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Positive physiologic and cognitive responses to aerobic exercise have resulted in a proposed cardiorespiratory (CR) fitness hypothesis in which fitness gains drive changes leading to cognitive benefit. The purpose of this study was to directly assess the CR fitness hypothesis. Using data from an aerobic exercise trial, we examined individuals who completed cardiopulmonary and cognitive testing at baseline and 26 weeks. Change in cognitive test performance was not related to CR fitness change (r ² = .06, p = .06). However, in the subset of individuals who gave excellent effort during exercise testing, change in cognitive test performance was related to CR fitness change (r ² = .33, p < .01). This was largely due to change in the cognitive domain of attention (r ² = .36, p < .01). The magnitude of change was not explained by duration of exercise. Our findings support further investigation of the CR fitness hypothesis and mechanisms by which physiologic adaptation may drive cognitive change.

A trial was conducted to examine the effect of moderate aerobic exercise training (AET) on cardiorespiratory (CR) fitness. Previously sedentary participants, age 60-75 years, were randomly assigned to either AET treatment or a control group for 6 months. The AET consisted of walking for 40 min three times/week at an intensity that elevated heart rate to 65% of maximum heart rate reserve. The control group performed a supervised stretching program for 40 min three times/week. CR fitness was assessed before and after the treatments during a grade-incremented treadmill walking test. Both absolute and relative peak V̇O₂ significantly increased (p < .01) in the AET group, whereas they decreased modestly in the control group. Maximum treadmill time increased significantly (p < .01) in the AET group relative to the control group. These results indicate that CR fitness as measured by peak V̇O₂ modestly improves in the elderly with a moderate-intensity, relatively long-term aerobic exercise program.

One hundred forty-six abdominally obese adults age 60–80 yr were studied to investigate the interaction between cardiorespiratory fitness (CRF) and obesity on functional limitation. Obesity was determined by fat mass (FM), CRF was determined by a maximal treadmill test, and functional limitation was based on 4 different tasks that are predictive of subsequent disability. Both FM (r = –.34, p ≤ .01) and CRF (r = .54, p ≤ .01) were independently associated with functional limitation in bivariate analysis. After further control for sex, age, and the interaction term (CRF × FM), FM was no longer independently associated with functional limitation (p = .10). Analyses were also based on sex-specific tertiles of FM and CRF. The referent group demonstrated significantly lower functional limitation than the low-CRF/low-FM and the low-CRF/high-FM groups (both p ≤ .05). These results highlight the value of recommending exercise for abdominally obese adults.