The Accumulation of Performance Fatigue and Perceptual Responses across Consecutive High-Intensity Interval and Constant-Load Cycling Sessions.

Introduction: In numerous sport and occupational settings, individuals often need to perform multiple exercise sessions in 1 d or across consecutive days, yet performance and perceptual responses to such exercise paradigms are unclear.

Purpose: This study investigated performance fatigue and perceptual responses to repeated, consecutive sessions of high-intensity interval (HIIT) and constant-work rate (CWR) cycling bouts performed within 24 h.

Methods: Seventeen healthy adults (nine females, aged 25 ± 6 yr) exercised in the morning, same afternoon, and following morning. Sessions consisted of work- and duration-matched HIIT (2 min at 80% peak power output (PPO) interspersed by 2 min at 25% PPO) and CWR cycling (38 min at 54% PPO). A time-to-task failure (TTF) trial at 80% PPO was completed followed by both morning sessions. Neuromuscular assessments, including isometric knee extension maximal voluntary contraction coupled with superimposed and potentiated (Q tw ) twitches, elicited via electrical stimuli to the femoral nerve, were performed before and after workouts, and after the TTF. Blood lactate and perceptual responses were also measured.

Results: TTF trials were longer following CWR than HIIT ( P < 0.001). Across consecutive sessions, voluntary activation remained depressed, and this was accompanied by progressive impairments in cycling TTF following CWR ( P = 0.006). Conversely, maximal voluntary contraction and Q tw returned to baseline values by the beginning of each HIIT and CWR session. Perceived effort and dyspnea were higher in HIIT but were not exacerbated across sessions.

Conclusions: Although declined voluntary and evoked force-generating capacities did not persist in this study, consecutive exercise could compromise the recovery of voluntary activation and endurance performance.