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

• Home-based high-intensity interval training increases cardiorespiratory fitness in older adults • High cardiorespiratory fitness gains were associated with cerebral blood flow reductions • Exercise training did not affect arterial transit time or cognitive function 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 cognitive function changes. 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.