Changes in Selected Biochemical, Muscular Strength, Power, and Endurance Measures during Deliberate Overreaching and Tapering in Rugby League Players

Transcription

1 Changes in Selected Biochemical, Muscular Strength, Power, and Endurance Measures during Deliberate Overreaching and Tapering in Rugby League Players A. Coutts 1 P. Reaburn 2 T. J. Piva 3 A. Murphy Abstract Introduction The purpose of this study was to examine the influence of overreaching on muscle strength, power, endurance and selected biochemical responses in rugby league players. Seven semi-professional rugby league players (V O 2max = 56.1 ± 1.7 ml kg 1 min 1 ; age = 25.7 ± 2.6 yr; BMI = 27.6 ± 2.0) completed 6 weeks of progressive overload training with limited recovery periods. A short 7-day stepwise reduction taper immediately followed the overload period. Measures of muscular strength, power and endurance and selected biochemical parameters were taken before and after overload training and taper. Multistage fitness test running performance was significantly reduced (12.3%) following the overload period. Although most other performance measures tended to decrease following the overload period, only peak hamstring torque at 1.05 rad s 1 was significantly reduced (p < 0.05). Following the taper, a significant increase in peak hamstring torque and isokinetic work at both slow (1.05 rad s 1 ) and fast (5.25 rad s 1 ) movement velocities were observed. Minimum clinically important performance decreases were measured in a multistage fitness test, vertical jump, 3-RM squat and 3-RM bench press and chin-up max following the overload period. Following the taper, minimum clinically important increases in the multistage fitness test, vertical jump, 3-RM squat and 3-RM bench press and chin-up max and 10-m sprint performance were observed. Compared to resting measures, the plasma testosterone to cortisol ratio, plasma glutamate, plasma glutamine to glutamate ratio and plasma creatine kinase activity demonstrated significant changes at the end of the overload training period (p < 0.05). These results suggest that muscular strength, power and endurance were reduced following the overload training, indicating a state of overreaching. The most likely explanation for the decreased performance is increased muscle damage via a decrease in the anabolic-catabolic balance. Key words Athlete monitoring fatigue recovery hormones team sport overtraining A competitive game of professional rugby league is a high-impact collision sport played over approximately 90 min. Like other football codes, rugby league has been characterized as a high-intensity sport that combines intermittent bouts of very intense anaerobic exercise interspersed with longer lower-intensity periods of aerobic exercise. Due to these activity demands, rugby league players require both a high level of muscular strength and power combined with a well-developed aerobic capacity. Additionally, other physiological factors such as increased speed, speed-endurance, agility and quickness are considered important for success in rugby league [22]. Affiliation 1 School of Leisure, Sport and Tourism, University of Technology, Sydney, Australia 2 School of Health and Human Performance, Central Queensland University, North Rockhampton, Australia 3 School of Medical Sciences, RMIT University, Bundoora, Australia Correspondence Aaron Coutts Ph.D. School of Leisure, Sport and Tourism University of Technology Kuring-gai Campus P.O. Box 222 Lindfield, NSW 2070 Sydney Australia Phone: Fax: aaron.coutts@uts.edu.au Accepted after revision: March 27, 2006 Bibliography Int J Sports Med 2007; 28: Georg Thieme Verlag KG Stuttgart New York DOI /s Published online July 11, 2006 ISSN

2 The physical conditioning programs prescribed for rugby league players usually consist of a high volume of resistance training that focuses on strength and power development, aerobic fitness training, speed and agility sessions, as well as skill and tactical development sessions. Like most high-level team sport athletes, rugby league players often complete a large volume of high-intensity training during the preseason preparation period so that these physical capacities can be optimized prior to the competition season. These high training loads may increase the risk of rugby league players developing overreaching (OR) or over training (OT). High training loads with insufficient periodization of recovery periods has been suggested to cause OR and OT in team sport players, such as soccer [18, 25], European handball [8] and basketball [14]. To date, there have only been a few studies that have examined the influence of OR on muscular strength, power and endurance in team sport athletes [8,18]. These studies have shown that when inappropriate physical training is completed with inadequate recovery or regeneration, both reduced strength performance and physiological function ensues. For example, Kraemer et al. [18] demonstrated that soccer players entering a competition with symptoms of OR such as low plasma testosterone concentration and elevated plasma cortisol, experienced performance reductions in 20-yard sprint velocity, vertical jump height and peak torque production during a maximal isokinetic leg extension in the course of an 11-week soccer season. This study highlighted that biochemical measures could be used to identify fatigue in team sport athletes during the season. However, at present, there is still relatively little information about the usefulness of these markers monitoring for fatigue in team sport athletes. Relatively few studies have systematically examined the use of biochemical measures for monitoring fatigue and recovery in team sport athletes [3 5,15, 25]. In these studies, various hormonal [3 5, 25], hematological [34], and immunological [5] parameters have been used to identify early signs of OR/OT. However, in accordance with similar studies that have been conducted on endurance trained athletes [10], these studies have not been able to provide clear and consistent biochemical markers of impending OR/OT for team sport athletes. The aim of this research was to examine the influence of overreaching on muscle strength, power and endurance characteristics in rugby league players. This is the only investigation, to date, to deliberately induce a state of OR in rugby league players or team sport players in general. Additionally, this study is also the first to examine changes in various performance and biochemical markers of OR/OT in a team sport using a prospective overload-training study. In accordance with similar research with endurance athletes [9], it was hypothesized that increased physical training will result in decreased performance and physiological function, but will not significantly alter biochemical markers previously used to identify OR/OT. Methods Subjects Seven rugby league players (V O 2max = 56.1 ± 1.7 ml kg 1 min 1 or ± 8.2 ml kg bm 0.75 min 1 ; age = 25.7 ± 2.6 yrs; BMI = 27.6 ± 2.0) from the same club volunteered to participate in the study. The club competed in a state level rugby league competition (Queensland Cup, Australia), which is the highest level of competition in the state for regional teams and players. Prior to participation in this study, all players received written and verbal explanation of the study informing them of all risks and benefits associated with participation. Written informed consent was then obtained. University Human Ethics Review Panel approval was given for all experimental procedures. Physical training All subjects completed six weeks of physical training that included 5 7 sessions week 1 of field-based specific rugby league training, aerobic endurance development, resistance, skill and speed/agility training. The physical training in this study was completed during the specific preparation period of the training season and commenced 8 weeks prior to the first official competition match of the season. The physical training program was designed to progressively overload the players during the initial six weeks so that a state of OR was induced. The mean training duration was progressively increased from 6 to 13 h week 1 during the 6-week overload training period, through the addition of both resistance training, match play and rugby league specific training (Table 4). The training load and monotony for each subject was calculated according to the methods of Foster et al. [6]. This method has previously been shown to be useful for measuring a team sport athlete s perception of physical training loads [17]. Following the 6 weeks of physical training, all subjects completed the same taper. A step-reduction taper consisting of three field sessions and two resistance training sessions was completed over a 7-day period (Fig. 1). During the taper, there was a reduction in both training time (55%) and training intensity (17.4%). Resistance training All players completed the same 7-week periodized resistancetraining program during the study. Resistance training sessions were completed 2 3 days week 1. The resistance training exercises prescribed during the overload period and taper are shown in Tables 1 and 2, respectively. The resistance exercises completed on day 1 and 2 in Tables 1 and 2 were alternated throughout the training period. The weight on the bar for core exercises was calculated according to the methods suggested by Baker [1]. The players were encouraged to adjust these weights if they were too heavy or too light. When training loads were altered, players were instructed to inform the chief investigator. A detailed description of the resistance training periodization is shown in Table 3. All resistance-training sessions were completed with at least 24-h recovery from the previous resistance training session. 117 Testing procedures Various physiological and performance measures were taken in the 24 h prior to commencing the 6-week training protocol, fol-

3 Fig.1 Mean (± SD) daily training load (AU = Arbitrary unit). 118 Table 1 Resistance training exercises completed during the 6-week training overload period Day 1 Day 2 Prone hamstring flicks* Box jumps (40 cm)* Hang clean* Back squat Deadlift Barbell step-ups (40 cm) Hami-glut-raise * Power exercises internal/external shoulder bench throw* push press* underhand weighted chin-ups DB incline bench press front military press abdominal circuit Table 3 Description of prescribed resistance training completed during the 7-week training period Week Taper Repetitions per set Sets per session Goal intensity (%1-RM)* Rest period (min) Sessions week * General goal intensities are given only as a guide. Power exercises were completed at lighter %1-RM than strength exercises and the actual weight was individualized by the coach lowing the 6-week overload training and at the completion of the 7-day taper. Additionally, to determine the time-course of changes in endurance shuttle running performance, the multistage fitness test (MSFT) was conducted 24 h prior to training, following the overload training period, and 5 days of the taper. All measures were taken under standardized conditions and at the same time of day. Table 2 Resistance training exercises completed during the 7-day taper period Day 1 Day 2 Prone hamstring flicks Full squat Bench throw* Clean pull* Push press* Hami-glut-raise Abdominal circuit * Power exercises internal/external shoulder hang clean* power shrug* split jerk* narrow grip bench press close grip pulldown Performance tests All subjects were tested for various anthropometric, muscular endurance, strength and power measures before and after the training and taper periods. All tests, except the MSFT, were conducted following 24 h of rest. The MSFT was measured during the final day of training during the taper (day 5). Anthropometry measures of the sum of nine skinfolds, body mass, stature and girths were taken by a trained anthropometrist using standard laboratory methods [27]. Multistage fitness test Endurance performance was measured using the MSFT, using previously reported methods [28]. For this test, the subjects were required to run back and forth along a 20-m grassed track, keeping in time with a series of audio signals from a compact disk (Australian Coaching Council, Canberra, ACT). The running speed was progressively increased until the players reached volitional exhaustion. MSFT performance was taken as final distance travelled when the player reached volitional fatigue. The intraclass correlation coefficient (ICC) for test-retest reliability and typical error of measurement (TEM) for the MSFT were 0.93 and 3.5%, respectively. Isoinertial strength testing Muscle strength testing included a standardized warm-up followed by a 3-RM parallel squat, 3-RM bench press and chin-up maximum (chin-up max ). The 3-RM parallel squat and bench press testing procedures included two to three warm-up sets of five to

4 Table 4 Mean training load, monotony and frequency measured during the study period (mean ± SD) Measure Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Taper 6-week training period Training load (AU) 1387 ± ± 159 # 2285 ± 121 # 2403 ± 167 # 2712 ± 219 # 3296 ± 298 # 1420 ± 25 # 2316 ± 86 Monotony 1.35 ± ± 0.10 # 1.85 ± 0.13 # 1.51 ± 0.23 # 2.00 ± 0.16 # 1.84 ± ± 0.01 # 1.57 ± 0.32 Sessions completed # Significantly different to previous measure (p < 0.05); AU = arbitrary unit eight repetitions with light to moderate resistance. A successful parallel squat required the thigh to descend to a parallel position, where the trochanter head of the femur was in the same horizontal plane as the superior border of the patella. A successful bench press required the bar to be slowly lowered to the chest of the subject and returned to full extension of both elbow joints. The subjects were required to keep their hips and feet on the bench and floor, respectively, at all times during each lift attempt. The reliability of parallel squat (ICC: r = 0.96 and TEM% 2.32) and bench press (ICC: r = 0.98 and TEM% 1.5) measures for this group was high. The chin-up max test was completed at least 10 min after the bench press test. During this test, the subjects were instructed to attempt as many full, unassisted, chin-ups as possible until volitional fatigue. Each chin-up was completed on a horizontal bar raised 2.5 m above the floor. A successful chin-up required the subject to start with their chin above the horizontal bar and to lower their body until full extension in both elbows and then lift their body weight until the subjects chin returned to the starting position. If assistance was offered by a spotter during any lifting attempt, then the subject was instructed to stop. Subjects were allowed three chin-up max trials with the highest number of repetitions being recorded. The reliability of the chin-up max test (ICC: r = 0.99 and TEM% 2.6) for this group was high. Speed Running speed was assessed by 10-m and 40-m sprint times using electronic timing gates (Swift, Lismore, Australia) with the photo-electric cells set at approximately chest height. Timing gates were positioned in a straight direction at 10 m and 40 m from a marked starting point. On an audible command, the players sprinted as quickly as possible along the 40-m course. Timing commenced when the photoelectric cells positioned at the start were initiated. Time to cover the 10-m and 40-m distance was measured to the nearest 0.01 s, with the faster of two trials being recorded. The reliability of 10-m (ICC: r = 0.91 and TEM% 2.0) and 40-m (ICC: r = 0.91 and TEM% 1.9) sprint tests was high. 818E, Monark, Stockholm, Sweden) at a cadence of 50 rpm with a load of 0.5 kp. The subject was then seated on the dynamometer in an adjustable chair, and stabilized by straps so that the axis of rotation of the knee joint was aligned with the axis of rotation of the dynamometer shaft. A resistance pad was positioned on the thigh proximal to the knee joint so that the knee extensors and flexors could be isolated. Straps were used to stabilize the upper body, hips and nondominant leg. The cuff of the dynamometers lever arm was attached proximal to the medial malleoli. All positions were recorded and standardized to assure reliability of testing conditions. Prior to each test set, a series of submaximal trials at each testing velocity were conducted to prepare them for each test. Concentric strength of the knee extensors and flexors was determined during one set of three maximal concentric contractions of the quadriceps and hamstring muscles through a 908 range of motion at 1.05 rad s 1 and 5.25 rad s 1. The highest gravity-corrected torque produced (Nm) during each set was taken as the maximal isokinetic strength for that velocity. Total work (J) completed for each set at both lifting velocities was also calculated during each testing session. Vertical jump Vertical jump (VJ) height was assessed using a Vertec jumping device consisting of a series of moveable marker vanes spaced at 1-cm intervals (Sports Imports, Columbus, OH, USA). Each subject stood side-on to the Vertec with their heels placed on the ground. Prior to each test jump, the subjects were asked to reach upward as high as possible fully elevating the shoulder to displace the zero reference vane. The take-off was from two feet with no preliminary steps or shuffling. An arm swing and counter movement was used with the subject jumping as high as possible to displace the vane. The height of the jump (cm) was calculated as the difference between the highest vane reached and the zero reference vanes. Each subject performed three trials, with the best of these trials being recorded. The reliability of VJ measures for this test was high (ICC: r = 0.97 and TEM% 2.1). 119 Isokinetic strength Isokinetic strength of the knee extensors and knee flexors (dominant leg) was measured using an isokinetic dynamometer (Biodex 3.0, Biodex Corporation, Shirley, NY, USA), which recorded instantaneous muscular torques at preset constant angular velocities of 1.05 rad s 1 and 5.25 rad s 1. Prior to beginning the isokinetic strength assessment, subjects completed a standardized 5-min warm-up of cycling on a cycle ergometer (Monark Biochemistry Testosterone, cortisol, adrenocorticotrophic hormone (ACTH), creatine kinase (CK), erythrocytes, hemoglobin, hematocrit, plasma glutamine and glutamate measures were taken prior to, and following the 6-week overload period and also following the 7- day taper. All hematological measures were taken in a fasted state between 5:30 and 7:30 a.m. in the mornings of testing to avoid circadian variations.

5 Table 5 Training time (min) for the field and resistance training during the study period (mean ± SD) Training Mode Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Taper 6-week training period Field training (min) 239 ± ± 6 # 326 ± 7 # 339 ± ± ± 16 # 185 ± 3 # 332 ± 78 Resistance training (min) 104 ± ± 24 # 205 ± ± ± ± ± 8 # 197 ± 63 Combined training (min) 343 ± ± 23 # 531 ± 12 # 560 ± 27 # 612 ± 18 # 732 ± 38 # 332 ± 9 # 531 ± 134 # Significantly different to previous measure (p < 0.05) 120 Blood samples were taken by a trained phlebotomist in a quiet laboratory room maintained at constant temperature ( C). All subjects were asked to refrain from drinking coffee, tea, chocolate or cola drinks that morning or the previous evening, as well as avoiding alcohol during the previous 24-h period. All blood samples were taken with the subject in a resting, seated position, following 20 min of seated rest. Three 10-mL samples (1 lithium heparin tubes [10 ml]; 1 pre-chilled ethylenediaminetera-acteic acid (EDTA) [10 ml]; 1 serum separator tube (SST) tube [10 ml]) of blood were collected from the antecubital vein on each occasion, using a winged cannula attached to a vacutainer (Becton Dickinson, Rutherford, NJ, USA) bleeding system. All samples were then stored within an ice-bath immediately following collection. The lithium heparin tubes were centrifuged for 5 min at 4000 g. The samples were then transported in a refrigerated transport pack for immediate analysis. Once the samples arrived at the diagnostic laboratory (approximately 10 min), they were prepared for analysis. Plasma total testosterone was determined via a solid-phase 125 I radioimmunoassay using a gamma radiation counter (LKB Wallac, St Albans, UK). Plasma cortisol was determined via immunoassay, through a fluorescence polarization immunoassay (FPIA) using a TDx/TDxFLx analyser (Axysm, Abbott, Irving, TX, USA). Hematocrit, hemoglobin and erythrocyte number were determined with a Coulter MaxM A/L Flow Cytometer (Coulter Electronics Limited, Luton, UK). Plasma glutamine and glutamate were also determined enzymatically using the method of Lund [21]. All blood analyses, except for ACTH, were conducted at Dr. T. B. Lynch Research and Diagnostic Laboratories, Rockhampton, Australia. All diagnostic laboratories used in this study held current quality assurance certification (ISO 9001). Statistical analyses The means and standard deviations (SD) were calculated for each dependent variable. The data were analyzed using an analysis of variance (ANOVA) for repeated measures to determine if there were differences between each testing occasion. When a significant F-value was achieved, Scheffé post hoc test procedures were used to locate the difference between the means. The minimum clinically important difference (MCID), or smallest worthwhile change perceived to be practically significant for the average athlete, was calculated for most performance variables. MCID was determined to be greater than the typical error of measurement in the performance tests [16]. The MCID for MSFT, vertical jump, 3-RM bench press, 3-RM squat, chin-up max, 10-m sprint and 40- m sprint were 1.4 ml kg 1 min 1, 1.3 cm, 1.7 kg, 3.3 kg, 0.4 reps, 0.04 s and 0.10 s, respectively. Pearson correlation coefficients were calculated to determine relationships between selected variables. The SPSS statistical software package, version 11.5 (SPSS Inc., Chicago, IL, USA), was used for statistical calculations. The level of significance was set at p Results Physical training In the present study, all subjects completed 6 weeks of progressive overload training (Table 4). Training duration was progressively increased for each week followed by a significant reduction in training load during the 7-day taper (p < 0.001) (Table 5). The training time during the taper period was 55% less than the previous training week. The training intensity was significantly lower in the taper than the final week of the overload period (RPE: 4.6 ± 0.2 vs. 3.8 ± 0.1; p < 0.01). The time spent during both field and resistance training during the week prior to the taper and during the 7-day taper can be seen in Table 5. During the 6- week overload period, significantly more time (90%, p < 0.001) was spent in field training compared to resistance training. Physiology and performance Table 6 shows the physiological variables that changed significantly during the 6-week overload training period. There were significant main effects observed in MSFT performance over time (p < 0.01) during the 6-week training period and five-day taper. A significant correlation was observed between the change in MSFT performance and the change in training load (r = 0.84; p < 0.001). Peak torque developed by both the knee extensors and flexors and the total amount of work completed at a movement velocity of 1.05 rad s 1 was significantly decreased following the overload period (p < 0.05) and significantly increased following the taper (p < 0.05). MCID (reductions) were observed for MSFT, VJ, 3-RM bench press, 3-RM squat and chin-up max performance following the overload training period. In contrast, MCID (increases) were observed in MSFT, VJ, 10-m sprint, isoinertial 3- RM bench press, isoinertial 3-RM squat and chin-up max performance following the taper period. The only MCID for improvements in performance from before training to following taper was in chin-up max. Biochemistry Table 7 shows hormonal changes during the 6-week overload training period. The testosterone to cortisol (T/C) ratio was significantly decreased with overload training (p < 0.05). No significant changes were observed in plasma cortisol measures. Addi-

6 Table 6 Performance and physiological variables during 6 weeks of overload training and 7-day taper (mean ± SD) Table 7 Hormonal variables of OR rugby league players during 6 weeks of overload training and 7-day taper (mean ± SD) Measure Pretraining Post-training Taper Body mass (kg) 86.1 ± ± ± 9.6 MSFT (m) 2291 ± ± 199* M 2437 ± 67 #M Vertical jump (cm) 61.7 ± ± 9.6 M 62.4 ± 9.9 M Running speed 10 m (s) 1.89 ± ± ± 0.10 M 40 m (s) 5.42 ± ± ± 0.19 Isoinertial strength 3-RM squat (kg) ± ± 18.2 M ± 24.8 M 3-RM bench press (kg) tionally, there were no significant changes in any hormonal values during the taper (p > 0.05). Table 8 shows the changes in the hematological variables during the course of the training and taper periods. CK activity significantly increased during the 6-week training period. No significant changes were observed over time in erythrocyte number, hematocrit or hemoglobin. Significant changes in CK activity (p < 0.01) were measured during the taper. There were no significant changes in plasma glutamine concentration over the 6-week overload training period. However, plasma glutamate was significantly elevated at the end of the training period (p < 0.05). Accordingly, the glutamine to glutamate ratio (Gln/Glu) was also significantly lower at the end of the training period (p < 0.05) (Table 8). During the taper, plasma glutamate (p < 0.05) and Gln/Glu (p < 0.05) were significantly decreased. Discussion ± ± 17.9 M 115 ± 17.3 M Chin-up max (reps) 15.6 ± ± 2.1 M 16.0 ± 1.7 M Isokinetic strength and power 1.05 rad s 1 Peak quadriceps torque (Nm) ± ± 19.5* ± 38.2 # Peak hamstrings torque (Nm) ± ± 20.4* ± 16.2 # Set work (J) 967 ± ± 116* 1074 ± 152 # * 5.25 rad s 1 Peak quadriceps torque (Nm) ± ± ± 28.7 Peak hamstrings torque (Nm) 96.5 ± ± ± 22.3* Set work (J) 603 ± ± ± 103* # Significantly different to previous measure (p < 0.05); * significantly different to pretraining (p < 0.05); M minimally clinically important difference compared to previous measure The purpose of this research was to examine the influence of OR on muscle strength, power and endurance characteristics in rugby league players. The present findings show that with deliberate Measure In this study, 7 semi-professional rugby league players were deliberately overreached by increasing resistance training, endurance and rugby league specific skill training workloads over a 6- week period. Training load was progressively increased during the 6-week overload period by increasing training frequency and duration, which lead to a reduction in MSFT performance. The 12.3% reduction in MSFT performance during the overload period is well above the typical error of measurement for this test (3.5%) showing that there was both a practically [16] and statistically significant reduction in maximal aerobic running performance. Previous research has shown V O 2max to decrease following increased training loads in endurance-trained athletes [9, 20,33], but not in team sport players [4, 35]. The decreased MSFT performance following the 6-week overload training in the present study may be due to a number of physiological and biochemical factors such as reduced muscle glycogen levels, increased muscle damage, or simply due to acute fatigue diminishing maximal effort. The significant reduction in the T/C ratio and elevated CK activity following the 6-week overload training peri- Pretraining Posttraining Taper Testosterone (ng dl 1 ) 573 ± ± ± 111 Cortisol (μg dl 1 ) 21.2 ± ± ± 4.0 T/C ratio 31.4 ± ± 5.4* 23.9 ± 3.1* Values are means ± SD; T/C = testosterone to cortisol ratio; * significantly different to pretraining (p < 0.05) Table 8 Mean (± SD) hematological measures during a 6-week overload training and 7-day taper period Measure Creatine kinase (U L 1 ) Erythrocytes ( 10 6 mm 3 ) Pretraining Posttraining Taper 414 ± ± 1003* 498 ± 402* 5.07 ± ± ± 0.10 Hemoglobin (g dl 1 ) ± ± ± 6.0 Hematocrit (%) 46.1 ± ± ± 2.2 Glutamine (μmol L 1 ) ± ± ± Glutamate (μmol L 1 ) ± ± 0.029* ± Gln/Glu ratio 4.70 ± ± 0.81* 4.41 ± 0.50 * Significantly different to pretraining (p < 0.05) OR, semi-professional rugby league players have a decreased capacity to produce force at slower movement velocities. Additionally, the present results also demonstrate that inappropriate high-intensity training for rugby league may also cause a temporary reduction in MSFT and thus aerobic endurance performance. 121

7 122 od suggests that the players were in a catabolic state with elevated levels of muscle damage when the MSFT performance was reduced. Although there were not significant correlations between the changes in physiological measures and performance, it is likely that these factors did contribute to the reduction in aerobic performance. There were no statistically significant changes in VJ or isoinertial strength tests in the present study. Nonetheless, MCID changes were identified for these test measures. For example, the reduction in VJ, isoinertial 3-RM bench press, isoinertial 3-RM squat and chin-up max tests during the overload training period were - 3.7%, 5.0%, 5.3% and 13.8%, respectively. Since the reduction in each test score was greater than the respective typical error of measurement, it is suggested that the changes in each of these tests are of practical importance. Significant reductions in peak torque developed by the knee flexors at 1.05 rad s 1 were observed following the overload training period. In contrast to our initial hypothesis, we found that knee flexor and extensor strength measured at slower speeds (1.05 rad s 1 ) was significantly reduced during OR. However, there was a nonsignificant increase in isokinetic knee extensor and flexor strength at faster movement velocities (5.25 rad s 1 ). The results suggest that the training undertaken during the 6- week overload period in this study, which consisted of a 68% greater time spent in field training than resistance training, had a greater negative influence on the type I motor units than the type II motor units. This phenomenon was also previously observed in 11 elite college level starting soccer players whose peak isokinetic knee extensor strength was reduced at 1.05 rad s 1, but not 5.25 rad s 1 during an 11-week soccer season [18]. These previous investigators suggested that the majority of training for soccer players mainly involved type I motor units and, therefore, they were the most effected by the insufficient recovery period. Furthermore, other studies have suggested that the type I myosin heavy chains (MHC) are more affected by run training than resistance training [12]. Accordingly, the greater volume of lower intensity on legs exercise (e.g., running and skill training; see Table 5) in this study may explain why the isokinetic strength at the lower speeds were more affected than the higher speeds during the overload training period. A reduction in the T/C ratio is generally considered as an indicator of the bodies anabolic-catabolic balance and has previously been considered a useful tool for diagnosing OR/OT. It is possible that the change in T/C ratio was due to inadequate recovery between exercise sessions at the end of the overload period, which also reduced the rate of muscle protein and glycogen resynthesis, increased muscle damage and increased inflammation, which ultimately lead to reduced ability to generate force. The reduced ability to generate muscular force may also be related to muscular performance measures such as speed, VJ and isoinertial strength. It is also likely that short-term peripheral fatigue may partially explain the diminished muscular strength, power and endurance performance following the overload training period. A recent review clearly demonstrated that muscle damage can result in immediate and prolonged reduction in muscle force generating capacity in both isotonic and isokinetic tests [2]. The measures of muscle damage in the present study, CK activity and plasma glutamate, were both significantly elevated at the end of the overload period, which coincided with significant changes in isokinetic force at slow velocity and practical reductions in isoinertial strength measures. These results are in agreement with many previous studies showing that overreached athletes usually suffer considerable levels of muscle trauma [7,19, 31]. Recent investigators have suggested that elevated plasma glutamate levels can be used to identify impaired recovery from highintensity training or an inadequate recovery period [30]. The present results are in agreement with previous studies that have shown increased plasma glutamate and reduced exercise performance following intensified training periods [11, 30]. Glutamate along with glutamine has a role in acid-base balance and de novo synthesis of nucleotides, and is also an important regulator of protein synthesis and degradation [29]. Due to these properties, it is most likely that glutamate plays an important role in the repair/regenerative responses to daily muscle loading. Accordingly, we hypothesize that the decreased muscle glutamate observed in the present study may also be associated with reduced strength performance following the overload training period. Further research needs to be completed to determine the role that glutamate plays in these processes. In the present study, hormone and other blood measures were assessed in order to elucidate the mechanisms underlying the changes in muscular strength and power with fatigue and recovery. The hormone results show a nonsignificant tendency for a reduction in testosterone concentration and an increase in cortisol concentration following the overload training period (Table 7). There was also a significant reduction in the T/C ratio following the overload period. These results agree with other similar research that show that monitoring T/C ratio measures maybe useful for monitoring adaptation and recovery to training and match play stress in team sport athletes [3]. A limitation in the practical application of the results of this study to field is that venipuncture is required which can be intimidating for some players. To overcome this limitation, coaches and scientists may like to consider measuring T/C ratio using noninvasive salivary samples [3]. Recent studies have also shown the Gln/Glu ratio to decrease following intensified training with levels lower than 3.58 suggested, indicating a state of OR [11,30]. In agreement with these previous studies, the significant change in the Gln/Glu ratio observed in the current study appeared to be due to increased plasma glutamate levels rather than a reduction in glutamine concentration alone. Furthermore, we also measured a rebound effect following the taper where plasma glutamate decreased and glutamine levels increased so that the Gln/Glu ratio returned to levels previously suggested to represent that athletes were tolerating training [30]. The failure of the Gln/Glu ratio to return to pretraining levels, in the present study, may suggest a longer taper period may have been warranted. This is supported by recent research that has suggested that tapers up to 28 days can show improvements adaptations in physiology and performance [23, 24].

8 This study, to our knowledge, is the first to report on endurance, strength, power and biochemical changes during a preseason taper in team sport athletes. Most performance tests tended to improve following the seven-day taper, suggesting some adaptation had taken place. Following the taper, only isokinetic measures of set work at 1.05 and 5.25 rad s 1 and peak hamstring torque at 5.25 rad s 1 were significantly improved from baseline measures following the 7-day taper. Notably, however, most other performance variables (MSFT, VJ, 3-RM squat, 3-RM bench press, chin-up max and 10-m sprint) demonstrated MCID changes with tapering. Combined, these results show that a short, stepwise taper can concurrently improve endurance, strength and power measures in team sport athletes. The MCID increases in MSFT, VJ and 10-m sprint performance, combined with the significant increases in isokinetic strength, show that muscular strength, power and endurance were improved with the short taper. It is most likely that the improvements in performance are related to changes in muscle fiber properties. Previous studies have shown activity specific changes in myocellular size, power and contractility are dependent upon the type of training completed during the taper [12,26, 32]. Despite all biochemical variables reported in this study tending to return to baseline values, only CK activity was significantly changed during the taper, suggesting that training intensity was reduced or an increased tolerance to training loads occurred. These findings agree with the majority, but not all previous research employed tapers of between 6 28 days in duration with endurance athletes [24]. To our knowledge, no studies have examined CK activity in response to tapering in team sport athletes. However, previous investigators suggested that CK activity has extremely high variability amongst individual athletes and that significant reductions in CK activity are observable during a reduction in training loads following days of intensive, prolonged exercise [13]. The most likely cause for the reduction in CK activity during the taper in the present study is a reduction in the damage to tissue cell membrane from both the repeated strenuous exercise and direct muscle trauma. On this basis, we suggest that CK can be used to monitor for acute recovery from heavy training loads in team sport athletes. In conclusion, this study showed that when relatively large loads of aerobic endurance, resistance, speed and skill training with inadequate periods for recovery are completed, reductions in physical performance could occur. 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