Change Of Direction Research Articles

Acute effects of different loading protocols upon performance and kinematics of 180 degrees change of direction

ABSTRACT This study examined the acute effects of different loading protocols on 180° change of direction (COD) performance in eleven male handball players. Participants performed a 10-0-5 COD test under seven conditions: without an external load, and with 3, 6, and 9 kg loads applied under two modes—assisted into the COD and resisted out of it and resisted into the COD and assisted out of it. While total COD time was not affected (p = 0.098; η2 = 0.16), significant phase effects were observed (p < 0.001; η2 ≥ 0.55). Loading protocols significantly influenced velocity, acceleration, and their distances from COD (p < 0.001; η2 ≥ 0.37). Significant phase effects were observed for all step kinematic variables (p ≤ 0.037; η2 ≥ 0.67), except contact time, and significant interaction (phase*condition) effects for all variables (p ≤ 0.004; η2 ≥ 0.08), except for step frequency. Assisted-resisted protocols increased deceleration demands through higher COD entry velocities, displaying fewer but longer steps in the acceleration phase and greater steps taken during the deceleration phase. Resisted-assisted protocols decreased deceleration demands due to lower COD entry velocities, displaying shorter, but more steps taken in the acceleration phase, and fewer steps taken in the deceleration phase. These findings suggest that assisted-resisted and resisted-assisted loading protocols can be used to selectively overload specific phases of COD performance.

Acute responses to a potentiation warm-up protocol on sprint and change of direction in female football players: a randomized controlled study.

To evaluate the acute effect of exposure to a potentiation warm-up protocol compared to a usual warm-up program. Randomized parallel control trial. Synthetic grass in the club's facilities (Portugal). Seventeen female football players (age: 23.9 ± 3.9 years), were randomly allocated to a control (n = 8) and an experimental group (n = 9). To allocate the players, a table was computer-generated by a research team member with no involvement in the trial. The control group performed their usual warm-up program, while the experimental group performed a potentiation warm-up protocol with jumps combined with sprints with change of direction. The players were tested pre- and post-intervention for a 40-m linear sprint and pre-planned change of direction using the T-test. An intention-to-treat analysis was performed, with all the participants originally randomized being involved. The normal distribution was verified by the Shapiro-Wilk test. The assumption of sphericity was analyzed. Effect sizes were calculated using partial eta squared. No significant pre-post differences in the T-test and in the 40-m sprint were detected for any group. However, in the T-test, large effect sizes in time increments were observed within the experimental (0.27s; p > 0.05, ηp2 = 0.176) and control groups (0.06s; p > 0.05, ηp2 = 0.176). Also, in the 40-m sprint, large effect sizes in time increments were observed within the experimental (0.05s; p > 0.05, ηp2 = 0.251) and control groups (0.09s; p > 0.05, ηp2 = 0.251). The performance-enhancing ability of the potentiation method performed at warm-up was not verified when applied to female football players. Thus, the potentiation methods may not improve sprint and COD ability for this population. However, the lack of statistical significance may have been due to reduced statistical power, as three of four effects suggest acute performance impairment after a supposed potentiation-oriented warm-up. Nevertheless, the presence of a statistical type 2 error cannot be ruled out. NCT06555185; Project URL: https://clinicaltrials.gov/study/NCT06555185 .

Experimental Assessment between Dissimilar Techniques and Methodologies to Sports Knee Injury using Magnetic Resonance Imaging

The anterior cruciate ligaments, which are crucial for conserving the normal biomechanics of human being knees, are the majority commonly injured knee-ligaments. An anterior cruciate ligament injury is originated by a split or wrench of the anterior cruciate ligaments, which are imperative ligaments in the knee. ACL injure is mainly and frequently caused by sports like football, soccer, and the like that require quick pauses or direction changes, jumping, and landings. These days, the area of diagnostics heavily relies on magnetic resonance imaging. It is effective in determining the presence of meniscal tears and damage to the cruciate ligament. This study's primary objective is to use magnetic resonance imaging knee images to find anterior cruciate ligament tears, which can be useful in identifying issues with the knee. Inception-v3, an established deep transfer learning (DTL) model based on a DCNN was used in this study to classify anterior cruciate ligament tears in MRI scans. Classification, Preprocessing, and feature extraction are the major processes used in the current study executions. The dataset type utilized in this article of research study was built using the MRNet database. Seventy percent of the data set is used for preparation and testing, while the lingering thirty percent is utilized for performance analysis in this comparison model. The future augmented methodology can improve upon the present models' performance through the application of DL and ML techniques.

Process model for multifactorial characteristics of the sense of place in the case of Budapest (Hungary) District VII

The existence of residential well-being of the locals in the sense of equilibrium-state is a competitive advantage for tourism in a given destination. The rise of overtourism could jeopardize this equilibrium and ultimately the effectiveness of tourism in a vulnerable destination. The research question of the study aimed to answer: what are the spiral dynamics of the multifactorial characteristics of the sense of place that can be mapped under the influence of overtourism. Answering the question draws attention to the sense of place—which can be interpreted as a synonym for local character—of the issues of overtourism and residential well-being. Mapping the mechanism of action of the multifactorial characteristic of locality can help to identify non-supportive functions, to pinpoint the balance point for moving towards a supportive quality, and to answer the “how yes” questions at individual, local and collective levels. The answer to the research question is the result of concluding three district-specific sub-questions. The assessment of the results was based on the content analysis of 251 posts (2017–2021) in the local public Facebook group (supplemented by a questionnaire survey of local residents (2022), 30 in-depth interviews with experts and residents (2022) conducted as part of the cross-sectional research, and 10 additional in-depth interviews with residents (2024) conducted for the last sub-question. The flowchart showing the current state of the district along a negative spiral dynamic, the possibility to turn it in a positive direction, and the mind-map-like summary of local, individual and collective mitigation and solution alternatives supporting the change of direction can be considered as a novel scientific result.

Associations Between Sprint Mechanical Properties and Change of Direction Ability and Asymmetries in COD Speed Performance in Basketball and Volleyball Players

This study aimed to assess the associations between sprint force–velocity profile variables with change of direction (COD) performance and to investigate the impact of these variables on asymmetries in COD speed performance. Ninety-nine participants (volleyball players: n = 44, basketball players: n = 55) performed 40 m sprints for Fv relationship calculation, two COD tests (Modified Agility T-test and 505 test). A partial least squares (PLS) regression analysis was conducted to determine the relationships between the variables. The V0 was the most influential variable; it was negatively associated with COD performance variables (β = −0.260, −0.263 and −0.244 for MAT, 505-D and 505-ND, respectively), and F0 (β = 0.169, 0.163) was associated with the COD performance variables (COD deficit D and COD deficit ND, respectively), slightly larger than the effects of Fvslope (β = −0.162, −0.146), DRF (β = −0.159, −0.142) and Pmax (β = −0.162, −0.146). For COD deficit imbalance, the DRF (β = −0.070) was the most influential variable followed by Fvslope (β = −0.068), F0 (β = 0.046) and gender (β = 0.031). V0 and RFmax were the critical variables for improving COD performance that includes linear sprints, while DRF, Fvslope, F0 and Pmax collectively influence 180° COD performance. Meanwhile, DRF and Fvslope were important factors for asymmetries in COD speed performance. It is recommended to use the Fv profile to diagnose different COD movement patterns and then develop training plans accordingly for team sports played on smaller courts, such as basketball and volleyball.

Kinetic analysis of change of direction simulating a defensive action in soccer players with and without acute fatigue.

The objective of this study is to analyse the kinetic effects of acute fatigue during a 45° change of direction executed with the non-dominant limb, emulating a typical defensive action during pressing in soccer. Seventeen male professional soccer players (age: 21.7 ± 5.4 years) performed a 45° change of direction before and after a fatigue protocol. Participants were instructed to execute an approach run as quickly as possible, to change direction with their non-dominant foot on a force platform, and then continue running with the aim of stopping against an opponent. Times, forces, impulses, and force rates for different subphases during support were compared. Speeds remained consistent across pre-fatigue (4.53 ± 0.55 m s-1) and post-fatigue (4.58 ± 0.70 m s-1) trials. The results indicated a decrease in braking time (p = 0.01), impulse associated with the braking phase (p < 0.01), and impulse during body weight lifting (p = 0.01) under acute fatigue conditions. These changes suggest that, under acute fatigue, soccer players may not decelerate sufficiently in the initial direction of the run and may raise their body less in the first step after the change of direction. Maximum force values and force rates did not show significant changes; however, they were sufficiently high to suggest a potential injury risk in both conditions.

Change-of-Direction Performance and Its Deficits in Relation to Countermovement-Jump Height and Phase-Specific Performance Among Female Athletes.

Jump and linear sprint performances both correlate with pro-agility performance. However, correlation does not imply causation, and potential confounders may affect the correlation. Therefore, this study aimed to determine the relationship between change-of-direction (COD) performance and COD deficits (COD-D) in linear-sprint and countermovement-jump (CMJ)-related performance using multiple stepwise linear-regression models. The study included 42 female national-level intercollegiate athletes. The 10- and 20-m linear-sprint and pro-agility times, COD-D, CMJ height, and phase-specific force production and rate of force development during eccentric unloading, eccentric braking, and the concentric phases of CMJ were measured. Stepwise linear-regression analyses were used to predict the factors related to COD and COD-D. CMJ height was the sole predictor in the 10-m pro-agility model (adjusted R2 = .234, P = .001). Modified Reactive Strength Index (standardized coefficient, -.710) and the lowest center-of-mass depth during the CMJ (standardized coefficient, .323) were predictors in the 20-m pro-agility model (adjusted R2 = .330, P < .001). For the 10- and 20-m COD-D models, the rate of force development at 30 and 60milliseconds, respectively, during the concentric phase was the only predictor of performance (adjusted R2 = .183, P = .003 and .237, P = .001, respectively). These results suggest that athletes should concentrate on improving their CMJ height, increasing their ability to lower their center of mass more deeply, and increasing their instantaneous force-production abilities immediately after the eccentric braking phase of CMJ to improve their COD performance.

Augmented and Virtual Reality Based Segmentation Algorithm for Human Pose Detection in Wearable Cameras

Pose graph optimisation is a crucial method that helps reduce cumulative errors while estimating visual trajectories for wearable cameras. However, when the posture graph's size increases with each additional camera movement, the optimization's efficiency diminishes. In terms of ongoing sensitive applications, such as extended reality and computer-generated reality, direction assessment is a major test. This research proposes an incremental pose graph segmentation technique that accounts for camera orientation variations as a solution to this challenge. The computation only improves the cameras that have seen large direction changes by breaking the posture chart during these instances. As a result, pose graph optimisation is essentially slowed down and optimised more quickly. For every camera that hasn't been optimised using a pose graph, the algorithm employs the wearable cameras at the start and end of each camera's trajectory segment. The final camera in attendance is then determined by weighted average the various postures evaluated with these wearable cameras; this eliminates the need for lengthy nonlinear enhancement computations, reduces disturbance, and achieves excellent accuracy. Experiments on the EuRoC, TUM, and KITTI datasets demonstrate that pose graph optimisation scope is reduced while maintaining camera trajectories accuracy.

Jehovah’s Witnesses: a change of direction for ‘surgical’ children?

Our Legal Editor looks at a significant change in how consent for 'surgical' children who refuse treatment is handled.

Effects of Light Versus Very Heavy Resisted Sprint Training on Multidirectional Speed in Semi-professional Soccer Players.

Baena-Raya, A, Robles-Ruiz, J, Pérez-Castilla, A, Pareja-Blanco, F, and Rodríguez-Pérez, MA. Effects of light versus very heavy resisted sprint training on multidirectional speed in semi-professional soccer players. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to evaluate the effects of an 8-week resisted linear sprint training (RST) program with 2 loading conditions (light vs. very heavy) on linear sprint (LS), curve sprint (CS), and change of direction (COD) performance in young soccer players. Thirty-eight male under-19 soccer players were assessed for 30-m LS, CS, and modified 505 COD tests. Players were randomly allocated into 3 groups: control (n = 18), light (n = 10), and very heavy RST (n = 10). Light and very heavy RST groups performed RST with external loads resulting in a 25 and 75% velocity loss from the player's maximal LS velocity, respectively. The control group did not perform any sprint training. Significant group × time interactions were observed for LS, CS, and COD performances (p < 0.05). The control group showed no performance improvement. Both RST groups showed significant improvements in LS at 10-, 20-, and 30-m (p ≤ 0.03; effect size [ES] ≥ 0.62), whereas no significant changes were observed for the split times (p > 0.05). CS performance was significantly increased by the 2 RST groups (p ≤ 0.03; ES ≥ 0.60), except for light RST on CS right side at 17-m (p = 0.09; ES = 0.46). Change of direction performance was only significantly enhanced by the very heavy RST group (p ≤ 0.001; ES ≥ 0.80). No significant changes between RST groups were observed. In conclusion, using both light and very heavy RST can enhance LS and CS performance, whereas very heavy RST is recommended to optimize COD performance in young soccer players.

Effects of a Short-Term Detraining Period on the Physical Fitness in Elite Youth Soccer Players: A Comparison Between Chronological Age Groups.

Padrón-Cabo, A, Lorenzo-Martínez, M, De Dios-Álvarez, V, Rey, E, and Solleiro-Durán, D. Effects of a short-term detraining period on the physical fitness in elite youth soccer players: a comparison between chronological age groups. J Strength Cond Res XX(X): 000-000, 2024-The aim of this study was to examine the effects of a 2-week in-season training cessation on neuromuscular and endurance performance in 2 different age groups of elite youth soccer players. A total of 30 players belonging to the under-15 (U15, n = 17) and under-17 (U17, n = 13) age groups of a Spanish professional soccer academy participated in the study. The following tests were assessed before and after the training cessation period: squat jump (SJ), countermovement jump (CMJ), 20-m sprint with 5-m and 10-m split times, modified 505 change of direction, and 30-15 Intermittent Fitness Test (30-15 IFT). The results showed significant and similar performance impairments between the 2 age groups in SJ (p = 0.020), CMJ (p = 0.044), 20-m sprint (p < 0.001), and 30-15 IFT (p < 0.001). The U17 players evidenced greater impairment than the U15 players in 5-m (p = 0.006) and 10-m (p = 0.002) sprint performance. However, there was no significant change (p = 0.070) in the players' change of direction performance. These findings provide valuable information for strength and conditioning coaches, suggesting the need for targeted interventions to mitigate the effects of detraining on neuromuscular and endurance performance during short-term in-season training cessation periods in elite youth soccer players. Special attention should be paid to maintaining sprint performance during short-term detraining periods in U17 players.

No Post-Activation Performance Enhancement Following a Single Set of Plyometric or Flywheel Exercises in National Team Rugby Players

Post-activation performance enhancement (PAPE) is a key objective following regular warm-up routines, especially in sports that rely heavily on sprinting speed and power. Rugby is a team sport characterized by a range of repeated high-intensity efforts, irrespective of positional roles or match demands. In this study, we examined and compared the effects of two different conditioning activities (CAs) on the power- and speed-related abilities of National Team rugby players. Thirteen male rugby union players sequentially performed countermovement jump (CMJ), 30 m sprint, and change-of-direction (COD) tests (pre-testing session) 5 min before executing either one set of six repetitions of 45 cm drop jumps or one set of six repetitions of flywheel eccentric-overload squats. In addition to the sport-specific tests, the muscle mechanical properties of the athletes were also assessed through the use of tensiomyography (TMG). At post-testing sessions conducted 5 and 10 min after the PAPE protocols, no significant changes were observed in any of the assessed variables, either in positions as backs or forwards. However, some meaningful variations were detected at the individual level when using the “true-changes” analysis. Despite some positive individual changes, it can be concluded that these specific protocols did not elicit the expected responses typically observed in other team-sport athletes. Practitioners are encouraged to implement more comprehensive (but not exhaustive) and tailored PAPE interventions prior to training sessions and competitions.

Correlations between Metabolic Parameters, Blood Cytokine Levels, and Behavioral Parameters in Male and Female Rats of Different Age after Intrauterine Stress.

We studied interrelationships between behavioral parameters, metabolic processes, and cytokine content in the blood of male and female rats at different stages of postnatal ontogeny after intrauterine stress (mothers were forced to swim in cold water from the 10th to the 16th day of pregnancy). Correlations between behavioral and metabolic parameters in prenatally stressed rats were revealed at an earlier age (day 21 of life) than in controls. In comparison with intact rats, in males exposed to intrauterine stress no relationships between these parameters were revealed at older age, while in females, their direction and character change on day 60 of life. In prenatally stressed males, correlations of the blood levels of IL-6 were revealed: inverse relationships with behavioral parameters on the days 21 and 30 and direct relationships with metabolic parameters on day 60 of life. In prenatally stressed females on day 30 of life, we observed negative correlations between IL-4 levels and metabolic parameters that were absent under normal conditions. Thus, intrauterine stress leads to reorganization of the relationships between the parameters of metabolic and immune processes, which are essential for the purposeful behavior of mammals. The effects of stress seem to depend on the sex of the offspring and stage of postnatal development.

Is the Modern Arctic Marginal Ice Zone More Susceptible to Summer Cyclones?

Abstract As Arctic sea ice melts, cyclones potentially enhance the mechanical and thermodynamic forces that influence the vulnerable ice edge. However, examples can be found in satellite observations and reanalyses where cyclones either locally increase or decrease ice within the marginal ice zone (MIZ). Two case studies with these opposing ice responses are presented. Guided by the tendencies during these events, 264 strong (minimum surface pressure below 984 mb) summer cyclones were sorted by prevailing wind direction and SST changes within the MIZ to quantify the net ice impacts in the present-day Arctic (2010–2019) and early satellite era (1982–1991). By tracking MIZ ice area from one week before the cyclone’s formation through two weeks after, we find cyclones that enhance southerly winds mostly decrease ice area, whereas enhanced northerlies generally increase ice area within the MIZ later in the season. Furthermore, early-summer storms tend to decrease MIZ ice area more than late-summer storms. A shift towards more frequent early-summer storms is observed from the 1980s to 2010s, resulting in almost two-thirds of recent storms decreasing area. Consequently, recent summer cyclones have more negative impacts, resulting in a decline of more than 40,000 km2 of MIZ ice area on average, whereas 1980s cyclones had little aggregate impact. Wind direction and SST trends partially reconcile the wide range of MIZ ice area changes due to cyclone passage, yet considerable variations in individual cyclones’ impacts remain even when controlling for these factors. These bulk diagnostics therefore only explain part of the complex ice-cyclone relationship.

The effect of multi-directional sprint training on change-of-direction speed and reactive agility of collegiate tennis players.

The aim of this study was to evaluate the effect of random route multi-directional sprint training (MDST) compared to fixed route MDST on change-of-direction speed (CODS) and reactive agility (RA), and to investigate the correlation between CODS, RA and short-distance straight sprint speed (SDSS). A total of 19 collegiate tennis players from Beijing Sport University were randomly assigned to either the random route MDST group (RR group, N = 9, age: 22.22 ± 2.22 years) or the fixed route MDST group (FR group, N = 10, age: 21.90 ± 1.66 years). Both groups completed a progressive load intervention training for 3 weeks, three times a week. The RR group's random route, mirroring the distance and number of change-of-direction (COD) in the FR group's fixed route, was specifically designed. The spider run, T-drill, RA test and 5-m straight line sprint test were performed before and after the intervention. Both groups showed improved performance in the spider run (p < 0.05), T-drill (p < 0.01) and 5-m straight (p < 0.001) line sprint test after the intervention. Additionally, there was no significant difference in the improvement of CODS and SDSS between the two groups (p > 0.05). The RA of the RR and FR groups after the intervention was significantly higher than before intervention (p < 0.001), and RR group showed greater improvement in RA compared to the FR group. There was a moderate correlation between spider run and T-drill (r = 0.523), RA (r = 0.388), and no significant correlation between spider run and 5-m straight sprint (p > 0.05). T-drill was moderately correlated with RA (r = 0.347) and 5-m straight sprint (r = 0.321). RA was moderately correlated with 5-m straight sprint (r = 0.551). Three-week multi-directional sprint training can effectively improve the change-of-direction speed, reactive agility and short-distance straight sprint speed of collegiate tennis players. And random route multi-directional sprint training has better effect on improving reactive agility.

The effects of university badminton class on health and well-being in untrained college students

This study investigated the effects of a 6-week activity course on health and well-being in untrained college students. Twenty-two participants (ages 18–23) engaged in either badminton or soccer twice a week. Using Badminton World Federation (BWF) Shuttle Time Lesson Plans, both groups showed significant improvements in the quadrant jump and standing long jump tests, with badminton participants demonstrating greater gains in the quadrant jump. In addition, Resilience levels increased in both groups and exercise self-efficacy saw a larger rise in the soccer class. The data suggested that badminton might improve agility more due to the need for rapid direction changes in a smaller court. Further, university activity classes could enhance both physical and mental well-being, though prior soccer experience and limited badminton court access may boost self-efficacy more in soccer participants. Lastly, BWF Shuttle Time Lesson Plans proved effective for introducing badminton to beginners.

Effect of touch on proprioception: non-invasive trigeminal nerve stimulation suggests general arousal rather than tactile-proprioceptive integration.

Proprioceptive error of estimated fingertip position in two-dimensional space is reduced with the addition of tactile stimulation applied at the fingertip. Tactile input does not disrupt the participants' estimation strategy, as the individual error vector maps maintain their overall structure. This relationship suggests integration of proprioception and tactile information improves proprioceptive estimation, which can also be improved with trained mental focus and attention. Task attention and arousal are physiologically regulated by the reticular activating system (RAS), a brainstem circuit including the locus coeruleus (LC). There is direct and indirect evidence that these structures can be modulated by non-invasive trigeminal nerve stimulation (nTNS), providing an opportunity to examine nTNS effect on the integrative relationship of proprioceptive and tactile information. Fifteen right-handed participants performed a simple right-handed proprioceptive estimation task with tactile feedback (touch) and no tactile (hover) feedback. Participants repeated the task after nTNS administration. Stimulation was delivered for 10 min, and stimulation parameters were 3,000 Hz, 50 μs pulse width, with a mean of 7 mA. Error maps across the workspace are generated using polynomial models of the participants' target responses. Error maps did not demonstrate significant vector direction changes between conditions for any participant, indicating that nTNS does not disrupt spatial proprioception estimation strategies. A linear mixed model regression with nTNS epoch, tactile condition, and the interaction as factors demonstrated that nTNS reduced proprioceptive error under the hover condition only. We argue that nTNS does not disrupt spatial proprioceptive error maps but can improve proprioceptive estimation in the absence of tactile feedback. However, we observe no evidence that nTNS enhances tactile-proprioceptive integration as the touch condition does not exhibit significantly reduced error after nTNS.

Joint torque estimation method of industrial robot by combining error compensation model based on LSTM and iterative weighted parameter identification

It is essential for human-robot interaction to accurate joint torque value estimation of industrial robots without force/torque (F/T) sensors. The most common method to estimate the value of robot joint torque is based on dynamic model parameter identification. However, no matter how elaborate the modeling methods are used, there are always uncertainty errors when robot’s joint rotation direction changes. In this paper, an identification framework is proposed to estimate optimal model parameters, and a deep learning network is proposed to compensate for the uncertainty errors caused by the unmodeled dynamics part. At first, the dynamic parameters are estimated during the Least Squares (LS) identification process considering the noise influence and data outliers, and the nonlinear friction model is unified into the identification framework. Secondly, based on Long-Short Term Memory (LSTM) network, an error compensation model (ECM) is proposed to establish the mapping relationship between the joint motion and the identification errors. Finally, a 6-DOF robot is used for parameter identification and ECM validation. Experimental results show that the proposed identification method is better than the LS method. Compared with the torque value estimated by the identification method, the proposed ECM can compensate for the uncertainty errors and improve the torque estimation accuracy.

Welding Defect Monitoring Based on Multi-Scale Feature Fusion of Molten Pool Videos.

Real-time quality monitoring through molten pool images is a critical focus in researching high-quality, intelligent automated welding. However, challenges such as the dynamic nature of the molten pool, changes in camera perspective, and variations in pool shape make defect detection using single-frame images difficult. We propose a multi-scale fusion method for defect monitoring based on molten pool videos to address these issues. This method analyzes the temporal changes in light spots on the molten pool surface, transferring features between frames to capture dynamic behavior. Our approach employs multi-scale feature fusion using row and column convolutions along with a gated fusion module to accommodate variations in pool size and position, enabling the detection of light spot changes of different sizes and directions from coarse to fine. Additionally, incorporating mixed attention with row and column features enables the model to capture the characteristics of the molten pool more efficiently. Our method achieves an accuracy of 97.416% on a molten pool video dataset, with a processing time of 16 ms per sample. Experimental results on the UCF101-24 and JHMDB datasets also demonstrate the method's generalization capability.

Relationship between the Reliability of Tennis-Specific Change of Direction (77COD) Test and Squat Jump–Countermovement Jump in Adolescent Tennis Players

The aim of this study was to investigate the reliability of the tennis-specific change of direction (77COD) test with vertical jump tests (Squat Jump and Countermovement Jump) in adolescent tennis players. A total of 58 athletes (31 girls, 27 boys) actively playing tennis, with an average age of 10.57 ± 2.54 years, participated in the study. Tests and retests were completed within 2 weeks. Bland–Altman (B&amp;A) plots were established and Pearson’s correlation analysis was conducted on the 77COD, CMJ, and SJ tests. Simple linear regression analysis (enter method) was used to determine the significant predictors of the 77COD variable from the SJ-CMJ variables. The SJ and CMJ were found to be highly negatively correlated with the 77COD test (−0.72 ≤ r ≤ −0.74). The test–retest reliability of the 77COD test was found to be very high, with an intraclass correlation coefficient (ICC) of 0.95. Our findings showed that the 77COD test is suitable for determining COD ability in adolescent tennis players. In addition, vertical jump heights are an informative and practical performance indicator for 77COD. In conclusion, the 77COD test is a COD test that can be used in coaching practices without the need for complex testing materials.