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.