PHYSICAL FATIGUE REDUCES MENTAL FUNCTION
Van Duinen, H., Browne, K., Renken, R. J., & Zijdewind, I. (2007). Brain activity during motor fatigue and cognitive task performance. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 699.
This study investigated which brain areas are involved in dual-task performance and to analyze the changes in activity in these areas during motor fatigue when performance declines. Healthy right-handed Ss (N = 15) participated in two sessions. Sessions consisted of: maximal voluntary contractions of the right index finger, an auditory two-choice reaction time task, and a sustained contraction at 5% or 30% maximal voluntary contractions. In one session, the sustained contraction was performed as a single task while in the other the cognitive task was performed concurrently (dual-task condition).
Stable force and EMG levels were observed during the 5% contractions. However, during the 30% contractions some Ss had difficulties maintaining the contraction at 30%. Fatigued Ss also showed an increase in force variability and EMG activity. Such changes were not observed in non-fatigued Ss.
The cognitive performance was stable during the 5% contractions. During the 30% contractions, fatigued Ss demonstrated a deterioration in cognitive performance, an increase in reaction times, and a decrease in accuracy. However, no change in cognitive task performance was seen in non-fatigued Ss. Preliminary analysis of the brain activity of the motor areas showed no change during the 5% contractions and an increase in the left primary sensorimotor cortex during the first phase of the 30% contractions. Fatigued Ss showed a progressive increase that was followed by a decrease. Non-fatigued Ss did not show this brain activity pattern.
Implication. Activity in the left primary sensorimotor cortex was influenced by fatigue and not by time-on-task in Ss fatigued by continual.
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