Background
Assessment of the thigh muscle fat composition using magnetic resonance imaging (MRI) can provide surrogate markers in subjects suffering from various musculoskeletal disorders including knee osteoarthritis or neuromuscular diseases. However, little is known about the relationship with muscle strength. Therefore, we investigated the associations of thigh muscle fat with isometric strength measurements.
Methods
Twenty healthy subjects (10 females; median age 27 years, range 22–41 years) underwent chemical shift encoding-based water-fat MRI, followed by bilateral extraction of the proton density fat fraction (PDFF) and calculation of relative cross-sectional area (relCSA) of quadriceps and ischiocrural muscles. Relative maximum voluntary isometric contraction (relMVIC) in knee extension and flexion was measured with a rotational dynamometer. Correlations between PDFF, relCSA, and relMVIC were evaluated, and multivariate regression was applied to identify significant predictors of muscle strength.
Results
Significant correlations between the PDFF and relMVIC were observed for quadriceps and ischiocrural muscles bilaterally (p = 0.001 to 0.049). PDFF, but not relCSA, was a statistically significant (p = 0.001 to 0.049) predictor of relMVIC in multivariate regression models, except for left-sided relMVIC in extension. In this case, PDFF (p = 0.005) and relCSA (p = 0.015) of quadriceps muscles significantly contributed to the statistical model with R2adj = 0.548.
Conclusion
Chemical shift encoding-based water-fat MRI could detect changes in muscle composition by quantifying muscular fat that correlates well with both extensor and flexor relMVIC of the thigh. Our results help to initiate early, individualised treatments to maintain or improve muscle function in subjects who do not or not yet show pathological fatty muscle infiltration.
Key points
- Magnetic resonance imaging detects changes in muscle composition by quantifying muscular fat.
- Muscular fat correlates well with extensor and flexor strength at the thigh.
- Muscular fat, not cross-sectional area, can predict muscle strength in thigh muscles.
- The interaction between muscular fat and strength could become the basis for a biomarker for muscle quality and function.
1Department of Sport and Health Sciences, Technische Universität München,Georg-Brauchle-Ring 60/62, 80992 Munich, Germany.
2Department ofDiagnostic and Interventional Neuroradiology, Klinikum rechts der Isar,Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany.
3Department of Diagnostic and Interventional Radiology, Klinikum rechts derIsar, Technische Universität München, Ismaninger Str. 22, 81675 Munich,Germany.