Force- and power-time curve comparison during jumping between strength-matched male and female basketball players

Differences in training load, jump performance and injury occurrence in elite youth volleyball players

BACKGROUND

External and internal training load are used to monitor training effects in volleyball. Occurrence of injuries in volleyball is dependent of training loads and state of fitness but also playing positions and gender. This study aims to investigate the impact of gender and playing positions on injury occurrence among young volleyball players, considering both training loads and fitness levels.

METHODS

Conducted from September 2021 to May 2022, this study involved 37 elite young volleyball players, comprising 16 female (176.8±3.6 cm; 65.3±5.7 kg; 13.9±1.1 years old) and 21 males (189.6±7.3 cm; 77.4±9.5 kg; 14.7±1.2 years old). G-Vert accelerometer was used to quantify training load. During these sessions, RPE, state of fitness and occurrence of injuries, were collected using a daily questionnaire.

RESULTS

The primary findings indicate that males demonstrated a higher number of jumps, mean intensity, mean training load per session, and reported higher fitness levels compared to females (P<0.001). However, females were more injured than males (P<0.001). Setters were identified as the players with the highest jump frequency, albeit at lower heights and intensities than their counterparts (P<0.001). Among males, middle blockers exhibited the highest mean intensity and training load per session (P<0.01).

CONCLUSIONS

The elevated frequency of injuries and a worse reported fitness levels among females, despite lower training loads, suggests a potential deficiency in physical preparation among young women, particularly in terms of their ability to perform repeated high-intensity jumps.

Differences in countermovement vertical jump force-time metrics between starting and non-starting professional male basketball players

With force plates being widely implemented for neuromuscular performance assessment in sport-specific settings and various force-time metrics being able to differentiate athletes based on their performance capabilities, the purpose of the present study was to examine the differences in countermovement vertical jump (CVJ) characteristics between starting and non-starting professional male basketball players (e.g., ABA League). Twenty-three athletes (height = 199.2 ± 7.7 kg, body mass = 94.2 ± 8.2 kg, age = 23.8 ± 4.9 years) volunteered to participate in the present investigation. Upon completion of a standardized warm-up protocol, each athlete performed three maximal-effort CVJs without an arm swing while standing on a uni-axial force plate system sampling at 1,000 Hz. Independent t-tests were used to examine statistically significant differences (p < 0.05) in each force-time metric between starters (n = 10) and non-starters (n = 13). No significant differences in any of the CVJ force-time metrics of interest were observed between the two groups, during both the eccentric and concentric phases of the movement (i.e., impulse, duration, peak velocity, and mean and peak force and power). Moreover, starters and non-starters demonstrated similar performance on CVJ outcome (e.g., jump height) and strategy metrics (e.g., countermovement depth). Overall, these findings suggest that at the professional level of play, the ability to secure a spot in the starting lineup is not primarily determined by the players' CVJ performance characteristics.

Comparing the Effects of Static Stretching Alone and in Combination with Post-Activation Performance Enhancement on Squat Jump Performance at Different Knee Starting Angles

We aimed to investigate the impact of isolated static stretching (4 sets of 30 seconds) and its combined form with 10 repetitive drop jumps on lower limb performance during squat jumps at different knee joint starting angles (60°, 90°, and 120°). Thirteen participants completed three randomly ordered experimental visits, each including a standardized warm-up and squat jumps at three angles, apart from the intervention or control. Information was gathered through a three-dimensional movement tracking system, electromyography system, and force platform. The electromyography data underwent wavelet analysis to compute the energy values across the four wavelet frequency bands. The average power (Pavg), peak power (Ppeak), peak ground reaction force (GRFpeak), peak center of mass velocity (Vpeak), and force-velocity relationship at peak power (SFv) were extracted from the force and velocity-time data. The results revealed no significant influence of isolated static stretching, or its combined form with drop jumps, on the energy values across the frequency bands of the gastrocnemius, biceps femoris and rectus femoris, or the Pavg or Ppeak (P > 0.05). However, at 120°, static stretching reduced the GRFpeak (P = 0.001, d = 0.86) and SFv (P < 0.001, d = 1.12), and increased the Vpeak (P = 0.001, d = 0.5). The GRFpeak, Pavg, Ppeak, and SFv increased with an increase in the joint angle (P < 0.05), whereas the Vpeak decreased (P < 0.05). These findings suggest that static stretching does not diminish power output during squat jumps at the three angles; however, it alters GRFpeak, Vpeak, and the relative contributions of force and velocity to peak power at 120°, which can be eliminated by post-activation performance enhancement. Moreover, compared to 60° and 90°, 120° was more favorable for power and peak force output.

Differences in lower extremity joint stiffness during drop jump between healthy males and females

The primary purpose of this study was to examine sex differences in lower extremity joint stiffness during vertical drop jump performance. A secondary purpose was to examine the potential influence of sex on the relationship between joint stiffness and jump performance. Thirty healthy and active individuals performed 15-drop jumps from 30 and 60 cm boxes. Hip, knee, and ankle joint stiffnesses were calculated for subphases of landing using a 2nd order polynomial regression model. Males had greater hip stiffness during the loading phase in drop jumps from both box heights than females' drop jump from 60 cm box. Also, males had a greater ground reaction force at the end of eccentric phase, net jump impulse, and jump height regardless of box height. The 60 cm box height increased knee stiffness during the loading phase, but reduced hip stiffness during the loading phase and knee and ankle stiffness during the absorption phase regardless of sex. Joint stiffnesses significantly predicted drop jump height for females (p < .001, r2 = 0.579), but not for males (p = .609, r2 = -0.053). These results suggest that females may have different strategies to maximize drop jump height as compared to males.

Ultrasound Measurements and Physical Fitness of Elite Youth Basketball Players

The countermovement jump, the V-cut test, the muscle thickness and the adjacent subcutaneous fat thickness of the gastrocnemius medialis and rectus femoris are important physiological indicators for success in basketball. The aims of this study were to evaluate between-age-category and between-gender differences in these indicators and examine the relationships between physical tests and ultrasound measurements. The measurements were recorded in a sample of 131 elite basketball players (66 males) who played in three age-categories (U14, U16, or U18). We performed two-way analysis of covariance tests and age-adjusted partial correlation analyses. U16 and U18 males showed better performance in the countermovement jump and V-cut tests and lower adjacent subcutaneous fat thickness of the gastrocnemius medialis and rectus femoris compared to the U14 males (p≤.001) and to age-category equivalent female players (p≤.001). Comparisons between the age categories in females did not show significant differences in any of the study variables. Adjacent subcutaneous fat thickness of the gastrocnemius medialis explained 22.3% of the variation for the countermovement jump result and 12.9% of the variation for the V-cut result in males (p<.01). This study is the first to show the association and predictive role of subcutaneous fat thickness measured by ultrasound in physical performance of male and female elite youth basketball players.

Influence of muscle volume on jumping performance in healthy male and female youth and young adults

BACKGROUND

Sex differences that appear throughout puberty have a substantial impact on the training process. It remains unclear what effect these sex differences should have on how training programs are planned and performed and what objectives should be established for boys and girls of different ages. This study aimed to investigate the relationship between vertical jump performance and muscle volume based on age and sex.

METHODS

One hundred eighty healthy males (n = 90) and females (n = 90) performed three different types of vertical jumps (VJ): squat jump (SJ), counter movement jump (CMJ), and counter movement jump with arms (CMJ with arms). We used the anthropometric method to measure muscle volume.

RESULTS

Muscle volume differed across age groups. There were significant effects of age, sex, and their interaction on the SJ, CMJ, and CMJ with arms heights. From the age of 14-15, males exhibited better performances than females, and large effect sizes became apparent in the SJ (d = 1.09, P = 0.04), CMJ (d = 2.18; P = 0.001) and CMJ with arms (d = 1.94; P = 0.004). For the 20-22-year-old age group, there was a significant difference in VJ performance between males and females. Extremely large effect sizes became apparent in the SJ (d = 4.44; P = 0.001), CMJ (d = 4.12; P = 0.001) and CMJ with arms (d = 5.16; P = 0.001). When performances were normalized to the lower limb length, these differences persisted. After normalization to muscle volume, males exhibited better performance when compared to females. This difference persisted only for the 20-22-year-old group on the SJ (p = 0.005), CMJ (p = 0.022) and CMJ with arms (p = 0.016). Among male participants, muscle volume was significantly correlated with SJ (r = 0.70; p < 0.01), CMJ (r = 0.70; p < 0.01) and CMJ with arms (r = 0.55; p < 0.01).

CONCLUSIONS

The results indicate that muscle volume may be one of the major determining factors in sex differences in vertical jumping performance.

Technical-Tactical Demands of 3 × 3 International Basketball Games According to Game Outcome, Player Sex, and Competition Phase

ABSTRACT

Ferioli, D, Conte, D, Scanlan, AT, and Vaquera, A. Technical-tactical demands of 3 × 3 international basketball games according to game outcome, player sex, and competition phase. J Strength Cond Res 37(2): 403-412, 2023-Despite the popularity of 3 × 3 basketball rapidly growing on a global scale, a paucity of data exist on player demands during competition, particularly considering various factors. This study aimed to quantify the technical-tactical demands of international-level 3 × 3 basketball games according to game outcome, player sex, and competition phase. Overall, 96 players from 24 national teams (48 players across 12 teams in each sex) competing at the 2019 European Basketball Cup 3 × 3 were included in this study. Technical-tactical demands during games including shooting, game-related, and possession-related statistics were retrospectively gathered from public sources or analyzed using video analyses. Linear mixed models and effect size analyses were used to determine differences in demands according to game outcome (wins vs. losses), player sex (males vs. females), and competition phase (group games vs. finals games). Winning teams ( p < 0.05, small-large ) scored more shots, shot more efficiently, secured more rebounds, committed fewer turnovers and fouls, and drew more fouls to shoot free-throws. Differences between sexes ( p < 0.05, small-moderate ) showed male teams shot more efficiently, scored more 2-point shots, and scored more points, whereas female teams attempted more 1-point shots, committed more turnovers, and had more possessions. Considering the competition phase, more blocks were completed during group games, and more points per possession were achieved during finals games ( p < 0.05, small ). This study provides foundation normative values regarding the technical-tactical demands of 3 × 3 game-play during an international competition, with reported data able to be used by practitioners in developing precise, sex-specific training and tactical strategies to optimize team success.

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 × 15 m 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.

Phase-Specific Verbal Cue Effects on Countermovement Jump Performance

ABSTRACT

Krzyszkowski, J, Chowning, LD, and Harry, JR. Phase-Specific Verbal Cue Effects on Countermovement Jump Performance. J Strength Cond Res 36(12): 3352-3358, 2022-The aim of this study was to determine whether countermovement vertical jump (CMVJ) phase-specific cues can improve jump performance and phase-specific force-time characteristics. Twenty-nine subjects (14 males and 15 females) performed 15 total CMVJ trials (5 per condition) while being provided with a control and phase-specific (unloading phase and eccentric braking phases) foci of attention. Jump height, reactive strength index-modified, countermovement depth, time-to-takeoff, and CMVJ subphase force-time characteristics were compared between each phase-specific verbal cues and the control condition using paired samples t-tests ( α = 0.05) and Cohen's d effect sizes ( d ; large >1.2). Female ( d = 0.242; p = 0.012) and male ( d = 1.96; p = 0.047) subjects achieved greater jump heights in the control condition compared with the unloading phase condition. Females demonstrated a faster unloading phase, less unloading force, greater unloading yank, and greater braking force during the unloading condition, as well as greater eccentric braking force during the eccentric braking condition compared with the control condition ( p ≤ 0.014; d ≥ 0.242). Males exhibited less body mass unloading, greater unloading yank, faster eccentric braking time, greater eccentric braking force, and greater eccentric braking yank for both the unloading and eccentric braking conditions compared with the control condition ( p ≤ 0.047; d ≥ 0.196). Collectively, these results suggest that phase-specific foci of attention do not acutely improve jump performance but can enhance phase-specific force-time characteristics in recreationally active individuals. Specifically, practitioners should consider using an eccentric braking phase instruction for individuals need to improve eccentric braking force generation.

Comparison of the Reliability of Four Different Movement Thresholds When Evaluating Vertical Jump Performance

Analyzing vertical jumps performed on a force plate can be useful for the strength and conditioning professional in managing neuromuscular fatigue. The purpose of this study was to compare different movement thresholds when analyzing countermovement (CJ) and squat jump (SJ) performance. Twenty-one college-aged participants (9 female, 12 male) performed five CJs and five SJs. Movement initiation was identified when the vertical ground reaction force (VGRF) deviated five standard deviations (5SD), four standard deviations, (4SD), 2.5% of system weight (2.5%SW), and 10% of system weight (10%SW) from their starting position. For CJs, movement was determined when the VGRF deviated either above or below these thresholds (5SDAB, 4SDAB, 2.5%SWAB, 10%SWAB) and was compared to when VGRF deviated below these thresholds (5SDB, 4SDB, 2.5%SWB, 10%SWB) in terms of peak force (Fmax), net impulse (netIMP), braking impulse (brIMP), propulsive impulse, jump height (JHT), peak power (Pmax), peak velocity (Vmax), and RSImod. For SJs, movement was determined when VGRF initially rose above these thresholds (5SD, 4SD, 2.5%SW, and 10%SW) for Fmax, netIMP, JHT, and Vmax. Significant differences were observed among several methods except for Fmax. However, these differences were small. All CJ measures demonstrated good-to-excellent relative reliability (ICC: 0.790−0.990) except for netIMP for 2.5%SWAB (ICC: 0.479). All methods demonstrated good absolute reliability as measured by percent coefficient of variation (CV%) except brIMP and RSImod. This may be due to instructions given to each jumper as well as skill level. For SJs, no differences in Fmax or netIMP were found across all methods. Small differences were seen for JHT, Pmax, and Vmax across several methods. All methods produced acceptable CV% (<10%) and excellent ICCs (0.900−0.990). However, some jumpers produced CV% that was greater than 10% when determining JHT for 5SD, 4SD, and 2.5%SW methods. This could be due to our method of obtaining system weight. Based on our findings, we recommend using the 10%SW method for assessing SJ performance on a force plate.

Countermovement Jump and Squat Jump Force-Time Curve Analysis in Control and Fatigue Conditions

ABSTRACT

Hughes, S, Warmenhoven, J, Haff, GG, Chapman, DW, and Nimphius, S. Countermovement jump and squat jump force-time curve analysis in control and fatigue conditions. J Strength Cond Res 36(10): 2752-2761, 2022-This study aimed to reanalyze previously published discrete force data from countermovement jumps (CMJs) and squat jumps (SJs) using statistical parametric mapping (SPM), a statistical method that enables analysis of data in its native, complete state. Statistical parametric mapping analysis of 1-dimensional (1D) force-time curves was compared with previous zero-dimensional (0D) analysis of peak force to assess sensitivity of 1D analysis. Thirty-two subjects completed CMJs and SJs at baseline, 15 minutes, 1, 24, and 48 hours following fatigue and control conditions in a pseudo random cross-over design. Absolute (CMJ ABS /SJ ABS ) and time-normalized (CMJ NORM /SJ NORM ) force-time data were analyzed using SPM 2-way repeated measures analysis of variance with significance accepted at α = 0.05. The SPM indicated a magnitude of difference between force-time data with main effects for time ( p < 0.001) and interaction ( p < 0.001) observed in CMJ ABS , SJ ABS, and SJ NORM, whereas previously published 0D analysis reported no 2-way interaction in CMJ and SJ peak force. This exploratory research demonstrates the strength of SPM to identify changes between entire movement force-time curves. Continued development and use of SPM analysis techniques could present the opportunity for refined assessment of athlete fatigue and readiness with the analysis of complete force-time curves.

Relationship between Upper and Lower Body Strength and Basketball Shooting Performance

Strength is one of the key physiological performance attributes related to optimal on-court basketball performance. However, there is a lack of scientific literature studying how strength relates to shooting proficiency, as a key basketball skill capable of discriminating winning from losing game outcomes. Thus, the purpose of the present study was to examine the relationship between maximal upper and lower body strength and free-throw, two-point, and three-point shooting accuracy. Ten males and seven females performed bench press and back squat one repetition maximum (1RM) and basketball shooting testing during two laboratory visits. The shooting protocol consisted of five sets of 15 free-throw, two-point, and three-point shots performed in sequential order. Each set was separated by a 30 min rest interval to minimize the influence of fatigue. Each subject attempted 225 shots, combining for a total of 3825 shots. The average free-throw, two-point, and three-point shooting accuracy for men were 74.5 ± 11.9, 68.4 ± 9.9, and 53.3 ± 14.9%, and for women 79.2 ± 11.2, 65.5 ± 8.4, and 51.2 ± 15.3%, respectively. The average bench press and back squat 1RM for men was 88.2 ± 18.6 and 117.0 ± 21.2 kg, and for women, 40.6 ± 7.5 and 66.9 ± 9.9 kg, respectively. The findings of the present study revealed no significant relationships between maximal upper and lower body strength and basketball shooting performance for both male and female participants. Neither bench press nor back squat 1RM was a good predictor of free-throw, two-point, and three-point shooting performance.

Deaf and non-deaf basketball and volleyball players' multi-faceted difference on repeated counter movement jump performances: Height, force and acceleration

The aim of this study was to compare the performances of Repetitive Counter Movement Jumping (basketball/volleyball) of deaf/non-deaf athletes. Athletes playing in the Turkish Deaf Basketball and Volleyball national teams and in Basketball and Volleyball First Leagues participated in the study. The study group consisted of 51 male athletes, including deaf basketball (n = 11; age: 26.18 ± 4.79 years), deaf volleyball (n = 12, age: 26.33 ± 4.27 years), non-deaf basketball (n = 14, age: 26.93 ± 4.87 years), and non-deaf volleyball (n = 14, age: 24.93 ± 5.10 years) players. As a result of the test, Jump Height from Take Off Velocity, Jump Height from Take Off Velocity, Jump Height from Flight Time, Counter Movement Acceleration, Push Off Acceleration, Average Velocity, Average Power, and Average Force were analyzed. Differences in the jump performances among the groups (deaf basketball and volleyball, non-deaf basketball, and volleyball) were tested by one-way analyses of variance (ANOVA) with Tukey's post-hoc follow-up testing when necessary for jump test. As a result, this is the first study to investigate the number of jumps and jump height, the force produced, acceleration at the time of jump, and jump velocity during 30 s in deaf and non-deaf basketball and volleyball players within the scope of individual Repeated Counter Movement Jump test. Based on the biomechanical changes according to our results, our findings show a greater decrease in the number of jumps and jump heights, the force produced, the acceleration at the moment of the jump and the jump velocity in all athletes, especially those that affect the deaf.

Multidisciplinary Neuromuscular and Endurance Interventions on Youth Basketball Players: A Systematic Review with Meta-Analysis and Meta-Regression

The main aims of this systematic review with meta-analysis and meta-regression were to describe the effect of multidisciplinary neuromuscular and endurance interventions, including plyometric training, mixed strength and conditioning, HIIT basketball programs and repeated sprint training on youth basketball players considering age, competitive level, gender and the type of the intervention performed to explore a predictive model through a meta-regression analysis. A structured search was conducted following PRISMA guidelines and PICOS model in Medline (PubMed), Web of Science (WOS) and Cochrane databases. Groups of experiments were created according to neuromuscular power (vertical; NPV and horizontal; NPH) and endurance (E). Meta-analysis and sub-groups analysis were performed using a random effect model and pooled standardized mean differences (SMD). A random effects meta-regression was performed regressing SMD for the different sub-groups against percentage change for NPV and NPH. There was a significant positive overall effect of the multidisciplinary interventions on NPV, NPH and E. Sub-groups analysis indicate differences in the effects of the interventions on NPV and NPH considering age, gender, competitive level and the type of the intervention used. Considering the current data available, the meta-regression analysis suggests a good predictability of U-16 and plyometric training on jump performance. Besides, male and elite level youth basketball players had a good predictability on multidirectional speed and agility performance.

Phase-Specific Predictors of Countermovement Jump Performance That Distinguish Good From Poor Jumpers

ABSTRACT

Krzyszkowski, J, Chowning, LD, and Harry, JR. Phase-specific predictors of countermovement jump performance that distinguish good from poor jumpers. J Strength Cond Res 36(5): 1257-1263, 2022-The modified-reactive strength index (RSImod) is commonly examined during the countermovement vertical jump (CMJ) to assess neuromuscular characteristics (i.e., explosiveness, fatigue, adaptation, etc.) of an athlete. However, both phase-specific variables explaining RSImod and corresponding differences between good and poor jumpers are not well understood in trained populations. This study sought to (a) identify predictors of RSImod during the CMJ based on phase-specific temporal and rate of force development (RFD) variables, and (b) identify differences in those predictors between performers with high and low RSImod performances from a sample of collegiate male basketball players (n = 22; 20 ± 2 years; 1.99 ± 0.06 month; 93.8 ± 7.5 kg). Subjects performed 3 maximal effort CMJ trials while ground reaction force data was recorded using 2 force platforms. Phase-specific temporal and RFD variables were calculated and entered into separate stepwise regression models using backward elimination to identify predictors RSImod. Individuals were then categorized into high (n = 11; RSImod = 0.68 ± 0.10) and low (n = 11; RSImod = 0.48 ± 0.04) RSImod groups according to the overall median RSImod (RSImod = 0.55). Independent t-tests (α = 0.05) were conducted and supplemented by Cohen's d effect sizes (d ≥ 1.2, large) to compare groups relative to significant predictors identified by the linear regression models and related variables. The temporal regression model (R2 = 0.530) retained unloading time and concentric time, whereas the RFD regression model (R2 = 0.429) retained unloading RFD and braking RFD. The high RSImod group exhibited significantly greater RSImod scores (d = 2.51, p < 0.001) and jump heights (d = 1.58, p < 0.001), shorter times to takeoff (d = 1.27, p = 0.007) and concentric times (d = 1.51, p = 0.002), and a greater braking RFD (d = 1.41, p = 0.005) than the low RSImod group. Individuals targeting enhanced CMJ performance may consider exploring strategies or interventions to develop quicker unloading and concentric phases and increasing eccentric RFD abilities.

Countermovement Jump Force–Time Curve Analysis between Strength-Matched Male and Female Soccer Players

The purpose of this study was to compare countermovement jump force–time measures between strength-matched male and female soccer players. Males (n = 11) and females (n = 11) were strength-matched via isometric mid-thigh pull testing, whereby peak force values were normalised to body mass. Subjects performed three maximal-effort countermovement jumps (CMJs) on a force platform from which a range of kinetic and kinematic variables were calculated via forward dynamics. Thereafter, differences in gross measures were examined via independent t-tests, while differences in force–, power–, velocity–, and displacement–time curves throughout the entire CMJ were analysed using statistical parametric mapping (SPM). Jump height, reactive strength index modified, propulsion mean force, propulsion impulse, and propulsion mean velocity were all greater for males (d = 1.50 to 3.07). Relative force– and velocity–time curves were greater for males at 86–93% (latter half of the concentric phase) and 85–100% (latter half of the concentric phase) of normalized movement time, respectively. Time to take-off, braking phase time, braking mean velocity and impulse, propulsion phase time and centre of mass displacement were similar between males and females (d = −0.23 to 0.97). This research demonstrates the strength of SPM to identify changes between entire force-time curves. Continued development and the use of SPM analysis could present the opportunity for a refined comparison of strength-matched male and female CMJ performance with the analysis of entire force–time curves.

Stretch-Shortening Cycle Performance and Muscle-Tendon Properties in Dancers and Runners

The purpose of this investigation was to elucidate whether ankle joint stretch-shortening cycle performance, isometric and isokinetic plantarflexion strength, and maximal Achilles tendon force and elongation differ between dancers, endurance runners, and untrained controls. To differentiate between dancers, endurance runners, and controls, the authors measured maximal Achilles tendon force and elongation during isometric ramp contractions with ultrasonic imaging, maximal isometric and isokinetic plantarflexion strength with dynamometry, and stretch-shortening cycle function during countermovement hopping and 30-cm drop hopping with a custom-designed sled. The Achilles tendon of dancers elongated significantly (P ≤ .05) more than runners and controls. Dancers were significantly stronger than controls during isometric contractions at different ankle angles. Concentric and eccentric strength during isokinetic contractions at 60°·s-1 and 120°·s-1 was significantly higher in dancers and runners than controls. Dancers hopped significantly higher than runners and controls during hopping tasks. Dancers also possessed significantly greater countermovement hop relative peak power, drop hop relative impulse, and drop hop relative peak power than controls. Finally, dancers reached significantly greater velocities during countermovement hops than runners and controls. Our findings suggest dancing and running require or likely enhance plantarflexion strength. Furthermore, dancing appears to require and enhance ankle joint stretch-shortening cycle performance and tendon elongation.

Relationships among countermovement vertical jump performance metrics, strategy variables, and inter-limb asymmetry in females

Dependent variables commonly studied during countermovement vertical jump (CMVJ) tests largely stem from male-only studies despite females'distinct energy storage and reutilisation strategies. This could limit progress among females seeking increased CMVJ performance through targeted changes in certain variables. We explored relationships between CMVJ performance metrics (jump height, modified reactive strength index, jump power, and takeoff momentum) and (a) temporal and force application variables and (b) inter-limb force and yank (i.e., rate of force development) asymmetry in 31 recreationally active females. Participants performed eight CMVJs while ground reaction force (GRF) data were obtained. Pearson product-moment correlation coefficients assessed the strength and direction of the associations. Twenty-six significant relationships (r ≥ ±0.357; p < 0.05) were detected across the CMVJ performance variables. The significantly correlated variables were generally isolated to only one of the four performance metrics. Only the percentage of concentric phase inter-limb force asymmetry was significantly associated with CMVJ performance, specifically jump power and takeoff momentum. Coaches and physical performance professionals should be aware of popular strategy variables' association or lack of association with commonly studied performance metrics when seeking to understand or improve specific CMVJ jumping abilities in females.

Strength and Speed Profiles Based on Age and Sex Differences in Young Basketball Players

Team sports are in continuous evolution, and physical performance is acquiring greater importance in the game. The assessment of physical fitness is the most reliable method for knowing if the athlete’s physical fitness is appropriate. Therefore, the objectives of this research were to identify profiles of physical-physiological demands with different specific tests of physical fitness related to the maximum strength of the lower body and speed. Moreover, some differences based on the sex and age of the players were identified. One hundred and forty-nine basketball players were analyzed (men n = 103 vs. women n = 46, weight: 74.74 ± 11.65 kg vs. 56.89 ± 3.71 kg, height: 184.66 ± 11.67 vs. 164 ± 4 and BMI: 21.7 ± 0.83 vs. 21.6 ± 0.90). The players performed an Abalakov test, a multi-jump test, and a repeat sprint ability test. Each player was equipped with a WIMU PRO device, and photoelectric cells were used. A MANOVA was performed to discover the differences between ages, and a t-test was used regarding sex. The results showed significant differences based on age and sex in variables related to time and Player Load/min (p < 0.001). The variables related to steps (contact, step, flight) also showed significant differences as a function of age (p < 0.001) and sex (p < 0.05). The multi-jump test showed differences based on age (p < 0.05 except in between jumps), but not on sex. These results confirm the importance of working together on lower body strength and speed skills. In addition, the planning of the work on these abilities must be individualized and according to the characteristics of the athlete.

The Effect of Height on Drop Jumps in Relation to Somatic Parameters and Landing Kinetics

The aim of this study was to assess the effect of drop height and selected somatic parameters on the landing kinetics of rebound jumps in force and power production, performed by male and female student athletes. Twenty female and forty male students with a sports background participated in the experiment (mean and standard deviation (± SD): age 20.28 ± 1.31 years, height 166.78 ± 5.29 cm, mass 62.23 ± 7.21 kg and 21.18 ± 1.29, 182.18 ± 6.43, 78.65 ± 7.09). Each participant performed three maximal jumps on two independent and synchronized force platforms (Bilateral Tensiometric Platform S2P) at each of the two assigned drop-jump heights (20-, and 40-, cm for female and 30-, and 60-, cm for the male special platform). Significant between-sex differences were observed in all variables of selected somatics, with men outperforming women. Statistically significant differences were noted in four parameters, between men and women, in both DJs from 20/40 and 30/60 cm. The height of the jump was 6 cm and 4 cm higher for men. A slightly higher statistical significance (p = 0.011) was demonstrated by the relative strength (% BW) generated by the left limb in both men and women. Only women showed a significant relationship between body mass, body height, and five parameters, dropping off of a 20 cm box. In men, only the left leg—relative maximal F (p =−0.45)—showed a relationship with body mass. There were no relationships between the above-mentioned dependencies in both groups, in jumps from a higher height: 40 cm and 60 cm. From a practical application, the DJ with lower 20/30 cm or higher 40/60 cm (women/men) respectively emphasizes either the force or power output via an increase in the velocity component of the rebound action or increased height of the DJ jump.

Neuromuscular Fatigue in Pitchers Across a Collegiate Baseball Season

Stone, BL and Schilling, BK. Neuromuscular fatigue in pitchers across a collegiate baseball season. J Strength Cond Res 34(7): 1933-1937, 2020-Neuromuscular fatigue in baseball pitchers has become an important aspect of injury risk. It is imperative to understand how fatigue is manifested to enhance resiliency and mitigate injury risk. Secondarily, collecting data on neuromuscular characteristics of baseball pitchers provides a framework to address these concerns. Using the countermovement jump, this study observed neuromuscular performance during the preseason, midseason, and postseason of a collegiate baseball season with college baseball pitchers. No statistically significant changes were noted in any of the main variables at any testing timepoint (p > 0.05). However, several variables, including concentric mean force (ConMF, d = 0.59) and concentric peak force (ConPF, d = 0.59) in addition to eccentric mean force (EccMF, d = 0.54) and eccentric mean power (EccMP, d = -0.66), displayed moderate effects from preseason testing to midseason testing. Furthermore, jump height displayed a large negative effect from preseason to midseason (d = -0.89). Secondarily, descriptive data for both concentric and eccentric variables were also determined from the present findings. There were moderate changes in neuromuscular fatigue in Division I collegiate pitchers across a competitive season and has provided descriptive data for neuromuscular characteristics in collegiate baseball pitchers.

The prediction of swim start performance based on squat jump force-time characteristics

Background

Depending on the stroke and distances of the events, swim starts have been estimated to account for 0.8% to 26.1% of the overall race time, with the latter representing the percentage in a 50 m sprint front crawl event (Cossor & Mason, 2001). However, it is still somewhat unclear what are the key physiological characteristics underpinning swim start performance. The primary aim of this study was to develop a multiple regression model to determine key lower body force-time predictors using the squat jump for swim start performance as assessed by time to 5 m and 15 m in national and international level swimmers. A secondary aim was to determine if any differences exist between males and females in jump performance predictors for swim start performance.

Methods

A total of 38 males (age 21 ±  3.1 years, height 1.83 ±  0.08 m, body mass 76.7 ±  10.2 kg) and 34 females (age 20.1 ±  3.2 years, height 1.73 ±  0.06 m, body mass 64.8 ±  8.4 kg) who had competed at either an elite (n = 31) or national level (n = 41) participated in this study. All tests were performed on the same day, with participants performing three bodyweight squat jumps on a force platform, followed by three swim starts using their main swimming stroke. Swim start performance was quantified via time to 5 m and 15 m using an instrumented starting block.

Results

Stepwise multiple linear regression with quadratic fitting identified concentric impulse and concentric impulse² as statistically significant predictors for time to 5 m (R² = 0.659) in males. With time to 15 m, concentric impulse, age and concentric impulse² were statistically significant predictors for males (R² = 0.807). A minimum concentric impulse of 200–230 N.s appears required for faster times to 5 m and 15 m, with any additional impulse production not being associated with a reduction in swim start times for most male swimmers. Concentric impulse, Reactive strength index modified and concentric mean power were identified as statistically significant predictors for female swimmers to time to 5 m (R² = 0.689). Variables that were statistically significant predictors of time to 15 m in females were concentric impulse, body mass, concentric rate of power development and Reactive strength index modified (R² = 0.841).

Discussion

The results of this study highlight the importance of lower body power and strength for swim start performance, although being able to produce greater than 200 or 230 N.s concentric impulse in squat jump did not necessarily increase swim start performance over 5 m and 15 m, respectively. Swimmers who can already generate greater levels of concentric impulse may benefit more from improving their rate of force development and/or technical aspects of the swim start performance. The sex-related differences in key force-time predictors suggest that male and female swimmers may require individualised strength and conditioning programs and regular monitoring of performance.

Sex differences in competitive surfers' generic and specific strength capacity

To compare the pop-up and counter movement jump (CMJ) and to analyse the relationships among the variables between sexes and different ages [under (U16), over (O16) 16 years] in male and female competitive surfers. Eighty-three surfers were divided according to sex, male (n = 55) and female (n = 28), and to age, U16 (n = 47) and O16 (n = 36). Vertical jump and pop-up movements were measured through the vertical ground reaction force with a force plate. CMJ demonstrated that the O16 male group exhibited significantly greater force compared to females in the concentric phase of the jump (CMJ_FMAX) (p < 0.01, ES = 1.82, large). Female U16 and O16 groups presented increased unloading rates in the eccentric phase compared to male surfers (CMJ_ULR) (p < 0.05, ES = 0.73, moderate and p < 0.05, ES = 0.12, trivial, respectively). O16 males obtained significantly greater values than O16 females in the push-up phase (POP_PUSH) (p < 0.05, ES = 0.76, moderate). Moderate correlations were found between lower-body power capacity and the pop-up (r = 0.32; ± 0.16 CL, p < 0.01, 98.1/1.9/0, very likely, moderate). General and skill-specific strengths are different in competitive male and female surfers, dependent upon their age range. The moderate association between CMJ and pop-up suggests that the pop-up might be influenced by other factors such as coordination or upper-body strength. Therefore, competitive surfers should also train the upper body strength and overall coordination in order to improve the performance of the pop-up movement.

Reliability and magnitude of loaded countermovement jump performance variables: a technical examination of the jump threshold initiation

Different thresholds have been used to determine the start of the force-time analysis during countermovement jump testing. This study examined the influence of the jump starting threshold on the reliability and magnitude of loaded countermovement jump (CMJ) performance variables. Seventeen males were tested during two sessions using five loading conditions (17-30-45-60-75 kg). The CMJ performance was analysed with a force platform. The initiation of the eccentric phase was defined as the first instant in which the vertical ground reaction force was below system weight by 10 N, 50 N, 1% of system weight (1%SW), 10% of system weight (10%SW) and five standard deviations of system weight minus 30 ms (5SDSW). The 50 N, 10%SW and 5SDSW provided a higher reliability for the mean values of velocity and power as well as for the temporal variables only during the eccentric phase compared to the 10 N and 1%SW threshold (CV ratio>1.15). The magnitude of several variables collected during both phases for the 50 N, 10%SW and 5SDSW thresholds significantly differed with respect to 10 N and 1%SW thresholds (p< 0.05). These results suggest that the jump starting threshold may influence both the reliability and magnitude of loaded CMJ performance variables, especially during the eccentric phase.

Relationship of simple reaction time and aerobic and anaerobic capacities with performance of recreational adult orienteers

Abstract This study aimed to examine the effects of Simple Reaction Time (SRT), MaximalOxygen Uptake ( V ? V ? O2max) and Maximal Anaerobic Power (Pmax) on the performance of category A recreational adult orienteers of both sexes. Sixteen subjects (8 men and 8 women; age: 30 ± 4 and 27 ± 5 years; body mass 78.8 ± 5.9 and 69.2 ± 10.4 kg; SRT: 1.391 ± 0.19 and 1.317 ± 0.25 ms; V ? V ? O2max: 67.4 ± 3.22 and 48.5 ± 8.28 ml.kg-1.min-1; Pmax: 675.0 ± 149.6 and 458.4 ± 88.62 W), were submitted to three evaluation sessions: sample characterization (1st session); SRT - Reaction Time Task v.2.0, V ? V ? O2max, and Pmax - Running Anaerobic Sprint Test (2nd session); official Orienteering test (3rd session). Results of comparison (Student’s T-test) and relation (Pearson Product-Moment Correlation and Multiple Linear Regression) tests showed significant relationships between independent variables and performance. Pmax presented strong predictive power in the male group (41%), followed by SRT (32%) and V ? V ? O2max (27%). In the female group, SRT was the most predictive variable (54%), followed by V ? V ? O2max (32%) and Pmax (12%). These findings indicated that SRT, V ? V ? O2max, and Pmax are variables predictive of performance in recreational category A orienteers. Specifically in recreational orienteers with high cardiorespiratory capacities, Pmax seems to be the mainpredictor variable. Conversely, SRT becomes the variable with the greatest predictive power.

Lower Leg Morphology and Stretch-Shortening Cycle Performance of Dancers

Greater levels of bone ultimate fracture load, bone stress–strain index, muscle cross-sectional area, and maximal voluntary isometric plantarflexion (MVIP) strength of the lower leg may be adaptations from chronic exposure to stretch-shortening cycle (SSC) actions. Dancers, a population that habitually performs SSC movements primarily about the ankle joint, may serve as a novel population to gain broader understanding of SSC function. A total of 10 female collegiate dancers and 10 untrained controls underwent peripheral quantitative computed tomography scans of both lower legs and performed MVIPs, countermovement hops, and drop hops at 20, 30, and 40 cm on a custom-made inclined sled. Dancers had greater right and left ultimate fracture load values and significantly (P ≤ .05) greater left leg stress–strain index than controls. Dancers had significantly larger right and left muscle cross-sectional area and MVIP values and hopped significantly higher during all hopping conditions in comparison with controls. Average force–time and power–time curves revealed significantly greater relative force and power measurements during the concentric phase for all hopping conditions in dancers when compared with controls. This investigation provides evidence that dance may be a stimulus for positive muscle and bone adaptations, strength levels, and enhanced SSC capabilities.

Is a Bimodal Force-Time Curve Related to Countermovement Jump Performance?

A countermovement jump (CMJ) represents one of the most frequently used performance tests for monitoring neuromuscular function in athletes. An often-overlooked feature that may provide some useful diagnostic information is the actual shape of the force-time curve. The aim of this study was therefore to consider how the shape of the force-time curve influences jump performance. Thirty-three male rugby union players performed two CMJs on a force plate, with discrete variables and continuous curve analysis used. The subjects were dichotomized based on shape of the force-time curve during the propulsion phase and by jump height. The differences between the unimodal and bimodal groups were unclear for jump height (ES = 0.28, ±0.58) and reactive strength index-modified (ES = −0.30, ±0.59). A substantial difference between high (40.2 ± 2.9 cm) and low (31.2 ± 3.2 cm) jumpers only existed in the late propulsion phase by 79.0% to 97.0% of the normalized force-time curve. A bimodal force-time curve is not representative of an optimal pattern of performance and simply reflects an inefficient stretch-shortening cycle. The inter-individual variability that exists in braking COM displacement renders temporal phase analysis impractical in cross-sectional type studies.

Sex Differences in Countermovement Jump Phase Characteristics

The countermovement jump (CMJ) is commonly used to explore sex differences in neuromuscular function, but previous studies have only reported gross CMJ measures or have partly examined CMJ phase characteristics. The purpose of this study was to explore differences in CMJ phase characteristics between male and female athletes by comparing the force-, power-, velocity-, and displacement-time curves throughout the entire CMJ, in addition to gross measures. Fourteen men and fourteen women performed three CMJs on a force platform from which a range of kinetic and kinematic variables were calculated via forward dynamics. Jump height (JH), reactive strength index modified, relative peak concentric power, and eccentric and concentric displacement, velocity, and relative impulse were all greater for men (g = 0.58⁻1.79). Relative force-time curves were similar between sexes, but relative power-, velocity-, and displacement-time curves were greater for men at 90%⁻95% (immediately before and after peak power), 47%⁻54% (start of eccentric phase) and 85%⁻100% (latter half of concentric phase), and 65%⁻87% (bottom of countermovement and initial concentric phase) of normalized jump time, respectively. The CMJ distinguished between sexes, with men demonstrating greater JH through applying a larger concentric impulse and, thus, achieving greater velocity throughout most of the concentric phase, including take-off.