| The aim of the project is to investigate the relation between motor fatigue and cognitive task performance. To study this interaction a dual task paradigm is used. During fatiguing submaximal contractions a constant force production can be obtained at the cost of an increasing central commend intensity. Lorist (2002, J. Physiol.) has shown that during motor fatigue there is a mutual interaction between the cognitive functions and the central mechanisms driving motor behaviour. Besides fatigue associated with motor behavior, there have also been numerous studies of fatigue of a more central origin, related to factors such as mental fatigue and time-on-task for cognitive tasks (Holding 1983; Hockey, 1993; Meijman 1997). These forms of central or mental fatigue may be associated with a considerable deterioration of cognitive functions (Lorist et al., 2000). It is known that caffeine has an stimulating effect on the central nervous system. The issue of this research is to study whether caffeine can influence these underlying central mechanisms. Subjects performed three tasks on two different days. The tasks were an auditory choice reaction task (CRT), a CRT simultaneously with a fatiguing submaximal muscle contraction task, and again the single CRT. One day the subjects received a cup of decaffeinated coffee (control) and the other day they received caffeinated coffee (3 mg/kg body weight). The order of the sessions was random and double-blind. Preliminary results show that performance in the single-CRT condition was relatively stable, however, caffeine reduces the reaction time. During the fatiguing dual task, performance levels in the cognitive CRT deteriorated drastically with time on task. Caffeine seems to prolong the endurance of the subjects, though it has no effect on the cognitive task performance in the dual task. In conclusion, the preliminary data showed a decrease in the reaction times due to caffeine intake. But no significant difference was observed in the interaction between the fatiguing motor task and the cognitive task. Future perspectives are related to the precise nature of the observed interference between central mechanisms driving motor behaviour and cognitive functions. To study this we will use EEG and fMRI. |
