Effects of differential stretching protocols during warm-ups on high-speed motor capacities in professional soccer players

The purpose of this study was to examine the effects of different modes of stretching within a pre-exercise warm-up on high-speed motor capacities important to soccer performance. Eighteen professional soccer players were tested for countermovement vertical jump, stationary 10-m sprint, flying 20-m sprint, and agility performance after different warm-ups consisting of static stretching, dynamic stretching, or no stretching. There was no significant difference among warm-ups for the vertical jump: mean +/- SD data were 40.4 +/- 4.9 cm (no stretch), 39.4 +/- 4.5 cm (static), and 40.2 +/- 4.5 cm (dynamic). The dynamic-stretch protocol produced significantly faster 10-m sprint times than did the no-stretch protocol: 1.83 +/- 0.08 seconds (no stretch), 1.85 +/- 0.08 seconds (static), and 1.87 +/- 0.09 seconds (dynamic). The dynamic- and static-stretch protocols produced significantly faster flying 20-m sprint times than did the no-stretch protocol: 2.41 +/- 0.13 seconds (no stretch), 2.37 +/- 0.12 seconds (static), and 2.37 +/- 0.13 seconds (dynamic). The dynamic-stretch protocol produced significantly faster agility performance than did both the no-stretch protocol and the static-stretch protocol: 5.20 +/- 0.16 seconds (no stretch), 5.22 +/- 0.18 seconds (static), and 5.14 +/- 0.17 seconds (dynamic). Static stretching does not appear to be detrimental to high-speed performance when included in a warm-up for professional soccer players. However, dynamic stretching during the warm-up was most effective as preparation for subsequent high-speed performance.     

The effects of adding different whole-body vibration frequencies to preconditioning exercise on subsequent sprint performance

R?nnestad, BR and Ellefsen, S. The effects of adding different whole-body vibration frequencies to preconditioning exercise on subsequent sprint performance. J Strength Cond Res 25(12): 3306-3310, 2011-The phenomenon postactivation potentiation can possibly be used to acutely improve sprint performance. The purpose of this study was to investigate the effect of adding whole-body vibration (WBV) to body-loaded half-squats, performed as preconditioning activity to the 40-m sprint test. Nine male amateur soccer players performed 1 familiarization session and 6 separate test sessions. Each session included a standardized warm-up followed by 1 of the after preconditioning exercises: 30-seconds of half-squats with WBV at either 50 or 30 Hz or half-squats without WBV. The 40-m sprint was performed 1 minute after the preconditioning exercise. For each subject, each of the 3 protocols was repeated twice on separate days in a randomized order. Mean values were used in the statistical analysis. Performing the preconditioning exercise with WBV at a frequency of 50 Hz resulted in a superior 40-m sprint performance compared to preconditioning exercise without WBV (5.48 ± 0.19 vs. 5.52 ± 0.21 seconds, respectively, p < 0.05). There was no difference between preconditioning exercise with WBV at a frequency of 30 Hz and the no-WBV condition. In conclusion, preconditioning exercise performed with WBV at 50 Hz seems to enhance 40-m sprint performance in recreationally trained soccer players. The present findings suggest that coaches can incorporate such exercise into the warm-up to improve sprint performance or the quality of the sprint training.     

Relationships between repeated sprint testing, speed, and endurance

Repeated sprint testing is gaining popularity in team sports, but the methods of data analysis and relationships to speed and endurance qualities are not well described. We compared three different methods for analyzing repeated sprint test results, and we quantified relationships between repeated sprints, short sprints, and endurance test scores. Well-trained male junior Australian Football players (n = 60, age 18.1 +/- 0.4 years, height 1.88 +/- 0.07 m, mass 82.0 +/- 8.1 kg; mean +/- SD) completed a 6 x 30-m repeated sprint running test on a 20-second cycle, a 20-m sprint test (short sprint), and the 20-m multistage shuttle run for endurance. Repeated sprint results were evaluated in three ways: total time for all six sprints (TOTAL), percent change from predicted times (PRED) from the fastest 30-m sprint time, and percent change from first to last sprint (CHANGE). We observed a very large decrement (CHANGE 6.3 +/- 0.7%, mean +/- 90% confidence limits) in 30-m performance from the first to last sprint (4.16 +/- 0.10 to 4.42 +/- 0.11 seconds, mean +/- SD). Results from TOTAL were highly correlated with 20-m sprint and 20-m multistage shuttle run tests. Performance decrements calculated by PRED were highly correlated with TOTAL (r = 0.91), but neither method was directly comparable with CHANGE (r = -0.23 and r = 0.12 respectively). TOTAL was moderately correlated with fastest 20-m sprint time (r = 0.66) but not the 20-m multistage shuttle run (r = -0.20). Evaluation of repeated sprint testing is sensitive to the method of data analysis employed. The total sprint time and indices of the relative decrement in performance are not directly interchangeable. Repeated sprint ability seems more related to short sprint qualities than endurance fitness.     

The effects of a constant sprint-to-rest ratio and recovery mode on repeated sprint performance

It is unclear if a constant sprint-to-rest ratio allows full performance recovery between repeated sprints over different distances. This is important for the development of sprint-training programs. Additionally, there is conflicting evidence on whether active recovery enhances sprint performance. Three repeated sprint protocols were used (22 × 15, 13 × 30, and 8 × 50 m), with each having an active and passive recovery. Each trial was conducted with an initial sprint-to-rest ratio of 1:10. Repeated sprints were analyzed by comparing the first sprint to the last sprint. For the 15-m trials, there were no significant main effects for recovery or time and no significant interaction. For the 30-m trials, there was no main effect for recovery, but a main effect for time (F[1,10] = 15.995, p = 0.003; mean difference = 0.20 seconds, 95% confidence interval [CI] = 0.09-0.31 seconds, d = 1.4 [large effect]). There was no interaction of recovery and time in the 30-m trials. For the 50-m trials, there was no main effect for recovery, but a main effect for time (F[1,10] = 34.225, p = 0.0002; mean difference = 0.39 seconds, 95% CI = 0.24-0.55 seconds, d = 1.3 [large effect]). There was no interaction of recovery and time in the 50-m trials. The results demonstrate that a 1:10 sprint-to-rest ratio allows full performance recovery between 15-m sprints, but not between sprints of 30 or 50 m, and that recovery mode did not influence repeated sprint performance.     

The acute effects of heavy-load squats and loaded countermovement jumps on sprint performance

The purpose of this investigation was to determine whether performing high force or explosive force movements prior to sprinting would improve running speed. Fifteen NCAA Division III football players performed a heavy-load squat (HS), loaded countermovement jump (LCMJ), or control (C) warm-up condition in a counterbalanced randomized order over the course of 3 weeks. The HS protocol consisted of 1 set of 3 repetitions at 90% of the subject's 1 repetition maximum (1RM). The LCMJ protocol was 1 set of 3 repetitions at 30% of the subject's 1RM. At 4 minutes post-warm-up, subjects completed a timed 40-m dash with time measured at 10, 30, and 40 m. The results of the study indicated that when preceded by a set of HS, subjects ran 0.87% faster (p < or = 0.05) in the 40-m dash (5.35 +/- 0.32 vs. 5.30 +/- 0.34 seconds) in comparison to C. No significant differences were observed in the 10-m or 30-m split times between the 3 conditions. The data from this study suggest that an acute bout of low-volume heavy lifting with the lower body may improve 40-m sprint times, but that loaded countermovement jumps appear to have no significant effect.     

The effect of warm-ups incorporating different volumes of dynamic stretching on 10- and 20-m sprint performance in highly trained male athletes

Recently, athletes have transitioned from traditional static stretching during warm-ups to incorporating dynamic stretching routines. However, the optimal volume of dynamic drills is yet to be identified. The aim of this repeated-measures study was to examine varying volumes (1, 2, and 3 sets) of active dynamic stretching (ADS) in a warm-up on 10- and 20-m sprint performance. With a within-subject design, 16 highly trained male participants (age: 20.9 ± 1.3 years; height: 179.7 ± 5.7 cm; body mass: 72.7 ± 7.9 kg; % body fat: 10.9 ± 2.4) completed a 5-minute general running warm-up before performing 3 preintervention measures of 10- to 20-m sprint. The interventions included 1, 2, and 3 sets of active dynamic stretches of the lower-body musculature (gastrocnemius, gluteals, hamstrings, quadriceps, and hip flexors) performed approximately 14 times for each exercise while walking (ADS1, ADS2, and ADS3). The active dynamic warm-ups were randomly allocated before performing a sprint-specific warm-up. Five minutes separated the end of the warm-up and the 3 postintervention measures of 10- to 20-m sprints. There were no significant time, condition, and interaction effects over the 10-m sprint time. For the 0- to 20-m sprint time, a significant main effect for the pre-post measurement (F = 10.81; p < 0.002), the dynamic stretching condition (F = 6.23; p = 0.004) and an interaction effect (F = 41.19; p = 0.0001) were observed. A significant decrease in sprint time (improvement in sprint performance) post-ADS1 (2.56%, p = 0.001) and post-ADS2 (2.61%, p = 0.001) was observed. Conversely, the results indicated a significant increase in sprint time (sprint performance impairment) post-ADS3 condition (2.58%, p = 0.001). Data indicate that performing 1-2 sets of 20 m of active dynamic stretches in a warm-up can enhance 20-m sprint performance. The results delineated that 3 sets of ADS repetitions could induce acute fatigue and impair sprint performance within 5 minutes of the warm-up.     

Familiarization and reliability of multiple sprint running performance indices

The aims of this study were to evaluate the time-course of the familiarization process associated with a test of multiple sprint running performance and to determine the reliability of various performance indices once familiarization had been established. Eleven physically active men (mean age: 21 +/- 2 years) completed 4 multiple sprint running trials (12 x 30 m; repeated at 35-s intervals) with 7 days between trials. All testing was conducted indoors, and times were recorded by twin-beam photocells. Results revealed no apparent learning effects as evidenced by no significant (p > 0.05) between-trial differences in measures of fastest or mean 30-m sprint time. Within-subject test-retest reliability determined over 4 trials by coefficient of variation (CV) and intraclass correlation coefficient (ICC) showed excellent reliability for measures of fastest and mean sprint times (CV range: 1.34-2.24%; ICC range: 0.79-0.94). Pre- and posttrial blood lactate concentrations showed good reliability when judged in context with typical values (CV range: 12.08-18.21%; ICC range: 0.72-0.78). In contrast, and in line with previous research, fatigue data showed much greater variability (CV: 26.43%; ICC: 0.66). The results of this study suggest that high degrees of test-retest reliability can be obtained in many multiple sprint running indices without the need for prior familiarization.     

The acute effects of combined static and dynamic stretch protocols on fifty-meter sprint performance in track-and-field athletes

The purpose of this study was to investigate the effect of manipulating the static and dynamic stretch components associated with a traditional track-and-field warm-up. Eighteen experienced sprinters were randomly assigned in a repeated-measures, within-subject design study with 3 interventions: active dynamic stretch (ADS), static passive stretch combined with ADS (SADS), and static dynamic stretch combined with ADS (DADS). A standardized 800-m jogged warm-up was performed before each different stretch intervention, followed by two 50-m sprints. Results indicated that the SADS intervention yielded significantly (p < or = 0.05) slower 50-m sprint times then either the ADS or DADS intervention. The decrease in sprint time observed after the ADS intervention compared to the DADS intervention was found to be nonsignificant (p > 0.05). The decrease in performance post-SADS intervention was attributed to a decrease in the musculotendinous unit (MTU) stiffness, possibly due to a reduction in muscle activation prior to ground contact, leading to a decrease in the MTU's ability to store and transfer elastic energy after the use of passive static stretch techniques. The improved 50-m sprint performance associated with the ADS and DADS interventions was linked to the rehearsal of specific movement patterns, helping proprioception and preactivation, allowing a more optimum switch from eccentric to concentric muscle contraction. It was concluded that passive static stretching in a warm-up decreases sprint performance, despite being combined with dynamic stretches, when compared to a solely dynamic stretch approach.     

The effect of warm-up on high-intensity, intermittent running using nonmotorized treadmill ergometry

The aim of this study was to investigate the effect of previous warming on high-intensity intermittent running using nonmotorized treadmill ergometry. Ten male soccer players completed a repeated sprint test (10 x 6-second sprints with 34-second recovery) on a nonmotorized treadmill preceded by an active warm-up (10 minutes of running: 70% VO2max; mean core temperature (Tc) 37.8 +/- 0.2 degrees C), a passive warm-up (hot water submersion: 40.1 +/- 0.2 degrees C until Tc reached that of the active warm-up; 10 minutes +/- 23 seconds), or no warm-up (control). All warm-up conditions were followed by a 10-minute static recovery period with no stretching permitted. After the 10-minute rest period, Tc was higher before exercise in the passive trial (38.0 +/- 0.2 degrees C) compared to the active (37.7 +/- 0.4 degrees C) and control trials (37.2 +/- 0.2 degrees C; p < 0.05). There were no differences in pre-exercise oxygen consumption and blood lactate concentration; however, heart rate was greater in the active trial (p < 0.05). The peak mean 1-second maximum speed (MxSP) and group mean MxSP were not different in the active and passive trials (7.28 +/- 0.12 and 7.16 +/- 0.10 m x s(-1), respectively, and 7.07 +/- 0.33 and 7.02 +/- 0.24 m x s(-1), respectively; p > 0.05), although both were greater than the control. The percentage of decrement in performance fatigue was similar between all conditions (active, 3.4 +/- 1.3%; passive, 4.0 +/- 2.0%; and control, 3.7 +/- 2.4%). We conclude that there is no difference in high-intensity intermittent running performance when preceded by an active or passive warm-up when matched for post-warm-up Tc. However, repeated sprinting ability is significantly improved after both active and passive warm-ups compared to no warm-up.     

Optimal elastic cord assistance for sprinting in collegiate women soccer players

Overspeed exercises are commonly integrated into a training program to help athletes perform at a speed greater than what they are accustomed to when unassisted. However, the optimal assistance for maximal sprinting has not been determined. The purpose of this study was to determine the optimal elastic cord assistance for sprinting performance. Eighteen collegiate women soccer players completed 3 testing sessions, which consisted of a 5-minute warm-up, followed by 5 randomized experimental conditions of 0, 10, 20, 30, and 40% body weight assistance (BWA). In all BWA sessions, subjects wore a belt while attached to 2 elastic cords and performed 2 maximal sprints under each condition. Five minutes of rest was given between each sprint attempt and between conditions. Split times (0-5, 5-10, 10-15, 15-20, and 0-20 yd) for each condition were used for analysis. Results for 0-20 yd demonstrated a significant main effect for condition. Post hoc comparisons revealed that as BWA increased, sprint times decreased up to 30% BWA (0%: 3.20 ± 0.12 seconds; 10%: 3.07 ± 0.09 seconds; 20%: 2.96 ± 0.07 seconds; 30%: 2.81 ± 0.08 seconds; 40%: 2.77 ± 0.10 seconds); there was no difference between 30 and 40% BWA. There was also a main effect for condition when examining split times. Post hoc comparisons revealed that as BWA increased, sprint times decreased up to 30% BWA for distances up to 15 yd. These results demonstrate that 30% of BWA with elastic cords appears optimal in decreasing sprint times in collegiate women soccer players for distances up to 15 yd.     

The acute effects of heavy back and front squats on speed during forty-meter sprint trials

The purpose of the present study was to investigate the effects of performing heavy back squats (HBS) and heavy front squats (HFS) on the average speed during each 10-m interval of 40-m sprint trials. In a randomized, cross-over design, 10 strength-trained men performed a HBS, HFS, or control treatment before performing three 40-m sprint trials separated by 3 minutes. The HBS and HFS treatments consisted of performing parallel back or front squats with 30%, 50%, and 70% of the subject's 1 repetition maximum after 5 minutes of cycling. The control treatment consisted of cycling for 5 minutes. The sprint trials were performed 4 minutes after completing the HBS, HFS, or control treatments. Significant increases in speed were found during the 10- to 20-m interval for the HBS compared with the control treatment (mean difference, 0.12 m x s(-1); 95% likely range, 0.05-0.18 m x s(-1); P = 0.001). During the 30- to 40-m interval, HBS produced significantly greater speeds compared with the HFS treatment (mean difference, 0.24 m x s(-1); 95% likely range, 0.02-0.45 m x s(-1); P = 0.034) and the control treatment (mean difference, 0.18 m x s(-1); 95% likely range, 0.03-0.32 m x s(-1); P = 0.021). The differing effects of the treatments may reflect different levels of muscular activation or different mechanical aspects of the squat exercises. Similarly, the multidimensional nature of sprint running means that other specific exercises may confer improvements in sprinting performance during other intervals. It is suggested that coaches could incorporate HBS into the warm-up procedure of athletes to improve sprinting performance.     

The reliability and validity of fatigue measures during multiple-sprint work: an issue revisited

The ability to repeatedly produce a high-power output or sprint speed is a key fitness component of most field and court sports. The aim of this study was to evaluate the validity and reliability of eight different approaches to quantify this parameter in tests of multiple-sprint performance. Ten physically active men completed two trials of each of two multiple-sprint running protocols with contrasting recovery periods. Protocol 1 consisted of 12 x 30-m sprints repeated every 35 seconds; protocol 2 consisted of 12 x 30-m sprints repeated every 65 seconds. All testing was performed in an indoor sports facility, and sprint times were recorded using twin-beam photocells. All but one of the formulae showed good construct validity, as evidenced by similar within-protocol fatigue scores. However, the assumptions on which many of the formulae were based, combined with poor or inconsistent test-retest reliability (coefficient of variation range: 0.8-145.7%; intraclass correlation coefficient range: 0.09-0.75), suggested many problems regarding logical validity. In line with previous research, the results support the percentage decrement calculation as the most valid and reliable method of quantifying fatigue in tests of multiple-sprint performance.     

The effect of static stretching on phases of sprint performance in elite soccer players

The purpose of this study was to determine which phase of a 30-m sprint (acceleration and/or maximal velocity) was affected by preperformance static stretching. Data were collected from 20 elite female soccer players. On two nonconsecutive days, participants were randomly assigned to either the stretch or no-stretch condition. On the first day, the athletes in the no-stretch condition completed a standard warm-up protocol and then performed three 30-m sprints, with a 2-minute rest between each sprint. The athletes in the stretch condition performed the standard warm-up protocol, completed a stretching routine of the hamstrings, quadriceps, and calf muscles, and then immediately performed three 30-m sprints, also with a 2-minute rest between each sprint. On the second day, the groups were reversed, and identical procedures were followed. One-way repeated-measures analyses of variance revealed a statistically significant difference in acceleration (p < 0.0167), maximal-velocity sprint time (p < 0.0167), and overall sprint time (p < 0.0167) between the stretch and no-stretch conditions. Static stretching before sprinting resulted in slower times in all three performance variables. These findings provide evidence that static stretching exerts a negative effect on sprint performance and should not be included as part of the preparation routine for physical activity that requires sprinting.     

A comparison of maximal squat strength and 5-, 10-, and 20-meter sprint times, in athletes and recreationally trained men

The purpose of this study was to identify whether there was a relationship between relative strength during a 1 repetition maximum (1RM) back squat and 5-, 10-, and 20-m sprint performances in both trained athletes and recreationally trained individuals. Professional rugby league players (n = 24) and recreationally trained individuals (n = 20) participated in this investigation. Twenty-meter sprint time and 1RM back squat strength, using free weights, were assessed on different days. There were no significant (p ≥ 0.05) differences between the well-trained and recreationally trained groups for 5-m sprint times. In contrast, the well-trained group's 10- and 20-m sprint times were significantly quicker (p = 0.004; p = 0.002) (1.78 + 0.06 seconds; 3.03 + 0.09 seconds) compared with the recreationally trained group (1.84 + 0.07 seconds; 3.13 + 0.11 seconds). The athletes were significantly stronger (170.63 + 21.43 kg) than the recreationally trained individuals (135.45 + 30.07 kg) (p = 0.01); however, there were no significant differences (p > 0.05) in relative strength between groups (1.78 + 0.27 kg/kg; 1.78 + 0.33 kg/kg, respectively). Significant negative correlations were found between 5-m sprint time and relative squat strength (r = -0.613, power = 0.96, p = 0.004) and between relative squat strength and 10- and 20-m sprint times in the recreationally trained group (r = -0.621, power = 0.51, p = 0.003; r = -0.604, power = 0.53, p = 0.005, respectively). These results, indicating that relative strength, are important for initial sprint acceleration in all athletes but more strongly related to sprint performance over greater distances in recreationally trained individuals.     

The influence of recovery duration after heavy resistance exercise on sprint cycling performance

ABSTRACT: Thatcher, R, Gifford, R, and Howatson, G. The influence of recovery duration after heavy resistance exercise on sprint cycling performance. J Strength Cond Res 26(11): 3089-3094, 2012-The aim of this study was to determine the optimal recovery duration after prior heavy resistance exercise (PHRE) when performing sprint cycling. On 5 occasions, separated by a minimum of 48 hours, 10 healthy male subjects (mean ± SD), age 25.5 ± 7.7 years, body mass 82.1 ± 9.0 kg, stature 182.6 ± 87 cm, deadlift 1-repetition maximum (1RM) 142 ± 19 kg performed a 30-second sprint cycling test. Each trial had either a 5-, 10-, 20-, or 30-minute recovery after a heavy resistance activity (5 deadlift repetitions at 85% 1RM) or a control trial with no PHRE in random order. Sprint cycling performance was assessed by peak power (PP), fatigue index, and mean power output over the first 5 seconds (MPO5), 10 seconds (MPO10), and 30 seconds (MPO30). One-way analysis of variance with repeated measures followed by paired t-tests with a Bonferroni adjustment was used to analyze data. Peak power, MPO5, and MPO10 were all significantly different during the 10-minute recovery trial to that of the control condition with values of 109, 112, and 109% of control, respectively; no difference was found for the MPO30 between trials. This study supports the use of PHRE as a strategy to improve short duration, up to, or around 10-second, sprint activity but not longer duration sprints, and a 10-minute recovery appears to be optimal to maximize performance.     

Effects of six warm-up protocols on sprint and jump performance

The purpose of this study was to compare the effects of 6 warm-up protocols, with and without stretches, on 2 different power maneuvers: a 30-m sprint run and a vertical countermovement jump (CJ). The 6 protocols were: (a) walk plus run (WR); (b) WR plus exercises including small jumps (EJ); (c) WR plus dynamic active stretch plus exercises with small jumps (DAEJ); (d) WR plus dynamic active stretch (DA); (e) WR plus static stretch plus exercises with small jumps (SSEJ); and (f) WR plus static stretch (SS). Twenty-six college-age men (n = 14) and women (n = 12) performed each of 6 randomly ordered exercise routines prior to randomly ordered sprint and vertical jump field tests; each routine and subsequent tests were performed on separate days. A 2 x 6 repeated measures analysis of variance revealed a significant overall linear trend (p < or = 0.05) with a general tendency toward reduction in jump height when examined in the following analysis entry order: WR, EJ, DAEJ, DA, SSEJ, and SS. The post hoc analysis pairwise comparisons showed the WR protocol produced higher jumps than did SS (p = 0.003 < or = 0.05), and DAEJ produced higher jumps than did SS (p = 0.009 < or = 0.05). There were no significant differences among the 6 protocols on sprint run performance (p > or = 0.05). No significant interaction occurred between gender and protocol. There were significant differences between men and women on CJ and sprint trials; as expected, in general men ran faster and jumped higher than the women did. The data indicate that a warm-up including static stretching may negatively impact jump performance, but not sprint time.     

Effect of creatine supplementation on intermittent sprint running performance in highly trained athletes

This study examined the impact of short-term (7-day), high-dose (0.35 g.kg(-1).d(-1)) oral creatine monohydrate supplementation (CrS) on single sprint running performance (40 m, <6 seconds) and on intermittent sprint performance in highly trained sprinters. Nine subjects completed the double-blind cross-over design with 2 supplementation periods (placebo and creatine) and a 7-week wash-out period. A test protocol consisting of 40-m sprint runs was performed, and running velocity was continuously recorded over the total distance. The maximal sprint performance, the relative degree of fatigue at the end of intermittent sprint exercise (6 x 40 m, 30-second rest interval), as well as the degree of recovery (120-second passive rest) remained unchanged following CrS. There were no significant changes related to CrS in absolute running velocity at any distance between start and finish (40 m). It was concluded that no ergogenic effect on single or repeated 40-m sprint times with varying rest periods was observed in highly trained athletes.     

Changes evaluated in soccer-specific power endurance either with or without a 10-week,in-season,intermittent, high-intensity training protocol

The purpose of this study was to evaluate changes in soccer-specific power endurance of 34 female high school soccer players throughout a season either with or without an intermittent, high-intensity exercise protocol. Thirty-four female high school soccer players were tested prior to the 2000 fall season and again 10 weeks later. The tests included an abridged 45-minute shuttle test (LIST), hydrostatic weighing, vertical jump, 20-m running-start sprint, and 30-second Wingate test. The experimental group (EG; n = 17, age 16.5 +/- 0.9 years) completed a 10-week in-season plyometric, resistive training, and high-intensity anaerobic program. The control group (n = 17, age 16.3 +/- 1.4 years) completed only traditional aerobic soccer conditioning. Statistical significance was set at alpha < 0.05. The experimental group showed significant improvements in the LIST (EG = delta 394 seconds +/- 124 seconds), 20-m sprint (EG = Delta-0.10 seconds +/- 0.10 seconds), increase in fat-free mass (EG = delta 1.14 kg +/- 1.22 kg), and decreases in fat mass (EG = Delta-1.40 kg +/- 1.47 kg) comparing pre- to postseason. This study indicates that a strength and plyometric program improved power endurance and speed over aerobic training only. Soccer-specific power endurance training may improve match performance and decrease fatigue in young female soccer players.     

The effect of different warm-up stretch protocols on 20 meter sprint performance in trained rugby union players

The purpose of this study was to determine the effect of different static and dynamic stretch protocols on 20-m sprint performance. The 97 male rugby union players were assigned randomly to 4 groups: passive static stretch (PSS; n = 28), active dynamic stretch (ADS; n = 22), active static stretch (ASST; n = 24), and static dynamic stretch (SDS; n = 23). All groups performed a standard 10-minute jog warm-up, followed by two 20-m sprints. The 20-m sprints were then repeated after subjects had performed different stretch protocols. The PSS and ASST groups had a significant increase in sprint time (p < or = 0.05), while the ADS group had a significant decrease in sprint time (p < or = 0.05). The decrease in sprint time, observed in the SDS group, was found to be nonsignificant (p > or = 0.05). The decrease in performance for the 2 static stretch groups was attributed to an increase in the musculotendinous unit (MTU) compliance, leading to a decrease in the MTU ability to store elastic energy in its eccentric phase. The reason why the ADS group improved performance is less clear, but could be linked to the rehearsal of specific movement patterns, which may help increase coordination of subsequent movement. It was concluded that static stretching as part of a warm-up may decrease short sprint performance, whereas active dynamic stretching seems to increase 20-m sprint performance.     

Effect of different warm-up procedures on subsequent swim and overall sprint distance triathlon performance

This study investigated the effect of 3 warm-up procedures on subsequent swimming and overall triathlon performance. Seven moderately trained, amateur triathletes completed 4 separate testing sessions comprising 1 swimming time trial (STT) and 3 sprint distance triathlons (SDT). Before each SDT, the athletes completed 1 of three 10-minute warm-up protocols including (a) a swim-only warm-up (SWU), (b) a run-swim warm-up (RSWU), and (c) a control trial of no warm-up (NWU). Each subsequent SDT included a 750-m swim, a 500-kJ (～20 km) ergometer cycle and a 5-km treadmill run, which the athletes performed at their perceived race intensity. Blood lactate, ratings of perceived exertion, core temperature, and heart rate were recorded over the course of each SDT, along with the measurement of swim speed, swim stroke rate, and swim stroke length. There were no significant differences in individual discipline split times or overall triathlon times between the NWU, SWU, and RSWU trials (p > 0.05). Furthermore, no difference existed between trials for any of the swimming variables measured (p > 0.05) nor did they significantly differ from the preliminary STT (p > 0.05). The findings of this study suggest that warming up before an SDT provides no additional benefit to subsequent swimming or overall triathlon performance.