In-Season Physical and Physiological Variations in Junior Basketball: A Longitudinal Analysis

This longitudinal study aimed to examine the in-season variations in morphological, cardiorespiratory, muscular, and motor fitness components in junior male basketball players during an 8-month competitive season. Eighteen male basketball players (16.56 ± 0.90 years) were tested at three time points (T1, T2, T3). Assessed variables included body fat (BF), fat-free mass (FFM), muscle mass (MM), total body water (TBW), maximal oxygen uptake (VO2max), final running speed in the 30-15 Intermittent Fitness Test (VIFT), maximum and average heart rate (HRmax, HRavg), squat jump (SJ), countermovement jump with arm swing (CMJmax), drop jump (DJ), 20 m sprint with 5 m and 10 m splits, T-test (TT), and Lane Agility Drill (LAD). Significant improvements were observed in body mass (T1–T3, p = 0.002; T2–T3, p = 0.039), along with reductions in BF (T1–T2 and T1–T3, p < 0.05) and increases in FFM and MM (especially T2–T3, p < 0.05). VO2max increased significantly from T1 to T2 and T3 (p < 0.01), while HRaverage decreased across all intervals (p < 0.001), and HRmax declined slightly from T1 to T3 (p = 0.031). VIFT improved significantly between T1 and both T2 and T3 (p < 0.001). Measures of explosive strength (SJ, CMJmax, DJ) and agility (TT, LAD) showed consistent improvement across the season (p < 0.001), with moderate gains from T2 to T3 (p < 0.01 for SJ). These findings suggest meaningful physical and physiological adaptations during the competitive season, highlighting the importance of structured and continuous training throughout critical phases of athletic development in junior basketball players.