All-out intermittent exercise on a one-leg knee extension ergometer: mechanical and physiological responses to different resistance forces

This study aimed to evaluate mechanical and physiological responses to all-out high-intensity interval training (HIIT) sessions (10 maximal efforts of 30 seconds each with 4 min of rest) performed against different resistance forces on a one-leg knee extension ergometer. Eighteen men conducted an incremental test to determine the resistance associated with its maximal power (R_max), followed by all-out HIIT sessions at 120%, 160%, and 200% of R_max, while oxygen consumption and neuromuscular function were measured. Mechanical power output was higher during the session at 200% of R_max compared to the other sessions (p < 0.001), but its absolute anaerobic energy contribution was similar to that at 160% of R_max. Notably, the all-out efforts at 200% R_max led to inconsistent kicking cadence and some participants were unable to complete the session. Therefore, 160% R_max was the highest suitable resistance force for a consistent all-out HIIT session on a knee extension ergometer.