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_GM) reductions and lengthening arterial transit time (ATT_GM). Exercise training can improve aspects of brain health in older adults, yet its effects on CBF_GM and ATT_GM remain unclear. This randomised controlled trial assessed responses of CBF_GM and ATT_GM 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_GM or ATT_GM were associated with changes in cognitive functions. Multiple-delay pseudo-continuous arterial spin labelling data were used to estimate resting global and regional CBF_GM and ATT_GM. Results showed no between-group differences in CBF_GM or ATT_GM following the intervention. However, exercise participants with the greatest cardiorespiratory gains (n = 17; ∆V̇O_2peak >2 mL/kg/min) experienced global CBF_GM 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_GM or ATT_GM. Our findings indicate that exercise training in older adults may induce global CBF_GM reductions when high cardiorespiratory fitness gains are induced, but this does not appear to affect cognitive functions.