Acute effects of different warm-up protocols with and without a weighted vest on jumping performance in athletic women

The purpose of this study was to examine the acute effects of 3 different warm-up protocols with and without a weighted vest on vertical jump (VJ) and long jump (LJ) performance in athletic women. Sixteen subjects (19.7 +/- 1.4 years, 67.0 +/- 10.7 kg, 165.7 +/- 11.4 cm) participated in 3 testing sessions in random order on 3 nonconsecutive days. Prior to the testing of the VJ and LJ, the subjects performed 1 of the following 10-minute warm-up protocols: (a) low- to moderate-intensity stationary cycling followed by 4 lower-body static stretches (SS) (3 x 20 seconds); (b) 12 moderate- to high-intensity dynamic exercises (DY); and (c) the same 12 dynamic exercises with a weighted vest (10% of body mass) worn for the last 4 exercises (DYV). Analysis of the data revealed that VJ performance was significantly greater (p < 0.05) following DYV (43.9 +/- 6.7 cm) and DY (43.6 +/- 6.5 cm) as compared to SS (41.7 +/- 6.0 cm). Long jump performance was significantly greater (p < 0.05) following DYV (186.8 +/- 19.5 cm) as compared to DY (182.2 +/- 19.1 cm), which in turn was significantly greater (p < 0.05) than performance following SS (177.2 +/- 18.8 cm). Warm-up protocols that include dynamic exercise may be a viable method of enhancing jumping performance in athletic women as compared to stationary cycling and static stretching. In addition, these data suggest that it may be desirable for athletic women to perform dynamic exercises with a weighted vest on some movements prior to the performance of the long jump.     

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.     

The effects of proprioceptive neuromuscular facilitation and dynamic stretching techniques on vertical jump performance

The purpose of this study was to investigate the effects of 3 different warm-ups on vertical jump performance. The warm-ups included a 600-m jog, a 600-m jog followed by a dynamic stretching routine, and a 600-m jog followed by a proprioceptive neuromuscular facilitation (PNF) routine. A second purpose was to determine whether the effects of the warm-ups on vertical jump performance varied by gender. Sixty-eight men and women NCAA Division I athletes from North Dakota State University performed 3 vertical jumps on a Just Jump pad after each of the 3 warm-up routines. The subjects were split into 6 groups and rotated between 3 warm-up routines, completing 1 routine each day in a random order. The results of the 1-way repeated measures analysis of variance showed no significant differences in the combined (p = 0.927), men's (p = 0.798), or women's (p = 0.978) results. The results of this study showed that 3 different warm-ups did not have a significant affect on vertical jumping. The results also showed there were no gender differences between the 3 different warm-ups.     

Surface electromyographic assessment of the effect of dynamic activity and dynamic activity with static stretching of the gastrocnemius on vertical jump performance

The purpose of this study was to investigate the effects of dynamic activity and dynamic activity/static stretching of the gastrocnemius muscle on vertical jump (VJ) performance. Additionally, muscle activity was recorded using electromyography. Thirteen healthy adults (7 men and 6 women) with a mean age of 26 +/- 4 years served as subjects. The average jump height and muscle activity from 3 separate maximal VJ attempts were performed at the start of each session to be used as baseline measures using the Kistler force plate and the Noraxon telemetry EMG unit. Subjects then performed 1 of 2 protocols: dynamic activity only or dynamic activity with static stretching. Each protocol was followed by 3 maximal VJ trials. Average VJ height was analyzed using a 2 (time: pre, post) x 2 (prejump protocol: dynamic activity, dynamic activity + stretching) analysis of variance with repeated measures on both factors. A paired-samples t-test was used to compare the intraday difference scores for EMG activity between the 2 conditions. Jump height was not influenced by the interaction of pre-post and protocol (p = 0.0146. There was no difference for the main effects of time (p = 0.274) and pre-jump protocol (p = 0.595). Gastrocnemius muscle activity was likewise not different for the 2 prejump protocols (p = 0.413). The results from this study imply that the use of static stretching in combination with dynamic activity of the gastrocnemius muscle does not appear to have an adverse affect on VJ height performance. The practical importance concerns the warm-up routine that coaches and athletes employ; that is, they may want to consider including an aerobic component when statically stretching the gastrocnemius immediately prior to a vertical jumping event.     

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 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.     

A dynamic warm-up model increases quadriceps strength and hamstring flexibility

Research suggests that static stretching can negatively influence muscle strength and power and may result in decreased functional performance. The dynamic warm-up (DWU) is a common alternative to static stretching before physical activity, but there is limited research investigating the effects of a DWU. The purpose of this study was to compare the acute effects of a DWU and static stretching warm-up (SWU) on muscle flexibility, strength, and vertical jump using a randomized controlled trial design. Forty-five volunteers were randomly assigned into a control (CON), SWU, or DWU group. All participants rode a stationary bicycle for 5 minutes and completed a 10-minute warm-up protocol. During this protocol, the DWU group performed dynamic stretching and running, the SWU group performed static stretching, and the CON group rested. Dependent variables were measured immediately before and after the warm-up protocol. A digital inclinometer measured flexibility (degrees) for the hamstrings, quadriceps, and hip flexor muscles. An isokinetic dynamometer measured concentric and eccentric peak torque (N·m/kg) for the hamstrings and quadriceps. A force plate was used to measure vertical jump height (meters) and power (watts). In the DWU group, there was a significant increase in hamstring flexibility (pretest: 26.4 ± 13.5°, posttest: 16.9 ± 9.4°; p < .0001) and eccentric quadriceps peak torque (pretest: 2.49 ± 0.83 N·m/kg, posttest: 2.78 ± 0.69 N·m/kg; p = 0.04). The CON and SWU did not significantly affect any flexibility, strength, or vertical jump measures (p > 0.05). The DWU significantly improved eccentric quadriceps strength and hamstrings flexibility, whereas the SWU did not facilitate any positive or negative changes in muscle flexibility, strength, power, or vertical jump. Therefore, the DWU may be a better preactivity warm-up choice than an SWU.     

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.     

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.     

Effects of drop jumps added to the warm-up of elite sport athletes with a high capacity for explosive force development

The purpose of this study was to evaluate the immediate influence of eccentric muscle action on vertical jump performance in athletes performing sports with a high demand of explosive force development. In this randomized, controlled crossover trial, 13 Swiss elite athletes (national team members in ski jump, ski alpine, snowboard freestyle and alpine, ski freestyle, and gymnastics) with a mean age of 22 years (range 20-28) were randomized into 2 groups. After a semistandardized warm-up, group 1 did 5 jumps from a height of 60 cm, landing with active stabilization in 90 degrees knee flexion. One minute after these modified drop jumps, they performed 3 single squat jumps (SJ) and 3 single countermovement jumps (CMJ) on a force platform. The athletes repeated the procedure after 1 hour without the modified drop jumps. In a crossover manner, group 2 did the first warm-up without and the second warm-up with the modified drop jumps. Differences of the performance (jump height and maximal power) between the different warm-ups were the main outcomes. The mean absolute power and absolute height (without drop jumps) were CMJ 54.9 W.kg(-1) (SD = 4.1), SJ 55.0 W.kg(-1) (SD = 5.1), CMJ 44.1 cm (SD = 4.1), and SJ 40.8 cm (SD = 4.1). A consistent tendency for improvement with added drop jumps to the warm-up routine was observed compared with warm-up without drop jumps: maximal power CMJ +1.02 W.kg(-1) (95% confidence interval [CI] = +0.03 to +2.38), p = 0.045; maximal power SJ +0.8 W.kg(-1) (95% CI = -0.34 to +2.02), p = 0.148; jump height CMJ +0.48 cm (95% CI = -0.26 to +1.2), p = 0.182; SJ +0.73 cm (95% CI = -0.36 to +1.18), p = 0.169. Athletes could add modified drop jumps to the warm-up before competitions to improve explosive force development.     

The best warm-up for the vertical jump in college-age athletic men

The purpose of this study was to determine the effectiveness of specific and nonspecific warm-ups on the vertical jump test performed by athletic men. Twenty-nine men (18-23 years) in athletics (speed positions in football) performed vertical jump tests on 4 separate days after completing 4 different warm-up protocols. The 4 warm-up protocols were (a) submaximal jump warm-up, (b) weighted jump warm-up, (c) stretching warm-up, and (d) no warm-up. The weighted jump warm-up protocol required 5 countermovement jumps onto a box, with the athletes holding dumbbells equaling 10% of their body weight. The submaximal jump warm-up protocol required the athletes to perform 5 countermovement jumps at 75% intensity of their past maximum vertical jump score. The stretching warm-up protocol required the athletes to perform 14 different stretches, each held for 20 seconds. The no warm-up protocol required the athletes to perform no activity prior to being tested. Three vertical jumps were measured following each warm-up; the score for analysis was the best jump. The data were analyzed with a repeated measures analysis of variance and Bonferroni post hoc tests. The Bonferroni post hoc tests showed a significant difference (p < 0.001) between the weighted jump warm-up and all other warm-ups. The effect size was 0.380 and the power was 1.00 for the statistical analyses. We concluded that utilizing a weighted resistance warm-up would produce the greatest benefit when performing the vertical jump test.     

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 static and ballistic stretching on measures of strength and power

Preactivity stretching is commonly performed by athletes as part of their warm-up routine. However, the most recent literature questions the effectiveness of preactivity stretching. One limitation of this research is that the stretching duration is not realistic for most athletes. Therefore, the purpose of this study was to determine the effects of a practical duration of acute static and ballistic stretching on vertical jump (VJ), lower-extremity power, and quadriceps and hamstring torque. Twenty-four subjects performed a 5-minute warm-up followed by each of the following three conditions on separate days with order counterbalanced: static stretching, ballistic stretching, or no-stretch control condition. Vertical jump was determined with the Vertec VJ system and was also calculated from the ground-reaction forces collected from a Kistler force plate, which also were used to calculate power. Torque output of the quadriceps and hamstrings was measured through knee extension and flexion on the Biodex System 3 Dynamometer at 60 degrees x s(-1). Data normalized for body weight were analyzed using five separate, 3 (stretch condition) x 2 (gender) analysis-of-variance procedures with repeated measures on the factor of stretch condition. The gender x stretch interaction was not significant for any of the four measures, suggesting that the stretching conditions did not affect men and women differently. The results of this study reveal that static and ballistic stretching did not affect VJ, or torque output for the quadriceps and hamstrings. Despite no adverse effect on VJ, stretching did cause a decrease in lower-extremity power, which was surprising. Because of the mixed results, strength coaches would be better served to use dynamic stretching before activity; this has been consistently supported by the literature.     

Acute effects of heavy preloading on vertical and horizontal jump performance

The purpose of this study was to investigate the acute effects of a heavy dynamic preload, consisting of 1 set of 5 repetition maximum (5RM) back squats, on countermovement vertical jump (VJ) and horizontal jump (HJ) performance. The study also investigated the ability of subjects to learn to apply the effects of the preload over subsequent training sessions. Nineteen (N = 19) resistance-trained men (age = 25.0 +/- 4.8 years; weight = 79.3 +/- 6.6 kg) participated in the study. Each subject took part in 4 practice and 4 testing sessions. The 4 practice sessions were included to allow for any learning effects of VJ and HJ to stabilize and to establish a true 5RM back squat. The 4 testing sessions were included to see if subjects were able to capitalize on the repeat exposure to the protocol. One practice session consisted of a 10-minute warm-up (5 minutes of cycling and 5 minutes of stretching), 2 sets of VJ and HJ (each set of VJ and HJ consisted of 4 jump repetitions) with a 5-minute rest between sets, progressive 5RM back squat evaluation, and 2 final sets of VJ and HJ. Both VJ and HJ increased approximately 2% over the 4 practice sessions, and 5RM back squat strength improved from 164.2 +/- 25.1 kg to 196.9 +/- 23.0 kg (p < or = 0.05). The 4 testing sessions each consisted of the standardized warm-up, 1 set of 4 VJs and HJs, a 5-minute rest, 5RM back squat, a 5-minute rest, and the final set of VJs and HJs. Pre- and post-5RM VJ and HJ order was randomly assigned. The results indicated no significant differences occurred between the mean or maximal values for either VJ or HJ as a consequence of the dynamic preload exercise. In addition, the results reflected an inability of subjects to benefit from the repeated exposure to the heavy dynamic preload exercise protocol.     

Sling exercise and traditional warm-up have similar effects on the velocity and accuracy of throwing

Throwing is a complex motion that involves the entire body and often puts an inordinate amount of stress on the shoulder and the arm. Warm-up prepares the body for work and can enhance performance. Sling-based exercise (SE) has been theorized to activate muscles, particularly the stabilizers, in a manner beneficial for preactivity warm-up, yet this hypothesis has not been tested. Our purpose was to determine if a warm-up using SE would increase throwing velocity and accuracy compared to a traditional, thrower's 10 warm-up program. Division I baseball players (nonpitchers) (16 men, age: 19.6 ± 1.3, height: 184.2 ± 6.2 cm, mass: 76.9 ± 19.2 kg) volunteered to participate in this crossover study. All subjects underwent both a warm-up routine using a traditional method (Thrower's 10 exercises) and a warm-up routine using closed kinetic chain SE methods (RedCord) on different days separated by 72 hours. Ball velocity and accuracy measures were obtained on 10 throws after either the traditional and SE warm-up regimens. Velocity was recorded using a standard Juggs radar gun (JUGS; Tualatin, OR, USA). Accuracy was recorded using a custom accuracy target. An Analysis of covariance was performed, with the number of throws recorded before the testing was used as a covariate and p < 0.05 was set a priori. There were no statistical differences between the SE warm-up and Thrower's 10 warm-up for throwing velocity (SE: 74.7 ± 7.5 mph, Thrower's 10: 74.6 ± 7.3 mph p = 0.874) or accuracy (SE: 115.6 ± 53.7 cm, Thrower's 10: 91.8 ± 55 cm, p = 0.136). Warming up with SE produced equivalent throwing velocity and accuracy compared to the Thrower's 10 warm-up method. Thus, SE provides an alternative to traditional warm-up.     

Influence of closed skill and open skill warm-ups on the performance of speed, change of direction speed, vertical jump, and reactive agility in team sport athletes

In this study, we evaluated the efficacy of two different dynamic warm-up conditions, one that was inclusive of open skills (i.e., reactive movements) and one that included only preplanned dynamic activities (i.e., closed skills) on the performance of speed, change of direction speed, vertical jump, and reactive agility in team sport athletes. Fourteen (six male, eight female) junior (mean +/- SD age, 16.3 +/- 0.7 year) basketball players participated in this study. Testing was conducted on 2 separate days using a within-subjects cross-over study design. Each athlete performed a standardized 7-minute warm-up consisting of general dynamic movements and stretching. After the general warm-up, athletes were randomly allocated into one of two groups that performed a dynamic 15-minute warm-up consisting entirely of open or closed skills. Each of the warm-up conditions consisted of five activities of 3 minute duration. At the completion of the warm-up protocol, players completed assessments of reactive agility, speed (5-, 10-, and 20-m sprints), change of direction speed (T-test), and vertical jump. No significant differences (p > 0.05) were detected among warm-up conditions for speed, vertical jump, change of direction speed, and reactive agility performances. The results of this study demonstrate that either open skill or closed skill warm-ups can be used effectively for team sport athletes without compromising performance on open skill and closed skill tasks.     

Relative net vertical impulse determines jumping performance

The purpose of this investigation was to determine the relationship between relative net vertical impulse and jump height in a countermovement jump and static jump performed to varying squat depths. Ten college-aged males with 2 years of jumping experience participated in this investigation (age: 23.3 ± 1.5 years; height: 176.7 ± 4.5 cm; body mass: 84.4 ± 10.1 kg). Subjects performed a series of static jumps and countermovement jumps in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth (static jump depth = 0.38 ± 0.08 m, countermovement jump depth = 0.49 ± 0.06 m). During the concentric phase of each jump, peak force, peak velocity, peak power, jump height, and net vertical impulse were recorded and analyzed. Net vertical impulse was divided by body mass to produce relative net vertical impulse. Increasing squat depth corresponded to a decrease in peak force and an increase in jump height and relative net vertical impulse for both static jump and countermovement jump. Across all depths, relative net vertical impulse was statistically significantly correlated to jump height in the static jump (r = .9337, p < .0001, power = 1.000) and countermovement jump (r = .925, p < .0001, power = 1.000). Across all depths, peak force was negatively correlated to jump height in the static jump (r = -0.3947, p = .0018, power = 0.8831) and countermovement jump (r = -0.4080, p = .0012, power = 0.9050). These results indicate that relative net vertical impulse can be used to assess vertical jump performance, regardless of initial squat depth, and that peak force may not be the best measure to assess vertical jump performance.     

The effects of two stretching protocols on the reactive strength index in female soccer and rugby players

The purpose of this study was to investigate the effects of 2 stretching protocols on stretch-shortening cycle performance in female Division I soccer players and female club rugby players. Fifteen soccer and rugby players (20.1 ± 5.9 years, 170.5 ± 14.2 cm, 70.4 ± 22.3 kg) participated in 3 test sessions with different treatments. The first treatment involved a warm-up of 10 minutes of exercise on a cycle ergometer (warm-up only [WO]), the second was this warm-up followed by static stretching (SS), and the third was this warm-up followed by dynamic stretching (DS). The treatments were administered randomly to negate an order effect. Each treatment was immediately followed by a reactive strength index (RSI) test requiring the athletes to drop off a box (45 cm in height) on to a force plate and upon landing immediately jump into the air while minimizing contact time (CT, milliseconds) and maximizing flight time (FT, milliseconds). The RSI was FT: CT. Repeated measures analysis of variance indicated that a significant treatment effect existed for RSI (F = 7.95, 2; p = 0.002) and FT (F = 7.43, 2; p = 0.003) but no significant effect for CT (F = 1.53, 2; p = 0.235). The RSI and FT were significantly greater in DS compared with that in SS and WO. Dynamic stretching is the preferred warm-up before an athletic event involving considerable jumping.     

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.     

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.