Publications
A novel muscle property score and its sex-specific associations with fatigue, physical activity, and nutrition in middle-aged adults
Authors: Mijin Kim 1, Toshiro Kobori 1, Taeho Kim 2, Sechang Oh 3
Affiliations:
- Institute of Food Research, National Agricultural and Food Research Organization, Tsukuba 305-8642, Japan
- The Center for Sports Medicine and Health Sciences, University of Tsukuba Hospital, Tsukuba 305-8576, Japan
- Faculty of Rehabilitation, R Professional University of Rehabilitation, Tsuchiura 300-0032, Japan
Journal: Nature - Scientific Reports - September 2026 (DOI: 10.1038/s41598-026-68443-4)
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Field & Applications:
- Medical
- Gerontology / Ageing
- Musculoskeletal health
- Fatigue / Overtraining
A single measure cannot adequately represent overall muscle health. Although muscle properties include structural, functional, and mechanical dimensions, an integrated metric combining muscle mass, strength, and mechanical properties is lacking. This study developed a composite muscle health index, the Total Score of Muscle Properties (TSMP), and examined its associations with fatigue, physical activity, and nutrient intake in middle-aged Japanese adults.
A total of 122 participants (59% women; aged 40–64 years) were assessed for appendicular muscle properties, including muscle mass, handgrip strength, knee extensor strength, muscle tone, and stiffness. Principal component analysis was performed separately by sex, with the first principal component defined as TSMP. Fatigue, physical activity, and nutrient intake were assessed using validated questionnaires.
The first principal component explained 43.4% of the variance in men and 40.4% in women. In women, higher TSMP was associated with lower upper-body fatigue, instability, uneasiness, and local pain or dullness. In men, higher TSMP was associated with lower risks of physical inactivity and insufficient total physical activity after adjustment, and with higher intake of dietary fiber, calcium, magnesium, iron, B-complex vitamins, and vitamin D.
These findings provide initial support for TSMP as an index of musculoskeletal health.
Keywords: muscle quality, muscle properties, micronutrient intake, physical activity, fatigue
In this study, we proposed the TSMP as a composite measure integrating muscle mass, strength, tone, and stiffness and provided preliminary evidence supporting its potential as a multidimensional muscle health index. In men, higher TSMP was associated with lower odds of moderate-intensity and total physical inactivity (<600 MET-min/week), as well as higher intakes of dietary fiber, minerals, and vitamins. In women, higher TSMP was associated with lower self-reported upper-body fatigue, instability, uneasiness, and localized pain. These findings suggest that TSMP may serve as a promising multidimensional indicator of muscle health; however, its clinical applicability remains to be established. Further validation in larger, longitudinal, and diverse populations is required to confirm its interpretability, construct validity, reproducibility, generalizability, and predictive performance before broader clinical application.