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ABSTRACT Purpose To compare the effects of 8 weeks 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 years, 30 females) were randomly allocated into either 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 (BA FMD). Secondary measures included arterial stiffness (pulse wave velocity, PWV); cardiorespiratory fitness (VO 2 peak); body composition; and quadriceps muscle strength. Results There were no differences in BA FMD 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 PWV, and increases in absolute and relative VO 2 peak after 8 weeks (HEAT: ∆-0.27 -0.53, -0.02 m/s, ∆0.18 0.06, 0.29 L/min, ∆2.18 0.60, 3.76 ml/kg/min, respectively; HEATEX: ∆-0.33 -0.58, -0.09, ∆0.21 0.11, 0.32 L/min, ∆2.59 1.06, 4.12 ml/kg/min, 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 weeks 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.
Cheng et al. (Mon,) studied this question.