Acute and adaptive cardiovascular and metabolic effects of passive heat therapy or high‐intensity interval training in patients with severe lower‐limb osteoarthritis

Exercise is painful and difficult to perform for patients with severe lower‐limb osteoarthritis; consequently, reduced physical activity contributes to increased cardiometabolic disease risk. The aim of this study was to characterize the acute and adaptive cardiovascular and metabolic effects of two low or no impact therapies in patients with severe lower‐limb osteoarthritis: passive heat therapy (Heat) and high‐intensity interval training (HIIT) utilizing primarily the unaffected limbs, compared to a control intervention of home‐based exercise (Home). Participants completed up to 12 weeks of either Heat (20–30 min immersed in 40°C water followed by ~15‐min light resistance exercise), HIIT (6–8 × 60‐s intervals on a cross‐trainer or arm ergometer at ~90–100% peak [Formula: see text] O(2)) or Home (~15‐min light resistance exercise); all 3 sessions/week. Reductions in systolic (12 & 10 mm Hg), diastolic (7 & 4 mm Hg), and mean arterial (8 & 6 mm Hg) blood pressure (BP) were observed following one bout of Heat or HIIT exposure, lasting for the duration of the 20‐min monitoring period. Across the interventions (i.e., 12 weeks), resting systolic BP and diastolic BP decreased with Heat (−9 & ‐4 mm Hg; p < 0.001) and HIIT (−7 & ‐3 mm Hg; p ≤ 0.011), but not Home (0 & 0 mm Hg; p ≥ 0.785). The systolic and diastolic BP responses to an acute exposure of Heat or HIIT in the first intervention session were moderately correlated with adaptive responses across the intervention (r ≥ 0.54, p ≤ 0.005). Neither intervention improved indices of glycemic control (p = 0.310). In summary, both Heat and HIIT induced potent immediate and adaptive hypotensive effects, and the acute response was moderately predictive of the long‐term response.