Changes in Bereitschaftspotential during fatiguing and non-fatiguing hand movements.

This study investigates the electroencephalographic Bereitschaftspotential (Bp) during muscular-fatiguing and non-fatiguing rhythmical hand contractions at 20%, 50%, and 80% maximum voluntary contraction (MVC). A feedback arrangement was provided so that subjects were able to adjust the force as required. The results confirm that Bp depends on force level. An increase in force results in a Bp increase. Further, they show that muscular-fatiguing contractions at 80% MVC are accompanied by an increased Bp. This could be the result of an increase in the central nervous activation required when preparing for motor activity with fatigued muscles. A decrease in Bp was observed during non-fatiguing repetitive hand contractions at 50% MVC. Possibly, the decrease reflects a decrease in subjects intentional involvement due to the monotony of the exercise. Repetitive movements at 20% MVC, which require a high degree of concentration and attention to adjust exactly to this very small force level, also result in an increased Bp, perhaps due to the higher intentional involvement. It may be concluded that the influence of muscular fatigue on Bp should be investigated with consideration of the psychological aspects of repetitive movements.