Acute Effects of Cluster-Set vs. Traditional-Set Plyometric Loading on Countermovement Jump and Reactive Strength Index in Young Tennis Players

The present study aimed to compare the acute effects of cluster-set (CS) and traditional-set (TS) plyometric loading protocols on countermovement jump (CMJ) performance and reactive strength index (RSI-mod) in young tennis players. It was hypothesized that the CS method would elicit superior acute improvements in jump parameters and recovery due to reduced fatigue compared to the TS method. A total of 28 male adolescent tennis players, aged 13-17 years, voluntarily participated. Volunteers were randomly allocated into two experimental groups: Cluster Set Group (CS) and Traditional Set Group (TS). ). Participants were eligible if they met the following criteria.

i. Engaged in tennis training for ≥2 years, with a frequency of ≥3 sessions/week and participation in ≥4 tournaments annually.

ii. Had ≥6 months of experience with resistance and plyometric training. iii. No history of lower extremity muscle or joint injuries within the last three months.

iv. No regular use of drugs or stimulants for at least six months prior to the study.

The study consisted of two sessions: a familiarization session and an experimental session involving either the Cluster Set (CS) or Traditional Set (TS) protocol. Participants refrained from any exhaustive exercise for at least 48 hours prior to the familiarization session, and a 48-hour passive recovery period was observed between sessions. During the familiarization session, anthropometric measurements (height, body mass, body fat %) were recorded, and participants completed the Physical Activity Readiness Questionnaire (PAR-Q+). Following this, subjects performed a standardized warm-up and familiarization with the testing procedures. The experimental session included the following sequence: (i) Pre-test measurements: Countermovement Jump (CMJ) and Drop Jump (DJ), (ii) execution of either CS or TS plyometric protocol, (iii) immediate Post-15s): CMJ and DJ, (iv) passive recovery (3 min) followed by CMJ and DJ, and assessment using the Total Recovery Quality Scale (TQR), (v) additional passive recovery (3 m) followed by CMJ and DJ and TQR, (vi) final post-test (6 min): CMJ and DJ. Total workout 7 minutes and passive rest 6 minutes (Table 2). Participants were instructed to sleep at least 8 hours the night before testing. Maintain a normal diet and avoid medications, stimulants, ergogenic aids, or performance-enhancing substances. Before testing, all participants completed a 10-minute standardized warm-up, consisting of jogging, galloping, multidirectional running and jumping, calisthenic exercises for joint mobility, static and dynamic stretching. The procedure of the study is shown in Figure 1. All interventions were conducted between 15:00 and 17:00 in a synthetic-floored gym under controlled conditions (temperature: 18-24°C; humidity: 40-60%). Two Way ANOVA repeated measures analysis of variance, 2 groups (CS and TS) x 4 time (Pre, Post-15s; Post-3m and Post-6m) test was performed to compare the data and determine the differences. Bonferroni test was used for pairwise time and group comparisons.