Effect of high-intensity interval training in physiotherapy primary care for patients with inflammatory arthritis: the ExeHeart randomised controlled trial
Question
Does a 12-week HIIT program delivered in physiotherapy primary care improve cardiorespiratory fitness in patients with inflammatory arthritis, and what are its effects on cardiovascular risk factors, disease activity, broader outcomes, and safety?
Summary
In this assessor-blinded randomized trial, 60 adults with inflammatory arthritis were assigned to usual care or usual care plus 12 weeks of supervised HIIT in physiotherapy primary care. The HIIT group improved peak oxygen uptake more than controls at 3 months, and the difference was maintained at 6 months. Secondary cardiometabolic, disease activity, pain, fatigue, and exercise belief outcomes were mostly small and non-significant. The intervention was generally well tolerated, with minimal adverse events and no apparent worsening of disease activity.
Methodology
- Adults aged 18-70 with rheumatologist-verified inflammatory arthritis, able to walk unaided for at least 15 minutes, recruited in Norway.
- 60 participants.
- Uphill walking/running recommended; cycling, rowing, and elliptical machines acceptable.
- Work intervals: 4 minutes at 90%-95% HRpeak, RPE 16-18.
- Recovery: 2-3 minutes active recovery at 60%-70% HRpeak, RPE 11-13.
- Intensity: Prescribed by heart rate and RPE; achieved mean 92% HRpeak and RPE 16.
- Approximately 34-38 minutes for HIIT components; third weekly moderate session was 40 minutes.
- Two supervised HIIT sessions per week plus one self-guided moderate session.
- 12 weeks.
- Assessor-blinded randomized controlled trial comparing usual care plus supervised HIIT with usual care alone in a 1:1 allocation.
- VO2peak, Cardiovascular risk factors, Disease activity, and Physical activity index were tracked.
Outcomes
VO2peak
Exercise group improved VO2peak more than control at 3 months and maintained the difference at 6 months.
3 months: between-group difference 2.5 mL/kg/min (95% CI 0.9 to 4.0), p<0.01; 6 months: 2.6 mL/kg/min (95% CI 0.8 to 4.3), p<0.01.
Per-protocol VO2peak
Participants who adhered to at least 70% of HIIT sessions had a larger VO2peak difference versus controls not doing regular aerobic exercise.
3.2 mL/kg/min (95% CI 1.7 to 4.8) at 3-month follow-up.
Physical activity
Self-reported physical activity improved more in the exercise group at both follow-ups.
3 months: 7.0 points (95% CI 3.4 to 10.7), p<0.01; 6 months: 4.7 points (95% CI 0.1 to 9.4), p=0.05.
Cardiovascular risk factors and symptoms
Most secondary outcomes related to blood pressure, lipids, anthropometry, pain, fatigue, and exercise beliefs were small and non-significant.
Article reports no significant group differences for these outcomes at follow-up.
Disease activity
HIIT did not significantly change disease activity category and did not appear to worsen disease activity.
Disease activity category p=0.08 at both 3 and 6 months.
Insights
- A classic 4 x 4-minute aerobic HIIT format can be feasible in screened inflammatory arthritis patients when supervised and individually adjusted.
- Heart-rate targets paired with RPE allowed physiotherapists to monitor whether patients reached high intensity.
- A gradual 2-week familiarization/load-in period is a useful design feature for clinical populations.
- Clinical HIIT recommendations need safety screening, symptom monitoring, and clear escalation for palpitations or pain.
Limitations
- Potential selection bias toward motivated participants.
- Underpowered for secondary outcomes.
- Chance baseline imbalance in smoking and disease duration.
- SARS-CoV-2 infections may have affected exercise response.
- Participants were not blinded, affecting self-reported outcomes.
- Repeated CPET sessions may have motivated control participants.
- Bioelectrical impedance analysis limits body composition accuracy.
Safety
- Exercise group: knee pain following exercise adjuvant to the HIIT protocol.
- Exercise group: irregular heart rate during two consecutive HIIT sessions in a participant with prior palpitations; exercise ECG was normal and participant resumed without further complications.
- Control group: atrial flutter before study close-out and head concussion, both unrelated to study visits.
- Disease flares at 3 months: one exercise-group patient and two control-group patients.