Exercise and caffeine improve sustained attention following fatigue independent of fitness status

Abstract

Background: Exercise improves cognition, but whether fitness status and caffeine modulate this effect remains unclear. Purpose: To determine if sustained attention is improved following exercise with and without caffeine in endurance-trained vs. sedentary adults. Methods: A continuous performance task (CPT), that is, a 20 min measure of sustained attention to assess accuracy and precision, was used to induce mental fatigue. Following the 20 min CPT, trained (n = 12) and sedentary (n = 12) participants completed either 30-min rest or 30-min moderate-intensity cycling below lactate threshold. Exercise trials were completed with placebo and caffeine (3 mg/kg) followed by cycling to volitional fatigue. Results: Exercise, as compared to rest, improved (p < .05) accuracy and precision after a mentally fatiguing task (CPT) and was not different between endurance-trained and sedentary groups. During the CPT, accuracy and precision declined (p < .05) with placebo, but both were maintained with caffeine following both exercise and cycling to volitional fatigue. Mental energy declined (p < .05) after the CPT with placebo but not caffeine. Cycling to volitional fatigue resulted in lower mental energy/greater mental fatigue as compared to baseline and following moderate intensity exercise, for both caffeine and placebo (p < .05). Conclusions: Exercise improved sustained attention following a mentally fatiguing attentional task independent of fitness status; and, when coupled with caffeine, provided greater benefit on the attentional task for accuracy, precision, and mental energy. Although caffeine's beneficial effect on sustained attention persisted after cycling to volitional fatigue, it did not prevent a decline in mental energy/increase in mental fatigue.