Background: This study aimed to determine the validity and reliability of the countermovement jump (CMJ) as a dynamic eccentric (Ecc) strength test. Methods: Thirty-three college male student-athletes were recruited to participate in this study. The participants first performed CMJs with the second consisting of one repetition maximum back squat (1RM-BS) test. CMJ and 1RM-BS tests were performed on twin force plates. Results: The CMJ had significant correlations with the Ecc peak force (EccPF), and Ecc mean force (EccMF) of 1RM-BS, respectively (r = 0.61–0.69). Moreover, all parameters had a coefficient of variation (CV) < 10%. The intraclass correlation coefficient (ICC) values were moderate to excellent for each metric using the CMJ (0.94–0.97). The 1RM-BS and CMJ EccPF, EccMF Bland-Altman bias estimate variance ratio is 1.31–1.67, showing a moderate-large correlation in the Bland-Altman plot. Conclusions: CMJ ECC phase kinetics were associated with the 1RM-BS EccPF and EccMF. The CMJ can be an alternative tool for eccentric dynamic strength assessment.

This study focused on the effect of acute Judo training on countermovement jump (CMJ) performance and perceived fatigue among a group of highly trained collegiate judo athletes. Twenty male judo athletes participated in this study (age: 20.65 ± 1.22 years, weight: 84.17 ± 28.45 kg). Participants were assessed for CMJperformance changes before, immediately after (0 h), 12 h after, and 24 h after judo training (JT) using unloaded CMJ(CMJ_unloaded) and loaded CMJ(CMJ_loaded). All the jumps were performed on a force plate, and the force–time curves were collected for further analysis. Respondents’ perceptions were evaluated using the modified rating of perceived exertion (mRPE) before, after (0 h), 12 h, and 24 h after JT. CMJparameters were analyzed at four measured points using a one-way repeated analysis of variance. Effect sizes (ES) and percentage changes before versus 24 h after JT were calculated for comparison. Associations between the CMJparameters and mRPE were analyzed using the Pearson product–moment correlation. The ratio of flight time to contact time significantly decreased, whereas the eccentric duration, concentric duration, and total duration significantly increased (p < 0.05) in both CMJs 24 h after JT. Compared with CMJ_unloaded, CMJ_loaded had a significantly lower (p < 0.05) flight time, jump height, peak velocity, and peak power. The mRPE and CMJ_loaded peak velocity showed moderate- to high-level negative correlation results both 0 and 24 h after training (r = −0.543, p < 0.05; r = −0.479, p < 0.05). In this study, we only observed the effect of fatigue on the neuromuscular (NM) system 24 h after JT. CMJ_loaded height may help to better determine fatigue state compared with CMJ_unloaded. According to the results, the neuromuscular effects of fatigue were not observed until 24 h after a single high-intensity training. Therefore, when arranging high-intensity special training or strength and conditioning training, one should reduce the volume of training appropriately to avoid fatigue accumulation and reduce the risk of sports injuries.

The countermovement jump (CMJ) assessment is widely employed for monitoring sports performance, traditionally relying on heavy and expensive force plates to extract performance variables like jump height and peak force. Inertial measurement unit (IMU)-based approaches and mobile applications have been developed to analyse CMJ performance with cost-effective devices, but they still require technical expertise and manual annotations during operation. We developed a new camera-based pipeline that can measure CMJ performance automatically by utilising computer vision techniques and biomechanical approaches from video captured by a single uncalibrated camera. Human segmentation and pose estimation techniques are used to understand the movement of the centre of mass and take-off and landing times. Combined with the biomechanical principles of object parabolic motion and inverse dynamics, the force-time data can be estimated for extracting CMJ performance variables. We recruited 77 elite athletes (29 females; height: 170.0 ± 9.0 cm; mass: 72.2 ± 17.7 kg) to evaluate the developed method against a commercial force platform. The developed method enables fully automatic CMJ analysis for both force-time data and performance variables from video captured by a camera without calibration. The results showed superior correlations (R > 0.7) and high reliability (%CV < 10 %) for most CMJ variables compared to the IMU-based approach. This approach automates CMJ analysis, offering more variables than existing mobile apps while reducing the technical demands of IMU-based methods. It streamlines assessment, making it ideal for large-scale cohort studies. Grounded in biomechanics, it enhances sports and health monitoring, enabling data-driven optimisation of human performance.

Objectives: Skeletal muscle architecture (SMA) defines the mechanical limits of force production. However, its associations with force–time strategy under externally loaded conditions have received little research attention. This exploratory study examined associations between vastus lateralis (VL) and lateral gastrocnemius (LG) architecture and force–time strategy, jump-height retention, and stretch–shortening cycle (SSC) transfer-efficiency in collegiate basketball players. Methods: Seventeen collegiate male basketball players completed B-mode ultrasonographic assessment of VL and LG architecture, including muscle thickness, pennation angle (PA), and fascicle length. Athletes performed the squat jump (SJ), loaded squat jump (LSJ), countermovement jump (CMJ), and loaded countermovement jump (LCMJ) on force platforms, with a 20 kg external load applied for loaded conditions. Loaded retention, defined as the percentage of jump height preserved under load, was proposed as a unified construct. Pearson’s correlations were calculated, with Benjamini–Hochberg false discovery rate (FDR) corrections applied within predefined functional groups and pooled across morphology-sensitive correlations. Results: LG PA showed a large negative association with LCMJ rate of force development (r = −0.68 [−0.87, −0.30]) and a large positive association with LCMJ time to peak force (r = 0.68 [0.29, 0.87]), both surviving within-group FDR correction. VL PA was associated with eccentric acceleration time and concentric time across jump conditions (r = 0.52 to 0.61), interpreted as exploratory. Transfer-efficiency indices showed no significant associations with SMA, except for the LCMJ/LSJ concentric time ratio, which showed a moderate negative association with LG PA (r = −0.49 [−0.79, −0.01]). Conclusions: Resting muscle architecture was associated with the temporal and rate characteristics of force expression under load, rather than with the gross preservation of jump height. Integrating architectural assessment with loaded force–time profiling warrants further investigation as a means of characterizing individual force-development strategies.

Purpose : Optimizing performance while managing training load (TL) is a constant goal in high-performance sport. However, there is limited evidence on how year-long TL variations influence jumping and sprinting characteristics in collegiate basketball. This study aimed to analyze changes in TL and physical performance in a Taiwanese collegiate men’s basketball team during a full year-long season. Methods : Ten male basketball players who participated in a collegiate basketball training program were assessed using the countermovement jump (CMJ) and 20-m sprint test before the off-season (T1) and after the season (T4). In addition to the pretest and posttest, CMJ was assessed after the preparation phase (T2) and the precompetition phase (T3) to understand training adaptations. Session rating of perceived exertion was collected after each training session to calculate TL. Monthly TL values were then compared with those of the preceding month. CMJ, sprinting, and TL differences between time points were compared. Significance level was set at P < .05. Results : CMJ height significantly increased at T2 ( P = .04) and was maintained until T4. Twenty-meter sprint time did not significantly differ between T1 and T4. Monthly TL significantly decreased between off-season and preseason, as well as between off-season and precompetition phases ( P < .001). Conclusions : These findings suggest that the athletes improved CMJ and maintained sprint performance throughout the training plan. Tapering achieved through the manipulation of TL may improve performance outcomes before important competitions.

Background/Objectives: The underlying mechanisms of taekwondo-specific jumping ability among different competition levels are still unknown. This study aimed to compare vertical and horizontal stretch-shortening cycle (SSC) performance between athletes of different competitive levels and examine the relationships of force and power production abilities between those two directions in Taiwanese collegiate-level male taekwondo athletes. Methods: Seventeen male collegiate taekwondo athletes were divided into two groups: medalists (MG, n = 8) and non-medalists (NMG, n = 9); both groups performed countermovement jumps (CMJ) on a force platform and single-leg lateral hops (SLLHs) via an optoelectronic measurement system. Eccentric and concentric phase measures from CMJ and distant and temporal variables of SLLH were collected for further analysis. Results: The MG achieved statistically superior jump height (JH), concentric peak velocity, eccentric peak force, force at 0 velocity, and eccentric displacement than NMG (d = 1.05–1.36). Although non-significant differences showed in SLLH variables, MG had better results than NMG (d = 0.40–0.84). Moderate relationships were identified between SLLH step 1 and JH, reactive strength index modified, peak concentric power, and peak concentric velocity of CMJ (r = 0.50–0.57, p < 0.05). Furthermore, step 2 ground contact time and lateral reactive strength index from SLLH were associated with CMJ peak eccentric force, peak concentric force, and force at 0 velocity (r = 0.53–0.59, p < 0.05). Conclusions: Taekwondo MG achieved superior CMJ and SLLH performance. In addition, jumping abilities in vertical and lateral directions shared specific underlying mechanisms in collegiate male taekwondo athletes.