Exercise Dose and Aerobic Fitness Response in Alzheimer’s Dementia in the FIT-AD Trial

Abstract

The purpose of this study was to examine the effects of a 6-month cycling aerobic exercise intervention on cardiorespiratory fitness and the dose-response relationship in community-dwelling older adults with mild-to-moderate Alzheimer’s dementia. The FIT-AD trial was a single blind, 2-parallel group, pilot randomized controlled trial. The aerobic exercise group participated in a 6-month, thrice weekly, moderate-vigorous intensity cycling intervention while control group performed stretching. Cardiorespiratory fitness was evaluated by peak oxygen consumption from cardiopulmonary exercise test and peak walking distance from the shuttle walk test and 6-minute walk test. Aerobic exercise dose was calculated using the novel heart rate physical activity score. The aerobic exercise group significantly increased peak oxygen consumption (1.28 ml/kg/min; p=.03) in subgroup who achieved maximal criteria on cardiopulmonary exercise test. Changes in peak oxygen consumption and peak walking distance on the shuttle walk and 6-minute walk tests did not significantly differ between aerobic exercise and stretching groups. Notably, the aerobic exercise dose was strongly and significantly correlated to change in peak oxygen consumption (r=.60; n=16; p=.01), in subset who met maximal test criteria. Emphasis on exercise dose is needed in aerobic exercise programs to maximize cardiorespiratory fitness gains in persons with mild-moderate Alzheimer’s dementia.