Immediate and Delayed Cognitive Responses to Moderate Intensity Physical Activity in Older Adults

Abstract

Research on acute bouts of exercise is scarce and is limited by a focus on special populations and the failure to include a control condition. In addition, no research with any population has tested the duration of cognitive improvements as a function of the amount of time since an acute bout of exercise. PURPOSE: Therefore, the purpose of this study was to test the immediate and delayed effects of an acute bout of moderate intensity exercise on cognitive function in healthy older adults. Cognitive function was assessed using three conditions of the Stroop task. All three conditions of the Stroop task required participants to identify the color of visual stimuli. In the control condition the stimuli were neutral, in the interference condition the stimuli were color names, and in the inhibition condition the stimuli were color names and the color of each word was the same as the color name on the previous stimulus. METHODS: Older community-dwelling adults (60–90 yrs) who were self-reported to be healthy and had no diagnosed cognitive impairments, were randomly assigned to the exercise condition (5-min warm-up and 20 minutes of walking at 60% age-predicted HRR) or the control condition (25 minutes of sitting quietly). All three conditions of the Stroop task were administered at 13 test times (baseline and 12 post-treatment times: immediately, 5-, 10-, 15-, 20-, 30-, 45-, 60-, 75-, 90-, 105-, and 120-min post-treatment) in a random, counter-balanced order. Reaction times were analyzed using a mixed design analysis of variance with repeated measures on time, with treatment as the between-groups variable, and with baseline reaction time as a covariate. RESULTS: For the Stroop control and Stroop interference conditions, there were no significant effects. However, for the Stroop inhibition condition, there was a significant interaction of condition by time, F(11,88)=2.31, p <.02. An examination of the data demonstrated that the control group performed more quickly than the exercise group at every time point beginning at 5-min post-exercise. CONCLUSIONS: When inhibition is facilitated, performance on the inhibition condition should be slower. Therefore, although counter-intuitive, these results suggest that an acute bout of exercise has a beneficial effect on the inhibitory processes of older adults (as demonstrated by slower performance on the inhibition condition of the Stroop). Further, the time course of this effect is such that it is apparent 5-min post-exercise and lasts for up to 2 hours post exercise. Thus, it is concluded that a 5-min warm-up and 20-min of moderate intensity exercise benefit the inhibitory functions of older adults for 2-hrs following the exercise bout.