Statistical analysis
Statistical analyses were run in R (version 4.0.3). Group differences in vessel lumen diameter at follow-up between the exercise intervention group and control group were examined using analysis of covariance (ANCOVA) adjusting for baseline values of vessel lumen diameter and sex, age, and gestational age (<32, 32–37, >37 weeks). FSL’s randomise function was used to run voxel-based analyses brain maps to detect group differences in changes in CBF between baseline and follow-up and the association between vessel lumen diameter changes. Analyses were run with the vertebral artery supply mask (PCA), or the internal carotid artery supply mask (ICA, MCA M1, MCA M2, ACA). CBF values were averaged across voxels with significant associations between vessel lumen diameter and CBF changes over the exercise intervention period, and associations between vessel diameter changes and mean CBF values were investigated with a Pearson’s correlation analysis.