Ninety-three patients with severe knee or hip osteoarthritis were randomized to receive either high-intensity interval training (HIIT; n=30), passive heat therapy (Heat; n=30), or home-based exercise (Home; n=33) as prehabilitation before total hip or knee arthroplasty. The primary outcome of interest was peak oxygen consumption (peak 𝑉𝑂2). Secondary outcomes included the anaerobic threshold, physical function measures, and subjective health assessments. Outcomes were assessed over a 12-week period. Overall, the results revealed that HIIT significantly improved peak 𝑉𝑂2V and the anaerobic threshold compared to the other groups. Heat therapy also increased the anaerobic threshold but not peak 𝑉𝑂2. These findings suggest that both HIIT and heat therapy can enhance aspects of cardiorespiratory fitness preoperatively, potentially benefiting surgical outcomes.