Cerebral blood flow and arterial transit time responses to exercise training in older adults.

Brain vascular health worsens with age, as is made evident by resting grey matter cerebral blood flow (CBF) reductions and lengthening arterial transit time (ATT). Exercise training can improve aspects of brain health in older adults, yet its effects on CBF and ATT remain unclear. This randomised controlled trial assessed responses of CBF and ATT to a 26 week exercise intervention in 65 healthy older adults (control: n = 33, exercise: n = 32, aged 60-81 years), including whether changes in CBF or ATT were associated with changes in cognitive functions. Multiple-delay pseudo-continuous arterial spin labelling data were used to estimate resting global and regional CBF and ATT. Results showed no between-group differences in CBF or ATT following the intervention. However, exercise participants with the greatest cardiorespiratory gains (n = 17; ∆V̇O >2 mL/kg/min) experienced global CBF reductions (-4.0 [-7.3, -0.8] mL/100 g/min). Cognitive functions did not change in either group and changes were not associated with changes in CBF or ATT. Our findings indicate that exercise training in older adults may induce global CBF reductions when high cardiorespiratory fitness gains are induced, but this does not appear to affect cognitive functions.