Effects of Cognitive Loading on the Development of Muscle Fatigue

The aim of the present work was to study the effects of cognitive loading requiring activation of the attention systems on the development of muscle fatigue. The dynamics of measures of arm muscle fatigue were evaluated in two sessions, separated by 5 min, consisting of 250 maximum-strength dynamometer compressions in response to acoustic target signals in three tasks with different levels of cognitive loading. The first experiment used only the target signals; in experiment two, the subjects had to discriminate the target signal from an equal number (250) of nontarget signals, which required voluntary attention. In experiment three, the proportions of target stimuli were 17 and 83%, respectively, i.e., the target stimulus was random (deviant), activating not only voluntary attention, but also involuntary attention. Measurements of grip strength, maximum voluntary contraction strength, and subjective assessments of fatigue before and after the motor tasks showed that experiments involving voluntary and involuntary attention to sound stimuli produced a smaller rate of development of muscle fatigue. Activation of involuntary attention, accompanied by the appearance of mismatch negativity on the EEG, enhanced the effect of voluntary attention.

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