High-intensity interval training outperforms standard home exercise in improving fitness for patients with inflammatory muscle disease.
A new study from Karolinska Institutet, published in eBioMedicine, finds that high-intensity interval training improves physical fitness and muscle endurance more than standard home-based exercise in people recently diagnosed with inflammatory muscle disease.
Idiopathic inflammatory myopathies (IIM) are rare autoimmune conditions that lead to muscle weakness and fatigue. Treatment typically includes medication along with light or moderate exercise done at home, but this approach has shown limited benefits for aerobic fitness. To address this gap, researchers at Karolinska Institutet examined whether high-intensity interval training (HIIT) could provide greater improvements.
The study included 23 individuals with newly diagnosed IIM who were recruited from Karolinska University Hospital in Stockholm and Uppsala University Hospital. Participants were randomly divided into two groups. One group completed HIIT sessions on a stationary bicycle three times per week for twelve weeks, while the other followed a moderate-intensity home exercise program. Aerobic fitness, muscle endurance, and indicators of disease activity were measured both before and after the intervention.
Clear improvements with HIIT
The results showed that participants in the HIIT group increased their aerobic capacity by an average of 16 percent, compared with an improvement of 1.8 percent in the home exercise group. Gains in muscle endurance were also greater with HIIT, and muscle biopsies indicated improved mitochondrial function, which plays a central role in cellular energy production. Disease activity remained unchanged in both groups, suggesting that the higher intensity training was safe. The researchers found no evidence that exercise worsened inflammation or caused muscle damage.
“Common symptoms of IIM include muscle weakness and reduced endurance. Our study shows that high-intensity interval training is safe and markedly improves muscle function and aerobic capacity. Better fitness can lower the risk of cardiovascular disease, while patients gain more stamina and independence. This could become an important complement to medication in improving physical capacity and quality of life,” says Kristofer Andreasson, researcher at the Department of Medicine, Solna, Karolinska Institutet.
The researchers emphasize that the study is small and that further studies are needed to confirm the findings and assess long-term effects.
Reference: “High-intensity interval training outperforms moderate exercise to improve aerobic capacity in patients with recent-onset idiopathic inflammatory myopathies: a multicentre randomised controlled trial” by Kristofer M. Andreasson, Cecilia Leijding, Maryam Dastmalchi, Antonella Notarnicola, Stefano Gastaldello, Takashi Yamada, Heléne Sandlund, Dag Leonard, Håkan Westerblad, Ingrid E. Lundberg, Daniel C. Andersson and Helene Alexanderson, 27 November 2025, eBioMedicine.
DOI: 10.1016/j.ebiom.2025.106051
The study was mainly funded by the Swedish Research Council, Region Stockholm (ALF), the Swedish Rheumatism Association, King Gustaf V’s 80-Year Fund (Stiftelsen Konung Gustaf V:s 80-årsfond), and the Swedish Heart Lung Foundation.
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