Exercise, fitness, and neurocognitive function in older adults: the "selective improvement" and "cardiovascular fitness" hypotheses.

BACKGROUND Although basic research has uncovered biological mechanisms by which exercise could maintain and enhance adult brain health, experimental human studies with older adults have produced equivocal results. PURPOSE This randomized clinical trial aimed to investigate the hypotheses that (a) the effects of exercise training on the performance of neurocognitive tasks in older adults is selective, influencing mainly tasks with a substantial executive control component and (b) performance in neurocognitive tasks is related to cardiorespiratory fitness. METHODS Fifty-seven older adults (65-79 years) participated in aerobic or strength-and-flexibility exercise training for 10 months. Neurocognitive tasks were selected to reflect a range from little (e.g., simple reaction time) to substantial (i.e., Stroop Word-Color conflict) executive control. RESULTS Performance in tasks requiring little executive control was unaffected by participating in aerobic exercise. Improvements in Stroop Word-Color task performance were found only for the aerobic exercise group. Changes in aerobic fitness were unrelated to changes in neurocognitive function. CONCLUSIONS Aerobic exercise in older adults can have a beneficial effect on the performance of speeded tasks that rely heavily on executive control. Improvements in aerobic fitness do not appear to be a prerequisite for this beneficial effect.