The Impact of Running-Based and Drop Jumping Interval Interventions on Cardiorespiratory Fitness and Anaerobic Power of Collegiate Volleyball Players: A Comparative Analysis of Inter-Individual Variability in the Adaptive Responses

This study compared inter-individual variability in the adaptive responses of cardiorespiratory fitness, anaerobic power, and motor abilities of male volleyball players to high-intensity interval training (HIIT) prescribed as repetitive drop jumps (interval jumping) and running-based intervals (interval running). Twenty-four collegiate volleyball players were equally randomized to two training groups executing 11 minutes of interval running or interval jumping during which they ran or repeated drop-jumps for 15 seconds, alternating with 15 seconds of passive recovery. Before and after the 6-week training period, aerobic fitness, cardiac function, and anaerobic power were evaluated using a graded exercise test, impedance cardiography, and a lower-body Wingate test, respectively. Additionally, linear speed, agility, and jumping tests determined motor abilities. Both interventions significantly enhanced maximum oxygen uptake (V̇O_2max), velocity associated with V̇O_2max, first and second ventilatory thresholds (VT₁ & VT₂), maximal cardiac output (Q̇_max), stroke volume (SV_max), peak and average power output, vertical jump, change of direction, and linear sprint speed. Interval jumping group demonstrated a significantly greater improvement in squat jump (<i>p</i> = 0.001; 95% CI: 2.51-5.42) and countermovement jump (<i>p</i> = 0.001; 95% CI: 2.11-4.61) compared to interval running group. Conversely, interval running group elicited a greater enhancement in sprint speed (<i>p</i> = 0.002; 95% CI: 2.53-5.71) than interval jumping group. Examining the individual residual in the adaptive responses revealed that interval running induced more homogenized adaptations across individuals in VT₁ (<i>p</i> = 0.04; 95% CI: 0.03-1.33), Q̇_max (<i>p</i> = 0.03; 95% CI: 0.04-1.64), SV_max (<i>p</i> = 0.04; 95% CI: 0.02-1.75), and maximal sprint speed (<i>p</i> = 0.01; 95% CI: 0.72-1.95) in contrast to interval jumping. However, the uniformity of adaptations in countermovement jump in response to interval jumping surpassed that of interval running (<i>p</i> = 0.02; 95% CI: 0.08-1.32). Although both training modalities effectively improved the mentioned variables concurrently, tailoring the HIIT intervention to the reference intensity and training modality specific for each quality may enhance measured quality.