Effects Of Acute Exercise Intensity On Cerebral Blood Flow And Cognitive Function In Older Adults

INTRODUCTION: Aging is associated with a decrease in cognitive function (CF), perhaps in part, related to decreased cerebral blood flow (CBF). CBF is diminished at rest and in response to moderate intensity exercise in older adults. Strategies to increase CBF may be useful in restoring CF in these individuals. PURPOSE: To examine the effects of calorically matched acute bouts of continuous moderate intensity (MIC) exercise versus high intensity interval training (HIIT) on middle cerebral artery velocity (MCAv) and CF in older adults. METHODS: Seven healthy adults (6 males, 1 females) >65 years enrolled in this randomized cross-over study. Prior to randomization, subjects performed a maximal graded cycle ergometer lactate threshold (LT)/VO2 peak test. This data was used to determine exercise testing power output for conditions: Control (no exercise); MIC (power output at measured LT); and HIIT (1:1 work rest ratio corresponding to measured power output at 85% and 40% of their VO2 peak). Testing session energy expenditures were matched at 200 kcal. During each visit, MCAv was measured via transcranial doppler sonography and CF via 2-back test. MCAv and CF were analyzed pre-exercise and at 15, 30, and 45 mins post-exercise. A two-way repeated measures ANOVA was used to determine significant differences for time (pre vs.post measures) x condition (control/MIC/HIIT). MCAv was also collected at the start, 5 and 15 mins into, and at the end of exercise. Similar ANOVA analysis was used to determine significant differences at these times between MIC and HIIT. RESULTS (n = 7): There was a main effect of time on MCAv during exercise as it decreased in both MIC and HIIT, but no significant differences were found between the conditions. No significant differences in MCAv or CF were found between control, MIC and HIIT during pre- and post-measures. CONCLUSION: The present data contrasts previous studies in young adults that suggest higher MCAv during MIC compared to HIIT and do not support the hypothesis that HIIT would increase MCAv and CF to a greater extent than MIC in older adults. CBF was not significantly different regardless of measurement time or exercise condition. The main effect of time was possibly due to MIC power outputs being set too close to LT such that MCAv decreased during exercise rather than increased, as found in other studies.