Impact of HIIT, MICT, and Resistance Training on Endothelial Function in Older Adults.

PURPOSE: It is unclear if high-intensity-interval-training (HIIT) elicits superior improvements in brachial artery (BA) flow-mediated-dilation (FMD) responses (i.e., endothelial-dependent vasodilation) than moderate-intensity-continuous-training (MICT) or resistance training (RT) in otherwise healthy older adults. Whether HIIT enhances lower-limb FMD responses and/or augments low-flow-mediated-constriction (L-FMC; endothelial-dependent vasoconstriction) responses more than MICT or RT is also unknown. We tested the hypothesis that HIIT would improve BA and popliteal artery (POP) FMD and L-FMC responses more than MICT or RT in healthy older adults. METHODS: Thirty-eight older adults (age: 67+/-6 yrs) performed 6-weeks of either HIIT [2x20min bouts alternating between 15s intervals at 100% of peak power output (PPO) and passive recovery (0% PPO); n=12], MICT (34min at 60% PPO; n=12), or whole-body RT (8 exercises, 2x10 repetitions; n=14). L-FMC and FMD were measured before and after training using high-resolution ultrasound and quantified as the percent change in baseline diameter during distal cuff occlusion and following cuff release, respectively. RESULTS: Resting BA blood flow and vascular conductance (both, P 0.20). CONCLUSIONS: HIIT and MICT, but not RT, similarly improved lower-limb vasodilator and vasoconstrictor endothelial function in older adults. While HIIT and MICT groups enhanced BA vasodilator function, only HIIT improved resting conductance and endothelial sensitivity to low-flow in the BA. In the short-term, HIIT may be most effective at improving peripheral vascular endothelial function in older adults.