Home-Based High-Intensity Interval Training in Systemic Lupus Erythematosus

This is a single-arm, pilot, proof-of-concept study evaluating the clinical and biological effects of a 16-week personalized, home-based high-intensity interval training program in 20 adults with stable systemic lupus erythematosus and persistent fatigue and/or muscle pain.

SLE-related fatigue is common and may persist despite adequate control of inflammatory disease activity. Skeletal muscle mitochondrial dysfunction may impair cellular energy production and contribute to fatigability and exercise intolerance. In addition, intermuscular adipose tissue, defined as fat located within the muscle compartment, is increased in some people with SLE and may be associated with systemic inflammation, fatigue, and reduced physical function.

The exercise intervention will include three sessions per week:

One bodyweight high-intensity interval training session One strength-training session One walking-based high-intensity interval training session

Exercise duration and intensity will increase gradually during the 16-week intervention. The program will be personalized according to each participant's baseline fitness, mobility, exercise preferences, SLE manifestations, pain, and exercise tolerance. Exercise sessions will alternate between remotely supervised video sessions and self-directed sessions using individualized prerecorded videos. Participants will use a heart-rate monitor during exercise, and the study team will conduct regular check-ins to support adherence and safety. Exercise intensity may be reduced or modified if a participant develops increased pain, joint symptoms, or an SLE flare.

Participants will complete study assessments at baseline and after the 16-week intervention. Skeletal muscle mitochondrial function will be assessed noninvasively using phosphorus-31 magnetic resonance spectroscopy. The primary measure of mitochondrial function will be phosphocreatine recovery following a brief standardized muscle exercise.

Magnetic resonance imaging of the thigh will be used to quantify intermuscular adipose tissue and muscle composition. Additional imaging may assess abdominal and liver fat.

Physical performance will be evaluated using the six-minute walk test and the 30-second sit-to-stand test. Participants will also complete questionnaires assessing fatigue, fatigability, mobility, overall health, cognitive function, and SLE-related quality of life.

Blood and other biological samples will be collected before and after the intervention. Laboratory analyses will evaluate circulating markers of mitochondrial function, inflammation, and inflammasome activation. Exploratory analyses may include gene expression, proteomic, genetic, urine, and microbiome studies for participants who provide the required consent.

The study will compare each participant's measurements before and after the exercise intervention. The primary outcomes will evaluate changes in skeletal muscle mitochondrial function and intermuscular adipose tissue. Secondary and exploratory analyses will evaluate changes in physical performance, fatigue, quality of life, inflammatory markers, and other biological measures.

Because this is a small, uncontrolled pilot study, it is intended to identify preliminary signals of biological and clinical benefit rather than establish definitive efficacy. Results will inform the feasibility, outcome selection, and sample-size planning of future controlled trials of personalized exercise interventions in SLE.

Inclusion criteria

• Age 18 to 65 years.
• Diagnosis of systemic lupus erythematosus according to the 2019 European Alliance of Associations for Rheumatology/American College of Rheumatology classification criteria.
• Stable, non-organ-threatening systemic lupus erythematosus, defined as a Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score of 6 or less at screening, with no active renal or central nervous system involvement.
• Stable background lupus therapy, defined as no initiation of a new disease-modifying antirheumatic drug or biologic therapy and no change in the dose of immunosuppressive therapy within 8 weeks before enrollment.
• Persistent fatigue and/or muscle pain, with a PROMIS Fatigue T-score of 55 or greater.
• Stable prednisone dose, or equivalent glucocorticoid dose, of 5 mg per day or less for at least 12 weeks before enrollment.
• Able to safely participate in a moderate-intensity exercise program.
• Able and willing to provide informed consent.
• Able and willing to comply with the home-based exercise protocol and study procedures.

Exclusion criteria

• Prednisone dose greater than 5 mg per day, or receipt of a glucocorticoid burst within 8 weeks before enrollment.
• Pregnancy.
• Severe anemia, defined as hemoglobin less than 10 g/dL.
• Uncontrolled hypothyroidism.
• Severe systemic lupus erythematosus disease activity, defined as a SLEDAI-2K score greater than 8.
• End-stage kidney disease requiring renal replacement therapy or estimated glomerular filtration rate less than 30 mL/min/1.73 m².
• Uncontrolled hypertension, defined as blood pressure greater than 160/100 mmHg.
• Decompensated heart failure.
• Unstable pulmonary disease.
• Neurologic condition that limits exercise performance.
• Uncontrolled diabetes mellitus.
• Severe osteoarthritis that limits safe participation in the exercise intervention.
• Overlap autoimmune disease, including inflammatory myopathy, mixed connective tissue disease, or systemic sclerosis.
• History of solid-organ or bone marrow transplantation.
• Any contraindication to magnetic resonance imaging.
• Inability to fit safely on the magnetic resonance imaging scanner bed.
• Myocardial infarction or cerebrovascular event within the previous 3 months.
• Serious hemorrhage, including cerebral hemorrhage, within the previous 12 months.
• Acute infectious illness within 1 month before enrollment.
• Inability to provide informed consent.
• Inability to adhere to the home-based exercise protocol.
• Current participation in a structured exercise program.