The effect of acute stretching on agility performance

Static stretching (SS) has shown decreases in many areas including strength, anaerobic power, and sprinting time. Dynamic stretching (DS) has shown increases in anaerobic power and decreases in sprinting time. Research on the effects of stretching on agility performance is limited. The purpose of this study was to determine the effect of SS and DS on performance time of a sport agility test. Sixty male subjects consisting of collegiate (n = 18) and recreational (n = 42) basketball athletes volunteered for the study. Subjects were randomly assigned to 1 of 3 intervention groups: SS, DS, or no stretching (NS). All groups completed a 10-minute warm-up jog followed by a 3-minute rest. The SS and DS groups then completed an 8.5-minute stretching intervention. Next, all subjects completed 3 trials of the 505 agility test with 2-5 minutes of rest between trials. A 2-way repeated-measure analysis of variance (Stretch group, athlete category, group × athlete interaction) was used to determine statistical significance (p < 0.05). A Tukey post hoc test was performed to determine differences between groups. For all athletes, the DS group produced significantly faster times on the agility test (2.22 ± 0.12 seconds, mean ± SD) in comparison to both the SS group (2.33 ± 0.15 seconds, p = 0.013) and NS group (2.32 ± 0.12 seconds, p = 0.026). Differences between the SS and NS groups revealed no significance (p = 0.962). There was a significant difference in mean times for the type of athlete (p = 0.002); however, interaction between the type of athlete and stretching group was not significant (p = 0.520). These results indicate that in comparison to SS or NS, DS significantly improves performance on closed agility skills involving a 180° change of direction.     

Acute effect of static and dynamic stretching on hip dynamic range of motion during instep kicking in professional soccer players

The purpose of this study was to examine the effects of static and dynamic stretching within a pre-exercise warm-up on hip dynamic range of motion (DROM) during instep kicking in professional soccer players. The kicking motions of dominant legs were captured from 18 professional adult male soccer players (height: 180.38 ± 7.34 cm; mass: 69.77 ± 9.73 kg; age: 19.22 ± 1.83 years) using 4 3-dimensional digital video cameras at 50 Hz. Hip DROM at backward, forward, and follow-through phases (instep kick phases) after different warm-up protocols consisting of static, dynamic, and no-stretching on 3 nonconsecutive test days were captured for analysis. During the backswing phase, there was no difference in DROM after the dynamic stretching compared with the static stretching relative to the no-stretching method. There was a significant difference in DROM after the dynamic stretching compared with the static stretching relative to the no-stretching method during (a) the forward phase with p < 0.03, (b) the follow-through phase with p < 0.01, and (c) all phases with p < 0.01. We concluded that professional soccer players can perform a higher DROM of the hip joint during the instep kick after dynamic stretching incorporated in warm-ups, hence increasing the chances of scoring and injury prevention during soccer games.     

Acute effects of prolonged intermittent low-intensity isometric warm-up schemes on jump,sprint, and agility performance in collegiate soccer players

The aim of the present study was to compare the effects of different warm-up interventions on jump, sprint and agility performance in collegiate soccer players. Twenty-one healthy male college soccer players (age: 20.14 ± 1.65 years; body height: 179.9 ± 8.34 cm; body mass: 74.4 ± 13.0 kg; % body fat: 9.45 ± 4.8) participated in the study. Subjects underwent four different randomized warm-up protocols separated by at least 48 hours. The warm-up schemes were: 1. no conditioning contraction protocol (NCC); 2. dynamic stretching (DS); 3. prolonged intermittent low-intensity isometric exercise (ST); and, 4. ST with an additional external load equal to 30% of body weight (ST + 30% BW). All interventions were preceded by a general warm-up. Results from one-way repeated measures ANOVA demonstrated a significant difference in countermovement jump (CMJ) at F(3,60) = 10.2, ηρ² = 0.337, p < 0.01. Post hoc analysis revealed a significant difference in CMJ performance in DS when compared to NCC and ST + 30% BW. No significant difference in CMJ was observed between DS and ST. CMJ scores in NCC, ST, and ST + 30% BW were non-significant. There was a significant difference in speed; F(3, 60) = 6.61, ηρ² = 0.248, p < 0.01. Post hoc analysis revealed significantly better time in DS than NCC and ST. However, no difference in speed was observed between DS and ST + 30% BW. Similarly, speed was similar in NCC, ST and ST + 30% BW. A significant difference in agility performance was also observed; F(3, 60) = 24.1, ηρ²= 0.546, p < 0.01. Post hoc analysis revealed significantly greater performance gains in DS than NCC. No significant difference in agility was observed in DS, ST and ST + 30% BW. In conclusion, a prolonged intermittent low-intensity isometric protocol using bodyweight only showed similar benefits with dynamic stretching in countermovement jump performance. When the same isometric condition with additional load equal to 30% of bodyweight was applied, effects in speed and agility were similar to dynamic stretching.     

The acute effects of a warm-up including static or dynamic stretching on countermovement jump height, reaction time, and flexibility

The purpose of this research was to compare the effects of a warm-up with static vs. dynamic stretching on countermovement jump (CMJ) height, reaction time, and low-back and hamstring flexibility and to determine whether any observed performance deficits would persist throughout a series of CMJs. Twenty-one recreationally active men (24.4 ± 4.5 years) completed 3 data collection sessions. Each session included a 5-minute treadmill jog followed by 1 of the stretch treatments: no stretching (NS), static stretching (SS), or dynamic stretching (DS). After the jog and stretch treatment, the participant performed a sit-and-reach test. Next, the participant completed a series of 10 maximal-effort CMJs, during which he was asked to jump as quickly as possible after seeing a visual stimulus (light). The CMJ height and reaction time were determined from measured ground reaction forces. A treatment × jump repeated-measures analysis of variance for CMJ height revealed a significant main effect of treatment (p = 0.004). The CMJ height was greater for DS (43.0 cm) than for NS (41.4 cm) and SS (41.9 cm) and was not less for SS than for NS. Analysis also revealed a significant main effect of jump (p = 0.005) on CMJ height: Jump height decreased from the early to the late jumps. The analysis of reaction time showed no significant effect of treatment. Treatment had a main effect (p < 0.001) on flexibility, however. Flexibility was greater after both SS and DS compared to after NS, with no difference in flexibility between SS and DS. Athletes in sports requiring lower-extremity power should use DS techniques in warm-up to enhance flexibility while improving performance.     

An investigation into the recovery process of a maximum stretch-shortening cycle fatigue protocol on drop and rebound jumps

The aim of this study was to investigate the recovery process of a maximal stretch-shortening cycle (SSC) fatigue workout on the biomechanical performance of drop jump (DJ) and rebound jump (RBJ) on a force sledge apparatus. Thirteen elite level rugby players performed sledge DJs and RBJs before and 15, 45, 120, and 300 seconds after a maximum SSC fatigue workout. Flight time, ground contact time (CT), peak force, reactive strength index (RSI), and leg-spring stiffness were the dependent variables. The DJ results showed that after 15 seconds recovery, there was a significant reduction in flight time (FT) (p < 0.01), RSI (p < 0.001), peak force (p < 0.01), and leg stiffness (p < 0.001). Similarly, the results for the RBJ indicated that the fatigue workout significantly reduced FT (p < 0.001), peak force (p < 0.01), RSI (p < 0.01), and significantly increased CT (p < 0.05) at the 15-second interval. The results also indicated a potentiation effect at the 300-second interval because of significant increases in RSI, peak force, and leg stiffness (p < 0.05) for the RBJ and significant increases in RSI (p < 0.05), peak force, and leg stiffness (p < 0.01) and a significant decrease in ground CT (p < 0.05) for the DJ. A maximal SSC fatigue workout had both an inhibiting and potentiating effect on DJ and RBJ performance depending on the recovery interval. The efficiency of the SSC function was reduced immediately after the cessation of the fatigue workout. A potentiation effect was evident for both jumps 300 seconds postfatigue.     

Kinematics Analyses Related to Stretch-Shortening Cycle during Soccer Instep Kicking After Different Acute Stretching

ABSTRACT: Amiri-Khorasani, M, MohammadKazemi, R, Sarafrazi, S, Riyahi-Malayeri, S, and Sotoodeh, V. Kinematics analyses related to stretch-shortening cycle during soccer instep kicking after different acute stretching. J Strength Cond Res 26(11): 3010-3017, 2012-The purpose of this study was to examine the effects of static and dynamic stretching within a preexercise warm-up on angular velocity of knee joint, deepest knee flexion (DKF), and duration of eccentric and concentric contractions, which are relative to the stretch-shortening cycle (SSC) during instep kicking in professional soccer players. The kicking motions of dominant legs were captured from 18 Olympic professional male soccer players (height: 180.38 ± 7.34 cm; weight: 69.77 ± 9.73 kg; age: 19.22 ± 1.83 years) using 4 digital video cameras at 50 Hz. There was a significant difference in the DKF after the dynamic stretching (-3.22 ± 3.10°) vs. static stretching (-0.18 ± 3.19°) relative to the no-stretching method with p < 0.001. Moreover, there was significant difference in eccentric duration after the dynamic stretching (0.006 ± 0.01 seconds) vs. static stretching (-0.003 ± 0.01 seconds) relative to the no-stretching method with p < 0.015. There was a significant difference in the concentric duration after the dynamic stretching (-0.007 ± 0.01 seconds) vs. static stretching (0.002 ± 0.01 seconds) relative to the no-stretching method with p < 0.001. There was also a significant difference in knee angular velocity after the dynamic stretching (4.08 ± 3.81 rad·s) vs. static stretching (-5.34 ± 4.40 rad·s) relative to the no-stretching method with p < 0.001. We concluded that dynamic stretching during warm-ups, as compared with static stretching, is probably the most effective way as preparation for the kinematics characteristics of soccer instep kick, which are relative to the SSC.     

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.     

Acute effects of a warm-up including active, passive, and dynamic stretching on vertical jump performance

The purpose of this study was to examine the acute effects of 3 different stretching methods combined with a warm-up protocol on vertical jump performance. Sixteen young tennis players (14.5 ± 2.8 years; 175 ± 5.6 cm; 64.0 ± 11.1 kg) were randomly assigned to 4 different experimental conditions on 4 successive days. Each session consisted of a general and specific warm-up, with 5 minutes of running followed by 10 jumps, accompanied by one of the subsequent conditions: (a) Control Condition (CC)-5 minutes of passive rest; (b) Passive Stretching Condition (PSC)-5 minutes of passive static stretching; (c) Active Stretching Condition (ASC)-5 minutes of active static stretching; and (d) Dynamic Stretching Condition (DC)-5 minutes of dynamic stretching. After each intervention, the subjects performed 3 squat jumps (SJs) and 3 countermovement jumps (CMJs), which were measured electronically. For the SJ, 1-way repeated measures analysis of variance (CC × PSC × ASC × DC) revealed significant decreases for ASC (28.7 ± 4.7 cm; p = 0.01) and PSC (28.7 ± 4.3 cm; p = 0.02) conditions when compared with CC (29.9 ± 5.0 cm). For CMJs, there were no significant decreases (p > 0.05) when all stretching conditions were compared with the CC. Significant increases in SJ performance were observed when comparing the DC (29.6 ± 4.9 cm; p = 0.02) with PSC (28.7 ± 4.3 cm). Significant increases in CMJ performance were observed when comparing the conditions ASC (34.0 ± 6.0 cm; p = 0.04) and DC (33.7 ± 5.5 cm; p = 0.03) with PSC (32.6 ± 5.5 cm). A dynamic stretching intervention appears to be more suitable for use as part of a warm-up in young athletes.     

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.     

Effect of various warm-up devices on bat velocity of intercollegiate softball players

Numerous warm-up devices are available for use by softball players while they are in the on-deck circle. It is difficult to know which warm-up device produces the greatest bat velocity (BV) in the batter's box for softball players because on-deck studies with these individuals are sparse. Because the majority of warm-up device research has been conducted with baseball players, the primary purpose of this study was to examine the effect of various warm-up devices on the BV of female intercollegiate softball players and compare the results with those of male baseball players. A secondary purpose was to evaluate 2 new commercially available resistance devices as warm-up aids. Nineteen Division I intercollegiate softball players (age = 19.8 ± 1.2 years, height = 167.0 ± 4.7 cm, body mass = 69.2 ± 8.6 kg, lean body mass = 49.6 ± 3.6 kg, % body fat = 27.9 ± 5.9) participated in a warm-up with 1 of 8 resistance devices on separate days. Each of the 8 testing sessions had players perform a standardized dynamic warm-up, 3 maximal dry swings mimicking their normal game swing with the assigned warm-up device, 2 comfortable dry swings with a standard 83.8-cm, 652-g (33-in., 23-oz) softball bat followed by 3 maximal game swings (20-second rest between swings) while hitting a softball off a batting tee with the same standard softball bat. Results indicated that there were no statistically significant differences in BV after using any of the 8 warm-up devices (510.3-2,721.5 g or 18-96 oz) similar to in previous baseball research. This indicates that the results for both male and female intercollegiate players are similar and that intercollegiate softball players can use any of the 8 warm-up devices in the on-deck circle and have similar BVs. However, similar to in other previous baseball research, it is not recommended that female intercollegiate softball players warm up with the popular commercial donut ring in the on-deck circle because it produced the slowest BV.     

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.     

Validity of a squash-specific test of multiple-sprint ability

We examined the validity and reproducibility of a squash-specific multiple-sprint test. Eight male squash and 8 male soccer players performed Baker's 8 × 40-m sprints and a squash-specific-multiple-sprint test on separate days. The sum of individual sprint times in each test was recorded. Six squash and 6 soccer players repeated the tests 7 days later to assess reproducibility using intraclass correlation. In addition, 2 England Squash coaches independently ranked the squash players using knowledge of the player and recent performances in local leagues. Performance on the squash-specific (r = 0.97 and 0.90) and Baker's test (r = 0.95 and 0.83) was reproducible in squash and soccer players, respectively, and did not differ on Baker's test (mean ± SD 72.9 ± 3.9 and 72.9 ± 2.8 seconds for squash and soccer players, p = 0.969, effect size = 0.03). Squash players (232 ± 32 seconds) outperformed soccer players (264 ± 14 seconds) on the squash-specific test (p = 0.02, effect size = 1.39). Performance on Baker's and the squash-specific test were related in squash players (r = 0.98, p < 0.001) but not in soccer players (r = -0.08, p = 0.87). Squash-player rank correlated with performance on the squash-specific (ρ = 0.79, p = 0.02) but not the Baker's test (ρ = 0.55, p = 0.16). The squash-specific test discriminated between groups with similar non-sport-specific multiple-sprint ability and in squash players. In conjunction with the relationship between test performances, the results suggest that the squash-specific test is a valid and reproducible measure of multiple-sprint ability in squash players and could be used for assessing and tracking training-induced changes in multiple-sprint ability.     

Effect of various warm-up devices on bat velocity of intercollegiate baseball players

A variety of warm-up devices are available to baseball players to use before their game at-bat. Past baseball research evaluating warm-up devices indicates that implements that are ±12% of standard game bat weight produce the greatest bat velocities for high school and intercollegiate players. The purpose of this study was to examine the effect of various warm-up devices on bat velocity (BV) of intercollegiate baseball players. Twenty-two Division I intercollegiate baseball players (age = 20.0 ± 1.5 years, height = 182.6 ± 8.3 cm, body mass = 91.4 ± 11.4 kg, lean body mass = 78.8 ± 8.9 kg, % body fat = 13.6 ± 3.8) participated in a warm-up with 1 of 10 weighted devices on separate days. Each of the 10 testing sessions consisted of a standardized warm-up, 3 dry swings as hard as possible with the assigned warm-up device, 2 comfortable dry swings with a standard game baseball bat followed by 3 game swings (20-second rest between swings) while hitting a baseball off of a batting tee with the same standard game baseball bat. Results indicated that there were no statistically significant differences in BV after using any of the 10 warm-up devices. For male intercollegiate baseball players, results indicate that warm-up devices varying from 623.7 to 2,721.5 g (22-96 oz.) did not change mean BV of a standard game baseball bat, suggesting that intercollegiate players can use any of the 10 warm-up devices in the on-deck circle and maintain their BV. Therefore, personal preference as to which warm-up implement to use in the on-deck circle is advised.     

The impact of different warm-up protocols on vertical jump performance in male collegiate athletes

The purpose of this study was to compare the impact of different types of warm-up on countermovement vertical jump (VJ) performance. Sixty-four male Division I collegiate football players completed a pretest for VJ height. The participants were then randomly assigned to a warm-up only condition, a warm-up plus static stretching condition, a warm-up plus dynamic stretching condition, or a warm-up plus dynamic flexibility condition. VJ performance was tested immediately after the completion of the warm-up. The results showed that there was a significant difference (P < .05) in VJ performance between the warm-up groups. Posttest jump performance improved in all groups; however, the mean for the static stretching group was significantly lower than the means for the other 3 groups. The static stretching negated the benefits gained from a general warm-up when performed immediately before a VJ test.     

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.     

Do force-time and power-time measures in a loaded jump squat differentiate between speed performance and playing level in elite and elite junior rugby union players?

The purpose of this study was to investigate the discriminative ability of rebound jump squat force-time and power-time measures in differentiating speed performance and competition level in elite and elite junior rugby union players. Forty professional rugby union players performed 3 rebound jump squats with an external load of 40 kg from which a number of force-time and power-time variables were acquired and analyzed. Additionally, players performed 3 sprints over 30 m with timing gates at 5, 10, and 30 m. Significant differences (p < 0.05) between the fastest 20 and slowest 20 athletes, and elite (n = 25) and elite junior (n = 15) players in speed and force-time and power-time variables were determined using independent sample t-tests. The fastest and slowest sprinters over 10 m differed in peak power (PP) expressed relative to body weight. Over 30 m, there were significant differences in peak velocity and relative PP and rate of power development. There was no significant difference in speed over any distance between elite and elite junior rugby union players; however, a number of force and power variables including peak force, PP, force at 100 milliseconds from minimum force, and force and impulse 200 milliseconds from minimum force were significantly (p < 0.05) different between playing levels. Although only power values expressed relative to body weight were able to differentiate speed performance, both absolute and relative force and power values differentiated playing levels in professional rugby union players. For speed development in rugby union players, training strategies should aim to optimize the athlete's power to weight ratio, and lower body resistance training should focus on movement velocity. For player development to transition elite junior players to elite status, adding lean mass is likely to be most beneficial.     

Physiological and anthropometric correlates of tackling ability in junior elite and subelite rugby league players

This study investigated the tackling ability of junior elite and subelite rugby league players, and determined the relationship between selected physiological and anthropometric characteristics and tackling ability in these athletes. Twenty-eight junior elite (mean ± SD age, 16.0 ± 0.2 years) and 13 junior subelite (mean ± SD age, 15.9 ± 0.6 years) 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 (stature, body mass, and sum of 7 skinfolds), acceleration (10-m sprint), change of direction speed (505 test), and lower body muscular power (vertical jump). Junior elite players had significantly greater (p < 0.05) tackling proficiency than junior subelite players (65.7 ± 12.5 vs. 54.3 ± 16.8%). Junior elite players tended to be taller, heavier, leaner, and have greater acceleration, change of direction speed, and muscular power, than the junior subelite players. The strongest individual correlates of tackling ability were acceleration (r = 0.60, p < 0.001) and lower body muscular power (r = 0.38, p < 0.05). When multiple linear regression analysis was performed to determine which of the physiological and anthropometric characteristics predicted tackling ability, fast acceleration was the only variable that contributed significantly (r2 = 0.24, p < 0.01) to the predictive model. These findings demonstrate that fast acceleration, and to a lesser extent, lower body muscular power contribute to effective tackling ability in junior rugby league players. From a practical perspective, strength and conditioning coaches should emphasize the development of acceleration and lower body muscular power qualities to improve tackling ability in junior rugby league players.     

Maximal strength, number of repetitions, and total volume are differently affected by static-, ballistic-, and proprioceptive neuromuscular facilitation stretching

ABSTRACT: Barroso, R, Tricoli, V, dos Santos Gil, S, Ugrinowitsch, C, and Roschel, H. Maximal strength, number of repetitions, and total volume are differently affected by static-, ballistic-, and proprioceptive neuromuscular facilitation stretching. J Strength Cond Res 26(9): 2432-2437, 2012-Stretching exercises have been traditionally incorporated into warm-up routines before training sessions and sport events. However, the effects of stretching on maximal strength and strength endurance performance seem to depend on the type of stretching employed. The objective of this study was to compare the effects of static stretching (SS), ballistic stretching (BS), and proprioceptive neuromuscular facilitation (PNF) stretching on maximal strength, number of repetitions at a submaximal load, and total volume (i.e., number of repetitions × external load) in a multiple-set resistance training bout. Twelve strength-trained men (20.4 ± 4.5 years, 67.9 ± 6.3 kg, 173.3 ± 8.5 cm) volunteered to participate in this study. All of the subjects completed 8 experimental sessions. Four experimental sessions were designed to test maximal strength in the leg press (i.e., 1 repetition maximum [1RM]) after each stretching condition (SS, BS, PNF, or no-stretching [NS]). During the other 4 sessions, the number of repetitions performed at 80% 1RM was assessed after each stretching condition. All of the stretching protocols significantly improved the range of motion in the sit-and-reach test when compared with NS. Further, PNF induced greater changes in the sit-and-reach test than BS did (4.7 ± 1.6, 2.9 ± 1.5, and 1.9 ± 1.4 cm for PNF, SS, and BS, respectively). Leg press 1RM values were decreased only after the PNF condition (5.5%, p < 0.001). All the stretching protocols significantly reduced the number of repetitions (SS: 20.8%, p < 0.001; BS: 17.8%, p = 0.01; PNF: 22.7%, p < 0.001) and total volume (SS: 20.4%, p < 0.001; BS: 17.9%, p = 0.01; PNF: 22.4%, p < 0.001) when compared with NS. The results from this study suggest that, to avoid a decrease in both the number of repetitions and total volume, stretching exercises should not be performed before a resistance training session. Additionally, strength-trained individuals may experience reduced maximal dynamic strength after PNF stretching.     

Performance and reference data in the jump squat at different relative loads in elite sprinters,rugby players,and soccer players

The aims of this study were to compare the outcomes and provide reference data for a set of barbell mechanical parameters collected via a linear velocity transducer in 126 male sprinters (n = 62), rugby players (n = 32), and soccer players (n = 32). Bar-velocity, bar-force, and bar-power outputs were assessed in the jump-squat exercise with jump-squat height determined from bar-peak velocity. The test started at a load of 40% of the athletes’ body mass (BM), and a load of 10% of BM was gradually added until a clear decrement in the bar power was observed. Comparisons of bar variables among the three sports were performed using a one-way analysis of variance. Relative measures of bar velocity, force, and power, and jump-squat height were significantly higher in sprinters than in rugby (difference ranging between 5 and 35%) and soccer (difference ranging between 5 and 60%) players across all loads (40–110% of BM). Rugby players exhibited higher absolute bar-power (mean difference = 22%) and bar-force (mean difference = 16%) values than soccer players, but these differences no longer existed when the data were adjusted for BM (mean difference = 2.5%). Sprinters optimized their bar-power production at significantly greater relative loads (%BM) than rugby (mean difference = 22%) and soccer players (mean difference = 25%); nonetheless, all groups generated their maximum bar-power outputs at similar bar velocities. For the first time, we provided reference values for the jump-squat exercise for three different bar-velocity measures (i.e., mean, mean propulsive, and peak velocity) for sprinters, rugby players, and soccer players, over a wide range of relative loads. Practitioners can use these reference values to monitor their athletes and compare them with top-level sprinters and team-sport players.     

Stretching has no effect on tennis serve performance

Stretching prior to vigorous physical activity has been shown to decrease high-force muscular performance, but little is known about the effect of stretching on speed and accuracy movements. Serving percentage and radar measurements of ball speed were studied to examine the acute effect of stretching on tennis serve performance. Eighty-three tennis players from beginning level to advanced volunteered to serve following traditional (T) warm-up and traditional plus stretching (S) conditions. Service speeds and service percentage of each condition were measured. Dependent t-tests showed nonsignificant effects of stretching on service speed (p = 0.06) or accuracy (p = 0.35), and this lack of an effect was similar for all skill levels, age, and gender. The large sample and good statistical power in this study indicated that these observations are not likely type II errors. There was no short-term effect of stretching in the warm-up on the tennis serve performance of adult players, so adding stretching to the traditional 5-minute warm-up in tennis does not affect serve performance.