Aerobic exercise increases brain vessel lumen size and blood flow in young adults with elevated blood pressure. Secondary analysis of the TEPHRA randomized clinical trial

[Display omitted] •Exercise intervention increased internal carotid and middle cerebral artery lumen.•Exercise intervention did not change CBF.•Increased ICA lumen diameter was associated with a regional increase in CBF.•Cerebrovasculature is modifiable in young adults with high blood pressure. Cerebrovascular changes are already evident in young adults with hypertension and exercise is recommended to reduce cardiovascular risk. To what extent exercise benefits the cerebrovasculature at an early stage of the disease remains unclear. To investigate whether structured aerobic exercise increases brain vessel lumen diameter or cerebral blood flow (CBF) and whether lumen diameter is associated with CBF. Open, parallel, two-arm superiority randomized controlled (1:1) trial in the TEPHRA study on an intention-to-treat basis. The MRI sub-study was an optional part of the protocol. The outcome assessors remained blinded until the data lock. Single-centre trial in Oxford, UK. Participants were physically inactive (