Abstract
Regular physical activity is essential for maintaining cardiorespiratory and musculoskeletal fitness and health across the human life course. Traditional exercise such as walking and cycling can be difficult for people with degenerative joint disease of the lower limbs, such as osteoarthritis. Consequently, obtaining exercise-associated benefits is more challenging. End-stage osteoarthritis is commonly treated surgically via total joint arthroplasty. For patients who struggle to be active preoperatively, surgical risk and recovery may be negatively impacted.
The aim of this thesis was to investigate the effects of two low- / no-impact novel interventions on cardiorespiratory fitness (i.e., peak oxygen consumption, anaerobic threshold) and physical and subjective health in patients with severe lower-limb osteoarthritis scheduled for total hip or knee arthroplasty. Secondary aims were to 1) determine the optimal exercise modality for measuring cardiorespiratory fitness in such patients; 2) maintain cardiorespiratory fitness in an unsupervised setting following supervised prehabilitation; and 3) examine the role of preoperative cardiorespiratory fitness in the recovery from arthroplasty.
The gold standard for measuring cardiorespiratory fitness is cardiopulmonary exercise testing (CPET). However, consensus on the optimal modality for performing CPET in patients with lower-limb osteoarthritis was lacking. Therefore, Chapter Two was a crossover study (n=15) to compare CPET and subjective measures across treadmill, cross-trainer, cycle and arm ergometry in patients scheduled for total hip or knee arthroplasty. Lower-limb modalities elicited peak oxygen consumption (V ̇O2) and anaerobic threshold values ~20-50% above those for arm ergometry, albeit with greater joint pain. Arm ergometry was concluded to be a poor substitute for cycle ergometry as a perioperative risk stratification tool, and the commonly used cut-points (15 mL.min-1.kg-1 for peak V ̇O2 and 11 mL.min-1.kg-1 for anaerobic threshold) should be reconsidered if CPET is performed by upper-limb modalities.
Chapter Three was a randomised controlled trial (n=93) investigating the effectiveness of 12 weeks of passive heat therapy (Heat; spa pool), upper-limb high-intensity interval training (HIIT; cross-trainer or arm ergometer) and home-based exercise (Home) on cardiorespiratory fitness and physical and subjective health prior to total hip or knee arthroplasty. Peak V ̇O2 increased by 16% in HIIT only. Heat and HIIT were similarly effective in increasing the anaerobic threshold (by 10% and 12%) and lowering resting systolic (-9 and -7 mm Hg) and diastolic (-4 and -3 mm Hg) blood pressure; this chronic hypotensive effect is comparable to that achieved by typical anti-hypertensive pharmaceuticals. Additional benefits included a repeatable acute reduction in blood pressures and joint pain.
Many participants were still awaiting a confirmed surgical date upon completion of 12-weeks supervised prehabilitation. Therefore, the effectiveness of an individualised and home-based intervention for maintaining cardiorespiratory fitness and other measures of physical and subjective health was examined (n=18). Whilst compliance with the intervention was high, it was not effective for maintaining peak V ̇O2. However, it was effective for maintaining the anaerobic threshold and the hypotensive effects from the previous supervised intervention. Additionally, the subjective impact of osteoarthritis did not deteriorate across the intervention.
Chapter Four (n=44) showed that a low peak V ̇O2 (<15 mL.kg-1.min-1) was associated with poorer functional recovery at 6-weeks post-arthroplasty. Furthermore, many easily performed preoperative assessments (e.g. preoperative daily step count, timed up-and-go test, Duke Activity Status Index questionnaire) correlated moderately with preoperative peak V ̇O2 and may be useful for predicting functional recovery from total joint arthroplasty when preoperative CPET is not available or feasible.
This thesis substantiated epidemiological evidence from other major surgery types, showing that low cardiorespiratory fitness is associated with poorer functional recovery from surgery. Reassuringly, this thesis highlighted that preoperative cardiorespiratory fitness and other prognostic risk factors (e.g., resting blood pressure, physical function, skeletal muscle mass) can be improved during the surgical waitlisting period via passive heat therapy or upper-limb HIIT. Moreover, both interventions were enjoyable and joint pain decreased acutely. These forms of therapy have potential to benefit patients with other pain conditions, or other barriers to traditional exercise, either preoperatively or within the community for long-term health benefits.