sweat loss) to about 2% of body mass. When drinking for hydration is deemed necessary during exercise choose a drink with a composition that has minimal slowing effect on gastric emptying rate. During training and games/matches, consume a drink containing some sodium if significant amounts (3-4 g) are likely to be lost. When environmental conditions are such that large sweat losses are likely in some or most players, consider specific drink break opportunities for all players during match play. Between periods of play provide small salted snacked with beverages. Match officials: Treat as players. References 1. Baker LB, Dougherty KA, Chow M, Kenney WL. (2007) Progressive dehydration causes a progressive decline in basketball skill performance. Medicine and Science in Sports and Exercise, 39, Burke LM. (2005) Fluid balance testing for elite team athletes: An interview with Dr. Susan Shirreffs. International Journal of Sports Nutrition and Exercise Metabolism, 15, Cheuvront SN, Carter III R, Sawka MN. (2003) Fluid balance and endurance performance. Current Sports Medicine Reports, 2, Edwards AM, Mann ME, Marfell-Jones MJ, Rankin DM, Noakes TD, Shillington DP. (2007) The influence of moderate dehydration on soccer performance: physiological responses to 45-min of outdoors match-play and the immediate subsequent performance of sport-specific and mental concentration tests. British Journal of Sports Medicine, 41: Horswill CA, Stofan JR, Lacambra M, Toriscelli TA, Eichner ER, Murray R. (2009) Sodium balance during U.S. football training in the heat: cramp-prone vs. reference players. International Journal of Sports Medicine, 30, Judelson DA, Maresh, CM, Anderson JM, Armstrong LE, Casa DJ, Kraemer WJ, Volek JS. (2007) Hydration and muscular performance. Does fluid balance affect strength, power and high-intensity endurance? Sports Medicine 37, Kilding AE, Tunstall H, Wraith E, Good M, Gammon C, Smith C. (2009) Sweat rate and sweat electrolyte composition in international female soccer players during game specific training. International Journal of Sports Medicine, 30, Krustrup P, Mohr M, Amstrup T, Rysgaard T, Johansen J, Steensberg A, Pedersen PK, Bangsbo J. (2003) The yo-yo intermittent recovery test: physiological response, reliability, and validity. Medicine and Science in Sports and Exercise, 35, Maughan RJ, Shirreffs SM, Merson SJ, Horswill CA. (2005) Fluid and electrolyte balance in elite male football (soccer) players training in a cool environment. Journal of Sports Sciences, 23, Maughan RJ, Watson P, Evans GH, Broad N, Shirreffs SM. (2007) Water balance and salt losses in competitive football. International Journal of Sports Nutrition and Exercise Metabolism, 17, McGregor S, Nicholas C, Lakomy H, Williams C. (1999) The influence of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill. Journal of Sports Sciences, 17, Palmer MS, Spriet LL. (2008) Sweat rate, salt loss, and fluid intake during an intense on-ice practice in elite Canadian male junior hockey players. Applied Physiology Nutrition and Metabolism, 33, Shirreffs SM, Aragon-Vargas LF, Chamorro M, Maughan RJ, Serratosa L, Zachwieja JJ. (2005) The sweating response of elite professional soccer players to training in the heat. International Journal of Sports Medicine, 26, Shirreffs SM, Sawka MN, Stone M. (2006) Water and electrolyte needs for football training and match-play. Journal of Sports Sciences, 24, Yeargin SW, Casa DJ, Judelson DA, McDermott BP, Ganio MS, Lee EC, Lopez RM, Stearns RL, Anderson JM, Armstrong LE, Kraemer WJ, Maresh CM. (2010) Thermoregulatory responses and hydration practices in heat-acclimatized adolescents during preseason high school football. Journal of Athletic Training, 45,

28 S a l z b u r g for more information: and