Changes in brachial artery endothelial function and resting diameter with moderate-intensity continuous but not sprint interval training in sedentary men

Moderate-intensity continuous training (MICT) improves peripheral artery function in healthy adults, a phenomenon that reverses as continued training induces structural remodeling. Sprint interval training (SIT) elicits physiological adaptations similar to MICT despite a lower exercise volume and time-commitment; however, its effect on peripheral artery function and structure is largely unexplored. We compared peripheral artery responses to 12 weeks of MICT and SIT in sedentary, healthy men (age=27±8 years). Participants performed MICT (45-min of cycling at 75% peak heart rate; n=10) or SIT (3x20-sec 'all out' cycling sprints with 2 min of recovery; n=9) and responses were compared to a non-training control group (CTL, n=6). Allometrically scaled brachial flow-mediated dilation (FMD) increased 2.2% after 6 weeks of MICT and returned to baseline levels by 12 weeks, but did not change in SIT or CTL (group x time interaction, p=0.04). Brachial artery diameter increased after 6 and 12 weeks (main effect, p=0.03), with the largest increases observed in MICT. Neither training protocol affected popliteal relative FMD and diameter, or central and lower-limb arterial stiffness (carotid distensibility, central and leg pulse wave velocity) (p>0.05 for all). While earlier and more frequent measurements are needed to establish the potential presence and time course of arterial responses to low-volume SIT, our findings suggest that MICT was superior to the intense, but brief and intermittent SIT stimulus at inducing brachial artery responses in healthy men.

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