Abstract
Background: The purpose of the study was to examine the acute and adaptive analgesic effects of two separate therapies-hot-water immersion and upper-limb high-intensity interval exercise (HIIE)-in patients with severe lower-limb osteoarthritis.
Methods: Eligible and consenting participants scheduled for hip or knee arthroplasty were randomized to hot-water immersion (Heat, n=27); 20-30 min immersed in 40°C water followed by ~15 min light resistance exercise) or upper-limb high-intensity interval exercise (HIIE, n=25; 6-8 x 60 s intervals on a cross-trainer or arm ergometer at ~100% peak V̇O2, 60-90 s recovery); all for 36 sessions (3 sessions per week for 12 weeks). Joint pain (0-10 scale; 0 = no pain, 10 = worst pain) and accelerometry were assessed during and following acute exposure and across the intervention.
Results: Joint pain decreased by 3 arbitrary units (AU) and 2 AU during an acute exposure of heat therapy and HIIE (p≤0.035); this acute analgesic effect was still evident in the final week of the intervention. These acute analgesic effects did not translate to reduced joint pain adaptively across the intervention (p=0.684), or improved daily step count in the 24-h following acute exposure (p=0.855) or across the intervention (p=0.604).
Conclusions: The findings from this study highlight the acute analgesic effects of hot-water immersion and HIIE, and that patients with severe lower-limb osteoarthritis can participate in high-intensity upper-limb exercise, relatively pain free.
Significance: This research reports several novel findings: 1) acute hot-water immersion has a potent analgesic effect in people with severe lower-limb osteoarthritis; 2) this acute effect is lost within one hour of exposure; 3) people with severe lower-limb osteoarthritis can perform cardiovascularly meaningful exercise via HIIE using predominantly the upper limbs, while decreasing joint pain; 4) reassuringly, the acute analgesic effect of hot-water immersion or HIIE persists across 12-wk of repeated exposure.