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

Abstract

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. 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. 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. 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. 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.