Drop Jump Height Research Articles

Physiological Characteristics of Freestyle Snowboard and Freeski Athletes.

To investigate the physiological characteristics of freestyle snowboard and freeski athletes and explore potential differences between males and females. National-team athletes, snowboard (9 males, 21 [2.3] y; 8 females, 20 [4.1] y) and freeski (10 males, 21 [2.1] y; 8 females, 18 [2.2] y), underwent physiological assessments: maximal oxygen uptake (V˙O2max;indirect), countermovement-jumpheight, drop-jump (DJ) height, DJ contact time, reactive strength index, absolute peak force (PFabs), and relative peak force. Differences were analyzed using multivariate analyses of variance Wilks lambda (Λ) and magnitude with partial-eta squared (ηp2). Pairwise comparisons and the impact of sex and sport were analyzed with univariate tests, utilizing Cohen d. No physiological differences were found between snowboard and freeski (Wilks Λ = 0.8, P > .251, ηp2 = .169). Sex differences were observed (Wilks Λ = 0.2, P < .001, ηp2=.79), without an interaction between sex and sport (Λ = 0.8, P > .449, ηp2=.120). For snowboard, sex differences included V˙O2max (P < .001, d = 1.04), countermovement-jump height (P < .001,d = 2.5), DJ height (P < .001,d = 1.45), DJ contact time (P < .001,d = 0.36), reactive strength index (P < .001,d = 1.36), front-limb PFabs (P < .001,d = 1.77), rear-limb PFabs (P < .001,d = 1.36), front-limb relative PF (P < .003, d = 0.88), and rear-limb relative PF (P < .021, d = 0.65). In freeski, differences included V˙O2max (P = .005, d = 0.81), countermovement-jump height (P < .001, d = 1.3), DJ height (P < .001, d = 1.17), DJ contact time (P < .040, d = 0.54), reactive strength index (P < .001, d = 1.0), left-limb PFabs (P < .001, d = 2.2), right-limb PFabs (P < .001, d = 1.88), left-limb relative PF (P < .001, d = 1.1), and right-limb relative PF (P < .001, d = 1.33). Differences between the sexes, rather than between sports, explained the largest variance. Abroad concurrent training approach with the aim of developing resilient athletes is likely warranted while acknowledging and adapting to individual needs.

Eight-Week Flywheel Training Enhances Jump Performance and Stretch-Shortening Cycle Function in Collegiate Basketball Players.

The effects of flywheel (FW) training on jump performance, muscle function, and muscle mass in athletes have not been fully clarified. The purpose of the present study was to evaluate the effects of an 8-week FW training program on jump performance, stretch-shortening cycle (SSC) function, muscle strength, peak power and muscle thickness in collegiate basketball players. Twenty male college basketball players (mean age: 19.8±1.3years, height: 179.1±6.7cm, body mass: 72.9±6.3kg) were randomly assigned to either the FW training (n=11) or control group (n=9). The FW training group performed squat exercises, 5 sets of 8 repetitions, twice a week using the FW device. Baseline and post-training assessments of jump heights of squat jumps (SJs), countermovement jumps (CMJs), and drop jumps (DJs) were performed in both groups. Additionally, the reactive strength index (RSI), representing SSC function; isometric maximum voluntary contraction (MVC) torque during knee joint extension; peak power during squats; and quadriceps muscle thickness were evaluated. As the results, we observed that the FW training group demonstrated significant increases in post-training SJ height (15.1%, p=0.03), DJ height (23.2%, p=0.01), RSI (36.8%, p=0.04), MVC, peak power and muscle thickness compared with pre-training levels. Furthermore, between-group comparisons indicated significantly higher post-training SJ height, DJ height, RSI, MVC, peak power, and muscle thickness in the FW training group (p<0.05). Therefore, the FW training program effectively enhanced jump performance and SSC function in male basketball players and proved beneficial for muscle strength and hypertrophy.

The Effects of Static Stretching 2-Hours Prior to a Traditional Warm-Up on Performance.

Whereas prolonged static stretching (SS: >60-seconds per muscle) can increase range of motion (ROM) for up to 2-hours, it can also decrease maximal voluntary isometric contraction (MVIC) forces, countermovement (CMJ) and drop jump (DJ) heights, and muscle activation immediately after the stretching exercise. When an appropriate SS duration (<60-seconds per muscle) is incorporated into a dynamic warm-up, performance decrements are often trivial. However, there is a lack of studies that observed the effects of extensive SS (180-seconds) 2-hours prior to a dynamic warm-up. The objective was to investigate ROM and performance effects of prolonged SS, 2-hours prior to a traditional warm-up. This study investigated 9 female and 8 male healthy recreationally active, young adult participants on the effects of prolonged SS (180-seconds per muscle) of the quadriceps and hamstrings, 2-hours before a traditional warm-up compared to an active control condition on hip flexion ROM, knee extension and flexion MVIC forces, CMJ, DJ, and quadriceps and hamstrings electromyography (EMG). There were no significant changes in knee flexion/extension MVIC forces, EMG, CMJ, or DJ height. However, there was significant, small magnitude (p = 0.002) greater post-warm-up left hip flexion ROM (115.4° ± 17.2) than pre-SS (108.9° ± 17.13, Effect size [ES]: 0.28) and control post-warm-up (p = 0.05, ES: 0.31, 109.5° ± 20.55). Similarly, right hip flexion ROM (117.2° ± 16.5) also demonstrated significant small magnitude (p = 0.003) greater than the pre-SS (112.4° ± 18.4, ES: 0.22) and control post-warm-up (p = 0.046, ES: 0.33, 110.8° ± 20.5). Additionally, significant, large magnitude greater hip flexion ROM was observed with the women vs. men (ES: 1.29 - 1.34). Significant hip flexion ROM increases were not accompanied by significant changes in knee flexion/extension MVIC forces, EMG, or jump heights, suggesting that extensive SS can positively impact ROM without performance deficits when followed by a traditional warm-up, 2-hours after SS.

Validity and reliability of the My Jump 2 app for detecting interlimb asymmetry in young female basketball players.

The aim of this study was to examine the validity and reliability of the My Jump 2 app for the assessment of interlimb jump asymmetry in young female basketball players. Nine athletes (age 15 ± 0.9 years; weight 62.9 ± 5.8 kg; height 173.6 ± 6.1 cm) performed single-leg drop jumps (DJs) and both-leg drop jumps on a force plate (Kistler Quattro jump) and were simultaneously recorded on two smartphones using the My Jump 2 app. Jump height from flight time and contact time data were statistically analyzed to evaluate the validity of two different camera settings, drop jump performance, and interlimb jump asymmetry in basketball players. The testing was repeated after 1 week for test retest reliability. High test-retest reliability [intraclass correlation coefficient (ICC) > 0.88] was observed in DJ height. High correlation between the force plate and the My Jump 2 app was observed in DJ height (r = 0.99) and DJ contact time (r = 0.98). For the interlimb jump height asymmetries, mean differences were 0.6 percentages for the My Jump 2 app and the force plate, respectively (p = 0.77). Inter-device reliability revealed almost perfect correlation for the DJ height (ICC = 0.99, r = 0.98). The My Jump 2 app is a valid and reliable tool to assess drop jump performance and interlimb asymmetry in young female basketball players.

Assessing Jump Performance: Intra- and Interday Reliability and Minimum Difference of Countermovement Jump and Drop Jump Outcomes, Kinetics, Kinematics, and Jump Strategy

Understanding the reliability of jump testing is essential to determine the neuromuscular progress of athletes and make informed decisions. This study aimed to assess the reliability of several countermovement jump (CMJ) and drop jump (DJ) test metrics in female volleyball players. Sixteen (n = 16) semi-professional female volleyball players participated in this test-retest study. Intrasession and intersession reliability of CMJ and DJ metrics were evaluated using a randomized cross-over design. A dual force platform was used to collect CMJ and DJ data, and several dependent variables were calculated using forward dynamics. Intraclass correlation coefficients (ICC), coefficients of variation (CV), and minimum difference (MD) were calculated to assess intra- and interday reliability. During the same testing, the third attempt consistently yielded the highest values for both tests in jump height but presented excellent reliability (CMJ: ICC [95%CI] = 0.97 [0.93–0.99]; CV [95%CI] = 4.1% [1.2–7.0]; MD95 = 3.5 cm; MD90 = 2.9 cm; DJ: ICC [95%CI] = 0.91 [0.77–0.97]; CV [95%CI] = 6.7% [1.9–11.5]; MD95 = 6.0 cm; MD90 = 5.0 cm). CMJ height exhibited excellent reliability between sessions (ICC [95%CI] = 0.93 [0.81–0.97]; CV [95%CI] = 3.8% [1.1–6.4]; MD95 = 3.5 cm; MD90 = 3.0 cm), whereas DJ height demonstrated slightly lower but still acceptable intersession reliability (ICC [95%CI] = 0.81 [0.55–0.93]; CV [95%CI] = 6.1% [1.7–10.4]; MD95 = 5.2 cm; MD90 = 4.4 cm). Intersession reliability for CMJ kinetics and kinematics was excellent for 13 of the 24 metrics assessed. For DJ, only concentric (ICC [95%CI] = 0.91 [0.76–0.97]; CV [95%CI] = 3.0% [0.9–5.2]; MD95 = 15 Ns; MD90 = 12.6 Ns) and eccentric impulses (ICC [95%CI] = 0.99 [0.96–0.99]; CV [95%CI] = 1.7% [0.5–2.9]; MD95 = 9.2 Ns; MD90 = 7.7 Ns) demonstrated excellent intersession reliability. Most CMJ variables showed excellent reliability within sessions, while DJ had lower reliability in most metrics. These findings provide valuable information to physical trainers to select the metrics to assess athletes’ performance as well as to identify a minimum cut-off value that serves as a reference for each of the metrics reported in both tests.

Velocity-Specific Relationships Among Eccentric and Concentric Force Velocity Profiles and Jumping Performance

The purpose of this study is to determine the relationships among force velocity profiles during eccentric only movements (eFVP), concentric only movements (cFVP), and dynamic performance during a countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). Nineteen collegiate baseball players (1.85 ± 0.04 m, 86.4 ± 8.2 kg, 21.1 ± 1.8 years) from a single NCAA Division I team performed CMJ, SJ, and DJ, drop landings from varying heights, and hex bar jumps with varying weights. FVPs were created with a linear regression using the drop landings for eFVP and hex bar jumps for cFVP, which were used to calculate slopes and area under the entire FVP and velocity-specific regions. Correlations analyzed the results with bootstrapping for 95% confidence intervals. Area under eFVP correlated with cFVP at r=0.51 (p&lt;0.05), cFVP slope presented strong correlations with CMJ height and DJ height while eFVP slopes did not relate to jumping performance or metrics. Area under the faster regions of cFVP and eFVP produced moderate and strong relationships to jumping performance. The area under the FVP, especially when separated into velocity-specific bands, may be a key metric which can audit or provide insight into velocity-based training program effectiveness and athlete comparisons.

Reliability, interrelationships, and minimal detectable changes of strength and power metrics among well-trained rugby sevens players.

Despite the importance of strength and power in rugby skills and match outcomes, there exists a noticeable gap in the measurement consistency and estimation of a true change of typical assessments designed to assess these qualities. To address this gap, we investigated the between-session reliability, interrelationships, and minimal detectable changes (MDC) of commonly used strength and power measures in team sports. Sixteen national-level rugby 7 s players were tested on two occasions, one week apart. Both the best and average (of 2-3 trials) peak force, peak power, height, distance, and/or strength indices during countermovement jump (CMJ), drop jump (DJ), isometric mid-thigh pull (IMTP), plyometric push-up (PPU), and standing long jump (SLJ) were obtained. Furthermore, one-repetition maximum (1RM) strength for bench press and back squat, reactive strength index, and dynamic strength index were also determined. Reliability was assessed using intraclass correlation coefficients (ICC) and coefficients of variation (CV), and used for MDC calculations, and interrelationships between variables were determined using correlation coefficients. Reliability was excellent for bench press, back squat, and SLJ (ICCs > 0.91); high to excellent for IMTP peak force, all CMJ, and DJ (except best DJ height and contact time), and PPU peak force parameters (ICCs > 0.78), with < 10% CVs (except PPU peak power). MDCs were generally smaller for average than best values. Large to very large relationships (r = 0.60 to 0.85) were observed between bench press, back squat, and IMTP with selected parameters of CMJ and PPU (p < 0.05), but not in DJ and SLJ. In conclusion, selected measures of strength and power displayed high to excellent reproducibility, with average values (rather than best) offering more stable assessments, and "smaller" MDCs. Based upon the relationships, it can be inferred that maximising strength would likely contribute to enhanced explosive performance.

The influence of age and sex on speed-strength performance in children between 10 and 14years of age.

Introduction: Speed-strength performance is important during human movements such as jumping, sprinting, and change of direction (COD) tasks, which are a substantial part of sports practice. Sex and age seem to influence performance output in young persons; however, few studies have focused on the influence of sex and age measured via standard protocols of performance diagnostics. Method: Therefore, the aim of this study was to investigate the influence of age and sex on linear sprint (LS), COD sprint, countermovement jump (CMJ) height, squat-jump (SJ) height, and drop-jump (DJ) height performance in untrained children and adolescents via a cross-sectional analysis. This study comprised 141 untrained male and female participants 10-14 years of age. Results: The results showed the influence of age in male participants on speed-strength performance, while in female participants, age did not significantly influence performance parameters. Moderate to high correlations between sprint and jump performance (r = 0.69-0.72), sprint and COD sprint performance (r = 0.58-0.72), and jump and COD sprint performance (r = 0.56-0.58) were found. Discussion: Based on the data from this study, it appears that the growth phase of age 10-14 does not necessarily lead to improvements in athletic performance. To ensure holistic motor development, female subjects in particular should be provided with specific training interventions with a focus on strength and power.

The effects of velocity-based versus percentage-based resistance training on athletic performances in sport-collegiate female basketball players.

Introduction: The study compared the effects of 6-week (2 sessions/week) velocity-based resistance training (VBRT) and percentage-based resistance training (PBRT) on athletic performance in Sport-College female basketball players. Methods: Fifteen participants were assigned to the VBRT (n = 8) or PBRT (n = 7) groups. The load in VBRT group were determined through the sessional target velocity and velocity loss monitoring, whereas PBRT group used a fixed-load based on percentage of 1-repetition maximum (1RM). Both groups completed intervention that involved the free weight back squat and bench press using the same relative load (linear periodization from 65% to 95% 1RM). Training loads data was continuously recorded. Measurements at baseline (T0) and post-training (T2) included 1RM, countermovement-jump (CMJ), squat-jump (SJ), eccentric-utilization-ratio (EUR), drop-jump height and reactive-strength-index (DJ, DJ-RSI), plyometric-push-up (PPU), 505 change-of-direction (COD), 10-m、20-m sprint (T-10、T-20), 17 × 15m drill-lines (17-drill), Hexagon agility, and functional movement screen (FMS). A mid-term (T1) assessment was included to investigate the short-term effects of both methods and the fluctuation of personalized 1RM. Results: No between-group differences were observed at T0 for descriptive variables (p > 0.05). Both groups showed significant improvement in strength gains for back squat and bench press, but VBRT showed likely to very likely favorable improvements in CMJ, SJ, EUR, DJ-RSI, Hexagon and COD among athletic performance. The VBRT showed likely to very likely improvements in 17-drill and DJ, while PBRT showed unclear effects. The lifted weights adjusted by VBRT method were higher than prescribed by PBRT (p < 0.05) for the same subjects. Conclusion: Compared with fixed-load PBRT, VBRT enhanced power and athletic performance despite similar strength gains. VBRT can be regarded as a more functional resistance-training method under linear periodization.

THE INFLUENCE OF EXTERNAL AND INTERNAL FACTORS ON THE DROP JUMP HEIGHT

The Drop jump (DJ) is an important tool in muscle power development. There are different factors that determine DJ performance, of which the key external and internal are defined. The aim of this narrative review article is to present the factors that determine the performance of the DJ. The comparative analytical method is used to compare and comment on the results of available scientific studies. The results show that technique and instruction together, among external factors, highly determine DJ height. The highest determination of DJ height has age among its internal factors. These findings contribute to better management of motor abilities testing and the training process in order to accomplish high sports success.

Neuromuscular, kinetic and kinematic differences in drop jumping between male adolescents with and without intellectual disability

Individuals with intellectual disability (ID) have lower performance in vertical jumps compared to individuals without ID. Training programmes including drop jump (DJ) exercises to gap this deficit are required. However, there is a lack of knowledge on biomechanical variables may influence DJ performance in young people with ID. Are there differences in the neuromuscular, kinetic and kinematic parameters in DJ between male adolescents with and without ID (WID and NID, respectively). Thirteen male adolescents WID (Wisk III intelligence quotient: 55.6±11.2) and thirteen age-matched boys NID executed DJ from 30cm on a force-plate. The vastus lateralis (VL) and biceps femoris (BF) electromyogram (EMG) as well as the knee kinematics and kinetics were obtained. WID had significantly (p<.05) lower DJ height, knee power, peak angular velocity and stiffness compared to NID. VL activity was higher and BF/VL co-activation was lower in WID than NID. The deficit in DJ performance shown in WID was accompanied with lower power and stiffness, as well as lack of coordination in the lower limb muscles. Improving these variables, with specific and targeted training interventions, may diminish the performance gap with their age-matched counterparts.

Effects of Individualized Versus Traditional Power Training on Strength, Power, Jump Performances, and Body Composition in Young Male Nordic Athletes.

This study aimed to examine the effects of individualized-load power training (IPT) versus traditional moderate-load power training (TPT) on strength, power, jump performance, and body composition in elite young Nordic athletes. In a randomized crossover design, 10 young male athletes (ski jumpers, Nordic combined athletes) age 17.5 (0.6) years (biological maturity status: +3.5y postpeak height velocity) who competed on a national or international level performed 5weeks of IPT (4 × 5 repetitions at 49%-72% 1-repetiton maximum [RM]) and TPT (5 × 5 repetitions at 50%-60% 1-RM) in addition to their regular training. Testing before, between, and after both training blocks comprised the assessment of muscle strength (loaded back squat 3-RM), power (maximal loaded back squat power), jump performance (eg,drop-jump height, reactive strength index), and body composition (eg,skeletal muscle mass). Significant, large-size main effects for time were found for muscle strength (P < .01; g = 2.7), reactive strength index (P = .03; g = 1.6), and drop-jump height (P = .02; g = 1.9) irrespective of the training condition (IPT, TPT). No significant time-by-condition interactions were observed. For measures of body composition, no significant main effects of condition and time or time-by-condition interactions were found. Our findings demonstrate that short-term IPT and TPT at moderate loads in addition to regular training were equally effective in improving measures of muscle strength (loaded back squat 3-RM) and vertical-jump performance (reactive strength index, drop jump, and height) in young Nordic athletes.

Effects of Plyometric Jump Training in Sand or Rigid Surface on Jump-Related Biomechanical Variables and Physical Fitness in Female Volleyball Players.

Background: This study aims to assess the effects of 8 weeks of plyometric jump training (PJT) conducted on sand or a rigid court surface on jump-related biomechanical variables and physical fitness in female indoor volleyball players. Methods: Seventeen participants were randomly divided into a sand surface group (SsG, n = 8) and rigid surface group (RsG, n = 9). Both groups completed equal indoor volleyball training routines. Participants were assessed pre and post the 8-week PJT for jump-related biomechanical variables (countermovement jump (CMJ) RSI; drop jump (DJ) reactive strength index (RSI); spike jump (SJ) height; CMJ height; CMJ rate of force development (RFD); CMJ velocity at take-off; DJ height and CMJ peak force), 20 m linear sprint time, t test for change-of-direction sprint (CODs) time, Wingate test peak power (PP), cardiorespiratory endurance, and leg-press one-repetition maximum (1RM). Results: A two-way mixed analysis of variance (group × time) revealed that there was a significant group × time interaction between DJ height (p = 0.035) and CMJ peak force (p = 0.032) in favour of RsG and SsG, respectively. A significant interaction was also observed for cardiorespiratory endurance (p = 0.01) and 1RM (p = 0.002), both favouring the SsG. No other group × time interaction was observed. Conclusions: The type of surface used during PJT induced specific adaptations in terms of jump-related biomechanical variables and physical fitness in female indoor volleyball players. Based on the individual needs of the athletes, practitioners may prescribe one type of surface preferentially over another to maximize the benefits derived from PJT.

Plyometric Training in Normobaric Hypoxia improves Jump Performance.

Strength training in hypoxia has been shown to enhance hypertrophy and function of skeletal muscle, however, the effects of plyometric training in hypoxia is relatively unknown. Therefore, this study aimed to examine the effects of plyometric training in hypoxia compared to normoxia on body composition, sprint and jump parameters. Twenty-three male physical education students (20.4±2.0 years, mean±SD) participated in the study and were divided into a plyometric training in hypoxia (PTH, n=8), plyometric training in normoxia (PTN, n=7) or control group (C, n=8). The PTH group trained in normobaric hypoxia (approximately 3536 m) 3 days/week for 8 weeks, while the PTN trained in normoxia. PTH induced significant improvements from baseline to post-testing in countermovement-jump (37.8±6.7 cm, 43.4±5.0 cm, p<0.05), squat-jump (35.4±6.2 cm, 41.1±5.7 cm, p<0.05), drop-jump height (32.8±6 cm, 38.1±6 cm, p<0.05) and 20-m sprint performance (3257.1±109.5 ms, 3145.8±83.6 ms, p<0.05); whereas PTN produced significant improvement only in countermovement-jump (37.3±4.8 cm, 40.5±4.5 cm, p<0.05) and 20-m sprint performance (3209.: 3±76.1 ms, 3126.6±100.4 ms, p<0.05). Plyometric training under hypoxic conditions induces greater improvement in some jump measures (drop-jump and squat-jump) compared to similar training in normoxia.

Kinematic and Neuromuscular Measures of Intensity During Drop Jumps in Female Volleyball Players.

The aim of this study was to assess drop jump (DJ) performance variables (jump height, contact time, and reactive strength index) concomitant to surface electromyography (sEMG) of lower limb muscles during DJs from different drop heights (intensities). The eccentric and concentric phase sEMG from the gastrocnemius medialis, biceps femoris, and vastus medialis muscles were assessed during all tests, with sEMG activity normalized to maximal voluntary isometric contraction (MVIC). In a cross-sectional, study, 10 amateur female volleyball players (age 22.1 ± 1.8 years; body mass 72.9 ± 15.2 kg; height 1.70 ± 0.08 m) completed DJs from six heights [15–90 cm (DJ15 to DJ90)]. During DJs there was no jump-target box to rebound on to. Results of one-way analysis of variance (ANOVA) showed that the jump height, contact time, and reactive strength index were not significantly (p > 0.05) different between drop heights. Mean biceps femoris eccentric and concentric sEMG ranged from 27 to 50%, although without significant differences between drop heights. Mean gastrocnemius medialis eccentric and concentric sEMG remained relatively constant (∼60–80% MVIC) across DJs heights, although eccentric values reached 90–120% MVIC from DJ75 to DJ90. Mean variations of ∼50–100% MVIC for eccentric and ∼50–70% MVIC for concentric sEMG activations were observed in the vastus medialis across DJs heights. The biceps femoris eccentric/concentric sEMG ratio during DJ45 (i.e., 1.0) was lower (p = 0.03) compared to the ratio observed after DJ90 (i.e., 3.2). The gastrocnemius medialis and vastus medialis eccentric/concentric sEMG ratio were not significantly different between drop heights. In conclusion, jumping performance and most neuromuscular markers were not sensitive to DJ height (intensity) in amateur female volleyball athletes.

Different Drop Heights in Bilateral Asymmetry and Interjoint Coordination during Repetitive Drop-Jumps

The difference of drop heights will affect the biomechanics of lower extremities during drop-jump (DJ) landing. Therefore, this study explored the effects of drop heights and training volumes on interjoint coordination and the side-to-side asymmetry of the lower extremities during landing. Twenty males were randomly assigned to perform 200 DJs (DJs200) from 30, 40 and 50 cm (drop-jump height (DJH) 30, DJH40 and DJH50) platform. One-way ANOVA repeated measure, using MATLAB software, was used to compare the differences of interjoint coordination, side-to-side asymmetry of ground contact time (GCT) and the maximum impact in vertical ground-reaction forces peak (I-vGRFpeak) in the 1st, 50th, 100th, 150th and 200th jumps (DJ1, DJs50, DJs100, DJs150 and DJs200). To examine whether significant differences exist, the least significant difference’s (LSD) method was used for post-hoc comparison. The mean absolute relative phase (MARP) and deviation phase (DP) of hip–knee were lower than DJH50 at DJH30 and DJH40, while side-to-side asymmetry of GCT and I-vGRFpeak were greater than DJH30 and DJH40 at DJH50 within DJs200 (all p &lt;0.05). However, there was no significant difference in MARP and DP of hip–ankle and knee–ankle. Therefore, training at DJH30 may effectively improve jumping performance and reduce musculoskeletal injury risk.

Lack of Evidence for Non-Local Muscle Fatigue and Performance Enhancement in Young Adults.

Post-activation performance enhancement (PAPE) is an improvement to voluntary muscle performance following a conditioning activity. There is evidence of fatigue resistance deficits in non-exercised muscles following unilateral fatiguing exercise of a contralateral muscle. The purpose of this study was to determine if a unilateral conditioning exercise protocol could induce PAPE in a contralateral, non-exercised muscle in young healthy adults. Thirty-two recreationally trained (n = 16) and athletically trained (n = 16) participants (16 males; age: 22.9 ± 2.03 years; height: 1.81 ± 0.06 m; weight: 82.8 ± 9.43 kg, and 16 females; age: 23.1 ± 2.80 years; height: 1.67 ± 0.07 m; weight: 66.4 ± 11.09 kg) were randomly allocated into two groups (dominant or non-dominant limb intervention). The experimental intervention, involved a conditioning exercise (4-repetitions of 5-seconds knee extension maximal voluntary isometric contractions: MVIC) with either the dominant (DOM) (n = 16) or non-dominant (ND) (n = 16) knee extensors with testing of the same (exercised) or contralateral (non-exercised) leg as well as a control (no conditioning exercise: n = 32) condition. Testing was performed before, 1-minute and 10-minutes after a high intensity, low volume, conditioning protocol (2 sets of 2x5-s MVIC). Pre- and post-testing included MVIC force and F100 (force developed in the first 100 ms: a proxy measure of rate of force development) and unilateral drop jump (DJ) height and contact time. There were no significant MVIC peak force or EMG nor DJ height or contact time interactions (intervention x limb dominance x time). The pre-test (0.50 ± 0.13) dominant leg MVIC F100 forces exceeded (p = 0.02) both post-test and post-10 min by a small magnitude 8.7% (d = 0.31). There was also a significant (p = 0.02) time x intervention leg x testing leg intervention, although it was observed that the control condition was as likely to demonstrate small to large magnitude changes as were the dominant and non-dominant legs. Following the conditioning activity, there was no significant evidence for non-local improvements (PAPE), or performance decreases.

The Acute Effect of Foam Rolling and Vibration Foam Rolling on Drop Jump Performance.

The purpose of this study was to examine the acute effect of foam rolling and vibration foam rolling on drop jump performance. The optimal time interval between warm-up using foam rolling or vibration foam rolling and drop jump performance was identified. This study included 16 male NCAA Division I college volleyball athletes. Three interventions were performed in a randomized order: the foam rolling exercise (FRE), vibration foam rolling exercise (VFRE), and static rest (control). The drop jump was performed before interventions, as well as 2 and 5 min after interventions. The FRE exhibited higher values for drop jump height (DJH) (p = 0.001; η2 = 0.382; statistical power = 0.964) and mean power generation at the hip joint (p = 0.006; η2 = 0.277; statistical power = 0.857) at 2 min compared with before intervention but not at 5 min (p > 0.05). However, the VFRE showed no significant changes in DJH (p > 0.05), and found that hippower was decreased at 5 min (p = 0.027; η2 = 0.214; statistical power = 0.680). The FRE completed in 2 min before rapid single action competition (sprint, long jump, triple jump, etc.) could increase sports performance.

Influences of Different Drop Height Training on Lower Extremity Kinematics and Stiffness during Repetitive Drop Jump.

Drop jump (DJ) is often used as a plyometric exercise to improve jumping performance. Training from improper drop heights and for improper durations lead to unfavorable biomechanical changes in the lower extremities when landing, which result in reduced training effects and even lower extremity injuries. Purpose. To study the effects of repeated DJ training at drop heights of 30 cm, 40 cm, and 50 cm (drop jump height (DJH) 30, DJH40, and DJH50) on lower extremity kinematics and kinetics. The 1st, 50th, 100th, 150th, and 200th DJs (DJ1, DJs50, DJs100, DJs150, and DJs200) were recorded by using a BTS motion capture system and force platform. The MATLAB software was used to compare the kinematic and stiffness data of DJ1, DJs50, DJs100, DJs150, and DJs200 with one-way ANOVA repeated measure. If there were significant differences, the LSD method was used for post hoc comparisons. Methods. Twenty healthy male Division III athlete volunteers were selected as subjects, and 200 drop jumps (DJs200) were performed from DJH30, DJH40, and DJH50. Results. The jumping height (JH), contact time (CT), and GRF increased with drop height, and the stiffness of the legs and ankle at DJH30 was higher than that at DJH40 and DJH50 (p < 0.05). Conclusion. Within DJs200, training at DJH50 yield the high impact easily leads to lower extremity injury; training at DJH30 can increase the stiffnesses of the legs and ankle joints, thus effectively utilizing the SSC benefits to store and release elastic energy, reducing the risk of lower extremity musculoskeletal injury. Therefore, coaches can choose different drop heights and training quantities for each person to better prevent lower extremity injury.

Influence of Coaching Condition on the Magnitude and Reliability of Drop Jump Height in Men and Women.

This study examined the effect of different coaching conditions on the magnitude and reliability of drop jump height in men and women. Nineteen collegiate sport sciences students (10 men) performed two sets of 10 drop jumps under four different coaching conditions: neutral, augmented feedback, external focus of attention, and a combination of augmented feedback and external focus of attention. The augmented feedback condition revealed a significantly higher jump height than the neutral condition (p = .002), while no significant differences were observed for the remaining conditions (p ≥ .38). The external focus of attention condition was more reliable than the neutral and augmented feedback conditions (coefficient of variationratio ≥ 1.15), while no differences were observed between the remaining conditions. These results suggest that both the magnitude and reliability of the drop jump height performance are influenced by the coaching condition.