Abstract Maviel, C, Vercruyssen, F, Duché, P, Bourdin, S, Morin, J-B, and Couderc, A. In-season individualized resisted sprint session improves in-situ acceleration-speed profile in professional rugby backs. J Strength Cond Res XX(X): 000–000, 2026—This study aimed to evaluate how resisted sprint training sessions with individualized load calibration influence the in-situ acceleration-speed profile in professional rugby. Recent findings highlight the importance of individualized load prescription based on the force-velocity profile and horizontal propulsive power, both closely linked to sprint performance in rugby. Two groups of professional rugby backs were examined: a control group (CG, n = 11, 2023–2024 season) and an experimental group (EG, n = 17, 2024–2025 season). The CG completed standard in-season training with no resisted sprint work, whereas the EG performed a resisted sprint protocol using the 1080 Sprint system calibrated to 50% of each player's maximal sprint velocity (S 0 ), derived from the preintervention in-situ acceleration-speed profile. Sprint sessions were performed once per week and consisted of four 15 m resisted sprints at a constant target velocity. Significant improvements were observed in the EG for propulsive power (4.5 ± 3.0%, p < 0.001), S 0 (2.7 ± 2.1%, p < 0.001), and maximal acceleration (1.8 ± 2.7%, p = 0.03), whereas no significant changes were found in the CG. These findings suggest that implementing individualized resisted sprint training sessions is a promising strategy to improve in-situ sprint mechanical outputs during the competitive season.
Maviel et al. (Mon,) studied this question.