Effects of Lower Limb Heat Therapy, Exercise Training, or a Combined Intervention on Vascular Function: A Randomized Controlled Trial.

Purpose: The purpose of this study is to compare the effects of 8 wk of no intervention (CON), lower limb heat therapy (HEAT), moderate-intensity exercise training (EX), or combined training and therapy (HEATEX) in young, healthy recreationally active adults.

Methods: Sixty participants (23 ± 3 yr, 30 females) were randomly allocated into CON ( n = 15), HEAT ( n = 15), EX ( n = 14), or HEATEX ( n = 16). The primary outcome was vascular function, assessed through brachial artery flow-mediated dilation tests. Secondary measures included arterial stiffness (pulse wave velocity), cardiorespiratory fitness (V̇O 2peak ), body composition, and quadriceps muscle strength.

Results: There were no differences in brachial artery flow-mediated dilation between the groups before and after the interventions (all P > 0.05). Both interventions with a heating component were associated with within-group reductions in carotid-femoral pulse wave, and increase in absolute and relative V̇O 2peak after 8 wk (HEAT: ∆-0.27 [-0.53, -0.02] m s -1 , ∆0.18 [0.06, 0.29] L·min -1 , ∆2.18 [0.60, 3.76] mL·kg -1 ·min -1 , respectively; HEATEX: ∆-0.33 [-0.58, -0.09], ∆0.21 [0.11, 0.32] L·min -1 , ∆2.59 [1.06, 4.12] mL·kg -1 ·min -1 , respectively), but no between-group differences were observed ( P = 0.25, P = 0.21, and P = 0.55, respectively). There was also a within-group decrease in body fat percentage with EX (∆-1.37 [-2.45, -0.29] %), but no changes in leg strength in any of the groups ( P = 0.79).

Conclusions: This randomized controlled trial is the first to examine the efficacy of lower limb heating against traditionally prescribed exercise training. In our young cohort, 8 wk of training and/or therapy was insufficient to improve vascular function. More intense protocols and longer interventions involving lower limb heating may be required to elicit improvements in health outcomes.