The distracting role of stress: Impaired executive attention and delayed fatigue perception

Acute cognitive stress applied concurrently with fatiguing exercise affects neuromuscular fatigue. However, the underlying central mechanisms in men and women are poorly understood.

This study aimed to identify the influence of cognitive stress on central fatigue and associated functional changes in the cognitive and motor brain areas in men and women.

Thirty younger adults, balanced by sex, performed intermittent elbow flexion contractions at a duty cycle of ∼67% at 30% of their maximum strength till voluntary fatigue. Participants' strength, fatigability, and muscle activity were collected. Functional near-infrared spectroscopy was used to monitor the activation of the prefrontal cortex (PFC) and motor cortex (M1) to compute graph-theoretic metrics based on functional integration and segregation in the PFC and M1.

Results indicate that despite poorer motor performance, i.e., lower force steadiness, stress prolonged endurance among both men and women. Stress also stunted the perception of effort for exercise and reduced functional segregation of the PFC. Stress did not contribute to the sex differences in central mechanisms of fatigue.

Our findings suggest that cognitive stress has a distraction effect on higher-order executive attentional resources, resulting in a delayed perception of fatigue and impairing motor performance.

These findings help us understand the psychophysical limitations of workers who are often exposed to high cognitive stress due to high workload conditions. These findings show that a high cognitive load can mask the indicators of exercise fatigue, which may increase the risk of musculoskeletal injury in the long term.