Acute and adaptive cardiovascular and metabolic effects of passive heat therapy or high-intensity interval training in patients with severe lower-limb osteoarthritis
Question
What are the acute and 12-week adaptive cardiovascular and metabolic effects of passive heat therapy and upper-limb high-intensity interval training in patients with severe lower-limb osteoarthritis, and do acute blood-pressure responses predict longer-term blood-pressure adaptation?
Summary
This randomized controlled trial sub-study compared passive heat therapy, upper-limb-focused HIIT, and home-based exercise in patients with severe hip or knee osteoarthritis awaiting arthroplasty. The HIIT protocol used mostly unaffected limbs on an arm ergometer or cross-trainer, with 6-8 one-minute intervals, 60-90 seconds active recovery, and three sessions per week for up to 12 weeks. Both heat therapy and HIIT acutely lowered blood pressure after exposure and reduced resting systolic and diastolic blood pressure after training, whereas home exercise did not. Glycemic control did not improve. The study supports upper-limb HIIT as a feasible cardiovascular intervention for people who struggle with traditional lower-limb exercise, but outcomes were secondary and measured in a clinical surgical-waitlist population.
Methodology
- Seventy-eight patients with end-stage hip or knee osteoarthritis waitlisted for arthroplasty, with substantial cardiometabolic comorbidity.
- 78 participants.
- Cross-trainer or arm ergometer, selected based on capability and pain.
- Work intervals: 60 seconds.
- Recovery: Very-light active recovery, initially 90 seconds and progressing to 60 seconds.
- Intensity: Approximately 90%-100% peak VO2 in the abstract; RPE 7/10 very hard with less than 90% heart rate reserve in methods.
- Approximately 20 minutes including 3-5 min warm-up and cool-down/flexibility exercises.
- 3 sessions/week.
- Up to 12 weeks.
- Sub-study of a multi-arm, parallel-design randomized controlled trial comparing Heat, HIIT, and active home-based exercise control.
- Acute blood pressure response, Resting blood pressure adaptation, Glycemic control, and Heart rate and heart rate variability were tracked.
Outcomes
Acute systolic blood pressure after HIIT
During HIIT systolic BP rose, but by 10 minutes post-exposure and thereafter it was lower than baseline.
During HIIT, systolic BP was +42 mm Hg versus baseline (95% CI 32 to 52, p<0.001); by 10 min post-exposure and thereafter it was 8-10 mm Hg lower than baseline, all p<0.001.
Resting blood pressure after 12-week HIIT
HIIT reduced resting systolic and diastolic blood pressure compared with baseline, while Home did not change.
HIIT systolic BP -7 mm Hg (95% CI -11 to -3, p=0.001); diastolic BP -3 mm Hg (95% CI -5 to -1, p=0.011). Home systolic, diastolic, and mean arterial BP all unchanged, p>=0.785.
Resting blood pressure after heat therapy
Heat reduced resting systolic and diastolic blood pressure.
Heat systolic BP -9 mm Hg (95% CI -13 to -5, p<0.001); diastolic BP -4 mm Hg (95% CI -6 to -2, p<=0.001).
Acute-to-adaptive blood pressure prediction
Acute blood-pressure reduction after HIIT was moderately correlated with adaptive resting blood-pressure reduction.
For HIIT, 5-min recovery BP had the highest correlation with adaptive systolic BP change (r=0.618, p=0.001, 95% CI 0.29 to 0.82) and diastolic BP change (r=0.630, p=0.001, 95% CI 0.30 to 0.82).
Glycemic control
HbA1c and continuous glucose monitoring indices did not reliably improve.
HbA1c interaction p=0.310; CGM area under the curve interaction p=0.077, with no reliable changes observed.
Compliance
Compliance did not significantly differ between intervention groups.
Heat, HIIT, and Home completed 36 +/- 11, 33 +/- 11, and 40 +/- 23 sessions, respectively; p=0.312.
Insights
- For people with severe lower-limb osteoarthritis, HIIT can be shifted to upper-limb or low-impact modalities while still producing cardiovascular stress and blood-pressure benefits.
- A reproducible low-impact clinical HIIT template is 6-8 x 60-second very-hard intervals with 60-90 seconds active recovery, three times per week.
- This study supports blood-pressure benefits, not glycemic-control benefits, for the tested HIIT protocol.
Limitations
- Blood-pressure and metabolic variables were secondary outcomes from a trial primarily designed for cardiorespiratory fitness.
- Blood-pressure measurements were taken during single exposure or measurement sessions, so regression to the mean is possible.
- No extended post-intervention follow-up was reported.
- Generalizability is limited by clinical screening and severe osteoarthritis surgical-waitlist status.
- Specific adverse-event reporting was not available in the article text.
Safety
- No specific adverse events were reported in the article text.
- Participants were clinically screened with multiple cardiovascular and upper-limb exclusions.
- HIIT modality was selected based on participant capability and pain.
- HIIT intensity was adjusted with RPE and maintained below 90% heart rate reserve.