Effect of high-intensity interval training in physiotherapy primary care for patients

Key points

1. 01HIIT increased peak oxygen uptake by 2.5 mL/kg/min at 3 months and 2.6 mL/kg/min at 6 months versus usual care, both statistically significant.
2. 02Benefits were sustained six months after the study started, suggesting durable lifestyle change rather than a short-term effect.
3. 03No significant worsening of disease activity, inflammatory markers (CRP, ESR), pain, or fatigue was observed in the exercise group.
4. 04Self-reported physical activity was significantly higher in the exercise group at both 3 months (7.0 points, 95% CI 3.3 to 10.7) and 6 months (4.7 points, 95% CI 0.1 to 9.4).
5. 05The intervention was feasible in a non-specialist setting: physiotherapists without prior HIIT or rheumatology specialisation delivered it safely.

How it was conducted

Design

Single-blind (assessor-blinded) randomised controlled trial (ExeHeart trial, NCT04922840)

Participants

60 adults aged 18-70 with rheumatologist-verified inflammatory arthritis (RA, SpA or PsA); 82% had increased cardiovascular disease risk; recruited from a Preventive Cardio-Rheuma Clinic in Oslo, Norway

Groups

Exercise group (n=30): usual care plus 12 weeks of HIIT (2 supervised sessions per week at 90-95% peak heart rate plus 1 self-guided moderate session); Control group (n=30): usual care only

Primary outcome

Change in cardiorespiratory fitness measured as peak oxygen uptake (VO2peak in mL/kg/min) by cardiopulmonary exercise test at 3 months

Follow-up

Outcomes assessed at baseline, 3 months, and 6 months

Analysis

Intention-to-treat with multiple imputation for missing primary outcome data; ANCOVA adjusted for age, gender, and baseline value

What they found

• VO2peak (primary outcome): exercise group mean 32.9 vs control 30.3 mL/kg/min at 3 months; between-group difference 2.5 mL/kg/min (95% CI 0.9 to 4.0, p<0.01).
• VO2peak at 6 months: between-group difference 2.6 mL/kg/min (95% CI 0.8 to 4.3, p<0.01).
• Per-protocol analysis (participants completing at least 17 of 24 HIIT sessions vs non-exercising controls): between-group difference 3.2 mL/kg/min (95% CI 1.7 to 4.8) at 3 months.
• VO2peak absolute capacity (L/min): significant group difference at both 3 months (0.1 L/min, 95% CI 0.1 to 0.2, p=0.01) and 6 months (0.1 L/min, 95% CI 0.1 to 0.3, p=0.02).
• Oxygen pulse at 3 months: group difference 0.9 mL/beat/min (95% CI 0.3 to 1.5, p=0.01); at 6 months: 1.0 mL/beat/min (95% CI 0.4 to 1.7, p<0.01).
• Self-reported physical activity index at 3 months: group difference 7.0 points (95% CI 3.3 to 10.7, p<0.01); at 6 months: 4.7 points (95% CI 0.1 to 9.4, p=0.05).
• At 6-month follow-up, 64% of exercise group reported aerobic exercise at least once per week vs 27% of control group (chi-squared=8.3, p<0.01).
• Disease activity category change: chi-squared=8.3, p=0.08 at 3 months and chi-squared=9.8, p=0.08 at 6 months (non-significant trend favouring exercise group).
• No significant between-group differences in blood pressure, lipids, body composition, CRP, ESR, pain, fatigue, or exercise self-efficacy at either follow-up.
• Adverse events: 2 moderate events in the exercise group (knee pain in 1 patient, transient palpitations in 1 patient resolving after normal exercise ECG); 1 serious and 1 moderate event in the control group, both unrelated to study visits.
• Session adherence: mean 18 of 24 HIIT sessions attended (SD 5); 70% of exercise group completed at least 70% of sessions.

Limitations

• The sample likely consisted of motivated individuals referred from a specialist clinic, which may limit generalisability to the broader inflammatory arthritis population.
• The study was powered for the primary outcome only; secondary outcomes (CVD risk factors, disease activity) were exploratory and may have been underpowered to detect clinically meaningful differences.
• Most participants were already on statins and/or antihypertensives with blood pressure and lipids at target levels at baseline, creating a floor effect that may have prevented demonstrating exercise benefits on these risk factors.
• Lack of blinding among patients may have introduced bias in self-reported outcomes, and multiple CPET sessions in the control group may have encouraged vigorous exercise, partially attenuating the between-group difference.

Why it matters

For patients

People with rheumatoid arthritis, spondyloarthritis, or psoriatic arthritis can safely do high-intensity interval training supervised by a physiotherapist in a local clinic, with meaningful improvements in fitness lasting at least six months and no increase in joint inflammation or disease flares.

For clinicians

HIIT delivered in primary care physiotherapy is an effective and safe way to increase cardiorespiratory fitness in patients with inflammatory arthritis and elevated cardiovascular risk, and can be implemented by non-specialist physiotherapists with structured training and checklists.

For readers

This well-designed RCT provides the strongest evidence to date that HIIT in primary care physiotherapy improves an important modifiable cardiovascular risk factor in inflammatory arthritis, though effects on blood pressure, lipids, and disease activity remain uncertain.