Upper-Limb High-Intensity Interval Training or Passive Heat Therapy to Optimize Cardiorespiratory Fitness Prior to Total Hip or Knee Arthroplasty: A Randomized Controlled Trial

Objective: Preoperative exercise training, or prehabilitation, aims to optimize cardiorespiratory fitness before surgery to reduce the risk of adverse perioperative events and delayed recovery. However, traditional exercise such as walking and cycling can be difficult for people with degenerative joint diseases of the lower limbs, such as osteoarthritis. The purpose of this study was to compare the effect of three low-impact interventions on cardiorespiratory fitness, physical function, and subjective health before total hip or knee arthroplasty.

Methods: This was a randomized controlled trial involving 93 participants with severe knee or hip osteoarthritis awaiting joint replacement surgery. Participants underwent cardiopulmonary exercise testing (to measure peak oxygen consumption [ $\dot{V}$ O₂ ]), then were randomized to heat therapy (Heat; 20-30 min immersed in 40°C water followed by ~15 min light-resistance exercise), high-intensity interval training (HIIT; 6-8 × 60 s intervals on a cross-trainer or arm ergometer at ~90%-100% peak $\dot{V}$ O₂ ), or home-based exercise (Home; ~15 min light-resistance exercise); for up to 36 sessions (3 sessions per week for 12 weeks).

Results: Peak $\dot{V}$ O₂ increased by 16% across HIIT and to a greater extent than Heat (+2.5 mL × min^-1 × kg^-1 [95% CI: 0.5-4.4], P = 0.009) and Home (+3.2 mL × min^-1 × kg^-1 [1.2-5.2], P = 0.001). The anaerobic threshold increased across HIIT (+1.5 mL × min^-1 × kg^-1 [0.7-2.3], P < 0.001) and Heat (+1.2 mL × min^-1 × kg^-1 [0.4-1.9], P = 0.004), but not Home (-0.5 mL × min^-1 × kg^-1 [-1.3 to 0.3], P = 0.248). Subjective severity of osteoarthritis was unchanged with any intervention (P ≥ 0.250).

Conclusion: Heat therapy and HIIT improved indices of cardiorespiratory fitness preoperatively in patients who have difficulty performing lower-limb exercise.