The purpose of this study was to investigate the relationship between physical exercise and performance on a mental task, and to offer a possible explanation for this relationship.

Two experiments were conducted which examined the effects, in aerobically fit subjects of physical exercise on a mental task. Five male volunteer subjects between 23 and 30 years of age were used; two in Experiment 1 and three in Experiment 2. Prior to the experiments, all subjects were individually evaluated on a submaximal bicycle ergometer test conducted by Carleton Physical Recreation Centre. The subjects used in this study obtained maximum oxygen uptake scores equal to or above 48 ml/kgm/min, indicating well above average fitness levels.

Five intensities or stages of exercise were used (i.e.. Rest; 50% of maximum workload; 75% of maximum workload; Post 50% of maximum workload; Post 75% of maximum workload). This allowed for examination of the effects of both prior and concomitant exercise. At stages of concomitant exercise subjects pedalled a bicycle ergometer at a rate of 50 rpm at individually set resistance levels. The resistance settings were based on fitness test scores for each individual.

Subjects performed a mental task at each of the five stages of exercise. The task consisted of either a delayed comparison judgement about two line lengths, a digit pair comparison, or both of these task components combined. Thus attentional load and physical workload were manipulated in these experiments.

Speed and accuracy of performance on the mental task were measured. As well, a speed to accuracy ratio was computed as a measure of overall efficiency of task performance.

Results generally indicated the presence of a speed accuracy tradeoff at concomitant exercise, a slight improvement in performance following light exercise and a decrease in performance (particularly speed of performance) following a moderate level of exercise. Light exercise (both prior and concomitant) seemed to have a facilitating effect on overall efficiency of performance, whereas a moderate intensity of exercise caused a deterioration in efficiency. The effects of attentional load produced some unexpected results, as well as a neat replication of some previous studies in the perceptual area.

A tentative explanation, based on an Adaptation to Overall load model (Vickers, 1979), was proposed to account for these results. An ISI effect, present at a particular attention load level and stage of exercise, was explained in terms of time order error effects established in some previous studies (e.g., Jamieson and Petrusic, 1975a, b).