Physiological and anthropometric characteristics of junior rugby league players over a competitive season

This study investigated the physiological and anthropometric characteristics of junior rugby league players over a competitive season. Forty-five rugby league players were allocated into training (n = 36) and nonexercise control (n = 9) groups. The training group participated in 2 field-training sessions each week with training loads, match loads, and injury rates recorded. Subjects performed measurements of standard anthropometry (height, body mass, and sum of 7 skinfolds), muscular power (vertical jump), speed (10-, 20-, and 40-m sprint), agility ('L run'), and estimated maximal aerobic power (multi-stage fitness test) in December (off-season), March (preseason), May (midseason), and August (end-season). Training loads progressively increased in the general preparatory phase of the season (preseason period), and declined slightly during the competitive phase of the season. Match intensity and match loads decreased throughout the season. Increases in estimated maximal aerobic power and muscular power and reductions in skinfold thickness occurred during the general preparatory phase of the season, and were maintained throughout the competitive phase of the season. These findings suggest that high training loads in the general preparatory phase of the season and low match loads in the competitive phase of the season allow junior rugby league players to maintain a high level of fitness throughout an entire competitive season.     

Correlates of tackling ability in high-performance rugby league players

This study investigated the tackling ability of high-performance rugby league players and determined the relationship between physiological and anthropometric qualities and tackling ability in these athletes. Twenty professional (National Rugby League) and 17 semiprofessional (Queensland Cup) rugby league players underwent a standardized 1-on-1 tackling drill in a 10-m grid. Video footage was taken from the rear, side, and front of the defending player. Tackling proficiency was assessed using standardized technical criteria. In addition, all players underwent measurements of standard anthropometry (height, body mass, and sum of 7 skinfolds), acceleration (10-m sprint), change of direction speed (505 test), and lower body muscular power (vertical jump). Professional players had significantly greater (p ≤ 0.05) tackling proficiency than semiprofessional players (87.5 ± 2.0 vs. 75.0 ± 2.3%). Professional players were significantly (p ≤ 0.05) older, more experienced, leaner, and had greater acceleration than semiprofessional players. The strongest individual correlates of tackling ability were age (r = 0.41, p ≤ 0.05), playing experience (r = 0.70, p ≤ 0.01), skinfold thickness (r = -0.59, p ≤ 0.01), acceleration (r = 0.41, p ≤ 0.05), and lower body muscular power (r = 0.38, p ≤ 0.05). When hierarchical multiple regression analysis was performed to determine which of the variables predicted tackling ability, playing experience and lower body muscular power were the only variables that contributed significantly (r2 = 0.60, p ≤ 0.01) to the predictive model. From a practical perspective, strength and conditioning coaches should emphasize the development of acceleration, lower body muscular power, and lean muscle mass to improve tackling ability in high-performance rugby league players.     

Influence of fatigue on tackling technique in rugby league players

This study investigated the influence of fatigue on tackling technique in rugby league players and determined the relationship between selected physiological capacities and fatigue-induced decrements in tackling technique. Eight rugby league players underwent a standardized one-on-one tackling drill in a 10-m grid. Players performed the one-on-one tackling drill before strenuous exercise and following game-specific repeated-effort exercise of progressively increasing intensities (corresponding to moderate, heavy, and very heavy intensity) in order to induce fatigue that was representative of match conditions. Video footage was taken from the rear, side, and front of the defending player. Tackling technique was objectively assessed using standardized technical criteria. In addition, all players underwent measurements of standard anthropometry (height, body mass, and sum of 7 skinfold measurements), speed (10-, 20-, and 40-m sprint), muscular power (vertical jump), agility (L run), and estimated maximal aerobic power (VO2max multistage fitness test). A progressive increase in total repeated-effort time, heart rate, blood lactate concentration, and ratings of perceived exertion occurred throughout the repeated-effort protocol, demonstrating a progressive increase in intensity and fatigue. Fatigue resulted in progressive reductions in tackling technique. Players with the best tackling technique in a nonfatigued state demonstrated the greatest decrement in tackling technique under fatigued conditions. In addition, a significant association was observed between estimated VO2max (r = -0.62) and agility (r = 0.68) and fatigue-induced decrements in tackling technique. From a practical perspective, these findings suggest that strength and conditioning programs designed to develop endurance, change of direction speed, and anticipation skills may reduce fatigue-induced decrements in tackling technique. Furthermore, any defensive drills designed to improve tackling technique should be performed before and under fatigue.     

Normalizing expressions of strength in elite rugby league players

Physical strength has often been expressed per kilogram of body mass. Research suggests that strength increases in proportion to a body mass raised to a power between 0.6 and 0.7 rather than the ratio held exponent of 1. The current study was designed to identify differences in the strength of elite-level rugby league players and to identify whether ratio (per kg(-1)) expressions would penalize heavier subjects. Fifty-four elite rugby league players were recruited to the study during the preseason. Subjects were classified according to their highest playing level. Players performed 3 maximal lifts, using a dynamometer, to determine leg strength. Body mass and muscle mass estimations were also recorded. Results showed that absolute expressions of strength revealed differences by playing level (p < 0.05). These differences were removed when a ratio scaling technique was applied (p > 0.05). Mass and muscle mass exponents of 0.62 and 0.63 were derived and applied to the strength data. Differences in strength by playing level were reestablished following this adjustment (p < 0.05). These findings emphasize that ratio (per kg(-1)) expressions, despite being commonly used, can penalize heavier athletes and mask differences in performance. Coaches and sports scientists should reconsider using the ratio expression due to its potential for error when describing physical strength.     

Repeated-sprint and effort ability in rugby league players

The aim of this study was to (a) investigate the influence of tackling on repeated-sprint performance; (b) determine whether repeated-sprint ability (RSA) and repeated-effort ability (REA) are 2 distinct qualities; and (c) assess the test-retest reliability of repeated-sprint and repeated-effort tests in rugby league. Twelve rugby league players performed a repeated-sprint (12 × 20-m sprints performed on a 20-second cycle) and a repeated-effort (12 × 20-m sprints with intermittent tackling, performed on a 20-second cycle) test 7 days apart. The test-retest reliability of these tests was also established. Heart rate and rating of perceived exertion were recorded throughout the tests. There was a significantly greater (p ≤ 0.05) and large effect size (ES) differences for total sprint time (ES = 1.19), average heart rate (ES = 1.64), peak heart rate (ES = 1.35), and perceived exertion (ES = 3.39) for the repeated-effort test compared with the repeated-sprint test. A large difference (ES = 1.02, p = 0.06) was detected for percentage decrement between the 2 tests. No significant relationship was found between the repeated-sprint and repeated-effort tests for any of the dependent variables. Both tests proved reliable, with total sprint time being the most reliable method of assessing performance. This study demonstrates that the addition of tackling significantly increases the physiological response to repeated-sprint exercise and reduces repeated-sprint performance in rugby league players. Furthermore, RSA and REA appear to be 2 distinct qualities that can be reliably assessed with total time being the most reliable measure of performance.     

Performance changes following training in junior rugby league players

The purpose of this study was to investigate the time course of adaptations to training in young (i.e., <15 years) and older (i.e., <18 years) junior rugby league players. Fourteen young (14.1 +/- 0.2 years) and 21 older (16.9 +/- 0.3 years) junior rugby league players participated in a 10-week preseason strength, conditioning, and skills program that included 3 sessions each week. Subjects performed measurements of standard anthropometry (i.e., height, body mass, and sum of 7 skinfolds), muscular power (i.e., vertical jump), speed (i.e., 10-m, 20-m, and 40-m sprint), agility (505 test), and estimated maximal aerobic power (i.e., multistage fitness test) before and after training. In addition, players underwent a smaller battery of fitness tests every 3 weeks to assess the time course of adaptation to the prescribed training stimulus. During the triweekly testing sessions, players completed assessments of upper-body (i.e., 60-second push-up, sit-up, and chin-up test) and lower-body (i.e., multiple-effort vertical jump test) muscular endurance. Improvements in maximal aerobic power and muscular endurance were observed in both the young and the older junior players following training. The improvements in speed, muscular power, maximal aerobic power, and upper-body muscular endurance were greatest in the young junior players, while improvements in lower-body muscular endurance were greatest in the older junior players. These findings demonstrate that young (i.e., <15 years) and older (i.e., <18 years) junior rugby league players adapt differently to a given training stimulus and that training programs should be modified to accommodate differences in maturational and training age. In addition, the results of this study provide conditioning coaches with realistic performance improvements following a 10-week preseason strength and conditioning program in junior rugby league players.     

Strength and power characteristics in English elite rugby league players

The aim of this article is to present data on the strength and power characteristics of forwards and backs in a squad of elite English rugby league players and compare these findings to previously published literature from Australia. Participants were elite English rugby league players (n = 18; height 184.16 ± 5.76 cm; body mass 96.87 ± 10.92 kg, age 21.67 ± 4.10 years) who were all regular first team players for an English Superleague club. Testing included 5-, 10-, 20-m sprint times, agility, vertical jump, 40-kg squat jump, isometric squat, concentric and eccentric isokinetic knee flexion and extension. Independent t-tests were performed to compare results between forwards and backs, with paired samples t-tests used to compare bilateral differences from isokinetic assessments and agility tests. Forwards demonstrated significantly (p < 0.05) greater body mass (102.15 ± 7.5 kg), height (186.30 ± 5.47 cm), power during the 40-kg jump squat (2,106 ± 421 W), isometric force (3,122 ± 611 N) and peak torque during left concentric isokinetic knee extension (296.1 ± 54.2 N·m) compared to the backs (86.30 ± 8.97 kg; 179.87 ± 3.72 cm; 1,709 ± 286 W; 2,927 ± 607 N; 241.7 ± 35.2 N·m, respectively). However, no significant differences (p > 0.05) were noted between forwards and backs during right concentric isokinetic knee extension (274.8 ± 37.7 and 246.8 ± 25.8 N·m), concentric isokinetic knee flexion for both left (158.8 ± 28.6 and 141.0 ± 22. 7 N·m) and right legs (155.3 ± 22.9 and 128.0 ± 23.9 N·m), eccentric isokinetic knee flexion and extension, hamstring quadriceps ratios, or vertical jump (37.25 ± 4.35 and 40.33 ± 6.38 cm). In comparison, relative measures demonstrated that backs performed significantly better compared to the forwards during the 40-kg jump squat (20.71 ± 5.15 and 19.91 ± 3.91 W·kg?1) and the isometric squat (34.32 ± 7.9 and 30.65 ± 5.34 N·kg?1). Bilateral comparisons revealed no significant differences (p > 0.05) between left and right leg performances in the agility test (3.26 ± 0.18 and 3.24 ± 0.18 seconds), or between left (0.7 ± 0.10) and right (0.71 ± 0.17) leg eccentric hamstring concentric quadriceps ratios. The results demonstrate that absolute strength and power measures are generally higher in forwards compared to in backs; however, when body mass is taken into account and relative measures compared, the backs outperform the forwards.     

Relationship between physical fitness and playing ability in rugby league players

This study investigated the physiological, anthropometric, and skill characteristics of rugby league players and determined the relationship between physical fitness and playing ability in these athletes. Eighty-six rugby league players (mean +/- SD age, 22.5 +/- 4.9 years) underwent measurements of standard anthropometry (height, body mass, and sum of 4 skinfolds), muscular power (vertical jump), speed (10-, 20-, and 40-m sprint), agility (L run), and estimated maximal aerobic power (multistage fitness test). In addition, 2 expert coaches independently assessed the playing ability of players using standardized skill criteria. First-grade players had significantly greater (p < 0.05) basic passing and ball-carrying ability and superior skills under fatigue, tackling and defensive skills, and evasion skills (i.e., ability to beat a player and 2 verse 1 skills) than second-grade and third-grade players. While no significant (p > 0.05) differences were detected among playing levels for body mass; skinfold thickness; height; 10-, 20-, or 40-m speed; agility; vertical jump height; or estimated maximal aerobic power, all the physiological and anthropometric characteristics were significantly (p < 0.05) associated with at least 1 measure of playing ability. The results of this study demonstrate that selected skill characteristics but not physiological or anthropometric characteristics discriminate between successful and less successful rugby league players. However, all physiological and anthropometric characteristics were related to playing ability. These findings suggest that while physiological and anthropometric characteristics do not discriminate between successful and less successful rugby league players, a high level of physical fitness contributes to effective playing ability in these athletes. A game-specific training program that incorporates both physical conditioning and skills training may facilitate a greater transfer of physical fitness to competitive performances in rugby league.     

Changes in physiological and anthropometric characteristics of rugby league players during a competitive season

This study investigated the physiological and anthropometric characteristics of rugby league players during a competitive season. Sixty-eight rugby league players were allocated into training (n = 52) and nonexercise control (n = 16) groups. The training group participated in 2 field-training sessions per week, with training loads, match loads, and injury rates recorded. Subjects performed measurements of standard anthropometry (height, body mass, and sum of 7 skinfolds), muscular power (vertical jump), speed (10-, 20-, and 40-m sprint), agility (L run), and maximal aerobic power (multistage fitness test) in December (off-season), March (preseason), May (midseason), and August (end season). Increases in maximal aerobic power and muscular power and reductions in skinfold thickness were observed during the early phases of the season when training loads were highest. However, reductions in muscular power and maximal aerobic power and increases in skinfold thickness occurred toward the end of the season, when training loads were lowest and match loads and injury rates were highest. These findings suggest that high overall playing intensity and match loads in end-season matches increase in injury rates in the latter half of the season, and residual fatigue associated with limited recovery between successive matches may compromise the physical development of rugby league players.     

Performance changes following a field conditioning program in junior and senior rugby league players

This study investigated training loads, injury rates, and physical performance changes associated with a field conditioning program in junior and senior rugby league players. Thirty-six junior (16.9 [95% confidence interval: 16.7-17.1] years) and 41 senior (25.5 [23.6- 27.3] years) rugby league players participated in a 14-week preseason training program that included 2 field training sessions each week. Subjects performed measurements of standard anthropometry (height, body mass, and sum of 7 skinfolds), muscular power (vertical jump), speed (10-, 20-, and 40-m sprint), agility (L run), and maximal aerobic power (multistage fitness test) before and after training. Improvements in agility, muscular power, and maximal aerobic power were observed in both the junior and senior players following training; however, the improvement in maximal aerobic power and muscular power were greatest in the junior players. Training loads and injury rates were higher in the senior players. These findings demonstrate that junior and senior rugby league players adapt differently to a given training stimulus and that training programs should be modified to accommodate differences in training age.     

Performance of the Yo-Yo Intermittent Recovery Test by elite professional and semiprofessional rugby league players

The purpose of this study was to assess the performance of elite rugby league players by using the Yo-Yo Intermittent Recovery Test. Fifty players were recruited to the study during preseason and were classified as professional (P) or semiprofessional (SP). All performed the level 1 Yo-Yo Intermittent Recovery Test. Total distance achieved was taken as the performance index. Physiological (heart rate and blood lactate) correlates of performance were also assessed. Results showed that P players achieved a greater total distance than did SP players (p > 0.05). End heart rates did not differ significantly (p < 0.05). Semiprofessional players had significantly lower end blood lactate values than did P players (p < 0.05). Relationships between test performance and physiological variables were not significant (p > 0.05). These findings showed that P and SP players performed the test at a comparable level. Physiological indices indicated that performance was near maximal. The test is considered a useful measure of intermittent high-intensity performance for rugby league players.     

Physiological correlates of multiple-sprint ability and performance in international-standard squash players

From measures on a battery of fitness tests in elite-standard squash players on different tiers of a national performance program, we examined the relationships among test scores and player rank, and fitness factors important for squash-specific multiple-sprint ability. Thirty-one (20 men, 11 women) squash players from the England Squash performance program participated: n = 12 senior; n = 7 transition; n = 12 talented athlete scholarship scheme (TASS) players. In 1 test session and in a fixed order, the players completed a battery of tests to assess countermovement jump height, reactive strength, change-of-direction speed, and multiple-sprint ability on squash-specific tests and endurance fitness. Two-way analysis of variance compared senior, transition, and TASS players by sex on all measures except jump height where only senior and transition players were compared. Effect size (ES) was calculated for all comparisons. Pearson's correlation examined relationships among test scores and multiple-sprint ability. Spearman's ρ investigated relationships among test scores and players' rank in men and women separately. Regardless of sex, seniors outperformed TASS players on all except the endurance test (p < 0.05, ES at least 1.1). Seniors had better multiple-sprint ability than did transition players (p < 0.01, ES = 1.2). Transition outperformed TASS players on the reactive-strength test (p < 0.05, ES = 1.0). Men outperformed women in all tests at all performance program tiers (p < 0.05, ES at least 0.5). In men, rank was related to multiple-sprint ability, fastest-multiple-sprint-test repetition, and change-of-direction speed (ρ = 0.78, 0.86, 0.59, respectively). In women, rank was related to fastest multiple-sprint-test repetition (ρ = 0.65). In men and women, multiple-sprint ability was related to change-of-direction speed (r = 0.9 and 0.84) and fastest-multiple-sprint-test repetition (r = 0.96 for both) and to reactive strength in men (r = -0.71). The results confirm that high-intensity variable-direction exercise capabilities are important for success in elite squash.     

Influence of field size on the physiological and skill demands of small-sided games in junior and senior rugby league players

The purpose of this study was to investigate the effect of changes in field size on the physiological and skill demands of small-sided games in elite junior and senior rugby league players. Sixteen elite senior rugby league players ([mean ± SE] age, 23.6 ± 0.5 years) and 16 elite junior rugby league players ([mean ± SE] age, 17.3 ± 0.3 years) participated in this study. On day 1, 2 teams played an 8-minute small-sided game on a small field (10-m width × 40-m length), whereas the remaining 2 teams played the small-sided game on a larger sized field (40-m width × 70-m length). On day 2, the groups were crossed over. Movement was recorded by a global positioning system unit sampling at 5 Hz. Games were filmed to count the number of possessions and the number and quality of disposals. The games played on a larger field resulted in a greater (p < 0.05) total distance covered, and distances covered in moderate, high, and very-high velocity movement intensities. Senior players covered more distance at moderate, high, and very-high intensities, and less distance at low and very-low intensities during small-sided games than junior players. Although increasing field size had no significant influence (p > 0.05) over the duration of recovery periods for junior players, larger field size significantly reduced (p < 0.05) the amount of short-, moderate-, and long-duration recovery periods in senior players. No significant between-group differences (p > 0.05) were detected for games played on a small or large field for the number or quality of skill involvements. These results suggest that increases in field size serve to increase the physiological demands of small-sided games but have minimal influence over the volume or quality of skill executions in elite rugby league players.     

Physiological and anthropometric characteristics of Australian junior national, state, and novice volleyball players

The purpose of this study was to investigate the physiological and anthropometric characteristics of junior volleyball players competing at the elite, semi-elite, and novice levels and to establish performance standards for these athletes. One hundred and fifty-three junior national (N = 14 males; N = 20 females), state (N = 16 males; N = 42 females), and novice (N = 27 males; N = 34 females) volleyball players participated in this study. Subjects underwent measurements of standard anthropometry (body mass, height, standing reach height, and sum of 7 skinfolds), lower-body muscular power (vertical jump and spike jump), upper-body muscular power (overhead medicine ball throw), speed (5-m and 10-m sprint), agility (T-test), and estimated maximal aerobic power (multistage fitness test) during the competitive phase of the season, after obtaining a degree of match fitness. Significant differences (p < 0.05) were detected among junior national, state, and novice volleyball players for height, standing reach height, skinfold thickness, lower-body muscular power, agility, and estimated maximal aerobic power, with the physiological and anthropometric characteristics of players typically improving with increases in playing level. Male players were taller, heavier, leaner, and had greater standing reach height, speed, agility, muscular power, and estimated maximal aerobic power than female players. These findings provide normative data and performance standards for junior volleyball players competing at the elite, semi-elite, and novice levels. Given the improvements in lower-body muscular power, agility, and estimated maximal aerobic power with increased playing level, and given the importance of these qualities to competitive performances, conditioning coaches should train these qualities to improve the playing performances of junior volleyball players.     

Neuromuscular responses to impact and collision during elite rugby league match play

The purpose of this study was to investigate the relationship between the prematch and short-term postmatch neuromuscular responses to the intensity, number, and distribution of impacts associated with collisions during elite Rugby League match play. Twenty-two elite male Rugby League players were monitored during 8 regular season competition matches using portable global positioning system (GPS) technology. The intensity, number, and distribution of impact forces experienced by players during match play were recorded using integrated accelerometry. Peak rate of force development (PRFD), peak power (PP), and peak force (PF) were measured during a countermovement jump on a force plate 24 hours prematch, 30 minutes prematch, 30 minutes postmatch and then at 24-hour intervals for a period of 5 days postmatch. The change in the dependent variables at each sample collection time was compared with that at 24 hours prematch and 30-minute prematch measures. There were significant (p < 0.05) decreases in PRFD and PP up to 24 hours postmatch with PF significantly (p < 0.05) being decreased 30 minutes postmatch. Significant (p < 0.05) correlations were found between the total number of impacts and PRFD and PP 30 minutes postmatch. Impact zones 4 (7.1-8.0 G), 5 (>8.1-10.0 G), and 6 (>10.1 G) were significantly (p < 0.05) correlated to PRFD and PP 30 minutes postmatch with the number of zone 5 and 6 impacts significantly (p < 0.05) correlated to PRFD and PP 24 hours postmatch. Elite Rugby League match play resulted in significant neuromuscular fatigue and was highly dependent on the number of heavy collisions >7.1G. Results demonstrate that neuromuscular function is compromised for up to 48 hours postmatch indicating that at least 2 days of modified activity is required to achieve full neuromuscular recovery after elite Rugby League match play. Position-specific demands on energy systems and the influence of repeated blunt force trauma during collisions during elite Rugby League match play should be considered when planning postmatch recovery protocols and training activities to optimize subsequent performance.     

Aerobic capacities and anthropometric characteristics of elite female soccer players

Ingebrigtsen, J, Dillern, T, and Shalfawi, SAI. Aerobic capacities and anthropometric characteristics of elite female soccer players. J Strength Cond Res 25(12): 3352-3357, 2011-This study investigated aerobic capacities and anthropometric characteristics within a group of 29 elite female soccer players. The purpose was to identify and establish aerobic capacities and anthropometric characteristics for these players and to look for possible positional differences between keepers, defenders, midfielders, and attackers. We did this by measuring standard anthropometrical variables and maximal oxygen (VO(2)max) and anaerobic threshold (AT). One-way analysis of variance revealed no significant differences among anthropometric or physiological variables. However, a trend (p = 0.062) toward positional differences was found within running speed at AT. A subsequent Tukey post hoc test showed differences (p = 0.04) between keepers and defenders, with the latter running faster (～1.7 km·h) at AT. The present results suggest that few anthropometric and physiological differences exist between playing positions in elite female soccer players. Furthermore, the current results indicate that present elite players' physiological characteristics are similar to those previously shown, despite the rapid changes of the female soccer game. Based on well-established knowledge that different playing positions within a soccer team ought to have distinct capacities, we recommend regular testing programs to be able to construct and implement tailored training programs for players' physical capacities with respect to the demands of their playing positions.     

The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players

Tribulus terrestris is an herbal nutritional supplement that is promoted to produce large gains in strength and lean muscle mass in 5-28 days (15, 18). Although some manufacturers claim T. terrestris will not lead to a positive drug test, others have suggested that T. terrestris may increase the urinary testosterone/epitestosterone (T/E) ratio, which may place athletes at risk of a positive drug test. The purpose of the study was to determine the effect of T. terrestris on strength, fat free mass, and the urinary T/E ratio during 5 weeks of preseason training in elite rugby league players. Twenty-two Australian elite male rugby league players (mean +/- SD; age = 19.8 +/- 2.9 years; weight = 88.0 +/- 9.5 kg) were match-paired and randomly assigned in a double-blind manner to either a T. terrestris (n = 11) or placebo (n = 11) group. All subjects performed structured heavy resistance training as part of the club's preseason preparations. A T. terrestris extract (450 mg.d(-1)) or placebo capsules were consumed once daily for 5 weeks. Muscular strength, body composition, and the urinary T/E ratio were monitored prior to and after supplementation. After 5 weeks of training, strength and fat free mass increased significantly without any between-group differences. No between-group differences were noted in the urinary T/E ratio. It was concluded that T. terrestris did not produce the large gains in strength or lean muscle mass that many manufacturers claim can be experienced within 5-28 days. Furthermore, T. terrestris did not alter the urinary T/E ratio and would not place an athlete at risk of testing positive based on the World Anti-Doping Agency's urinary T/E ratio limit of 4:1.     

Amino acid supplementation affects hematological and biochemical parameters in elite rugby players.

Individual amino acid supplementation affects various types of athletic performance. However, little information on combinations of amino acids is currently available. This study evaluated an amino acid mixture containing L-leucine, L-isoleucine, L-valine, L-arginine, and L-glutamine to 3.6 g of total amino acids per dose. Twenty-three rugby players were given 3.6 g, twice, daily of the amino acid mixture for 90 days (June-August 1994) and blood samples were collected for analyses in September 1993, March 1994, September 1994, and September 1995. After 90 days of supplementation, almost all of the athletes reported improvement in vigor and earlier recovery from fatigue. Significant increases (P<0.05) were observed in hemoglobin, RBC count, hematocrit, and serum iron by amino acid supplementation. Significant increases (P<0.05) were also noted in total cholesterol and low-density lipoprotein along with decreased (P<0.05) alkaline phosphatase. All values reverted to original levels when measured after one year of continued training without supplementation.     

Effects of electromyostimulation training on muscle strength and power of elite rugby players

The present study investigated the influence of a 12-week electromyostimulation (EMS) training program performed by elite rugby players. Twenty-five rugby players participated in the study, 15 in an electrostimulated group and the remaining 10 in a control group. EMS was conducted on the knee extensor, plantar flexor, and gluteus muscles. During the first 6 weeks, training sessions were carried out 3 times a week and during the last 6 weeks, once a week. Isokinetic torque of the knee extensors was determined at different eccentric and concentric angular velocities ranging from -120 to 360 degrees .s(-1). Scrummaging and full squat strength, vertical jump height and sprint-running times were also evaluated. After the first 6 weeks of EMS, only the squat strength was significantly improved (+8.3 +/- 6.5%; p < 0.01). After the 12th week, the -120 degrees .s(-1) maximal eccentric, 120 and 240 degrees .s(-1) maximal concentric torque (p < 0.05), squat strength (+15.0 +/- 8.0%; p < 0.001), squat jump (+10.0 +/- 9.5%; p < 0.01), and drop jump from a 40-cm height (+6.6 +/- 6.1%; p < 0.05) were significantly improved. No significant change was observed for the control group. A 12-week EMS training program demonstrated beneficial effects on muscle strength and power in elite rugby players on particular tests. However, rugby skills such as scrummaging and sprinting were not enhanced.     

Relationships between force-time characteristics of the isometric midthigh pull and dynamic performance in professional rugby league players

There is considerable conflict within the literature regarding the relevance of isometric testing for the assessment of neuromuscular function within dynamic sports. The aim of this study was to determine the relationship between isometric measures of force development and dynamic performance. Thirty-nine professional rugby league players participated in this study. Forty-eight hours after trial familiarization, participants performed a maximal isometric midthigh pull, with ～120-130° bend at the knee, countermovement jump (CMJ), and a 10-m sprint. Force-time data were processed for peak force (PF), force at 100 milliseconds (F100ms), and peak rate of force development (PRFD). Analysis was carried out using Pearson's product moment correlation with significance set at p < 0.05. The PF was not related to dynamic performance; however, when expressed relative to body weight, it was significantly correlated with both 10-m time and CMJ height (r = -0.37 and 0.45, respectively, p < 0.05). The F100ms was inversely related to 10-m time (r = -0.54, p < 0.01); moreover, when expressed relative to body weight, it was significantly related to both 10-m time and CMJ height (r = -0.68 and 0.43, p < 0.01). In addition, significant correlations were found between PRFD and 10-m time (r = -0.66, p < 0.01) and CMJ height (r = 0.387, p < 0.01). In conclusion, this study provides evidence that measures of maximal strength and explosiveness from isometric force-time curves are related to jump and sprint acceleration performance in professional rugby league players.