Cardiorespiratory fitness is differentially associated with motor cortex laterality in middle-aged and older adults

Tasks associated with unilateral patterns of functional magnetic resonance imaging (fMRI) activation often demonstrate bilateral activation with aging (hemispheric asymmetry reduction). We examined relationships between the modifiable lifestyle variable cardiorespiratory fitness (CRF), hemispheric asymmetry reduction, and visuomotor task performance in middle-aged and older adults. Sixty-four participants aged 35-86 years completed progressive, maximal cardiopulmonary exercise testing to assess VO₂peak and a standardized test of motor coordination, the Grooved Pegboard Test. fMRI was acquired during a visuomotor task requiring a right-hand motor response. The relationships between hemispheric asymmetry during the fMRI task, CRF, and performance on simple (fMRI task) and complex (Grooved Pegboard Test) motor tasks were examined. Age moderated the relationship between CRF (VO₂peak) and hemispheric asymmetry. Among middle-aged adults, greater VO₂peak was associated with more hemispheric asymmetry; no association was observed in older adults. Age marginally moderated the relationship between hemispheric asymmetry and Grooved Pegboard performance. Among middle-aged adults, greater hemispheric asymmetry was marginally associated with better performance; among older adults, reduced asymmetry showed a trending association with better performance. These findings highlight age-related differences in the relationship between CRF, behavioral performance, and fMRI activation and emphasize the importance of investigating brain function, cognition, and age across the adult lifespan.