Concurrent Strength and Endurance Training Effects on Running Economy in Master Endurance Runners

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1 See discussions, stats, and author profiles for this publication at: Concurrent Strength and Endurance Training Effects on Running Economy in Master Endurance Runners ARTICLE in THE JOURNAL OF STRENGTH AND CONDITIONING RESEARCH NOVEMBER 2012 Impact Factor: 2.08 DOI: /JSC.0b013e Source: PubMed CITATIONS 8 READS AUTHORS, INCLUDING: Maria Francesca Piacentini Italian University of Sport and Movement "Fo 85 PUBLICATIONS 1,484 CITATIONS Gianluca Vernillo University of Milan 25 PUBLICATIONS 116 CITATIONS SEE PROFILE SEE PROFILE Antonio La Torre University of Milan 68 PUBLICATIONS 305 CITATIONS SEE PROFILE Available from: Antonio La Torre Retrieved on: 17 March 2016

2 CONCURRENT STRENGTH AND ENDURANCE TRAINING EFFECTS ON RUNNING ECONOMY IN MASTER ENDURANCE RUNNERS MARIA FRANCESCA PIACENTINI, 1 GIULIA DE IOANNON, 1 STEFANIA COMOTTO, 1 ALESSANDRO SPEDICATO, 1 GIANLUCA VERNILLO, 2 AND ANTONIO LA TORRE 2 1 Department of Human Movement and Sport Sciences, University of Rome Foro Italico, Rome, Italy; and 2 Department of Sport, Nutrition, and Health Sciences, Universita` degli Studi di Milano, Milan, Italy ABSTRACT Piacentini, MF, De Ioannon, G, Comotto, S, Spedicato, A, Vernillo, G, and La Torre, A. Concurrent strength and endurance training effects on running economy in master endurance runners. J Strength Cond Res 27(8): , 2013 Running economy (RE) has been seen to improve with concurrent strength and endurance training in young and elite endurance athletes. The purpose of this study was to evaluate effects of 2 different strength training protocols on RE and strength parameters in a group of regularly training master marathon runners. Sixteen participants were randomly assigned to a maximal strength training program (MST; n = 6; years), a resistance training (n = 5; years), and a control group (n =5; years). Before and after experimental period, resting metabolic rate, body composition, 1 repetition maximum (1RM), squat jump, countermovement jump, and RE were evaluated. The MST group showed significant increases (p, 0.05) in 1RM (+16.34%) and RE (+6.17 %) at marathon pace. No differences emerged for or groups (p. 0.05). Anthropometric data were unchanged after training intervention (p. 0.05). Taken toger, results of this preliminary study indicate that master endurance athletes seem to benefit from concurrent strength and endurance training because rate of force development may be crucial for RE improvement, one of major determinants of endurance performance. KEY WORDS maximal strength training, 1RM, marathon runners Address correspondence to Dr. Maria Francesca Piacentini, mariafrancesca. piacentini@uniroma4.it. 27(8)/ Journal of Strength and Conditioning Research Ó 2013 National Strength and Conditioning Association INTRODUCTION Over years, number of healthy older individuals practicing sport activities has markedly increased. This growth leads to a considerable increment of master athletes who perform at a high level for ir age category (10). In particular, master endurance athletes (i.e.,.35 years of age) represent largest proportion of participants in marathon competitions, and ir participation in se events has dramatically increased over past decades (22). In fact, se athletes train and compete regularly, following detailed and structured training schedules even though y do not have same technical support in terms of training and recovery. This is because, compared with younger athletes, y have to train between very busy schedules because of work or family duties. Neverless, se athletes are capable of (a) remarkable athletic and physiological functional performances (43), (b) training and competing regularly in long distance events and, in some cases, (c) improving performance achieved at a younger age. This is because peak exercise performance for age category seems to increase continuously each year (43) despite well-documented decrease in endurance performance that occurs with age. In fact, loss in performance ability shows a slow but progressive decline from ages of 30 to about 60 years (10). After that, a progressively steeper decrease is seen (43) even in athletes who are able to maintain sufficient training volume and intensity. Several studies have reported that regular endurance training throughout lifespan brings to half decline in maximal aerobic capacity as seen in sedentary individuals (35). Endurance-running events are strongly related to physiological determinants such as maximal aerobic capacity (V_ O2 max), running economy (RE), and exercise intensity at which a high fraction of V_ O2 max can be sustained (15). Particularly, decrease in V_ O2 max and reduction in lactate threshold appear to contribute to decline in endurance exercise performance from young adulthood to early middle age (43). Furr, RE is defined as V_ O2 required at a given absolute exercise intensity. Therefore, runners with a better RE use less O 2 than runners with a poor RE do at same running speed VOLUME 27 NUMBER 8 AUGUST Copyright National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

3 Maximal Strength Training in Master Athletes (6). Accordingly, RE seems to be a better predictor of endurance performance than maximal oxygen uptake (37) and does not seem to change with advancing age (8). Moreover, it has been suggested that re is a relationship between neuromuscular characteristics and RE (i.e., more economical an individual, higher level of contractile strength and muscular stiffness he or she presents) (2). Therefore, strength training programs have received more attention as powerful stimuli to improve mechanical efficiency, muscle coordination, motor unit recruitment patterns (36), and lower limb stiffness regulation with an overall enhancement in RE. In fact, it has been suggested that an overall increase in strength parameters can facilitate changes and corrections in technical model because of an enhancement in motor unit recruitment (21), especially for individuals who started training at a more advanced age such as Master athletes. Although a combination of strength and endurance training have been advocated for optimal physical function and health in elderly, most of se studies have been performed on an untrained population (19). Moreover, a number of studies involving young adults have reported impairment in strength development when endurance training is added to a strength training program (19). This potential conflict has been referred to as an interference phenomenon because endurance training seems to compromise optimal strength development (17). Neverless, studies performed on young trained or even elite athletes do support contention that concurrent training does not alter ability to positively adapt to endurance training (11). In fact, strength training for endurance athletes is finalized to optimize ir endurance performance. As a consequence, use of concurrent strength and endurance training in endurance training periodization has been shown to improve performance in different endurance sports such as crosscountry skiers (18), cyclists (41), and triathletes (33). Concurrent strength and endurance training has also been shown to increase RE in distance runners (14,21,38,40,46). Despite fact that master marathon runners represent largest proportion of participants in marathon events, studies have been mainly conducted on young or elite athletes, and it is not known if this older athletic population will respond in a similar manner as elite or younger athletes or if including extra training days will induce m to nonfunctional overreaching. Recent evidence (24) suggests that aging affects stress-response signaling. The study demonstrates that after same resistance training (RT) program, older individuals show no significant increase in myofiber hypertrophy adaptation, whereas younger individuals experience 2 times growth in type 2 myofibers compared with ir older counterparts. Only younger population was capable of type 1 myofiber growth. Moreover, older individuals have a higher percentage of type 1 muscle fibers and refore are able to generate less force (23). However, a cross-sectional study on master endurance athletes aged years demonstrated that a significant age-associated decline in leg strength and muscle fiber area and type distribution does not appear until after age of 70 (44). Therefore, purpose of this study was to answer question if incorporating regular strength training on top of normal running program of Master endurance athletes would be beneficial to RE, as already seen for younger or elite athletes. Our hyposis is that maximal strength training (MST) or RT added to regular endurance training would lead to different neuromuscular adaptations and consequently different effects on RE in master endurance runners. METHODS Experimental Approach to Problem The hyposis that MST or RT added to regular endurancerunning training would lead to different neuromuscular adaptations, and consequently, different effects on RE in master runners was tested. To answer this question, a 6-week training period was chosen because 4- to 8-week cycles of strength training are commonly used in literature (46), and it was hyposized that most of adaptations in RE may occur after 4 6 weeks of strength training (as presented in this study) and that longer protocols may not add furr improvements in RE. Thus, a parallel, 3-group, randomized, longitudinal (pretestposttest), experimental design was used. To investigate possible effects of 2 different strength training programs on RE during preparation of a marathon in Master endurance athletes, anthropometric data, resting metabolic rate (RMR), RE, rating of perceived exertion (RPE), maximal strength (1 repetition maximum [1RM]), squat jump (SJ), countermovement jump (CMJ), and stiffness (STIF) were measured before (at week 0) and after a 6-week strength training program (at week 7). All subjects performed familiarization trials before testing days. Sixteen marathon runners engaged in same endurance training program were randomly assigned to 1 of following groups: MST, RT, and a control group (CG). The MST and RT groups performed RT on top of ir normal running program, whereas CG only performed normal endurance training regimen. We used as independent variable, group, whereas dependent variables were body fat, body mass, 1RM, RMR, CMJ, SJ, and V_ O2.The 1RM on leg press has been shown to have high intraclass correlation coefficients (ICCs [0.99]) (28), whereas CMJ and SJ performances show high ICCs (range: ) for adult male individuals (13). Controlled reliability on RE has been seen indicating that results are relatively stable (37). Subjects Twenty-one master endurance runners from same running team (5 women and 16 men) were originally recruited to take part in study and were randomly divided into 1 of 3 experimental groups (n = 7 per group). The protocol was approved by University Ethical Committee and participants gave ir written 2296 Journal of Strength and Conditioning Research

4 Journal of Strength and Conditioning Research consent before participation. The participants had a history of consistently participating in road races (from 10 km to marathon distance). Five voluntarily discontinued participation and only 16 (12 men and 4 women) completed 6-week training period. Therefore, groups were formed as follows (mean 6 SD): MST (n = 6; 4 male and 2 female: years, height cm, body mass kg); RT (n =5;3male and 2 female: years, height cm, body mass kg) and a CG (n =5;5male: years, height cm, body mass kg). To prevent potential contaminating effects of athlete s ability level and different training schedules, participants included in this study had to fulfill following inclusion criteria: (a) be Master athletes (.35 years of age); (b) have at least 5 years of previous endurance training; (c) to be part of same track andfieldteamfollowedbysametrainer. Procedures All tests were performed before and after a 6-week intervention program during first 6 weeks of ir specific 12-week marathon-training program, and measurements were taken before (week 0) and after strength training interventions (week 7). The tests were separated by a 24-hour resting period. All tests were performed at same time of day 62 hours in a climate-controlled laboratory (;21 to 228 C, 53% relative humidity) except for RMR that was performed early in morning. The participants did not perform any physical activity in 24 hours resting period and were requested to refrain from using caffeine-containing food or beverages, alcohol, cigarette smoking, or any form of nicotine intake during this period. The subjects were requested to replicate same food intake before each test. All subjects performed familiarization trials. The participants were provided with written and oral instructions before all testing procedures. The MST and RT program was performed in addition to ir regular endurance training, twice a week and before and after experimental period, RMR, body composition, 1RM, SJ, CMJ, STIF, and an RE test at 3 running speeds were measured (Figure1).Alltestswererandomized; however, same order was respected in pretest and posttest for each individual. between 7:00 and 8:30 AM. Pretraining and posttraining measurements were performed at same time. After 5 minutes of sitting rest, subjects were fitted with a mask (Fitmate, Cosmed, Rome, Italy) to measure V_ O2. Thereafter, y were asked to lie down in a quiet room in a supine position, and a 30-minute habituation period was allowed (34) in a rmoneutral environment ( C). The subjects were given 15 minutes to rest, breathing through a mask, during which RMR was measured. After RMR measurements, body composition was assessed before and after training period using Jackson and Pollock (20) 7-site skinfold equation. Skinfold measurements were taken by same experienced operator on right side and recorded to nearest 0.1 mm using a Lange skinfold caliper (Cambridge Scientific Instrument, Cambridge, MD, USA). Measurements were taken 3 times per site, and mean value was recorded. Body density was calculated, whereas percent body fat was estimated with Siri equation (39). Body mass and body height were measured after RMR test at same time of day and under comparable nutritional and training conditions. Body weight and height were measured with a calibrated clinical balance to nearest gram. One-Repetition Maximum Maximal strength was estimated through 6RM test on leg press. All subjects were positioned on a horizontal leg press (Technogym, Gambettola, Italy) and knee angle (908) was fixed to maintain same position in all test occasions. The athletes were required to perform a 5-minute warm-up period at 40 60% of ir maximal predicted 1RM. After a brief recovery period, athletes were requested to perform first session with a preliminary load of 15 repetitions. Thereafter, load was increased every step by 30% until athlete could not successively complete a 6RM repetition (1). The 1RM was estimated through a conversion table (3). The 1RM was measured at week 0 and after training at week 7. All tests were performed for each individual at same time of day. Resting Metabolic Rate Measurements Individuals were asked to refrain from vigorous activity at least 24 hours before resting metabolic measurements, to eat same dinner day before RMR measurements, and to be 12 hours fasted. They were asked to plan ir arrival in laboratory Figure 1. Experimental timeline: testing periods in weeks 0 and weeks 7, training from weeks 1 to week 6. MST = maximal strength training group (performing MST + endurance training); RT = resistance training group (performing RT + endurance training). VOLUME 27 NUMBER 8 AUGUST

5 2298 Journal of Strength and Conditioning Research TABLE 1. Description of imposed strength training for MST, RT, and CG.* Week Strength training protocol Days per week Lower body exercise Upper body exercise Sets/reps MST 6 2 1/2 Squat with arm weights, calf exercise (leg press), lunges with arm weights, eccentric quadriceps contractions, leg press RT 6 2 1/2 Squat with arm weights, calf exercise (leg press), lunges with arm weights, leg press, eccentric quadriceps contractions, seated calf raise CG Bench press, lat machine, pulldown machine, cable machine (pushdown), triceps extension, dumbbell biceps curl Bench press, lat machine, push up, pulldown machine, core strength, cable machine, triceps extension, dumbbell biceps curl Regular endurance training protocol *MST = maximal strength training; RT = resistance training; CG = control group. Resistance was increased in each group every week to maintain correct number of repetitions per set. Recovery between sets (min) % 1RM % % Maximal Strength Training in Master Athletes TABLE 2. Body mass, FFM, FM, percent body fat, and RMR for all groups before and after 6-week intervention period.* MST RT CG Pre Post Change % Pre Post Change % Pre Post Change % Body mass (kg) % Body fat FM (kg) FFM (kg) RMR (kcal) 1, , , , , , *MST = maximal strength training; RT = resistance training; CG = control group; FFM = fat-free mass; FM = fat mass; RMR = resting metabolic rate. Data are presented as mean 6 SD and % change from prevalues.

6 Journal of Strength and Conditioning Research Jumping Performance All subjects performed an SJ, CMJ, and an STIF test during same test day. Each test was separated by a 5-minute rest period. Vertical jump performance was assessed using SJ and CMJ tests according to procedures suggested by Bosco et al. (5). Jumping height was calculated from flight time using kinematic equations (27). Flight time was recorded using an infrared photocell connected to a digital computer (Optojump System, Microgate SARL, Bolzano, Italy). All tests were performed in a randomized order. For SJ, participants were instructed to squat down and hold a knee position (;908 knee angle) for a few seconds with arms blocked. When cued, participant was instructed to jump as high as possible. A trial was considered successful when re was no furr squatting or countermovement before execution of jump. Three trials separated by 1 minute of passive recovery were performed. The best one was recorded for furr analysis. To perform CMJ, subjects were instructed to start in a standing position with ir arms blocked, perform a 2-legged CMJ consisting of a fast downward movement to a freely chosen angle, immediately followed by a fast maximal vertical thrust. Any jump that was perceived to deviate from required instructions was repeated. Three trials separated by 1 minute of passive recovery were performed. The best one was recorded for furr analysis. A multirebound test (7 consecutive jumps) was performed to measure STIF. The participants had 2 trials separated by a 5-minute passive recovery period. The participants were asked to keep ir knees as stiff as possible during test, to jump as high as possible, and to have shortest contact time. The results from best trial were used for furr analysis. Jumping performance was measured at week 0 and after training at week 7. All tests were performed for each individual at same time of day. Running Economy The RE was determined by measuring submaximal V_ O2 during 3 different running speeds on a treadmill: 5 minutes at 1 km$h 21 slower than marathon pace ( km$h 21 ), 5 minutes at marathon pace ( km$h 21 ), and 5 minutes at 1 km$h 21 faster than marathon pace ( km$h 21 ) after a standardized warm-up. Before each test, Cosmed flow meter (Quark b 2, Cosmed) was calibrated with a 3-L syringe, and oxygen analyzer was calibrated with known gas mixtures (16% O 2 and 5% CO 2 )and environmental air (20.9% O 2 and 0.03% CO 2 ). During each step, heart rate was continuously monitored using a heart rate monitor with an internal memory (Polar Team System, Polar, Kempele, Finland), and subjects were asked to rate ir perceived effort according to rating perceived exertion scale (CR-10 scale) (4) before, at end of each step, and after exercise. Throughout tests, respiratory and pulmonary gas-exchange variables were measured using a breath-by-breath gas analyzer (Quark b 2, Cosmed). The TABLE 3. The 1RM test, CMJ, SJ, and STIFF tests for all groups before and after 6 weeks of training.* MST RT CG Pre Post Change % Pre Post Change % Pre Post Change % 1RM (kg) z CMJ (cm) z 7 SJ (cm) z 13 STIFF (cm) z *MST = maximal strength training; RT = resistance training; CG = control group. Data are presented as mean 6 SD and % change from prevalues. zsignificant differences from PRE tests (p, 0.05). VOLUME 27 NUMBER 8 AUGUST

7 Maximal Strength Training in Master Athletes Figure 2. The V_ O2 measured pretraining and posttraining at 3 different running speeds on a treadmill: 5 minutes at 1 km$h 21 slower than marathon pace (step 1: km$h 21 ), 5 minutes at marathon pace (step 2: km$h 21 ), and 5 minutes at 1 km$h 21 faster than marathon pace (step 3: km$h 21 ); * = significant differences from PRE tests (p, 0.05); MSE = maximal strength training (black bars); RT = resistance training (gray bars); CG = control group (white bars). RE was defined as V_ O2 determined by averaging last 2 minutes of each running speed. The RE was measured at week 0 and after training at week 7. All tests were performed for each individual at same time of day. Training Protocol The subjects were well-trained master runners, who started season in September 2009 and already participated to different races (10 21 km) in months before study (from September to January 2010). The training interventions took place from beginning of January to Mid- February, and marathon was scheduled at end of March. All subjects were engaged in same endurance training program that consisted of 4 5 d$wk 21 for a total of 50 km$wk 21 distributed in slow runs, interval training, and tempo runs emphasizing improvement in V_ O2 max. The subjects were n divided into different strength training protocols while CG continued only with regular running program. Resistance was increased every week to maintain correct number of repetitions per set. The strength training program (Table 1) consisted of 2 training sessions a week and was supervised by a certified fitness instructor. The MST program consisted of 4 sets of 3 4 repetitions of exercises for lower and upper body at 85 90% of estimated 1RM. Rest intervals between sets were 3 minutes. The RT included a general conditioning of main muscle groups of body and consisted of 3 sets of 10 repetitions at 70% 1RM. Statistical Analyses SPSS statistical software (v10.1 for Windows) was used for all statistical analyses. The Kolmogorov-Smirnov test was applied to verify assumption of normality. One-way analysis of variance (ANOVA) was used to evaluate between-group 2300 Journal of Strength and Conditioning Research differences in dependent variables at pretest. Thereafter, a 1-way ANOVA for repeated measures was used to identify differences between 3 groups of subjects, by examination of group 3 time interaction to evaluate differences resulting from training programs. Post hoc assessment was undertaken by means of a Bonferroni multiple comparison test. Data are presented as mean 6 SD for each group (MST, RT, CG) or percent increase. For all statistical analyses, a p value of 0.05wasacceptedaslevel of statistical significance. RESULTS The data followed a normal distribution. The Kolmogorov-Smirnov test score was Before training period, subjects did not differ in terms of any variable measured (p. 0.05). After 6-week program, re were no significant changes in body mass, fatfree mass (FFM), fat mass, percent body fat, or RMR for all groups (Table 2). The MSTgroup showed a significant 17% increase (p, 0.05) in 1RM after training. In fact, premean and postmean values were and kg, respectively, whereas no significant differences (p. 0.05) were observed in RT group and in CG (Table 3). The MSTgroup showed no significant differences (p. 0.05) in CMJ, SJ, or STIF tests with 6-week training protocol. The RT group showed a significant 13% increase in STIF test (pre: cm vs. post: cm, p, 0.05) and no difference in CMJ or SJ (p. 0.05). The CG showed a significant 7% improvement in CMJ (pre: cm vs. post cm, p, 0.05) and a significant 13% improvement in SJ (pre cm vs. post cm, p, 0.01) with no difference observed for STIF. All data regarding 1RM and jumping ability tests are given in Table 3. The RE improved significantly (p, 0.05) in MST group (6.17%) only at marathon pace (second step, Figure 2). No significant differences were observed in RE for MST groups at or running speeds. The RT and CG did not show significant improvements in RE for any of running speeds (p. 0.05; Figure 2). The RPE showed no difference from pretraining values at all exercise intensities (p. 0.05). DISCUSSION Studies regarding master athletes have been mainly conducted to understand rate of performance decline with aging (10,22,43) more than impact of different training

8 Journal of Strength and Conditioning Research interventions on physiological variables implicated in endurance performance. Therefore, main focus of this study was to investigate impact of a concurrent strength and endurance training on RE in master athletes and understand if results are similar to those found in young or elite subjects. Accordingly, results of this study demonstrated a 6.17% improvement in RE in MST group, a significant 17% increase in 1RM, with no concomitant changes in body mass, FFM, percent body weight, fat mass, and RMR. The 17% increase in 1RM observed in this study is lower than what was found in previous studies that evaluated effects of RT on older adults (19,30). Strength development has been shown to be lower when endurance training is added to a strength training program (19) because physiological stimuli directed to skeletal muscle as a result of strength training and endurance training are divergent in nature (16). In adding endurance training to strength, a limitation in muscle hypertrophy has been suggested as a mechanism for decreasing gains in strength (31) compared with strength training alone, possibly because of a limited increase in type I fiber area (25). To be effective, especially on endurance athletes, program needs to maximize increases in 1RM primarily from coordination and neural adaptations and changes in recruitment patterns, with minimal muscle hypertrophy. Less interference is in fact evident when training simultaneously maximal aerobic power and maximal strength because training stimulus for increasing strength would be mainly directed at neural system, while adaptations for increasing maximal aerobic power will mainly induce peripheral adaptations and interference seems to be less pronounced (7). Moreover, a cross-sectional study on master endurance athletes aged years, demonstrated that a significant age-associated decline in leg strength and muscle fiber area and type distribution does not appear until after age of 70 (44); refore, chronic endurance training can delay age of significant decline in peak torque and changes in muscle morphology of vastus lateralis. This could explain lower increase in 1RM observed in our study compared with completely untrained older individuals performing an RT program. Only 1 study evaluated effects of a strength training program on recreational runners of same age as our runners (9) but with a lower weekly training volume compared with runners of this study. The authors found that inserting 2 times a week an MST program in recreational runners had no effect on body weight or composition and no effect on RE. However, y found an increase in muscular strength that most probably may be advantageous for endurance runner in a long-term perspective. More recently, Louis et al. (29) evaluated effects of concurrent strength and endurance training in master endurance cyclists. Their results indicated age-related differences in cycling efficiency, maximal and endurance torque generating capacities. In master athletes, MST program showed an enhancement in maximal and endurance torque production and a reduced age-related difference in performance. In fact, before strength training, younger individuals showed higher muscular strength and cycling efficiency, whereas after training, age-related differences were reduced, strengning hyposis that adding a 2 times per week MST to an endurance training program may help reduce age-related decrements in performance. Therefore, although older individuals have a larger percentage of type I muscle fibers and are refore able to generate less force (23), y seem to respond positively to RT programs (for a review see [30]) also when concurrent to endurance training. Although strength gains in our study are slightly lower, increase in RE (6% increase found only in MST) is similar to what was observed for younger individuals. In fact, with an increase in strength, a lower percentage of 1RM in lower limb extensors will be taxed in each stride, lowering actual demands of number of motor units recruited (18). Johnston et al. (21) was one of first groups to associate effects of inclusion of a whole-body RT program on RE in female distance runners. The protocol consisted of a 10-week regimen based on 2 3 sets of 6 20 RM (each set performed to momentary concentric failure) that resulted in significant increases in upper and lower body strength with no changes in body composition and a 4% increase in RE. Similarly, Millet et al. (33) found that addition of 14 weeks of heavy weight training to regular endurance program of elite triathletes determined a significant increase in RE with a 25% increase in lower limb force. Moreover, MST group showed a significant increase in velocity associated with V_ O2 max. Storen et al. (40) showed a 33% increase in 1RM and a 5% increase in RE in well-trained runners after an additional 2 times a week MST program for 8 weeks. Guglielmo et al. (14) added a 4-week MST and explosive strength training program in well-trained endurance runners. The authors found a 38% increase in 1RM in MSTand a 51% increase in 1RM in explosive strength training groups, whereas RE improved only in MST group. Similarly to Taipale et al. (42), we found an increase in 1RM only in MSTgroups andnochangeinrtandincg. Because of length of program and because FFM did not change, we can hyposize that strength gains result from a better motor unit recruitment pattern as previously shown (9). The RMR is largely related to amount of FFM, and strength training programs focused on hypertrophy have been successfully used in dieting individuals to preserve both RMR and FFM (12). In this study, no significant changes were observed in RMR and anthropometric parameters, confirming that strength gains observed are related to neural adaptations rar than to hypertrophy (41). It can refore be hyposized that most of adaptations in RE may occur already after 4 6 weeks of strength training (as presented in this study) and that longer protocols may not add furr improvements in RE because y might impair furr strength gains (31) and expose individuals to nonfunctional overreaching. Moreover, RE improvements of VOLUME 27 NUMBER 8 AUGUST

9 Maximal Strength Training in Master Athletes.2.4% can be attributed to training intervention and not to a day-to-day variability (37). Strength training has been reported to improve muscletendon stiffness (26), and this could be an advantage for improving rate of force development (47). Kubo et al. (26) was first group to show effects of strength training on elastic profiles of human tendon structures in vivo without noticing a significant hypertrophy. However, we found no difference in STIF in MST group, whereas CG and RT groups improved significantly. Animal models show that chronic exercise (endurance training) can modify elastic proprieties of tendon (48). This can explain improvements observed in CG and RT groups. Similarly to what we found, Millet et al. (33) observed no difference in hopping stiffness and ground contact time in MST group after 14 weeks of heavy weight training. In accordance with ir conclusions, it can be hyposized that characteristics of strength training performed is not optimal for showing improvements in stiffness with a hopping test. The improvement in CMJ and SJ only in CG denotes that improvements in 1RM are not sufficient to elicit improvements in jump performance (14). Similarly, Guglielmo et al. (14) found that jump performance increased only in explosive strength training group but not in heavy weight training group. Häkkinen et al. (16) showed that individuals who preformed strength training alone showed increases in rapid force production of trained leg extensors and a significant improvement in rapid neural activation, whereas concurrent strength and endurance training groups showed no significant changes. These results suggest that concurrent strength and endurance training lead to interferences in explosive strength development as seen also in our study. The authors hyposize that re may be a reduced improvement in rapid voluntary neural activation (16). Despite evidence of significant effects of MST on RE, endurance athletes and in particular Master athletes eir include very little or no RT in ir regular programs in particular when training volume increases (42). Most individuals still are reluctant and think that adding strength training may impair ir progression in endurance performance. Moreover, one of major concerns in adding strength to endurance training especially in a population that needs to train between already busy schedules is possible decrease in compliance to training and risk of nonfunctional overreaching. However, a shorter program (such as ours) seems to interfere less with decrease in strength gains and avoids risks of nonfunctional overreaching that are mainly caused when volume of training is extremely elevated and monotonous (32). PRACTICAL APPLICATIONS Master athletes are a great example of successful aging. They train regularly and in some cases are able to increase performance achieved at younger ages. Most of se athletes are serious and motivated, despite increasing age, and are willing to perform intensive training sessions for several months to prepare mselves for 1 specific event (45). However, what is till questionable is if y will benefit from same training programs normally reserved for younger or elite athletes. The results of this study indicate that a well-structured MST program for a limited amount of time during conditioning training period in preparation of long endurance events can increase RE, without inducing hypertrophy. What is most interesting is that RE improvements are similar to what was seen for younger individuals. Because this population has to squeeze training into very busy schedules and optimal training in older adults is fundamentally similar to optimal training in youngerathletes,particularattentionneedstobepaidto total volume of training during period of concurrent training to avoid nonfunctional overreaching. We suggest in preparation period for major competitions to add a 6-week MST protocol 2 times$per week concurrently to regular endurance training targeted to increase maximal aerobic power. This could be a beneficial methodology to improve performance in endurance events and a good way to diversify training program of master runners that often focus only on running, risking nonfunctional overreaching. Because of restricted age range of this study, se data cannot be generalized to all age categories that include master athletes. Moreover, a wider sample of athletes is needed to evaluate gender differences in response to an MST protocol. ACKNOWLEDGMENTS The authors would like to thank all participants of Villa Ada Green Runners for extra time y dedicated to this study. No grant support was provided for this study. The results of this study do not constitute endorsement of product by authors or National Strength and Conditioning Association. REFERENCES 1. American College of Sport Medicine. ACSM s Guidelines for Exercise Testing and Prescription (8th ed.). Baltimore, MD: Lippincott Williams & Wilkins, Arampatzis, A, De Monte, G, Karamanidis, K, Morey-Klapsing, G, Stafilidis, S, and Brüggemann, GP. Influence of muscle-tendon unit s mechanical and morphological properties on running economy. J Exp Biol 209: , Baechle, TR and Earle, RW. Essentials of Strength Training and Conditioning (2nd ed.). Champaign, IL: Human Kinetics, pp Borg, G. Perceived Exertion and Pain Scales. Champaign, IL: Human Kinetics, Bosco, C, Luhtanen, P, and Komi, PV. A simple method for measurement of mechanical power in jumping. 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