Systemic lupus erythematosus: Relationship of fatigue and muscle weakness with functionality

Abstract

Introduction: Systemic lupus erythematosus (SLE) can be associated with fatigue, reduced muscle strength, lower aerobic fitness, and limitations in functional performance, with potential repercussions on activities of daily living and quality of life. Although recent reviews have investigated the effects of physical exercise on SLE, it remains relevant to integrate evidence regarding the relationship between fatigue, muscle weakness, and functionality, distinguishing observational associations from the effects of interventions. Objective: To analyze available evidence regarding the relationship of fatigue and muscle weakness with the functionality of individuals with SLE, considering their associations with physical capacity, muscle strength, functional performance, and quality of life, as well as the effects of physical exercise on these components. Methods: An integrative literature review of a qualitative and descriptive nature was conducted on September 30, 2026, using the PubMed/MEDLINE, SciELO, and Virtual Health Library (VHL) databases. The search strategy was structured around the axes of systemic lupus erythematosus, fatigue and muscle strength/weakness, functionality, physical capacity, and exercise, utilizing MeSH and DeCS descriptors and free-text terms combined with AND and OR operators. Studies in Portuguese or English were included if they had full text available for free or via institutional access, investigated adults with SLE, and assessed fatigue, muscle strength or function, aerobic capacity, physical or functional capacity, functional performance, activities of daily living, or quality of life, in addition to exercise-based interventions. Study selection and data extraction were performed independently by two reviewers, with disagreements resolved by consensus. The synthesis was qualitative and organized into three axes: fatigue and functionality; muscle weakness, physical fitness, and functionality; and the effects of exercise. No formal, standardized assessment of risk of bias or methodological quality was performed. Results: Twelve studies comprised the final sample, including randomized controlled trials, an experimental study, observational and comparative studies, a case-control study, systematic reviews, and a systematic review with meta-analysis. Observational and comparative studies indicated greater fatigue, lower muscle strength, lower aerobic fitness, and poorer functional performance in individuals with SLE, although associations between fatigue and objective measures of strength or muscle metabolism were inconsistent. Muscle strength reductions ranging from approximately 11% to 26% were reported in a case-control study, while another study identified lower peak VO₂, shorter exercise duration, and lower quadriceps strength compared to controls. Exercise interventions showed benefits primarily regarding fatigue, aerobic capacity, muscle strength, functional performance, and certain quality-of-life domains, though without consistent improvement across all outcomes or disease activity. A recent meta-analysis showed a reduction in fatigue (g = −0.53; 95% CI −0.81 to −0.25) and improvements in physical function (g = 0.46; 95% CI 0.23–0.68) and aerobic capacity (g = 0.47; 95% CI 0.22–0.71), whereas a Cochrane review indicated low or very low certainty for several comparisons. Conclusion: Fatigue, muscle weakness, reduced physical fitness, and functional impairment are significantly associated in SLE, yet the findings do not establish a single causal chain linking these components. Physical exercise has yielded favorable results—particularly regarding fatigue, aerobic capacity, and certain aspects of physical function and quality of life—though the magnitude and consistency of these effects vary across studies. Methodological heterogeneity, the combined inclusion of primary studies and systematic reviews, the potential for overlapping evidence, the lack of standardized risk-of-bias assessment, language restrictions, and full-text access requirements limit confidence in the conclusions and underscore the need for more standardized, long-term studies.