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The aim of the study was to determine whether acute changes in neuromuscular performance can be detected through countermovement jumps (CMJs) conducted pre- and postpractice sessions in conditions of high or low intensity measured by microsensors technology. Using an observational repeated measures design, data were collected from 10 male collegiate basketball players. Countermovement jump data were collected before and after practice exposures over 4 weeks of preseason. Select CMJ kinetics were compared in conditions of high and low training load intensity to detect neuromuscular performance changes in displacement of the center of mass and kinetics. Kinetic measures were categorized as output, underpinning, and strategy-related variables. We investigated "output" defined as displacement (jump height [JH]), "underpinning" defined as force-related (mean eccentric force, mean concentric force, force at zero velocity), and "strategy" defined as time-related (countermovement depth [CMD], eccentric duration (EccDur), concentric duration [ConcDur]) variables. There were significant condition3time interactions in CMJ variables namely eccentric mean force (EccForce), force at zero velocity (Force@0), CMDepth, EccDur, and ConcDur. In conditions of high intensity, players had significant, but small decreases in EccForce and Force@0, with small increases in CMD, EccDur, and ConDur, respectively. However, there were no significant decreases in JH. High-intensity practice exposures did not impact neuromuscular performance specific to "output," suggesting that collegiate basketball athletes can maintain JH despite alterations in "underpinning" and "strategy-related" variables. This could have relevance in understanding how fatigue associated with higher-intensity training exposures may potentially alter jump strategy and force production capacities due to external load intensity in collegiate basketball athletes. [ABSTRACT FROM AUTHOR]

This study investigated whether the adoption of a self-selected recovery interval (SSI) is more effective than the use of a fixed recovery interval (FRI) to elicit postactivation performance enhancement (PAPE). Ten male professional volleyball athletes (20.6 ± 1.5 years; 92.8 ± 4.9 kg; 195 ± 8 cm) participated in 3 experimental sessions, in random order, following familiarization with countermovement jump (CMJ) exercises and determination of the load for 5-repetition maximum (5RM: 146 ± 27 kg) squat exercise. The 3 experimental sessions consisted of (a) control session (CON), with measurement of CMJ height 4 minutes before and 2, 4, 6, 8, and 10 minutes after subjects rested while sitting in a chair without performing any preactivation (PA) protocol; (b) session with FRI, with measurement of CMJ height 2, 4, 6, 8, and 10 minutes after performing a PA exercise consisting of 5 squats with 5RM load; and (c) session with SSI, with evaluation of CMJ height once after performing the PA adopting a SSI based on a readiness scale. No significant differences were found between CMJ height in the CON session. Countermovement jump height was higher (p,0.05) than the baseline measurement at minutes 4, 6, and 8 post-PA in the FRI session, for the best CMJ performance during the FRI session, and after the PA in the SSI session. No significant differences were found between the heights of the best CMJ in the FRI session (49.2 ± 6.8 cm) and post-PA in the SSI session (49.6 ± 6.6 cm). Therefore, adopting FRI and SSI is equally effective in eliciting PAPE in elite athletes. Despite being as effective as adopting FRI to elicit PAPE, SSI is more intuitive and easily applicable in contexts where PAPE can be implemented. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effect of complex training (CT) on post-activation performance enhancement (PAPE) effect magnitude, 5- and 30-m linear sprint, 5-0-5 change of-direction (COD), back squat (BS) and hip thrust (HT) one-repetition maximum [1RM], and jumping performance... [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate whether a 1-minute high-intensity Re-Warm Up (RWU) protocol on a cycle ergometer could attenuate the negative effects of passive rest on basketball players' performance. Twelve semiprofessional players completed two trials on consecutive days in a counterbalanced, randomized design with repeated measures. Following a structured warm-up (WU), the trials included: a) 15 minutes of passive rest (CON) and b) 13 minutes of passive rest, followed by 1 minute of cycling at 80% VO2max and 1 minute of rest (RWU80). Post-WU and post-RWU measurements included countermovement jump (CMJ), modified agility t-test (MAT), heart rate (HR), body temperature (BT), rating of perceived exertion (RPE), and perceived readiness rating (PRR). CON group showed significant decreases in all variables, while RWU80 attenuated these losses in HR (p = .127), RPE (p = .058) and PRR (p = .236). Between the two post-RWU measurements, the RWU80 showed significantly improved results in MAT (p = .05) and HR (p < .001) and higher RPE (p = .002). Although statistically significant differences did not appear in all variables, the RWU80 led to greater readiness of the substitute players to enter the game com-pared to the 15 minutes of passive rest. [ABSTRACT FROM AUTHOR]

Introduction: Alongside sarcopenia, the age-related loss of muscle strength and power, known as dynapenia, increases the risk of functional disability and mortality in older adults. However, engaging in sporting activities during old age appears to enhance functional capacity. The differences in effects between athletes and sedentary individuals, as well as between genders, have yet to be fully clarified. Methods: The vertical jump test is recognized as a measure of lower limb performance with almost no learning effect. In the present study, we quantified age-related countermovement jump (CMJ) height loss in 120 subjects over 58 years old among both master athletes and sedentary counterparts, and analysed gender differences. Results: Both male and female master athletes showed significantly higher jump heights results than their sedentary counterparts (male athletes 28.5 ± 4.3 cm vs. male sedentaries 15.1 ± 5.2 cm; p < 0.01; female athletes 22.7 ± 2.5 cm vs. female sedentaries 8.2 ± 3.3 cm; p < 0.01). Female athletes were found to have higher CMJ performance than even sedentary men (p < 0.01). The rate of decline in jumping ability was the same for male athletes and non-athletes, but female athletes had the shallower rate of decline of all the groups observed (2.78 cm per decade). Discussion: Sporting activity in the older age allows both men and women to perform at a higher level, with the latter also benefiting from a slower rate of decline, which can have a positive impact on functional ability and quality of life. [ABSTRACT FROM AUTHOR]

Vertical jump height from a countermovement jump is a widespread metric to assess the lower limb functionality. Motion capture systems and force platforms are considered gold standards to estimate vertical jump height; however, their use in ecological settings is limited. This study aimed to evaluate the feasibility of low-sampling-rate inertial measurement units as an alternative to the gold standard systems. The validity of three computational methods for IMU-based data—numerical double integration, takeoff velocity, and flight time—was assessed using data from 18 healthy participants who performed five double-leg and ten single-leg countermovement jumps. The data were simultaneously collected from a motion capture system, two force platforms, and an IMU positioned at the L5 level. The comparisons revealed that the numerical double integration method exhibited the highest correlation (0.87) and the lowest bias (2.5 cm) compared to the gold standards and excellent reliability (0.88). Although the takeoff velocity and flight time methods demonstrated comparable performances for double-leg jumps, their accuracy in single-leg jumps was reduced. Overall, the low-sampling-rate IMU with the numerical double integration method seems to be a reliable and feasible alternative for field-based countermovement jump assessment, warranting future investigation across diverse populations and jump modalities. [ABSTRACT FROM AUTHOR]

Although multiple lower-body strength capacities are required to change direction rapidly, there is limited knowledge about the relative importance of these factors. Therefore, the purpose of this studywas to assess the relationship between dynamic and isometric lower-body strength capacities and change of direction (COD) time in state-league netball players. Seventeen female athletes completed maximal isometric midthigh pull (IMTP), countermovement jump(CMJ), andmodified 5-0-5CODtests. Pearson's productmoment correlationswere used to determine the relationship between COD time and several IMTP and CMJ force-time curve characteristics. To assess the level of contribution of each force-time curve characteristic to COD time, multivariate-linear stepwise regression analyses were performed. A significantmoderate correlation was noted between net relative peak force (PF) during the IMTP and COD time (r = 0.488, p = 0.047), accounting for 23.8% of the variance in COD time. Moreover, concentric relative impulse during the CMJ was strongly correlated with CODtime (r=0.718; p=0.001), explaining 81.9% of the variance inCODtime when combinedwith net relative braking PF in a stepwise regression. Based on these findings, female netball players who display higher concentric and isometric strength, aswell as the ability to express higher impulses during the concentric phase of the CMJ, are likely to perform CODs faster. This may occur because COD requires the generation of greater propulsive forces, as well as reduced braking and contact times, along with greater isometric strength enabling effective repositioning of center of mass during COD tasks. [ABSTRACT FROM AUTHOR]

Maximal eccentric (MES) and isometric (MIS) muscle strength may enhance vertical jump performance by facilitating preloading and reducing energy loss during the eccentric (ECC) phase of the stretch-shortening cycle (SSC). However, the contributions of ECC and isometric (ISO) strength to the countermovement (CMJ) and depth jump (DJ) remain unclear due to variability in assessment methods (e.g., dynamometry, isometric mid-thigh pull) and the limited range of metrics examined in prior research. The aim of this study was to assess correlations between multi-joint lower extremity MES and MIS, obtained using a seated multi-joint isokinetic dynamometer, and 13 vertical ground reaction force (GRF) measures derived from the performance of three maximal effort DJs and CMJs. Twenty-five healthy young adults participated in this study (age = 21.9 ± 2.9 years). Pearson r correlation coefficients were used to assess the statistical significance (α = 0.05) of the relationships between absolute (N) and body mass normalized (BN) maximal strength measures and vertical jumping metrics. Moderate-to-strong positive correlations were identified between MES and MIS with broad performance metrics in CMJ and DJ, including reactive strength index (r = 0.45–0.53, p < 0.05), modified reactive strength index (r = 0.41–0.62, p < 0.05), and jump height (r = 0.59–0.75, p < 0.05). Moderate-to-strong positive correlations were also observed between MES and MIS with CON work (r = 0.58–0.71, p < 0.05) and CON peak power (r = 0.44–0.71, p < 0.05) for both the CMJ and DJ. In contrast, moderate-to-strong negative correlations were observed between MES and MIS with ECC work (r = 0.42–0.62, p < 0.005) and ECC peak power (r = 0.45–0.60, p < 0.05). These findings suggest that enhanced neuromuscular efficiency and joint stiffness in stronger musculature reduce energy absorption during the eccentric phase, minimizing mechanical deformation and preserving elastic energy for concentric propulsion. Combined, MES and MIS optimize force application, energy utilization, and control, which are crucial for maximizing jump height. These findings underscore the role of MES and MIS in influencing jumping performance across both the ECC and CON phases of the SSC. This insight is valuable for practitioners designing training programs aimed at improving vertical jumping ability. [ABSTRACT FROM AUTHOR]

Background/Objectives: Using advanced methodologies may enhance athlete profiling. This study profiled morphological and laboratory-derived performance biomechanics by position of American-style football players training for the draft. Methods: Fifty-five players were categorized into three groups: Big (e.g., lineman; n = 17), Big–skill (e.g., tight end; n = 11), and Skill (e.g., receiver; n = 27). Body fat (BF%), lean body mass (LBM), and total body mass were measured using a bioelectrical impedance device. Running ground reaction force (GRF) and ground contact time (GCT) were obtained using an instrumented treadmill synchronized with a motion capture system. Dual uniaxial force plates captured countermovement jump height (CMJ-JH), normalized peak power (CMJ-NPP), and reactive strength. Asymmetry was calculated for running force, GCT, and CMJ eccentric and concentric impulse (IMP). MANOVA determined between-group differences, and radar plots for morphological and performance characteristics were created using Z-scores. Results: There was a between-group difference (F(26,80) = 5.70, p < 0.001; Wilk's Λ = 0.123, partial η2 = 0.649). Fisher's least squares difference post hoc analyses showed that participants in the Skill group had greater JH, CMJ-NPP, reactive strength, and running GRF values versus Big players but not Big–skill players (p < 0.05). Big athletes had greater BF%, LBM, total body mass, and GCT values than Skill and Big–skill athletes (p < 0.05). Big–skill players had greater GCT asymmetry than Skill and Big players (p < 0.05). Asymmetries in running forces, CMJ eccentric, and concentric IMP were not different (p > 0.05). Morphological and performance biomechanics differences are pronounced between Skill and Big players. Big–skill players possess characteristics from both groups. Laboratory-derived metrics offer precise values of running and jumping force strategies and body composition that can aid sports science researchers and practitioners in refining draft trainee profiles. [ABSTRACT FROM AUTHOR]

There is little evidence of the acute effect of random practice, performed by solely varying the intensity but not the task itself, as compared to block practice, i.e. when one task is repeated in a constant manner. This study aimed to examine the acute neuromuscular effects of physical exercise consisting of repeated jumps of randomized length. Fifteen healthy young participants completed 2 separate sessions of 90 minutes. They did 20 minutes of fatiguing exercise, consisting of 100 repeated standing long jumps (SLJ), in two different manners: one session with targeted jump length kept constant (CO), and one with targeted jump length being varied and unpredictable (RA). Pre- and post-tests were conducted before and immediately after, including measurements of Countermovement Jump (CMJ), SLJ, leg extension maximal voluntary isometric contractions (MViC), EMG activities of leg muscles and patellar tendon reflex amplitude (T-reflex: strike force and evoked force). Results showed that performances decreased after the repeated SLJs, independently of the condition (MViC decreased from 448 ± 118 N to 399 ± 122 N; CMJ decreased from 36.7 ± 7.2 cm to 34.6 ± 6.6 cm). EMG during MViC decreased by 21 ± 28 % from pre- to post-intervention. T-reflex decreased after both conditions ([Force/Strike] ratio decreased by 38 ± 69 % from pre to post). Subjective measures showed a greater sense of personal performance and enjoyment after the RA session. Results suggest that a randomly organized intensity of effort led to a similar decrease in physical performance compared to constant intensity when the session loads were matched. It also led to similar fatigue of the neuromuscular system as shown by T-reflexes and EMG measures. Nonetheless, random practice presents the benefit of being markedly more appreciated by participants. [ABSTRACT FROM AUTHOR]

Supplementary high-intensity interval training (HIIT) programs, focusing on different aspects of fitness, are commonly used in soccer practice. This study examined the impact of two different HIIT formats applied during the competitive season on aerobic and neuromuscular performance. Twenty-six young players from two youth amateur soccer teams (aged 18.1 ± 0.7 and 18.7 ± 1.1 years) participated. In a randomized design, Team A served as an experimental group, performing either a 10s/10s linear running HIIT or a 15s/15s HIIT with changes of direction, both at 100% of maximum aerobic speed, twice per week for six weeks. In that period, team B acted as a control group, maintaining their usual training soccer regimen. Following two weeks of lower volume and frequency training, team B added the two HIIT formats in their training for six weeks, while team A acted as control. Before and after each 6-weeks period, aerobic fitness and neuromuscular performance was evaluated by the countermovement jump (CMJ). The 3-way ANOVA showed that both HIIT formats significantly enhanced Yo-Yo Intermittent Recovery Test Level 1 (Yo-YO IR1) performance compared to the respective control periods. However, the main finding was that the 10s/10s compared with the 15s/15s HIIT format induced 45 - 50% greater improvements in Yo-YO IR1 (total distance: 18.5 ± 11.7% vs. 9.0 ± 8.5%, VO2max: 5.6 ± 3.2% vs. 3.0 ± 2.7%, and vVO2max: (3.3 ± 1.9% vs. 1.8 ± 1.7%, all p = 0.39, d = 0.85). Countermovement jump performance remained unchanged across both groups (p > 0.68). During HIIT rating of perceived exertion was higher in the 15s/15s vs. the 10s/10s format (6.4 ± 0.5 vs. 4.7 ± 1.2 a.u., p < 0.001). These findings suggest that while both HIIT formats effectively enhance aerobic performance during the season, the 10s/10s format offers superior benefits with less perceived exertion, while the 15s/15s format induces higher internal load. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the skeletal muscle hypertrophic, architectural, and performance‐related adaptations in response to volume‐matched, total‐body flywheel versus traditional resistance training in a randomized, non‐exercise controlled study in physically active young adults. Thirty‐one healthy young adults (24 ± 3 y) were randomized to 10 weeks of traditional resistance training (TRT; n = 7F/5M), flywheel training (FWRT; n = 7F/4M), or a habitual activity control (CON; n = 5F/3M). Maximal voluntary isometric torque (MVIT), one repetition‐maximum (1RM) for the free weight squat and bench press, three repetition work maximum (3Wmax) for the flywheel squat and bench press, countermovement jump height, and broad jump distance, as well as site‐specific muscle hypertrophy, fascicle length (FL), and pennation angle, were measured. Both TRT and FWRT increased MVIT (p ≤ 0.021) and FFM (p ≤ 0.032) compared to CON. However, TRT promoted superior improvements in free weight squat and bench 1RM (p < 0.001), and FWRT improved flywheel 3Wmax squat and bench (p < 0.001). FWRT increased the FL and cross‐sectional area of the distal VL, countermovement jump height, and broad jump distance (p ≤ 0.048), whereas TRT increased the pennation angle and cross‐sectional area of the proximal VL. Therefore, 10 weeks of volume‐matched, total‐body traditional, and flywheel resistance training similarly increased maximal isometric strength and fat‐free mass. However, FWRT promoted unique skeletal muscle architectural adaptations that likely contributed to region‐specific VL hypertrophy and jump performance improvements. Thus, FWRT provides a novel training stimulus that promotes architectural adaptations that support improved athletic performance in a manner that is not provided by traditional resistance exercise training. Highlights: Participants using the flywheel isoinertial training device developed unique skeletal muscle adaptations in the vastus lateralis compared to the traditional resistance training group.The flywheel group also increased both their countermovement jump height and broad jump distance, whereas there were no improvements in the traditional resistance training group.The traditional training group had greater improvements in the free weight back squat and bench press compared to the flywheel group.Both groups improved fat‐free mass and isometric strength to a similar degree compared to the habitually exercising control group. [ABSTRACT FROM AUTHOR]

This exploratory study examines the relationship between the eccentric utilization ratio (EUR) and the rate of force development (RFD) in squat jumps (SJ). EUR, a key metric in sports science, compares performance in countermovement jumps (CMJ) and squat jumps (SJ). The study hypothesizes that a higher EUR is associated with a poorer RFD in SJ. Basketball and soccer players, long-distance runners, alongside physical education students (209 men; age: 23.2 ± 4.95 years and 104 women; age: 22.7 ± 4.42 years) participated. The EUR was calculated from jump height, peak force and peak power. The results indicated a small to moderate but significant negative correlation between EUR based on peak force or peak power and RFD in SJ (r = –.41 and −.27), suggesting that a higher EUR might be linked to a diminished ability to rapidly develop force in SJ. Thus, a higher EUR may not indicate superior athletic performance. [ABSTRACT FROM AUTHOR]

Background/Objectives: The aim of this study was to investigate the effects of a six-week integrated resisted sprint training (IRST) program on sprint performance and vertical jump height in a sample of U-14 male football players. This study also explored the potential benefits of incorporating variable resistive loads during pre-peak height velocity (pre-PHV) developmental stages, a period often overlooked in the training of young athletes. The IRST program alternated between heavy and light resistive sled loads to enhance sprint and jump capabilities, which are critical components of athletic performance in football. Methods: Nineteen healthy male football players (age: 13 ± 0.63 years) were divided into an experimental group (E, n = 10) and a control group (C, n = 9). The experimental group followed the IRST protocol, involving sled sprints with varying resistive loads (10–115% of the body mass) over specific distances, while the control group engaged in traditional unresisted sprint training. The sprint performance was assessed using 30 m sprint times, and the vertical jump height was measured using countermovement jump (CMJ) data collected via a force platform. Anthropometric measures and peak height velocity (aPHV) estimates were also recorded pre- and post-intervention. Results: The experimental group demonstrated significant improvements in 30 m sprint times (mean difference: −0.29 s; p < 0.01). Additionally, CMJ data revealed a positive trend in the take-off velocity and maximum concentric power, with an increase in jump height (mean difference: +0.44 cm). These results suggest enhanced sprint and explosive power capabilities following the IRST intervention. Conclusions: The findings suggest that the IRST program is an effective training method for enhancing sprint performance and maintaining jump capabilities in young football players. This approach highlights the importance of integrating variable resistance training in pre-PHV athletes to promote athletic development while ensuring safety and effectiveness. [ABSTRACT FROM AUTHOR]

Background: Raw data obtained through bioelectrical impedance analysis (BIA) have been applied in different populations to assess body fluids and cell integrity. Assessing raw BIA parameters in specific muscles is an emerging method for evaluating muscle function. We investigated the associations of the BIA-derived variables of resistance (R), reactance (Xc) and phase angle (PhA) measured through whole-body (WB) and muscle-localized (ML) methods with performance in the countermovement jump (CMJ) and 50-meter (m) sprint. Methods: Thirty-one male track and field athletes (16.5 ± 1.6 years) were assessed. Fat-free mass (FFM) and Fat mass percentage (%FM) were determined by skinfold thickness. BIA at 50 kHz was employed to obtain the WB and ML (right thigh) parameters. The WB and ML-BIA parameters were adjusted by height (R/H, Xc/H) and segment length (R/L, Xc/L). The CMJ assessment was conducted via a contact mat; the software recorded the jump height. The 50-m sprint time was measured via two sets of photocells. Pearson's correlation and linear multiple regression were performed. Results: ML-PhA was inversely related to the 50-m sprint (β=-0.56) and by itself explained 29% of the sprint time variation. It remained a significant predictor even after adjusting for age, height, FFM and peak height velocity (PHV). ML-R/L was directly related to 50-m sprint (β = 0.48) and inversely related to CMJ performance (β=-0.54), explaining 20% and 27% of the variation in 50-m sprint and CMJ performance, respectively. Similarly, it remained a significant predictor in the adjusted models. Correlations between WB-BIA (PhA, R/H) and performance tests were found to be dependent on covariates. Conclusions: In this sample, the ML-BIA parameters of R/L and PhA were significantly associated with performance independent of age, height, FFM and PHV. Higher ML-PhA values were associated with better sprint times, whereas higher ML-R/L values were associated with worse sprint times and CMJ performance. [ABSTRACT FROM AUTHOR]

This research examines the reliability, validity, and usefulness of the Jump Power application by comparing it with the reliable and validated Optojump photoelectric cell system in measuring squat jump (SJ) and countermovement jump (CMJ) in professional athletes. Twenty-two soccer players volunteered to participate in the research. The participants were the players of the U21 team in the 1st League. All athletes were subjected to SJ and CMJ tests. Jump Power app and Optojump data were acquired simultaneously during SJ and CMJ. Trial procedure was performed on three separate occasions (Session 1, Session 2, and Session 3), with 48 h intervals to examine the reliability of the data from session to session. For reliability analysis, coefficients of variation percent (%CV). Jump power app reliability values CV% is below 5%. In the validity analysis, significant differences were observed between the Optojump photoelectric cell system and the Jump Power App for SJ and CMJ. In conclusion, this study revealed that the Jump Power app is a reliable but not valid tool to measure vertical jumps in soccer players. [ABSTRACT FROM AUTHOR]

Background: Caffeine is a widely recognized ergogenic aid for enhancing exercise performance. However, its effect on throwing performance has been less studied, yielding contradictory results. Objectives: The main aim of the study was to analyze the potential ergogenic effects of a moderate dose of caffeine (3 mg·kg−1 body mass) on vertical jump performance and throwing distance during a simulated competition in trained discus and hammer throwers. Methods: In a randomized, counterbalanced, and repeated measures design, 14 well-trained throwers (9 hammer throwers and 5 discus throwers; age 24.8 ± 6.3 years old, training 14.9 ± 5.0 h per week, competing experience 10.5 ± 6.1 years) performed a countermovement jump (CMJ) test, a modified throw, and a complete throw after the ingestion of 3 mg·kg⁻¹ body mass of caffeine or a placebo. Each participant performed three maximal-effort valid modified throws of his/her respective event (i.e., hammer or discus throw), plus three maximal-effort valid official throws (up to five tries, respectively, in case any attempt was called as foul). Throwing distance was measured according to World Athletics regulations using a metal tape, while release speed was assessed with a radar device. After the performance measurements, participants completed a form about side effects prevalence. Results: Caffeine, compared to placebo, increased throw distance (3.0 ± 5.1%, p = 0.048) and speed release (5.7 ± 8.7%, p = 0.03) for the complete throw, and distance (3.6 ± 4.4%, p = 0.01) and speed release (4.8 ± 7.4 %, p = 0.01) for the modified throw. Caffeine ingestion did not significantly improve jump height (1.1 ± 4.3%, p = 0.28), although it improved force and power on braking and the propulsive phases of the CMJ (p < 0.05). Caffeine only increased the prevalence of activeness (p < 0.05). Conclusions: An acute moderate dose of caffeine enhanced hammer and discus throw performance in well-trained throwers during a simulated competitive setting, with minimal adverse side effects. [ABSTRACT FROM AUTHOR]

The purpose of this study was: i) to determine the reliability of alternate forms of the dynamic strength index (DSI) calculated over time-specific intervals that represent decisive actions in sport and ii) to assess the association between the original form of the DSI (DSItrad) and its variants. Twenty-three resistance-trained males (BM = 80.4 ± 10.18 kg; age = 26.3 ± 10.2 y; 1-RM squat kg/kg/BM = 1.61 ± 0.37) performed trials of the countermovement jump (CMJ) and isometric squat. Several variations of the DSI were calculated by dividing the mean force in the CMJ by the mean force in the isometric squat calculated over the following epochs: 100 ms (DSI100), 150 ms (DSI150) and CMJ propulsive phase duration (DSIprop). In the fourth method, mean force across the CMJ propulsive phase duration was divided by mean force in the isometric squat between initiation and peak force (DSIpeak). All alternate DSI measures achieved acceptable absolute reliability (CV < 10%), however they did not achieve at least a moderate relative reliability. DSIprop (R2 = 0.41), DSI100 (R2 = 0.03) and DSI150 (R2 = 0.14) demonstrated limited commonality with DSItrad. The alternate forms of DSI can cautiously be considered in strength assessment systems. [ABSTRACT FROM AUTHOR]

Force-time curves produced during a countermovement jump (CMJ) have traditionally been classified by visual observation as either unimodal (one concentric phase peak) or bimodal (two peaks). The association between CMJ modality and jump performance remains unclear and future studies may benefit from standardising and expanding modality classification. This study described a numerical method based on the timing and relative magnitude of concentric force-time curve prominences. Adult male elite rugby union players (n = 214) performed six CMJs on a force-instrumented treadmill and an algorithm using turning-point logic was applied to categorise jumps and define modality sub-groups. A sensitivity analysis demonstrated that the minimum prominence threshold (MPT) affected categorisation, as the proportion of bimodal jumps decreased with each 1% increase in MPT. Within-athlete consistency was also affected; between 43% and 63% of participants were consistently categorised as bimodal or unimodal depending on the selected MPT. Modified reactive strength index (RSImod), but not jump height or take-off momentum, was greater in unimodal jumps. Take-off momentum and RSImod were greater in subcategories where maximum force occurred early in the concentric phase. Future research should implement objective classification methods to enhance transparency and comparability and consider subcategories to investigate CMJ force production strategies. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the effect of traditional strength training on maximum strength (1 repetition maximum in front squat [FS] and back squat [BS]), jump (squat and countermovement jump), and linear sprint (LS) performance (5, 10, and 30 m) in elite young soccer players. A 12-month longitudinal design was chosen, and 48 elite male youth soccer players (age: 12-15 years) were included. The subjects were divided in 2 groups (a strength training group [STG] and a control group [CG]). The intervention group trained for 1 year over a competitive soccer season with additional sessions to their regular soccer practice (4 sessions per week), while the CG did not complete any additional sessions to the regular soccer training (4 sessions per week). The additional strength training (2 sessions per week [each approximately 30 minutes]) consisted of either parallel FS or BS. The squat variants switched in each session. Data were analyzed using a 2 3 3 (group 3 time) repeated-measures analysis of variance. The main findings of this study were that the STG resulted in significant pretest and post-test improvements in maximum strength (d53.75-5.58), jump (d50.84-1.14), and LS performance (d 5 20.25 to 0.44), while for the CG, smaller increases or performance decreases were measured (maximum strength: d 5 1.64-2.7; jump: d 5 0.12-0.31; sprint: d 5 0.00-025). A significant interaction effect in all variables indicated significant (p<0.05) stronger performance improvements compared with the CG. Traditional strength training in elite youth soccer players is recommended to increase strength and speed-strength (jump and sprint performance) and should be considered in longterm athletic development programs. [ABSTRACT FROM AUTHOR]

The effects of jump exercises as a conditioning activity (CA) on the rate of force development (RFD) measured during the isometric midthigh pull (IMTP) have not been investigated. Therefore, we aimed to investigate the effect of the CA comprising three sets of five countermovement jumps on the RFD measured during the IMTP, and furthermore to investigate whether post-activity potentiation (PAP) would be involved in this mechanism. Thirteen healthy male university students (age: 19.7 ± 0.6 years; training experience: 3.0 ± 1.4 years) participated in five sessions. Initially, the twitch torque was elicited by electrical stimulation after the CA to investigate whether PAP was elicited. Participants then completed the following four sessions: experimental condition sessions, in which the IMTP was performed 1 or 4 min after the CA, and control condition sessions, in which the IMTP was performed 7 or 10 min after the premeasurement because the experimental condition included a 2-min rest interval before the CA and approximately 4 min were required to perform the CA. One-way analysis of variance (ANOVA) with Bonferroni post-hoc adjustments revealed the presence of PAP 1 and 2 min after the CA. Two-way ANOVA revealed significant interaction effects for the 0-200 ms and 0-250 ms RFD at the 1st min, and the 0-150 ms and 0-250 ms RFD at the 4th min after the CA. However, the Bonferroni post-hoc test failed to detect any significant increase in the RFD index under the experimental conditions. The CA with jump exercises induced PAP up to 2 min after the CA implementation, but failed to significantly increase the RFD measured by the IMTP. [ABSTRACT FROM AUTHOR]

Maximal eccentric (MES) and isometric (MIS) muscle strength may enhance vertical jump performance by facilitating preloading and reducing energy loss during the eccentric (ECC) phase of the stretch-shortening cycle (SSC). However, the contributions of ECC and isometric (ISO) strength to the countermovement (CMJ) and depth jump (DJ) remain unclear due to variability in assessment methods (e.g., dynamometry, isometric mid-thigh pull) and the limited range of metrics examined in prior research. The aim of this study was to assess correlations between multi-joint lower extremity MES and MIS, obtained using a seated multi-joint isokinetic dynamometer, and 13 vertical ground reaction force (GRF) measures derived from the performance of three maximal effort DJs and CMJs. Twenty-five healthy young adults participated in this study (age = 21.9 ± 2.9 years). Pearson r correlation coefficients were used to assess the statistical significance (α = 0.05) of the relationships between absolute (N) and body mass normalized (BN) maximal strength measures and vertical jumping metrics. Moderate-to-strong positive correlations were identified between MES and MIS with broad performance metrics in CMJ and DJ, including reactive strength index (r = 0.45–0.53, p < 0.05), modified reactive strength index (r = 0.41–0.62, p < 0.05), and jump height (r = 0.59–0.75, p < 0.05). Moderate-to-strong positive correlations were also observed between MES and MIS with CON work (r = 0.58–0.71, p < 0.05) and CON peak power (r = 0.44–0.71, p < 0.05) for both the CMJ and DJ. In contrast, moderate-to-strong negative correlations were observed between MES and MIS with ECC work (r = 0.42–0.62, p < 0.005) and ECC peak power (r = 0.45–0.60, p < 0.05). These findings suggest that enhanced neuromuscular efficiency and joint stiffness in stronger musculature reduce energy absorption during the eccentric phase, minimizing mechanical deformation and preserving elastic energy for concentric propulsion. Combined, MES and MIS optimize force application, energy utilization, and control, which are crucial for maximizing jump height. These findings underscore the role of MES and MIS in influencing jumping performance across both the ECC and CON phases of the SSC. This insight is valuable for practitioners designing training programs aimed at improving vertical jumping ability.

Post-activation performance enhancement (PAPE) is a phenomenon that has been used as a warm-up strategy to enhance subsequent muscular performance. The purpose of this study was to examine the efficacy of a flywheel warm-up to elicit a PAPE effect in eight male youth rugby athletes. Participants completed three warm-up interventions (flywheel, stationary cycle, and no warm-up) across three days, each separated by 24 hours. A 5-minute rest followed each warm-up before assessing posterior chain flexibility, countermovement jump (CMJ), and linear acceleration. The results showed a significant increase (p < .05) in posterior chain flexibility and 10 m sprint performance following the flywheel warm-up compared to stationary cycling and no warm-up. However, the interventions had no significant differences in CMJ peak power or jump height (p > .05). The current findings suggest that the flywheel warm-up is effective in improving posterior chain flexibility and sprint performance in youth rugby players.

This exploratory study examines the relationship between the eccentric utilization ratio (EUR) and the rate of force development (RFD) in squat jumps (SJ). EUR, a key metric in sports science, compares performance in countermovement jumps (CMJ) and squat jumps (SJ). The study hypothesizes that a higher EUR is associated with a poorer RFD in SJ. Basketball and soccer players, long-distance runners, alongside physical education students (209 men; age: 23.2 ± 4.95 years and 104 women; age: 22.7 ± 4.42 years) participated. The EUR was calculated from jump height, peak force and peak power. The results indicated a small to moderate but significant negative correlation between EUR based on peak force or peak power and RFD in SJ (r = –.41 and −.27), suggesting that a higher EUR might be linked to a diminished ability to rapidly develop force in SJ. Thus, a higher EUR may not indicate superior athletic performance.

Background/Objectives: Using advanced methodologies may enhance athlete profiling. This study profiled morphological and laboratory-derived performance biomechanics by position of American-style football players training for the draft. Methods: Fifty-five players were categorized into three groups: Big (e.g., lineman; n = 17), Big–skill (e.g., tight end; n = 11), and Skill (e.g., receiver; n = 27). Body fat (BF%), lean body mass (LBM), and total body mass were measured using a bioelectrical impedance device. Running ground reaction force (GRF) and ground contact time (GCT) were obtained using an instrumented treadmill synchronized with a motion capture system. Dual uniaxial force plates captured countermovement jump height (CMJ-JH), normalized peak power (CMJ-NPP), and reactive strength. Asymmetry was calculated for running force, GCT, and CMJ eccentric and concentric impulse (IMP). MANOVA determined between-group differences, and radar plots for morphological and performance characteristics were created using Z-scores. Results: There was a between-group difference (F(26,80) = 5.70, p < 0.001; Wilk’s Λ = 0.123, partial η2 = 0.649). Fisher’s least squares difference post hoc analyses showed that participants in the Skill group had greater JH, CMJ-NPP, reactive strength, and running GRF values versus Big players but not Big–skill players (p < 0.05). Big athletes had greater BF%, LBM, total body mass, and GCT values than Skill and Big–skill athletes (p < 0.05). Big–skill players had greater GCT asymmetry than Skill and Big players (p < 0.05). Asymmetries in running forces, CMJ eccentric, and concentric IMP were not different (p > 0.05). Morphological and performance biomechanics differences are pronounced between Skill and Big players. Big–skill players possess characteristics from both groups. Laboratory-derived metrics offer precise values of running and jumping force strategies and body composition that can aid sports science researchers and practitioners in refining draft trainee profiles.

Abstract Background Raw data obtained through bioelectrical impedance analysis (BIA) have been applied in different populations to assess body fluids and cell integrity. Assessing raw BIA parameters in specific muscles is an emerging method for evaluating muscle function. We investigated the associations of the BIA-derived variables of resistance (R), reactance (Xc) and phase angle (PhA) measured through whole-body (WB) and muscle-localized (ML) methods with performance in the countermovement jump (CMJ) and 50-meter (m) sprint. Methods Thirty-one male track and field athletes (16.5 ± 1.6 years) were assessed. Fat-free mass (FFM) and Fat mass percentage (%FM) were determined by skinfold thickness. BIA at 50 kHz was employed to obtain the WB and ML (right thigh) parameters. The WB and ML-BIA parameters were adjusted by height (R/H, Xc/H) and segment length (R/L, Xc/L). The CMJ assessment was conducted via a contact mat; the software recorded the jump height. The 50-m sprint time was measured via two sets of photocells. Pearson’s correlation and linear multiple regression were performed. Results ML-PhA was inversely related to the 50-m sprint (β=-0.56) and by itself explained 29% of the sprint time variation. It remained a significant predictor even after adjusting for age, height, FFM and peak height velocity (PHV). ML-R/L was directly related to 50-m sprint (β = 0.48) and inversely related to CMJ performance (β=-0.54), explaining 20% and 27% of the variation in 50-m sprint and CMJ performance, respectively. Similarly, it remained a significant predictor in the adjusted models. Correlations between WB-BIA (PhA, R/H) and performance tests were found to be dependent on covariates. Conclusions In this sample, the ML-BIA parameters of R/L and PhA were significantly associated with performance independent of age, height, FFM and PHV. Higher ML-PhA values were associated with better sprint times, whereas higher ML-R/L values were associated with worse sprint times and CMJ performance.

Abstract This research examines the reliability, validity, and usefulness of the Jump Power application by comparing it with the reliable and validated Optojump photoelectric cell system in measuring squat jump (SJ) and countermovement jump (CMJ) in professional athletes. Twenty-two soccer players volunteered to participate in the research. The participants were the players of the U21 team in the 1st League. All athletes were subjected to SJ and CMJ tests. Jump Power app and Optojump data were acquired simultaneously during SJ and CMJ. Trial procedure was performed on three separate occasions (Session 1, Session 2, and Session 3), with 48 h intervals to examine the reliability of the data from session to session. For reliability analysis, coefficients of variation percent (%CV). Jump power app reliability values CV% is below 5%. In the validity analysis, significant differences were observed between the Optojump photoelectric cell system and the Jump Power App for SJ and CMJ. In conclusion, this study revealed that the Jump Power app is a reliable but not valid tool to measure vertical jumps in soccer players.

Studies on postactivation performance enhancement (PAPE) have used different exercises as a conditioning activity to investigate potentiation, but exclusively in upper limbs (UL) or lower (LL) limbs, or contralateral potentiation. A single exercise capable of inducing PAPE in both UL and LL is currently unknown. The present study explored the effect of the clean and jerk (C&J) as a conditioning activity for simultaneously producing PAPE interlimbs at the fourth, seventh, and 12th minutes postintervention. Twelve male weightlifters with 1-repetition maximum (1RM) in the C&J equivalent to ≥1.15 × body mass were randomly submitted to 2 experimental conditions (C&J and control [CON]). The C&J condition consisted of general warm-up (running on a treadmill and self-selected preparatory exercises) and 4 sets of 3 repetitions of C&J with 2 minutes between them (30%1RM, 50%1RM, 65%1RM, and 80%1RM) followed by a countermovement jump and a bench-press throw on a Smith machine after 4, 7, and 12 minutes, to measure the magnitude of PAPE in UL and LL. No previous exercise preceded countermovement-jump and bench-press-throw tests in the CON besides general warm-up. The main finding was that, regardless of time, the C&J resulted in greater height on countermovement jump and Smith machine bench-press throw when compared with the CON, presenting a similar effect size between UL and LL (34.6 [3.9] vs 33.4 [4.1] cm [+3.66%]; P =.038; effect size = 0.30 and 30.3 [4.7] vs 29.0 [5.1] cm [+4.44%]; P =.039; effect size = 0.26), respectively. Thus, C&J can be useful to produce PAPE simultaneously among members. [ABSTRACT FROM AUTHOR]

Purpose: To map anthropometric and physical performance profiles in Norwegian premier league female football players. Methods: During preseason, the physical qualities of 107 players were tested on Keiser leg press, countermovement jump, 40-meter sprint, and agility. Descriptive statistics were presented as mean (SD) and median [interquartile range]. Pearson correlations analyses were made for all performance tests, and results presented as R value with 95% CIs. Results: The female players were 22 (4) years of age, stature 169.0 (6.2) cm, body weight 65.3 (6.7) kg; force 2122 (312) N, power 1090 (140) W, sprint 40 m 5.75 (0.21) seconds, agility dominant 10.18 (0.32) seconds, nondominant 10.27 (0.31) seconds, and countermovement jump 32.6 (4.1) cm. Outfield players were faster and more agile than goalkeepers, a difference of 40 m, agility of dominant, and nondominant leg, respectively: 0.20 [0.09–0.32], 0.37 [0.21–0.54], and 0.28 [0.12–45]; P <.001. Goalkeepers and central defenders were taller and heavier compared with fullbacks, central midfielders, and wide midfielders (P ranging from <.02). A difference was found between dominant and nondominant legs for the agility test, showing that players are faster when changing direction with the dominant leg. Conclusions: Our study presents anthropometric and physical performance profiles of Norwegian premier league female football players. We found no difference for the physical qualities strength, power, sprint, agility, and countermovement jump between any outfield playing positions in female premier league players. There was a difference between outfield players and goalkeepers for sprint and agility. [ABSTRACT FROM AUTHOR]

Purpose: To assess objective strain and subjective muscle soreness in "Bigs" (offensive and defensive line), "Combos" (tight ends, quarterbacks, line backers, and running backs), and "Skills" (wide receivers and defensive backs) in American college football players during off-season, fall camp, and in-season phases. Methods: Twenty-three male players were assessed once weekly (3-wk off-season, 4-wk fall camp, and 3-wk in-season) for hydroperoxides (free oxygen radical test [FORT]), antioxidant capacity (free oxygen radical defense test [FORD]), oxidative stress index (OSI), countermovement-jump flight time, Reactive Strength Index (RSI) modified, and subjective soreness. Linear mixed models analyzed the effect of a 2-within-subject-SD change between predictor and dependent variables. Results: Compared to fall camp and in-season phases, off-season FORT (P ≤.001 and <.001), FORD (P ≤.001 and <.001), OSI (P ≤.001 and <.001), flight time (P ≤.001 and <.001), RSI modified (P ≤.001 and <.001), and soreness (P ≤.001 and <.001) were higher for "Bigs," whereas FORT (P ≤.001 and <.001) and OSI (P =.02 and <.001) were lower for "Combos." FORT was higher for "Bigs" compared to "Combos" in all phases (P ≤.001,.02, and.01). FORD was higher for "Skills" compared with "Bigs" in off-season (P =.02) and "Combos" in-season (P =.01). OSI was higher for "Bigs" compared with "Combos" (P ≤.001) and "Skills" (P =.01) during off-season and to "Combos" in-season (P ≤.001). Flight time was higher for "Skills" in fall camp compared with "Bigs" (P =.04) and to "Combos" in-season (P =.01). RSI modified was higher for "Skills" during off-season compared with "Bigs" (P =.02) and "Combos" during fall camp (P =.03), and in-season (P =.03). Conclusion: Off-season American college football training resulted in higher objective strain and subjective muscle soreness in "Bigs" compared with fall camp and during in-season compared with "Combos" and "Skills" players. [ABSTRACT FROM AUTHOR]

Background: Exercise-induced oxidative stress and inflammation can impair muscular function in humans. The antioxidant and anti-inflammatory properties of molecular hydrogen (H2) highlight its potential to be as an effective nutritional supplement to support muscular function performance in healthy adults. However, the effects of H2 supplementation on muscular endurance performance in trained individuals have not been well characterized. This study aimed to assess the effects of intermittent hydrogen-rich water (HRW) supplementation before, during, and after resistance training on muscular endurance performance, neuromuscular status, and subjective perceptual responses after a 48-h recovery period. Methods: This randomized, double-blinded, placebo-controlled cross-over study included 18 trained men aged 19.7 ± 0.9 years. Participants in this study were instructed to consume 1,920 mL of HRW or pure water (Placebo) daily for 7 days. Additionally, participants were required to supplement with HRW or pure water five times during the training day (1,260 mL total). This included drinking 210 mL 30 min and 1 min before training, 210 mL between training sets, 210 mL immediately after training, and 420 mL 30 min into the recovery period. Participants performed half-squat exercises with the load set at 70% of one repetition maximum for six sets (half-squat exercise performed to repetitions failure each set). We measured the power output and number of repetitions in the free barbell half-squat used to assess muscular endurance performance in participants. The countermovement jump (CMJ) height, total quality recovery scale (TQRS), and muscle soreness visual analog scale (VAS) scores were measured to assess fatigue recovery status after training, as well as at 24 and 48 h of recovery. Results: The total power output (HRW: 50,866.7 ± 6,359.9W, Placebo: 46,431.0 ± 9,376.5W, p = 0.032) and the total number of repetitions (HRW:78.2 ± 9.5 repetitions, Placebo: 70.3 ± 9.5 repetitions, p = 0.019) in the H2 supplemented group were significantly higher than in the placebo group. However, there was no statistically significant difference (p< 0.05) between the H2 and placebo groups in CMJ, TQRS, and VAS. Conclusion: Eight days of intermittent HRW intake could significantly improve muscular endurance performance in trained individuals, making it a promising strategy for athletes or fitness enthusiasts looking to boost muscular endurance during resistance training or competitions. However, it should be noted that HRW intake alone may not be adequate to accelerate recovery from muscle soreness or fatigue following high-intensity training. [ABSTRACT FROM AUTHOR]

To examine whether musculoskeletal injury history is a factor that influences countermovement jump (CMJ) performance in rugby players and to compare CMJ performance between player's position (forwards or backs). Thirty rugby players (15 with an injury history and 15 without an injury history) performed the CMJ using an inertial sensor (Baiobit®) to evaluate kinematic (Jump Height, Velocity and Phase duration) and kinetic data (rate of force development [RFD], impact peak [IP], take-off force and Stiffness]. The group comparison was performed with an independent t -test, and the association between CMJ performance, sociodemographic variables and injury history was investigated with Pearson's correlation test. Rugby players with and without history of musculoskeletal injury differed in age and playing experience, but there was no difference in CMJ performance between groups. Jump height of uninjured players was positively correlated with take-off force and RFD and negatively correlated with concentric phase duration and RFD. Injured players demonstrated a negative correlation between take-off force and IP. Compared to backs, forwards were heavier and taller, showed greater IPs and were more likely to have an injury history. There were no differences in CMJ performance between rugby players with and without an injury history. Forwards showed greater IPs and were more likelier to have an injury history than backs. [ABSTRACT FROM AUTHOR]

myofascial pain syndrome (MPS) is associated with reductions in range of movement (ROM), decrease in physical function and performance and increase in pain in different populations. Elucidating the best prevention and treatment strategies for MPS has been one of the main goals in the last decade. The objective of the present study was to compare the acute effects of self-myofascial foam rolling release (SFR) and dry-needling (DN) techniques on ankle dorsiflexion ROM, soreness post-needling and performance through countermovement jump (CMJ) height. a prospective crossover design composed by 12 active adults, aged 23.41 ± 1.68 years (weight: 78.33 ± 9.02 Kg; height: 1.79 ± 0.088 m) with active ankle dorsiflexion restriction was performed. Participants were randomized into the SFR and DN techniques to analyze its effects on ankle dorsiflexion ROM, muscle soreness and jump height at pre, post and 24 h post-intervention. significant improvements were found by DN on ankle dorsiflexion at 24 h post intervention and muscle soreness by SFR at the same time point. No significant differences were found between conditions. Both SFR and DN are effective in improving ankle dorsiflexion and performance in young adults without producing an acute effect in muscle soreness. [ABSTRACT FROM AUTHOR]

This study aims to utilize Genome-Wide Association Analysis (GWAS) to identify genetic markers associated with enhanced power resulting from resistance training. Additionally, we analyze the potential biological effects of these markers and establish a predictive model for training outcomes. 193 Han Chinese adults (age: 20 ± 1 years) underwent resistance training involving squats and bench presses at 70% 1RM, twice weekly, 5 sets x 10 repetitions, for 12 weeks. Whole-genome genotyping was conducted, and participants' countermovement jump (CMJ) height, lower limb muscle strength, and body muscle mass were assessed. CMJ height change was used to assess changes in power and subjected to Genome-Wide Association Analysis (GWAS) against genotypes. Employing Polygenic Score (PGS) calculations and stepwise linear regression, a predictive model for training effects was constructed. The results revealed a significant increase in CMJ height among participants following the resistance training intervention (Δ% = 16.53%, p < 0.01), with individual differences ranging from -35.90% to 125.71%. 38 lead SNPs, including PCTP rs9907859 (p < 1 x 10-8), showed significant associations with the percentage change in CMJ height after training (p < 1 x 10-5). The explanatory power of the predictive model for training outcomes, established using PGS and phenotypic indicators, was 62.6%, comprising 13.0% from PGS and 49.6% from phenotypic indicators. SNPs associated with power resistance training were found to participate in the biological processes of musculoskeletal movement and the Striated muscle contraction pathway. These findings indicate that individual differences in the training effect of CMJ exist after resistance training, partially explained by genetic markers and phenotypic indicators (62.6%). [ABSTRACT FROM AUTHOR]

The aim of this study was to assess whether tensiomyography is a tool sensitive enough to detect peripheral fatigue. Twenty-six strength-trained men were split into two groups: 1) a fatigued group (FG), who performed a fullsquat (SQ) standardized warm-up plus 3 x 8 SQs with 75% 1RM with a 5-min rest interval, and 2) a non-fatigued group (NFG), who only did the SQ standardized warm-up. The countermovement jump (CMJ), maximal isometric force (MIF) in the SQ at 90° knee flexion, and TMG in vastus medialis (VM) and vastus lateralis (VL) muscles were assessed preand post-protocols. Data were analyzed through mixed ANOVA, logistic regression analysis, and receiver-operating curves. There were significant group x time interactions (p < 0.01) for CMJ height, MIF, maximal radial displacement (Dm), and radial displacement velocity (Vrd90) since the FG acutely decreased in these variables, while no significant changes were observed for the NFG. The logistic regression showed a significant model for detecting fatigue, whether it used the CMJ or MIF, with only the relative change in VL-Vrd90 as a fatigue predictor. The determination of the area under the curve showed that Dm and Vrd90 had good to excellent discriminative ability. Dm and Vrd90 are sensitive to detect fatigue in VL and VM muscles in resistance training contexts. [ABSTRACT FROM AUTHOR]

This study estimated the reliability and validity of an artificial intelligence (AI)-driven model in the My Jump 2 (My Jump Lab) for estimating vertical jump height compared with the Force Platform (FP). The cross-sectional study involved 88 athletes (33 female and 55 male athletes), performing a total of 264 countermovement jumps with hands on hips. "Jump heights were simultaneously measured using the FP and the My Jump2app." The FP estimated jump heights using the impulse-momentum method, whereas My Jump 2 used the flight-time method, with the latter using an AI feature for automated detection of jump take-off and landing. Results indicated high reliability for the AI model (intraclass correlation coefficient [ICC1.3] = 0.980, coefficient of variation [CV] = 4.12) and FP (ICC1.3 = 0.990, CV = 2.92). Validity assessment showed strong agreement between the AI model and FP (ICC2,k = 0.973). This was also supported by the Bland-Altman analysis, and the ordinary least products regression revealed no significant systematic or proportional bias. The AI-driven model in My Jump 2 is highly reliable and valid for estimating jump height. Strength and conditioning professionals may use the AI-based mobile app for accurate jump height measurements, offering a practical and efficient alternative to traditional methods. [ABSTRACT FROM AUTHOR]

Purpose: Alpine ski racing is a complex sport where no single factor can exclusively account for performance. We assessed body composition, using bioelectrical impedance vector analysis (BIVA), and our purpose was to study its influence on the strength and power profile of young alpine skiers. Methods: Anthropometric measurements and advanced BIVA parameters were recorded on eighteen alpine ski racers (6 females/12 males; 17.0 ± 1.3 years; 172.2 ± 9.3 cm; 68.5 ± 9.8 kg). Dynamic force and power were assessed using countermovement jumps (CMJ), while maximal isometric strength was evaluated for hip flexion-extension and abduction-adduction movements. Stepwise regression models examined the relationship between BIVA-derived parameters and strength/power variables. Results: Body cellular mass (BCM) positively related to jump height (p =.021, R2 = 74%), jump momentum (p <.001, R2 = 89%), reactive strength index modified (p =.026, R2 = 75%) and peak concentric power (p <.001, R2 = 82%), while intracellular water (ICW) related to peak eccentric (p <.001, R2 = 76%) and concentric force (p <.001, R2 = 77%) as well as to concentric rate of force development together with the phase angle (PhA) (p =.008, R2 = 79% and R2 = 0.015). Regarding isometric assessment, ICW was a significant predictor for all four movement directions, and PhA contributed to hip adduction strength. Conclusions: Body composition, particularly BCM and ICW, significantly predict force- and power-related factors in young alpine skiers. [ABSTRACT FROM AUTHOR]

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Background: The lack of knowledge about physical responses to pickleball creates a clear gap about performance in this sport. The purpose of this study was to investigate neuromuscular fatigue caused by playing doubles pickleball. Methods: Recreational pickleball players (n = 32, mean age = 60.0 years) were recruited to perform sets of four countermovement jumps (CMJs) on a force plate before and after doubles pickleball matches. Results: For players who had not played a match prior to testing, there was a significant learning effect across trials within the baseline set of jumps for five outcomes from the CMJ test, including propulsive peak force (p = 0.005); however, there was no significant learning effect for jump height. There were significant improvements in the large effect size for all except one dependent variable (propulsive phase time) between the first and second set of jumps (i.e., after one match). Neither further increases nor decreases were seen after the second set of jumps. Conclusions: Participants saw significant increases in CMJ performance across trials after one pickleball match, indicating learning and potentiation effects. After three matches of doubles pickleball, no fatigue effect was detected. [ABSTRACT FROM AUTHOR]

This study investigates the predictive validity of lower extremity strength, strength asymmetry, and soccer-specific fitness in talent identification among elite male youth soccer players. Employing a Retrospective Cohort design, we established a cohort consisting of K-League registered youth players, totaling 219 individuals (all males, aged 16 ~ 17 years, in grade 2 of high school; equivalent to grade 11 in the US), with 38 progressing to the professional level and 181 not. Results from t-tests revealed significant differences between professional and nonprofessional groups for countermovement jump (CMJ; t = −2.423, Cohen’s d = −.448, p = .019) and change of direction with a ball (CODB; t = 2.202, Cohen’s d = .398, p = .032). CMJ demonstrated a significant correlation with the 30 m sprint (r = −.53, p < .001), and change of direction without a ball (COD) correlated with CODB (r = .52, p < .001). The robust Poisson regression, encompassing the interaction term of COD and CODB, produced an AUC of .73 (95% CI: .65 ~ .82). [ABSTRACT FROM AUTHOR]

The study was conducted to determine the effects of traditional, sprint and plyometric warm-up protocols on different variations of jumping performance in adolescent female volleyball players. 17 female volleyball players between the ages of 14-16 participated in the study voluntarily. Participants were randomly divided into 3 groups. The study was conducted in a cross-over design. All warm-up routines lasted 8 minutes. In the plyometric warm-up, 5 movements were performed as 2x5 repetitions. In the sprint warm-up, 10m, 20m, 30 and 50m sprint runs were performed in different repetitions. Squat jump (SJ), countermovement jump (CMJ) and vertical jump (VJ) measurements were made before and after the warm-up protocols of the participants. The measurement data were performed and recorded with a mobile application with proven validity and reliability. Data were analyzed with repeated measures two-way anova (two-way repeated measures ANOVA, within subject factor, exercise 3 x time 2). It was determined that there were statistically significant increases in three jump variations compared to pre-exercise in all warm-up protocols (p<0.05). However, no statistically significant difference was found in the pairwise comparisons (Bonferroni) between the protocols (p>0.05). As a result, although similar effects were observed between the warm-up protocols, it was observed that all three warm-up protocols were effective in increasing jump performance. In line with our findings, it can be said that coaches or athletes can apply all warm-up protocols before different training sessions according to the purpose of the training in order to diversify their pre-exercise warm-up routines. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to assess the relationship between the countermovement jump (CMJ) and sprint performance of professional football players, and to determine which strength and speed elements assessed by the CMJ translate into effective running. Methods: The research sample comprised 87 male professional football players (age 23.7 ± 4.20 years; body mass 82.33 ± 6.56 kg; body height 1.86 ± 0.05 m) who performed the CMJ on a dual-force platform, as well as the 30 m sprint test. The time and velocity of the run were recorded by photocells at 0, 5, 10, and 30 m of the distance. Results: No significant differences were noted in the time or velocity of the sprint over the initial 5 m between the groups of football players with a higher and lower braking rate of force development (RFD) in the CMJ (p > 0.05). However, at subsequent intervals (5–10 m and 10–30 m), players with a higher braking RFD achieved significantly better time and velocity than those with a lower RFD. Significant correlations in the group with a lower braking RFD between the CMJ and sprint variables occurred in the propulsion phase of the CMJ and most of them were in the first interval (0–5 m). In the group with a higher braking RFD, significant relationships were visible in both the propulsion (concentric) and braking (eccentric) phases of the CMJ, mainly during the second and third intervals of the sprint test. Conclusions: The noted observations may suggest that the relationship between strength and running performance is more complex than previously indicated, and that higher strength in the CMJ does not fully correlate with better sprinting. Therefore, it has been hypothesized that training aimed at generally increasing strength may not always be fully beneficial for running performance in football players and hence specific training guidelines are suggested for targeted strengthening of the required muscle performance characteristics. This may possibly contribute to reducing the unnecessary muscle overload during both training and matches, thereby preventing sports-related injuries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Identifying fast athletes is an important part of the National Football League (NFL) Combine. However, not all athletes partake in the 36.58-m sprint, and relying on this single test may miss potentially fast athletes. Therefore, the purpose of this study was to determine whether sprinting times can be predicted using simple anthropometric and jumping measures. Data from the NFL Combine between the years 1999-2020 inclusive were used (n = 4,149). Subjects had a mean (±SD) height = 1.87 ± 0.07 m and body mass = 111.96 ± 20.78 kg. The cross-validation technique was used, partitioning the data into a training set (n = 2,071) to develop regression models to predict time over the 9.14-, 9.14-to 18.29-, 18.29-to 36.58-m, and 36.58-m segments using vertical jump, broad jump, height, and mass as the independent variables. The models were then evaluated against a test set (n = 2,070) for agreement. Statistically significant (p < 0.01) models were determined for 9.14-m time (adjusted R² = 0.76, SEE = 0.05 seconds), 9.14- to 18.29-m time (adjusted R² = 0.74, SEE = 0.04 seconds), 18.29- to 36.59-m time (adjusted R² = 0.79, SEE = 0.07 seconds), and 36.58-m time (adjusted R² = 0.84, SEE = 0.12 seconds). When evaluated against the test set, the models showed biases of -0.05, -0.04, -0.02, and - 0.02 seconds and root-mean-square error of 0.07,0.05,0.07, and 0.12 seconds for the 9.14-, 9.14-to 18.29-, 18.29-to 36.58-m, and 36.58-m segments, respectively. However, 5-6% of the predictions lay outside of the limits of agreement. This study provides 4 formulae that can be used to predict sprint performance when the 36.58-m sprint test is not performed, and practitioners can use these equations to determine training areas of opportunity when working with athletes preparing for the NFL Combine. [ABSTRACT FROM AUTHOR]

The modified reactive strength index (mRSI) is a commonly used metric to quantify lower-body explosiveness during countermovement jump (CMJ) performance. However, few studies have attempted to examine its validity as a measure of explosiveness, particularly among high school athletes. The purpose of this study was to examine the validity of the mRSI as a measure of lower-body explosiveness among a relatively large sample of male and female high school athletes from various sports. As part of this study, male (n = 132) and female (n = 43) high school athletes performed CMJs, while ground reaction forces were recorded using a force platform. The vertical ground reaction force data collected during the CMJs were used to derive the following variables: peak force (PF), peak power, time to PF, time to take-off, peak rate of force development, and the mRSI. Principal component analysis was applied and reduced these variables into 2 components related to "force" and "speed." The mRSI loaded on both the force (loading = 0.82) and speed (loading = -0.46) components, indicating that it incorporates elements of both force and speed, although it loaded more strongly on the force component than the speed component. The observed pattern of cross-loading suggests that the mRSI is generally a valid measure of lower-body explosiveness for male and female high school athletes. [ABSTRACT FROM AUTHOR]

Reacting and responding to an external stimulus is an important component of human performance, and they inform us about a participant's neurophysiological capabilities. Our purpose in this study was to determine whether reaction times (REACT), response times (RT), and countermovement jump (CMJ) performance differ when responding to an auditory (AUD) versus visual (VIS) stimulus. Participants were 17 college-aged volunteers (6 females and 11 males; M age = 23.0, SD = 3.4 years; M height = 174.57, SD = 10.37 cm; M body mass = 73.37, SD = 13.48 kg). Participants performed CMJs on force plates immediately upon receiving an AUD or a VIS stimulus. The AUD stimulus was a beep noise, while the VIS stimulus was a light on a screen in front of the participants. We determined REACT for the tibialis anterior (TA), medial gastrocnemius (GM), vastus lateralis (VL), and biceps femoris (BF) muscles to be the amount of time between stimulus onset and the initiation of the muscle's electromyographic (EMG) signal. We determined RT to be the amount of time between stimulus onset and the beginning of the participant's force production. We assessed CMJ performance via ground reaction forces during the unweighting, braking, and propulsive phases of the jump. We quantified EMG amplitude and frequency during each CMJ phase. We found RT to be faster to the AUD versus the VIS stimulus (p =.007). VL and BF muscles had faster REACT than TA and GM muscles (p ≤.007). The AUD stimulus was associated with faster CMJ unweighting phase metrics (p ≤.005). Thus, individuals may react and respond faster to an AUD versus VIS stimulus, with limited improvements in their subsequent physical performance. [ABSTRACT FROM AUTHOR]

This study assessed the effects of squat training with different velocity loss (VL) thresholds on squat strength, heavy-load squat velocity (HLSV), light-load squat velocity (LLSV), countermovement jump (CMJ) height, and sprint time (ST). A systematic search of electronic databases was conducted. Meta-analysis was used to examine effects of trainings with different VL thresholds and used meta-regression to examine the interaction effects (correlation) between training effects and VL in different performance-based outcomes. Our systematic search yielded 1017 articles, 13 of which were included in the present study. Meta-analysis revealed that resistance training with both low (0%–20%) and high (30%–45%) VL thresholds improved squat strength, HLSV, LLSV, and CMJ height, but only low VL improved ST (p < 0.05). Training gains for HLSV, LLSV, CMJ (p = 0.088), and ST with low VL were superior to those with high VL (p < 0.05). Meta-regression revealed that CMJ (p = 0.076) and ST (p = 0.010) demonstrated improvements as VL decreased in the range of 0% to 45%. In conclusion, squat resistance training with low (≤20%) VL provides relatively more effective training stimuli, improving performance in power and speed tasks. Optimal VL ranges may be in the range 10% to 20%, ≤20%, and ≤10% for the HLSV and LLSV, CMJ, and ST, respectively. [ABSTRACT FROM AUTHOR]

Warm-up is a traditional pre-match routine that aims to enhance players' readiness to subsequent activity. Manipulating the warm-up structure may be important to enhance acute performance. This study aimed to investigate the effects of different warm-up durations on futsal players' physical performance. Twelve highly trained male futsal players participated in this study during the in-season. All players performed three different warm-up protocols on consecutive days that differed on its total duration: normal (28-minute), short (15-minute) and very short (10-minute). All protocols included the same exercises, performed in the same sequence and with equal time percentage. Testing included 5 and 10 m linear sprint, 505 change of direction, countermovement jump (CMJ) and reactive strength index (RSI) and was performed in three different moments: pre warm-up, post warm-up and post10' warm-up. CMJ and RSI improved in all protocols at post warm-up, with greater effects observed after very short protocol. However, no effects were observed at post10' for vertical jump after all protocols. Sprint was improved in post warm-up after short and very short warm-up. Normal warm-up promoted positive effects in sprint at post10'. None of the protocols promoted positive effects in COD at post10'. Very short warm-ups appear to positively influence jumping and running performances, although these effects may be attenuated over time. Normal warm-ups could be valid for maintaining readiness during longer inactive periods that may characterize pre-match routines. Also, different responses may emerge from the same warm-up structure, which reinforces the need of adjusting warm-up according to players' individual profiles. [ABSTRACT FROM AUTHOR]

During vertical jump evaluations in which jump height is estimated from flight time (FT), the jumper must maintain the same body posture between vertical takeoff and landing. As maintaining identical posture is rare during takeoff and landing between different jump attempts and in different individuals, we simulated the effect of changes in ankle position from takeoff to landing in vertical jumping to determine the range of errors that might occur in real-life scenarios. Our simulations account for changes in center of mass position during takeoff and landing, changes in ankle position, different subject statures (1.44–1.98 m), and poor to above-average jump heights. Our results show that using FT to estimate jump height without controlling for ankle position (allowing dorsiflexion) during the landing phase of the vertical jump can overestimate jump height by 18% in individuals of average stature and performing an average 30 cm jump or may overestimate by ≤60% for tall individuals performing a poor 10 cm jump, which is common for individuals jumping with added load. Nevertheless, as assessing jump heights based on FT is common practice, we offer a correction equation that can be used to reduce error, improving jump height measurement validity using the FT method allowing between-subject fair comparisons. [ABSTRACT FROM AUTHOR]