The Impact of Occupation and Mental Stress on Performance Fatigability

Performance fatigability is a decline in performance over time and can be influenced by mental stress, but the impact of occupation remains unclear. Eighteen career firefighters (FF) and fifteen white-collar workers (WC) (29.97±5.35 years) completed isometric leg extension maximal voluntary contractions (MVCs) before and following a sustained 20% MVC fatiguing protocol during a control and stressor (mental math) condition. Cardiovascular, perceptual, and surface electromyographic (EMG) measures were recorded. The FF had a lower workday sitting index (P=0.002) and smaller pre-ejection period (PEP; greater sympathetic activation) than WC (P=0.004). FF demonstrated longer (P=0.004) time to task failure (TTF) and a smaller slope of rating of perceived exertion (RPE) under stress whereas there was no significant difference between conditions for WC group. Torque fluctuations, EMG amplitude, coactivation, and heart rate increased throughout the fatiguing contraction (P<0.001) while PEP decreased (P<0.001). FF show altered fatigue perception under stress while neuromuscular responses remain unchanged.