Jelena Aleksic

Countermovement jumps are usually tested as self-initiated maximal efforts, although many sport actions require athletes to react to an external event and still jump as high as possible. Background and Objectives: We examined how this rapid-initiation requirement was associated with CMJ mechanics, whether the pattern was similar across levels of basketball-specific experience, and whether arm swing altered the response. Methods: Forty-four men (15 physically active non-basketball controls, 15 mid-level basketball players, and 14 high-level basketball players) performed countermovement jumps with and without arm swing in four fixed-order blocks. Trial-level linear mixed-effects models included 564 valid attempts. Results: In the signal-initiated blocks, movement time was 0.091 s shorter (95% CI −0.103 to −0.078) and jump height was 1.63 cm lower (95% CI −2.04 to −1.21). Unloading (−0.069 s), braking (−0.011 s), and propulsion (−0.010 s) were all shorter; countermovement depth decreased, peak downward speed increased, and net propulsive impulse fell by 0.052 N s/kg despite a small increase in mean net propulsive force. Movement time decreased in all six group-by-jump cells. The jump-height reduction was statistically clear at the group level but small and of uncertain practical relevance for individuals. Basketball-specific experience did not clearly moderate the main condition effects. Arm swing reduced the movement-time difference by 0.043 s but did not clearly reduce the jump-height difference. Conclusion: The rapid-initiation condition was associated with a broad reorganization of movement timing and force–time strategy, with a smaller change in endpoint performance. Because the conditions were always performed in the same order, these findings should be interpreted as fixed-order condition differences and confirmed in counterbalanced designs.

Affordable high-frame-rate cameras and open-source software, such as Kinovea (ver. 2025.1.0), have expanded the potential for conducting kinematic assessments outside laboratory settings. This study examined the reliability and validity of Kinovea’s semi-automated linear kinematics tracking tool by comparing its outputs with those from a 3D marker-based motion capture system (Qualisys). Ten recreationally active male basketball players (x̄ ± SD: age 23.7 ± 1.7 years; height 183 ± 5 cm; body mass 76.8 ± 9.8 kg) performed three CMJ trials, simultaneously recorded using both systems. Reflective markers placed on the shoulder, hip, and knee were tracked in Kinovea by two raters with different levels of experience to extract core CMJ variables (total take-off time and maximum vertical displacement) and complementary variables (eccentric and propulsion duration, and minimum vertical displacement). Inter-rater reliability and concurrent validity were evaluated using intraclass correlation coefficients (ICCs), coefficients of variation (CV%), standard error of measurement (SEM), and Bland–Altman analysis. Results showed excellent inter-rater reliability (ICC = 0.73–0.99) across all markers, with the hip and knee demonstrating the highest consistency. Strong validity relative to Qualisys was observed for both raters (ICC = 0.68–0.99; r > 0.80), with small systematic biases primarily in temporal variables. Collectively, these findings demonstrate that Kinovea’s semi-automated 2D analysis yields reliable and valid CMJ measurements comparable to 3D motion capture, even for less experienced users. As a free and easily deployable tool, it offers a widely accessible alternative for field-based performance monitoring and applied biomechanics research where laboratory-grade equipment is not available.

Vertical jump assessments are well-established in sports and rehabilitation to evaluate athletic performance. As demand increases for field-ready systems that maintain laboratory-grade accuracy, portable solutions like the CC Athletics PlateMate force plates show promising potential, especially due to their affordability and ability to export raw data without subscription fees. This study aimed to assess the concurrent validity of PlateMate by comparing it to a gold-standard AMTI force plate system during three vertical jump tasks: squat jump (SJ), countermovement jump (CMJ) and countermovement jump with arm swing (CMJH). Seventeen recreationally active participants performed five repetitions of each jump, while vertical ground reaction force data were recorded simultaneously from both systems (PlateMate stacked over AMTI). Subsequently, raw force-time signals were compared using Bland–Altman bias and 95% limits of agreement, root mean square error (RMSE), and Pearson’s correlation (r). Additionally, 24 derived variables across the three jump types were analyzed using intraclass correlation coefficients (ICC), coefficients of variation (cV%), standard error of measurement (SEM) and Pearson’s r. Across all jump conditions, results showed excellent agreement for both the raw force-time signals (r ≥ 0.95) and most of the derived metrics (ICCs > 0.93, r ≥ 0.90). RMSE values for combined plate outputs remained under 50 N, while SEMs for jump height ranged between 0.2–0.9 cm, indicating minimal measurement error. These results confirm PlateMate as a valid alternative to laboratory-grade force plates, with notable benefits in portability, affordability, and unrestricted data access, making it well-suited for field-based vertical jump performance testing.

Objective: The purpose of this study was to investigate differences in countermovement jump (CMJ) force–time metrics between male and female youth basketball players. Methods: Twenty-two female and seventeen male basketball players (ages 12–16) performed CMJs on a portable force plate system (VALD Performance). The data collected were analyzed for differences in force–time characteristics, specifically during the concentric and eccentric phases of the CMJ. Results: The results showed no statistically significant differences in anthropometric characteristics between the sexes. However, male athletes demonstrated better performance in several force–time metrics during the concentric phase of the CMJ, including concentric impulse, peak velocity, and mean power, ultimately leading to higher vertical jump heights. Sex-specific differences in the eccentric phase were less pronounced, though males exhibited greater relative eccentric mean power. Conclusions: The findings suggest that male players tend to display greater force and power-producing capabilities during the propulsive (concentric) phase of the CMJ. These differences highlight the importance of tailoring training programs to address specific needs, particularly focusing on enhancing concentric force and power production in female basketball players.

The countermovement vertical jump (CMJ) is widely used in sports science and rehabilitation to assess lower body power. In controlled laboratory environments, a complex analysis of CMJ performance is usually carried out using motion capture or force plate systems, providing detailed insights into athlete’s movement mechanics. While these systems are highly accurate, they are often costly or limited to laboratory settings, making them impractical for widespread or field use. This study aimed to evaluate the accuracy of MMPose, a markerless 2D pose estimation framework, for CMJ analysis by comparing it with force plates. Twelve healthy participants performed five CMJs, with each jump trial simultaneously recorded using force plates and a smartphone camera. Vertical velocity profiles and key temporal variables, including jump phase durations, maximum jump height, vertical velocity, and take-off velocity, were analyzed and compared between the two systems. The statistical methods included a Bland–Altman analysis, correlation coefficients (r), and effect sizes, with consistency and systematic differences assessed using intraclass correlation coefficients (ICC) and paired samples t-tests. The results showed strong agreement (r = 0.992) between the markerless system and force plates, validating MMPose for CMJ analysis. The temporal variables also demonstrated high reliability (ICC > 0.9), with minimal systematic differences and negligible effect sizes for most variables. These findings suggest that the MMPose-based markerless system is a cost-effective and practical alternative for analyzing CMJ performance, particularly in field settings where force plates may be less accessible. This system holds potential for broader applications in sports performance and rehabilitation, enabling more scalable, data-driven movement assessments.

This study aimed to validate the automated temporal analysis of countermovement vertical jump (CMJ) using MMPose, a markerless pose estimation framework, by comparing it with the gold-standard 3D marker-based motion capture system. Twelve participants performed five CMJ trials, which were simultaneously recorded using the marker-based system and two smartphone cameras capturing both sides of the body. Key kinematic points, including center of mass (CoM) and toe trajectories, were analyzed to determine jump phases and temporal variables. The agreement between methods was assessed using Bland–Altman analysis, root mean square error (RMSE), and Pearson’s correlation coefficient (r), while consistency was evaluated via intraclass correlation coefficient (ICC 3,1) and two-way repeated-measures ANOVA. Cohen’s effect size (d) quantified the practical significance of differences. Results showed strong agreement (r > 0.98) with minimal bias and narrow limits of agreement for most variables. The markerless system slightly overestimated jump height and CoM vertical velocity, but ICC values (ICC > 0.91) confirmed strong reliability. Cohen’s d values were near zero, indicating trivial differences, and no variability due to recording side was observed. Overall, MMPose proved to be a reliable alternative for in-field CMJ analysis, supporting its broader application in sports and rehabilitation settings.

This paper presents a procedure and Python im-plementation for the offline synchronization of vertical jumping data from a motion capture system and from force plates when a hardware trigger is unavailable and the sampling rates of the systems are known. Experimental data from a total of 15 subjects was collected. The synchronized data is used to evaluate predictions of ground reaction force with a 6-degree-of-freedom rigid-body model of the human skeletal system. The motion capture kinematic data was used as an input to the inverse kinematics and the force plate data was used to evaluate the output of the inverse dynamics of the rigid-body model. The results of the synchronization procedure, the predictions of the ground reaction forces, and an analysis of the joint trajectories are presented. The typical metrics of vertical jumping performance over our dataset were computed and agreed with typical trends and values noted in the literature.

Given the multidirectional nature of the sport, handball athletes must frequently perform high-intensity decelerations to avoid defenders, generate space, or perform directional changes. The aim of the present study was twofold: (i) to investigate different kinematic measures of horizontal deceleration performance by comparing the acceleration-deceleration assessment (ADA) with the 5-0-5 test and (ii) to investigate relationships between force-time characteristics derived from the countermovement vertical jump (CVJ) and measures of horizontal deceleration performance. Eleven female handball players competing in the first-tier professional league in Europe performed three CVJs while standing on a uni-axial force plate system sampling at 1000 Hz, followed by two ADAs (i.e., maximal-effort acceleration over a 10 m distance, followed by rapid deceleration) and 5-0-5 test trials. Tripod-mounted radar sampling at 47 Hz, placed 5 m behind the start line, was used to record horizontal velocity data. Each test was separated by a 5–7 min rest interval to minimize the influence of fatigue. No statistically significant differences were found in horizontal deceleration performance parameters between ADA and the 5-0-5 test. However, athletes with a higher CVJ height and reactive strength index-modified showed better performance in terms of horizontal deceleration measures such as maximal approach velocity and average and maximal deceleration. Overall, these results may be of interest to practitioners working with multidirectional sport athletes such as handball players as they provide critical insight for the selection of assessments and training strategies targeted toward optimizing on-court athlete performance.

Joint range of motion (ROM) is an important indicator of physical functionality and musculoskeletal health. In sports, athletes require adequate levels of joint mobility to minimize the risk of injuries and maximize performance, while in rehabilitation, restoring joint ROM is essential for faster recovery and improved physical function. Traditional methods for measuring ROM include goniometry, inclinometry and visual estimation; all of which are limited in accuracy due to the subjective nature of the assessment. With the rapid development of technology, new systems based on computer vision are continuously introduced as a possible solution for more objective and accurate measurements of the range of motion. Therefore, this article aimed to evaluate novel computer vision-based systems based on their accuracy and practical applicability for a range of motion assessment. The review covers a variety of systems, including motion-capture systems (2D and 3D cameras), RGB-Depth cameras, commercial software systems and smartphone apps. Furthermore, this article also highlights the potential limitations of these systems and explores their potential future applications in sports and rehabilitation.