# High-intensity interval training outperforms moderate exercise to improve aerobic capacity in patients with recent-onset idiopathic inflammatory myopathies: a multicentre randomised controlled trial PMID: 41314147 Journal: EBioMedicine Published: 2025-12-01 Authors: Andreasson KM, Leijding C, Dastmalchi M, Notarnicola A, Gastaldello S, Yamada T, Sandlund H, Leonard D, Westerblad H, Lundberg IE, Andersson DC, Alexanderson H ## Question Is 12 weeks of high-intensity interval training more effective and still safe compared with clinical standard low-moderate intensity home-based exercise for improving aerobic capacity, muscle endurance, and mitochondrial function in patients with recent-onset idiopathic inflammatory myopathies? ## Summary This multicentre randomized controlled trial compared 12 weeks of HIIT with standard low-moderate intensity home-based exercise in 23 patients with recent-onset idiopathic inflammatory myopathies. HIIT used stationary-bike intervals, three sessions per week, progressing to six 30-second hard intervals with 2-minute moderate cycling rests, followed by one set of strength training. Compared with standard exercise, HIIT improved VO2peak, peak power, time to exhaustion, and mitochondrial protein expression without increasing serum muscle enzymes, disease activity, longstanding pain, fatigue, injuries, or falls. The findings are clinically relevant but come from a small, medically screened rare-disease sample with supervision and heart-rate monitoring. ## Population - 23 adults with recent-onset idiopathic inflammatory myopathies, including polymyositis, dermatomyositis, and antisynthetase syndrome, excluding inclusion body myositis. - Sample size: 23 - Age: Eligibility 18-70 years; median age HIIT 34.5 years and control 57 years. - Sex: HIIT 6 female/6 male; control 9 female/2 male at baseline. - Fitness level: Most participants had very low aerobic capacity at baseline. - Health status: Recent-onset IIM within 12 months of diagnosis and medical treatment; high-risk contraindications to intensive exercise excluded. ## Methodology - Multicentre randomized controlled trial comparing HIIT with low-moderate intensity home-based standard-of-care exercise. - 12 weeks. - Karolinska University Hospital and Akademiska Hospital clinical research settings, with clinic supervision and some home/gym or remote monitored sessions. - Randomized and controlled study design. ## Protocol - HIIT. - Modality: Stationary-bike intervals plus one set of strength training for shoulders, knee extensors, and core. - Work intervals: 30 seconds. - Recovery: 2 minutes of moderate biking between intervals. - Sets or repetitions: Progressed to six maximal intervals; strength training one set at 10 voluntary repetition maximum. - Intensity: At least 85% HRpeak during each interval; strength progressed when exertion was below 7 on Borg CR-10. - Session duration: Interval cycling component approximately 15 minutes after progression, plus strength training; exact full duration not reported. - Frequency: Three sessions per week. - Program length: 12 weeks. - Progression: Ramp-up over first 3-4 weeks from three submaximal intervals to three maximal intervals, then more sets until six maximal intervals; load or interval time increased to maintain >85% HRpeak. - Low-moderate intensive home-based training. - Modality: Home-based strengthening, balance/stretching exercises, and brisk walking. - Sets or repetitions: Eight exercises with ten repetitions per exercise: step up/walking on spot warm-up, shoulder flexion, grip squeeze, sitting knee extension, supine hip flexion, pelvic-lift hip extension, sit-ups without neck support, and stretching. - Intensity: Easy-to-moderate muscle fatigue, 3-4 on Borg CR-10; 15-minute brisk walk not surpassing 70% HRpeak. - Session duration: Includes 2-minute warm-up and 15-minute brisk walk; full exercise-program duration not reported. - Frequency: Five times weekly after one supervised session. - Program length: 12 weeks. - Progression: External resistance could be added if needed. ## Outcomes ### VO2peak Status: improved HIIT improved VO2peak more than control, both absolute and weight-adjusted. VO2peak L/min increased 16% in HIIT versus 1.8% in control; between-group estimate 0.29 L/min (95% CI 0.10 to 0.47). VO2peak ml/kg/min between-group estimate 2.97 (95% CI 0.83 to 5.10). ### Peak power and time to exhaustion Status: improved HIIT improved muscle endurance outcomes more than control. Peak power increased 18% in HIIT versus 8% in control; between-group estimate 17.3 W (95% CI 3.9 to 30.8). TTE increased 23% in HIIT versus 11.25% in control; between-group estimate 1:42 (95% CI 0:06 to 3:18). ### Mitochondrial adaptations Status: improved Muscle expression of mitochondrial respiratory chain complexes I and V, citrate synthase, and VDAC1 increased after HIIT but not control. Paired tests within HIIT showed p<0.05 for selected mitochondrial proteins; biopsy analysis included HIIT n=7 and control n=6. ### Disease activity and safety Status: no clear change HIIT did not increase group-level serum muscle enzymes or disease activity, and no longstanding pain, fatigue, injuries, or falls related to HIIT were reported. MDAAT muscle disease activity between-group estimate -0.08 (95% CI -1.2 to 1.0); pain and fatigue showed no statistically significant worsening after HIIT. ## Practical Insights - For selected clinical populations with very low aerobic capacity, a gradual ramp-up to short hard intervals can be feasible and effective when heart-rate monitored. - A 30-second work, 2-minute active recovery cycling structure at at least 85% HRpeak improved VO2peak and endurance in recent-onset IIM. - Clinical translation requires screening out serious contraindications and monitoring soreness, fatigue, pain, disease activity, and muscle enzymes. ## Limitations - Small sample due to the rarity of IIM. - Missing data and incomplete paired biopsy samples. - COVID-19 restrictions changed eligibility timing and limited inclusion of higher-risk patients. - Some secondary outcomes may have been underpowered. - The trial does not show long-term maintenance beyond 12 weeks. - The protocol is cycle-ergometer based and not directly translatable to bodyweight-only HIIT. ## Safety And Adherence - No participants reported longstanding pain or fatigue, injuries, or falls related to HIIT. - HIIT participants reported delayed-onset muscle soreness for 1-2 days after each session. - HIIT participants reported instant muscle fatigue subsiding after about 30-60 minutes. - Serum CK, AST, and ALT did not increase after HIIT or control exercise. - LD remained slightly elevated in both groups at all time points but did not change, supporting no increased inflammation from exercise in the authors' interpretation. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/41314147/) (pubmed) - [DOI](https://doi.org/10.1016/j.ebiom.2025.106051) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12703967/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.