A Comparison of the Consistency of Adaptive Changes in Biomotor Abilities Induced by Interval Training Individualized Using the 30–15 Intermittent Fitness Test Vs. Time-Matched Small-Sided Games in Well-Trained Soccer Players

ABSTRACT: Lyu, L, Wu, X-M, Li, Z, Qin, X-M, and He, Y. A Comparison of the consistency of adaptive changes in biomotor abilities induced by interval training individualized using the 30-15 intermittent fitness test vs. time-matched small-sided games in well-trained soccer players. J Strength Cond Res XX(X): 000-000, 2026-Adaptive changes from specific interventions are typically assessed by looking at the average responses of a group, with the assumption that these averages represent the adaptations of each individual. However, in practice, athletes exhibit varying responses to a given intervention. This study aimed to compare the effects of interval interventions prescribed using fixed reference intensities and small-sided games (SSG) on the homogeneity of adaptive responses in biomotor abilities in well-trained soccer athletes. Thirty national-level players were equally randomized to 2 high-intensity interval intervention groups individualized using 30-15 Intermittent Fitness Test (G-VIFT [2 sets of 5- to 8-minute intervals, comprising 15 seconds of running at 95% of VIFT followed by 15 seconds of passive recovery]), and time-matched SSG (4 sets of 2.5-4 minutes 3 v 3 efforts), and an active control group (CON), each of 10. Biomotor abilities including linear sprint speed, change of direction, jumping ability, muscular endurance, Yo-Yo intermittent recovery level 2 test, and anaerobic power were evaluated before and after an 8-week training period. Interindividual variability was examined using residual changes and coefficients of variation. Our results indicated that both G-VIFT and SSG groups significantly enhanced measures of biomotor abilities over the training period (p < 0.05). Comparative analysis indicated G-VIFT results in more homogenous adaptations in average power output and the subjects' ability to repeatedly perform and recover from intense exercise compared with SSG. Overall, individualizing high-intensity interval training using VIFT promotes more consistent adaptations in measures of anaerobic power and exercise tolerance compared with SSG.