Effect of work-to-rest ratio on acute responses to repeated-sprint training in hypoxia in elite track endurance cyclists

Repeated-sprint training in hypoxia (RSH) is increasingly used by athletes to improve repeat sprint ability in normoxia. However, the physiological responses to varying protocols remain unclear. This study aimed to determine how different RSH protocols affect acute physiological responses in elite cyclists. Nineteen elite cyclists were prescribed four RSH sessions (FiO₂: 14.5%) using three protocols: RSH-6: 4 sets × 5 reps (6 s sprint:24 s rest, W:R_1:4), RSH-10: 3 sets × 5 reps (10 s sprint:20 s rest, W:R_1:2), and RSH-6/10: 4 sets × 5 reps (sets 1 and 3-6 s sprint:24 s rest; sets 2 and 4-10 s sprint:20 s rest). Data were analysed using linear mixed models. Mean and peak power (<i>p</i> = 0.006), mean and peak torque (<i>p</i> = 0.001) and muscle re-oxygenation (<i>p</i> = 0.001) were greater in 6 s sprints. The 10 s sprints resulted in higher work per sprint(<i>p</i> = 0.001), larger sprint decrement (<i>p</i> = 0.001), higher blood lactate accumulation (<i>p</i> = 0.001), and greater muscle oxygen desaturation (<i>p</i> = 0.001). To improve neuromuscular capabilities (i.e. PPO and torque) cyclists should use shorter duration sprints with 1:4 W:R ratios. Alternatively, longer sprints and 1:2 W:R ratios are better suited to target metabolic adaptations.