Effects of repeated sprint exercise on brachial artery shear rate patterns in healthy adults

Endothelial cells are influenced by mechanical shear forces from blood flow, which increase considerably during exercise. Exercise-induced shear stimuli depend on several factors, including intensity and modality; though little is known about the effects of sprint exercise. This study investigated the effects of maximal sprint exercise on systemic shear patterns. Eighty-four healthy participants completed 2 × 20 s maximal cycling sprints (5-min rest between) or 10 min of moderate intensity (64%-76% HR_max) cycling (MOD). Ultrasound recordings of the brachial artery were taken at baseline and minutes 1 (M1), 3 (M3), and 5 (M5) of recovery after sprint 1 (S1), sprint 2 (S2), and MOD, and again 10- and 15-min post-exercise. Bayesian rmANOVA was used to compare shear rate and diameter over time. Average and antegrade shear rate increased after each sprint and were not different between sprints at M1 and M3 (all BF₁₀ ≤ 0.545), but antegrade was higher for S2 at M5 (BF₁₀ = 40.417). Retrograde shear developed progressively throughout. Elevated antegrade and retrograde shear responses were observed through 15 min in sprints but returned toward baseline by 10-15 min in MOD. Lasting effects of sprint exercise on non-local (systemic) shear patterns could promote vascular remodeling. Future training intervention studies should investigate potential long-term benefits.