RESUMEN
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 (VO2peak); 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 VO2peak 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.
RESUMEN
Habitual short sleep durations are associated with several cardiovascular diseases. Experimental research generally supports these findings as metrics of arterial function are impaired after complete deprivation of sleep and after longer periods of partial sleep restriction. The acute influence of a single instance of partial sleep restriction (PSR), however, has not been defined. We evaluated arterial structure and function among 32 university-aged participants on two occasions: once after normal habitual sleep (NS), and again the morning after an acute partial sleep restriction (PSR) intervention involving only 3 h of sleep for a single night. Endothelial function was measured using ultrasonography at the brachial artery via flow-mediated dilatation (FMD), and a ramp peak oxygen uptake test was used to evaluate cardiorespiratory fitness. Blood samples were collected from a subset of participants to investigate the influence of circulatory factors on cellular mechanisms implicated in endothelial function. Sleep duration was lower after a night of PSR compared to NS (P < 0.001); however, there were no appreciable differences in any haemodynamic outcome between conditions. FMD was not different between NS and PSR (NS: 6.5 ± 2.9%; PSR: 6.3 ± 2.9%; P = 0.668), and cardiorespiratory fitness did not moderate the haemodynamic response to PSR (all P > 0.05). Ex vivo cell culture results aligned with in vivo data, showing that acute PSR does not alter intracellular processes involved in endothelial function. No differences in arterial structure or function were observed between NS and acute PSR in healthy and young participants, and cardiorespiratory fitness does not modulate the arterial response to acute sleep restriction.