Countermovement Vertical Jump Height Research Articles

Changes in Countermovement Vertical Jump Force-Time Metrics Across Different Competitive Levels in Women’s Volleyball

As one of the most fundamental skills in volleyball, the countermovement vertical jump (CVJ) has been commonly implemented as a non-invasive and time-efficient method for the assessment of lower-body neuromuscular function. The purpose of the present study was to examine differences in CVJ performance between three different competitive levels in female volleyball players (i.e., national team [n=20], professional league [n=16], collegiate [n=16]). While standing on a uni-axial force plate system sampling at 1000 Hz, athletes performed three maximal-effort CVJs with no arm swing (i.e., hands on the hips during the entire movement). Each jump was separated by a 10-15 second rest interval to minimize the possible influence of fatigue. Significantly greater eccentric braking impulse, peak velocity, peak force, mean and peak power, vertical jump height, reactive strength index-modified, countermovement depth, and shorter braking phase, eccentric duration, and contraction times were observed for the national team and professional players when compared to collegiate athletes. Also, national team players demonstrated significantly greater eccentric braking impulse, peak velocity, mean and peak power, reactive strength index-modified, and countermovement depth than professional volleyball players. However, during the concentric phase of the CVJ, the only significant differences observed were between national team players and collegiate athletes, where national team players exhibited significantly greater peak velocity, impulse, and mean and peak power. Thus, it can be concluded that higher-level players may be more capable of effectively utilizing the eccentric phase of the CVJ and executing the stretch-shortening action more rapidly, which contributes to better CVJ height.

Effects of Age and Playing Position on Field-Based Physical Fitness Measures in Adolescent Female Netball Players.

This cross-sectional study investigated the impact of age and playing position, controlling for maturity, on physical fitness indicators in 303 adolescent female netball players aged 12.0 to 15.9 years. Assessments included estimated maximal oxygen uptake (VO2max) via the 20 m shuttle run test, 10 m and 20 m sprints, change of direction speed (CODS) using the 505 test, and muscle power via the medicine ball chest throw (MBCT) and countermovement vertical jump (CMJ). Participants were grouped by age (12 to 15 years) and playing position (non-circle and circle players), with age at peak height velocity as a covariate for maturity. Results revealed that, at 15 years, CMJ height was greater than at 12 years and 13 years (p < 0.05, partial η2 = 0.048). MBCT distance increased across age groups (p < 0.01, partial η2 = 0.323). Age had no impact on sprints, VO2max, or CODS. Non-circle players outperformed circle players in the 10 m sprint (p = 0.042, partial η2 = 0.016) and 20 m sprints (p = 0.010, partial η2 = 0.025) and displayed higher VO2max (p < 0.001, partial η2 = 0.036). Circle players were taller (p = 0.046, partial η2 = 0.014) and heavier (p < 0.001, partial η2 = 0.040) than non-circle players. Playing positions showed no differences in CMJ and MBCT. In adolescent female netball players, only muscle power is influenced by age, while non-circle players exhibit superior aerobic fitness and speed compared to circle players. Coaches may be able to utilize the distinct age and playing position traits of adolescent netballers to inform player selection and design targeted training programs.

DIFFERENCES IN BASELINE FITNESS LEVELS OF NROTC MIDSHIPMEN BETWEEN FALL 2020 AND FALL 2021

College students in Reserve Officer Training Corps (ROTC) programs must meet physical fitness standards in order to commission as a military officer. While physical fitness training is required during the semester, cadets are expected to continue training during the summer break. However, nationwide closures due to COVID-19 during the spring and summer of 2020 may have impeded training abilities and thereby fitness status of incoming cadets in Fall 2020. PURPOSE: The purpose of this analysis was to compare fitness levels of Naval ROTC (NROTC) midshipmen upon return to campus in Fall 2020 (FA20) compared to Fall 2021 (FA21). METHODS: NROTC midshipmen completed a battery of fitness tests within one month of arrival to campus in FA20 (N = 70; Age = 21 ± 2; 89% male) and repeated testing in FA21 (N = 85; Age = 20 ± 2; 80% male). Body mass index (BMI; kg/m2) was calculated from height and weight metrics. Performance tests consisted of a countermovement vertical jump (CMJ) and the 20-meter shuttle run test to estimate VO2max. Linear mixed effects models were used to determine overall battalion differences in BMI, CMJ height, and VO2max FA20 compared to FA21 with an alpha level of 0.05 to determine statistical significance. RESULTS: While there were no differences in BMI (P = 0.25), 47.2% of midshipmen were classified as ‘overweight’ in FA20 compared to 43.6 % in FA21. CMJ height was significantly higher at FA21 than FA20 (±1.4 cm; P = 0.02) but there were no differences in estimated VO2max (FA20 = 48.8 ± 5.2 ml/kg/min; FA21 = 49.2 ± 5.4 ml/kg/min; P = 0.45). CONCLUSIONS: While there were no differences in aerobic fitness, anaerobic fitness appeared to be higher in FA21. While it is not possible to determine the direct impacts of COVID-19 on fitness levels, it is plausible that pandemic-associated closures prevented strength and power training due to lack of fitness facilities and associated equipment, leading to decreased peak power measured as CMJ height. ROTC programs across the country may need to adjust their training programs upon return to in-person activities to ensure all cadets meet the required fitness standards, especially those related to strength and power.

Low-Volume High-Intensity Interval Training Sessions With Different Work–Recovery Durations and Muscle Damage in Trained Men

ABSTRACT Purpose: This study compared the effect of low-volume high-intensity training (LV-HIIT) sessions with different work-recovery durations on muscle damage markers.Methods: Twenty-four trained adult males (22.3 ± 2.9 years; 24.6 ± 2.7 kg∙m-2) performed two LV-HIIT sessions (10 x 60 s and 20 x 30 s at 100% of maximal aerobic speed on treadmill (Vmax) interspersed with equal time passive recovery, respectively) in a randomized, counter-balanced order, separated by a 1-week interval. Delayed onset muscle soreness (DOMS) and countermovement vertical jump height (CVJH) performance were assessed before, and 24-h and 48-h post sessions.Results: Pressure-pain threshold (PPT), pressure-pain tolerance (PPTol) and perceived pain intensity (PPI) using pressure algometry assessed DOMS in the rectus rectus femoris, biceps femoris and gastroctemius. A non-significant session by time interaction for PPT, PPTol and PPI in all muscles analyzed was observed (all P > 0.260). Additionally, a non-significant session by time interaction was observed for CVJH performance (P = 0.836).Conclusion: LV-HIIT sessions with different work-recovery durations elicited non-significant changes on muscle damage markers following 24- and 48-h in trained males.

Effects of Short-term Plyometric Training on Countermovement Vertical Jump Height and Kinematics of Take-Off

Background: Countermovement vertical jump is a crucial skill in many sports. Plyometric training is a prevalent method to improve athletes' jumping ability. Objectives: The present study aimed to investigate the effect of a 6-week plyometric training on the kinematics of take-off and countermovement vertical jump height. Methods: Fifteen young, healthy male subjects performed plyometric exercises in three sessions per week for six weeks. Digital videos of pre-training and post-training jumps were captured. The Kinovea software was used to measure the kinematic parameters of take-off in the sagittal plane. Pre and post-training values were compared by paired sample t-test with the statistical significance level of P &lt; 0.05. Results: Post-training results showed a higher jump height (P &lt; 0.05), more flexed shoulder, and more extensive hip and knee at take-off (P &lt; 0.05). Also, while hip extension velocity was decreased, shoulder flexion and knee extension velocities were significantly increased (P &lt; 0.05). Conclusions: The 6-week plyometric training, including 720 jumps, improved shoulder flexion, and hip and knee extensions at take-off, resulting in high CMJ height. We employed plyometric training to improve the shoulder flexion and hip and knee extension velocities and increase CMJ height.

Effects of different training strategies with a weight vest on countermovement vertical jump and change-of-direction ability in male volleyball athletes.

Weight vest training (WVT) is a strategy used to improve the physical performance of athletes. The objective of this study was to determine the effects of different training strategies with weight vests on vertical jump and change-of-direction ability (CODA) in male volleyball athletes. Fifteen volleyball athletes (22.87±3.04 years, 83.22±10.84 kg, 1.86±0.69 m) participated in a six-week training programme and were randomized into three groups: weight vest plyometric training (WPG), weight vest technical-tactical training (WTG) and a control group (CG). The additional weight of 7.5% of individual body mass was employed in the experimental groups. Before and after the WVT, athletes performed countermovement vertical jump (CMJ) and CODA (t-test) tests. Two-way ANOVA with repeated measures showed that CMJ height increased in all training groups (P<0.05), with the WTG inducing greater CMJ height gains in comparison to the CG (P<0.05). According to magnitude-based inference, the effects of the WTG strategy were "very likely" beneficial for the CMJ compared to the CG. In addition, t-test time decreased similarly among the three training groups (P<0.05). The results suggested that WVT may be incorporated in a volleyball training routine as an effective strategy for improving the CMJ performance in male volleyball athletes.

Effects of Integrative Neuromuscular Training on Motor Performance in Prepubertal Soccer Players.

Menezes, GB, Alexandre, DR, Pinto, JC, Assis, TV, Faigenbaum, AD, and Mortatti, AL. Effects of integrative neuromuscular training on motor performance in prepubertal soccer players. J Strength Cond Res 36(6): 1667-1674, 2022-The present study examined the effects of integrative neuromuscular training (INT) on motor performance in prepubertal soccer players. Subjects were randomly assigned to the experimental group (INT; n = 20, age: 8.2 ± 1.2 years; body mass: 28.4 ± 6.4 kg; height: 1.3 ± 0.1 m) or the control group (CON; n = 18, age: 8.5 ± 1.3 years; body mass: 32.8 ± 8.9 kg; height: 1.3 ± 0.1 m). Integrative neuromuscular training program was performed twice per week during the 12-week training intervention. Balance, flexibility, countermovement vertical jump height (CVJH), sprint speed, and change of direction speed (CODS) were assessed in both groups at baseline, sixth week and 12th week. A mixed model repeated measures analysis of variance was used to examine the group changes in performance for each variable. There was a time effect for balance in the INT from pre to 12th weeks (p < 0.001, g = 0.72), and from 6th to 12th weeks (p = 0.005, g = 0.34). An interaction effect for balance was also observed between INT and CON after the 12th week. A time effect in flexibility was observed in INT from baseline to 6th and 12th weeks (p = 0.02; g = 0.45 and p < 0.001; g = 0.71) and from 6 to 12th weeks (p = 0.003; g = 0.24). There was a time effect in CVJH, from baseline to 12th week and from 6th to 12th weeks (p < 0.05; g = 0.34 and g = 0.53, respectively). There was no significant between-group speed performance change. A time effect was found in CODS in INT, but only from baseline to 12th week (p = 0.02; g = 0.31). There were significant improvements in the percent change (Δ%) from baseline to 12 weeks (p < 0.05) for balance, flexibility, and CVJH in INT. These findings indicate that the addition of an INT program to soccer practice can improve selected motor performance skills in prepubertal soccer players.

Effects of Integrative Neuromuscular Training and Detraining on Countermovement Jump Performance in Youth Volleyball Players.

Nunes, ACCA, Cattuzzo, MT, Faigenbaum, AD, and Mortatti, AL. Effects of integrative neuromuscular training and detraining on countermovement jump performance in youth volleyball players. J Strength Cond Res 35(8): 2242-2247, 2021-The purpose of this study was to analyze the effect of integrative neuromuscular training (INT) on countermovement vertical jump height (CVJH) performance in youth volleyball players before and after a detraining period. Thirty-two novice volleyball players were cluster randomized into 2 groups: intervention group-INT (age: 13.1 ± 0.4 years; body mass: 55.3 ± 12.1 kg; and height: 161.1 ± 6.4 cm) and control group-CON (age: 12.8 ± 0.7 years; body mass: 51.8 ± 13.6 kg; and height: 160.1 ± 10.7 cm). The subjects were evaluated for somatic maturation (years from peak height velocity) and for CVJH performance at 4 time points during the 20-week study period: baseline, 6 weeks of INT, 12 weeks of INT, and 8 weeks after INT (detraining). The analysis used repeated-measures analysis of variance and Bonferroni post hoc test to identify possible differences in the CVJH delta in both groups. Spearman correlation was performed to verify the association between the values of the vertical jump tests and maturational levels found. The INT showed a significant improvement in the CVJH from baseline to 12 weeks and maintained training-induced gains after detraining period (p > 0.001). Significant increase in CVJH was found in the percentage of change (Δ%) from baseline to 6 weeks (p < 0.005), 12 weeks (p < 0.001), and detraining (p < 0.001) in INT compared with the CON. The results of this study indicate that INT was able to improve CVJH performance in novice youth volleyball players and these gains were sustained during the detraining period. These findings indicate that regular participation in supervised INT can enhance jumping performance in young volleyball players, and that this type of neuromuscular program may be particularly beneficial for youth with limited fundamental motor skill performance.

Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up.

Studies examining acute, high-speed movement performance enhancement following intense muscular contractions (frequently called "post-activation potentiation"; PAP) often impose a limited warm-up, compromizing external validity. In the present study, the effects on countermovement vertical jump (CMJ) performance of back squat exercises performed with or without elastic bands during warm-up were compared. After familiarization, fifteen active men visited the laboratory on two occasions under randomized, counterbalanced experimental squat warm-up conditions: (a) free-weight resistance (FWR) and (b) variable resistance (VR). After completing a comprehensive task-specific warm-up, three maximal CMJs were performed followed by three back squat repetitions completed at 85% of 1-RM using either FWR or VR Three CMJs were then performed 30seconds, 4minutes, 8minutes, and 12minutes later. During CMJ trials, hip, knee, and ankle joint kinematics, ground reaction force data and vastus medialis, vastus lateralis, and gluteus maximus electromyograms (EMG) were recorded simultaneously using 3D motion analysis, force platform, and EMG techniques, respectively. No change in any variable occurred after FWR (P>0.05). Significant increases (P<0.05) were detected at all time points following VR in CMJ height (5.3%-6.5%), peak power (4.4%-5.9%), rate of force development (12.9%-19.1%), peak concentric knee angular velocity (3.1%-4.1%), and mean concentric vastus lateralis EMG activity (27.5%-33.4%). The lack of effect of the free-weight conditioning contractions suggests that the comprehensive task-specific warm-up routine mitigated any further performance augmentation. However, the improved CMJ performance following the use of elastic bands is indicative that specific alterations in force-time properties of warm-up exercises may further improve performance.

Associations between Testosterone, Body Composition, and Performance Measures of strength and Power in Recreational, Resistance- Trained Men

Associations between Testosterone, Body Composition, and Performance Measures of strength and Power in Recreational, Resistance- Trained Men The objective of the current cross-sectional study was to determine whether relationships existed between testosterone (TEST), back squat (BS) one-repetition maximum (1RM), body composition, and power-oriented tests of horizontal ((standing long jump (SLJ)) and vertical ((countermovement vertical jump (CMVJ)) jumping ability in recreational, resistance-trained males. Twenty-nine men (mean ± SD; age 26.2 ± 4.5 years; height 176.6 ± 6.9 cm; weight 84.7 ± 11.7 kg; 15.2 ± 6.3 % body fat) participated. Total TEST, body composition, SLJ, CMVJ, and BS 1RM were assessed. Lower body power output was calculated from body mass and CMVJ height. Bivariate (Pearson) correlations were computed to determine significance (p<0.05). The 1RM BS-to-body-mass ratio was 1.80 ± 0.2. Total TEST was 34.3 ± 10.2 nmol•L-1. There were correlations between lean mass (LM) and peak power (r=0.48; p=0.01), LM and BS 1RM (r=0.64; p=0.001), BS 1RM and peak power (r=0.70, p=0.001), and CMVJ and SLJ (r=0.57, p=0.001). There were no correlations between TEST and performance measures (SLJ, r= -0.03; CMVJ, r= -0.18; 1RM BS, r= -0.21). Total TEST levels are not correlated with performance measures of lower body strength and power in this population; however, BS 1RM is correlated with lower body power and LM. TEST cannot be used to predict select measures of performance in a cross-sectional sample of recreational lifters, but consistent adherence to recreational resistance training may have a positive effect on SLJ and CMVJ performance.

The Influence of Athletic Status on the Passive Properties of the Muscle-Tendon Unit and Traditional Performance Measures in Division I Female Soccer Players and Nonathlete Controls

The purpose of this study was to determine if passive muscle-tendon properties of the posterior muscles of the hip and thigh and lower-body muscle power could discriminate between athletic status in division I female soccer athletes and nonathlete controls. Ten athletes (mean ± SE, age = 18.70 ± 0.34 years; mass = 64.61 ± 2.16 kg; height = 165.99 ± 1.46 cm; thigh muscle cross-sectional area = 94.08 ± 2.58 cm) and 11 nonathletes (mean ± SE, age = 19.64 ± 0.51 years; mass = 62.81 ± 2.60 kg; height = 162.44 ± 2.20 cm; thigh muscle cross-sectional area = 86.33 ± 2.81 cm) performed 2 instrumented straight-leg raise (iSLR) assessments using an isokinetic dynamometer programmed in passive mode to move the foot toward the head at 5°·s. During each iSLR, passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve, and maximum range of motion (ROM) was determined as the point of discomfort but not pain, as indicated by the participant. Lower-body power characteristics were assessed through a countermovement vertical jump (CMJ) test. The results indicated that phase 1 and 2 slopes, CMJ height, and peak power (Pmax) were significantly higher (p = 0.004-0.036) for the athletes compared with the nonathletes; however, maximum ROM was not different (p = 0.601) between groups. Significant relationships were also observed between phase 1 and 2 slopes, and CMJ height and Pmax (r = 0.483-0.827; p ≤ 0.001-0.027). These findings suggest that in addition to traditional power characteristics, passive stiffness may also be a sensitive and effective measure for discriminating athletes from nonathletes. Coaches and practitioners may use these findings when designing training programs aimed at increasing musculotendinous stiffness of the posterior hip and thigh muscles and to help identify athletes with high overall athletic potential.

The Acute Effect of a Commercial Bite-Aligning Mouthpiece on Strength and Power in Recreationally Trained Men

Because of the relative newness of mouthpieces, there are few investigations into using performance mouthpieces during sport and physical activity to substantiate claims of performance enhancement. The purpose of this study was to investigate the acute effect of a commercially available, noninjury preventive, performance mouthpiece on practical acute performance measures of power and strength. A within-subjects design was used to evaluate 21 (N = 21) recreationally trained college aged males on the performance of a maximum countermovement vertical jump (CMVJ) from a force platform and 1 repetition maximum (1RM) bench press exercise for the following conditions: with mouthpiece (MP) and without mouthpiece (noMP). Rate of force development (RFD) and peak vertical force (PF) were derived from force platform data. Statistical analysis revealed no significant differences between conditions for CMVJ height (p = 0.13), RFD at 200 ms (p = 0.09), PF (p = 0.08), and 1RM bench press (p = 0.45). These data indicate that the use of this particular jaw aligning mouthpiece specifically in an attempt to produce an ergogenic effect on performance is unwarranted.

The Effects of Resistance Training Prioritization in NCAA Division I Football Summer Training

Resistance training (RT) is an integral part of National Collegiate Athletic Association (NCAA) Division I Football performance programs. In the sport of football, there are several components that a strength and conditioning coach must be aware of. These include body mass, size, strength, power, speed, conditioning, and injury prevention, among others. The purpose of this study was to investigate if the RT component of a performance program could be prioritized for specific results using a nonlinear training model, grouping athletes by eligibility year. The NCAA Division I football student athletes were placed into 3 separate groups based on the playing year. All subjects participated in a 10-week, 4 days·week-1 off-season summer resistance training program. The training of group 1 (n = 20, age: 18.95 ± 0.76 years, height: 186.63 ± 7.21 cm, body mass: 97.66 ± 18.17 kg, playing year: 1.05 ± 0.22 years) prioritized hypertrophy-based RT to gain body mass. The training of group 2 (n = 20, age: 20.05 ± 1.05 years, height: 189.42 ± 5.49 cm, body mass: 106.99 ± 13.53 kg, and playing year: 2.35 ± 0.75 years) prioritized strength-based RT to gain strength. The training of group 3 (n = 20, age: 21.05 ± 1.10 years, height: 186.56 ± 6.73 cm, body mass: 109.8 ± 19.96 kg, playing year: 4.4 ± 0.50 years) prioritized power-based RT to gain power. Performance tests were evaluated during the first weeks of March (Spring) and August (Fall). The test measures included body mass (kilograms), 1-repetition maximum (1RM) bench press (kilograms), 1RM back squat (kilograms), 1RM power clean (kilograms), and countermovement vertical jump (CMVJ) height (centimeters). The primary findings of this investigation were as follows: group 1 saw significant increases in bench press maximum, back squat maximum, and power clean maximum (p ≤ 0.05). Group 2 saw significant increases in bench press maximum, back squat maximum, and power clean maximum (p ≤ 0.05). Group 3 saw a significant increase in power clean maximum (p ≤ 0.05). Group 1's significant increases were expected because of their low training age relatively shorter training history when compared with Groups 2 and 3. Group 1 did not see significant increases in body mass, with 7 out of 20 subjects being nonresponders. Group 2 and 3's significant increases were expected. Unexpectedly, no group saw significant increases in maximum CMVJ height. With so many factors that go into a football performance program contributing to football performance programing, it seems difficult to prioritize 1 RT goal over another without neglecting others during 10-week summer training program. Prioritization of strength appears to have the best overall affect on the RT portion of an off-season football performance program. Nonlinear periodization allows for the prioritization of 1 training goal without disregarding others with a smaller risk of neglecting other important components. This investigation showed that a performance program with a nonlinear model and prioritization on strength had produced the most desirable results.

Circadian rhythm effects on neuromuscular and sprint swimming performance

The aim of this study was to determine the effect of time-of-day on sprint swimming performance and on upper and lower body, maximum strength, and muscle power. Twelve well-trained junior swimmers (six male and six female) were tested for bench press (BP) maximum strength and muscle power, jump height countermovement vertical jump (CMJ), crank-arm peak power (10s Wingate test), and time to complete 25 m freestyle at 10:00 am and at 18:00 pm in a random order. Performance was significantly enhanced in the pm compared to the am in 25 m swimming time (1.7%; p = 0.01), BP maximum strength (3.6%, p = 0.04, ES = 1.87), BP muscle power (5.1%, p = 0.00, ES = 2.10), and CMJ height (5.8%; p = 0.02), but not in crank-arm power (4.1%; p = 0.08). Time-of-day increased swimming performance in a magnitude of one-third of the effects observed on upper and lower neuromuscular power, which suggests that factors beyond peak muscle power (i.e. swimming technique) affect 25 m freestyle performance.

The Reliability of Three Devices Used for Measuring Vertical Jump Height

The purpose of this investigation was to assess the intrasession and intersession reliability of the Vertec, Just Jump System, and Myotest for measuring countermovement vertical jump (CMJ) height. Forty male and 39 female university students completed 3 maximal-effort CMJs during 2 testing sessions, which were separated by 24-48 hours. The height of the CMJ was measured from all 3 devices simultaneously. Systematic error, relative reliability, absolute reliability, and heteroscedasticity were assessed for each device. Systematic error across the 3 CMJ trials was observed within both sessions for males and females, and this was most frequently observed when the CMJ height was measured by the Vertec. No systematic error was discovered across the 2 testing sessions when the maximum CMJ heights from the 2 sessions were compared. In males, the Myotest demonstrated the best intrasession reliability (intraclass correlation coefficient [ICC] = 0.95; SEM = 1.5 cm; coefficient of variation [CV] = 3.3%) and intersession reliability (ICC = 0.88; SEM = 2.4 cm; CV = 5.3%; limits of agreement = -0.08 ± 4.06 cm). Similarly, in females, the Myotest demonstrated the best intrasession reliability (ICC = 0.91; SEM = 1.4 cm; CV = 4.5%) and intersession reliability (ICC = 0.92; SEM = 1.3 cm; CV = 4.1%; limits of agreement = 0.33 ± 3.53 cm). Additional analysis revealed that heteroscedasticity was present in the CMJ when measured from all 3 devices, indicating that better jumpers demonstrate greater fluctuations in CMJ scores across testing sessions. To attain reliable CMJ height measurements, practitioners are encouraged to familiarize athletes with the CMJ technique and then allow the athletes to complete numerous repetitions until performance plateaus, particularly if the Vertec is being used.

Influence of Strength Training Background on Postactivation Potentiation Response

The aim of this study was to evaluate the influence of the subjects' level of maximal dynamic strength and training background on postactivation potentiation (PAP). A group of 23 subjects, composed of power track-and-field athletes (PT = 8), bodybuilders (BB = 7), and physically active subjects (PA = 8), participated in the study. Maximal dynamic strength (1 repetition maximum test) was assessed in the leg press exercise for subjects' characterization. Their countermovement vertical jump (CMJ) performance was assessed before and after 2 different conditioning activity (CA) protocols (1 or 3 maximum voluntary isometric contractions [MVICs] of 5-second duration in the leg press exercise) or after control (no CA), performed on separate days. No significant differences among groups were found for CMJ height or take-off velocity after any of the CA protocols (p ≤ 0.05). However, individual analysis showed that some subjects increased performance in response to the CA, despite their previous training history. We concluded that subjects' level of maximal dynamic strength and training background have no influence on PAP manifestation. Our data suggest that coaches should individually identify the athletes that are PAP responders before introducing MVICs as part of their warm-up routines.

Intersession Reliability of Three Devices Used to Measure Countermovement Vertical Jump Height

PURPOSE: The purpose of this investigation was to assess the intersession reliability of three devices that are commercially-available to measure countermovement vertical jump (CMJ) height. METHODS: Forty male and 39 female university students completed three maximal-effort CMJs during two testing sessions, which were separated by 24–48 hours. The height of the CMJ was measured from the three devices simultaneously. Device one (D1) was a jump-and-reach apparatus, device two (D2) was a contact mat, and device three (D3) was an accelerometer. For each device, systematic error in the CMJ height measurement was assessed using a dependent t-test. Relative reliability was assessed using an intraclass correlation coefficient (ICC), and absolute reliability was assessed using the standard error of measurement (SEM), coefficient of variance (CV), and limits of agreement. Also, the level of heteroscedasticity associated with each device was assessed by calculating the correlation coefficient between the maximal CMJ heights of each subject and the maximal CMJ height absolute differences between session one and session two of each subject. RESULTS: For all three devices, no systematic error was discovered (p > 0.05) when the maximal CMJ heights from the two sessions were compared. In males, D3 demonstrated the best intersession reliability (ICC = 0.88; SEM = 2.4cm; CV = 5.3%; limits of agreement = −0.08 ± 4.06cm), followed by D1 (ICC = 0.90; SEM = 3.0cm; CV = 5.9%; limits of agreement = −0.26 ± 8.27cm), and then D2 (ICC = 0.84; SEM = 3.6cm; CV = 6.3%; limits of agreement = 0.15 ± 7.13cm). In females, D3 demonstrated the best intersession reliability (ICC = 0.92; SEM = 1.3cm; CV = 4.1%; limits of agreement = 0.33 ± 3.53cm), followed D2 (ICC = 0.92; SEM = 1.7cm; CV = 4.4%; limits of agreement = 0.45 ± 4.74cm), and then D1 (ICC = 0.80; SEM = 2.7cm; CV = 8.6%; limits of agreement = −0.30 ± 7.66cm). Additionally, the CMJ height measurement demonstrated heteroscedasticity regardless of the device used to quantify the measurement. CONCLUSIONS: D3 demonstrated the best intersession reliability for measuring CMJ height in males and females. Furthermore, in both males and females, heteroscedasticity appears to be a natural phenomenon for the CMJ height measurement. This indicates that better jumpers demonstrate greater fluctuation in the maximal CMJ height measurement when the measurements are taken over two testing sessions separated by 24–48 hours. PRACTICAL APPLICATIONS: The jump-and-reach apparatus and contact mat are commonly used to assess CMJ height because they are easy to operate and provide immediate results. However, the current study has demonstrated that CMJ height measured from an accelerometer, which is also easy to operate while providing immediate results, tends to be more reliable. Consequently, the accelerometer may be better suited to detect real changes in CMJ height after participation in a training program.

The Acute Effect of Whole-Body Vibration on the Vertical Jump Height

To determine the effectiveness of a single, 1-minute bout of whole-body vibration (WBV) as a viable warm-up activity, 90 subjects (30 men; 60 women, mean age = 19 ± 1 years) were recruited and randomly assigned to either a nonvibration control group or 1 of 8 WBV treatments (4 frequencies × 2 AMplitudes). Subjects stood with the feet shoulder width apart and the knees flexed 10° on a Next Generation Power Plate for 1 minute with the frequency (30, 35, 40, or 50 Hz) and amplitude (2-4 or 4-6 mm) settings at the assigned levels. Before, 1, 5, 10, 15, 20, 25, and 30 minutes after the WBV or control treatment, subjects performed a series of countermovement vertical jumps (CMJs) measured using a Vertec vertical jump tester. Comparisons were made of changes in the countermovement vertical jump height (CMJH) over time and between groups, frequencies, and amplitudes using repeated measures analysis of variance (α ≤ 0.05). There were significant differences in CMJH over time (p = 0.008); however, these were similar for all groups, frequencies, and amplitudes (p > 0.88). Some athletes may benefit from using WBV as a warm-up activity, if the timing of WBV is optimized. The effect of WBV on performance is likely variable and minimal, with a small window of effectiveness. Gender differences were not examined, and the optimal duration, intensity, and postural position are still unclear and warrant further study.

Efeito agudo da vibração sobre o desempenho do agachamento em alta velocidade e salto vertical

The objective of this study was to assess the acute effect of whole-body vibration (WBV) on power production of the lower limbs during squat exercise and on vertical jump height. The performance of 30 strength-trained subjects was assessed during high velocity squat exercise (HVS) and countermovement vertical jump (CMJ) before and after being submitted to four different vibration protocols in a counterbalanced random manner. The HVS and CMJ assessments were performed 3 min before and 6, 9 and 12 min after the WBV interventions, and 6 min before and 9 and 15 min after the interventions, respectively. The different WBV protocols did not change relative peak or average power production during HVS and CMJ. However, time exerted a main effect, with a decrease in CMJ height at 3 min (-2%) and 15 min (-3.1%) after treatment. These results suggest that the WBV protocols employed in this study do not induce acute improvement in performance. However, this finding does not rule out the application of WBV as a useful strategy for training or warm-up routines.

Effects of Creatine Monohydrate and Polyethylene Glycosylated Creatine Supplementation on Muscular Strength, Endurance, and Power Output

The purpose of this study was to examine the effects of a moderate dose of creatine monohydrate (CM) and two smaller doses of polyethylene glycosylated (PEG) creatine on muscular strength, endurance, and power output. Fifty-eight healthy men (mean +/- SD: age, 21 +/- 2 years; height, 176 +/- 6 cm; body mass [BM], 75 +/- 14 kg) volunteered and were randomly assigned to 1 of 4 groups: (a) placebo (PL; 3.6 g of microcrystalline cellulose; n = 15), (b) CM (5 g of creatine; n = 13), (c) small-dose PEG creatine (1.25 g of creatine: PEG1.25; n = 14), or (d) moderate-dose PEG creatine (2.50 g of creatine: PEG2.50; n = 16). Testing was conducted before (pre-) and after (post-) a 30-day supplementation period. Measurements included body mass, countermovement vertical jump (CVJ) height, power output during the Wingate test (peak power [PP] and mean power [MP]), 1 repetition maximum bench press (1RMBP), 1RM leg press (1RMLP) strength, and repetitions to failure at 80% of the 1RM for bench press (REPBP) and leg press (REPLP). BM and MP (W) increased (p <or= 0.05) from pre- to postsupplementation for the CM group only, whereas 1RMBP and 1RMLP increased (p <or= 0.05) for the CM, PEG1.25, and PEG2.50 groups. CVJ height (cm and cm.kg), MP (W.kg), PP (W and W.kg), REPBP, and REPLP increased (p <or= 0.05) for all groups. These findings indicated that the recommended safe dose of 5 g.d of CM increased BM and improved muscle strength (1RMBP and 1RMLP). Smaller doses of PEG creatine (1.25 and 2.50 g.d) improved muscle strength (1RMBP and 1RMLP) to the same extent as 5 g.d of CM, but did not alter BM, power output, or endurance. When compared to the PL group, neither CM nor PEG creatine supplementation improved peak power output (CVJ or PP), MP, or muscle endurance (REPBP or REPLP). Thus, PEG creatine may have ergogenic effects that are comparable to those of CM, but with a smaller dose of creatine.