Association between TMG-derived contractile muscle parameters and MRI-based muscle structure in sarcopenia

Muscle fat fraction (MFF) obtained through magnetic resonance imaging (MRI) is the gold standard for assessing muscle quality, but it is expensive and time consuming. Portable methods to examine muscles such as tensiomyography (TMG) are emerging and could enable broader screening. This study aims to examine associations between TMG-derived muscle contractile parameters and MFF in older adults with and without sarcopenia. A sample of 51 Slovenian older adults (53% females) were scanned with Dixon MRIs to evaluate muscle MFF and contractile parameters were assessed with TMG estimating delay time (Td), maximal displacement (Dm) and radial contraction velocity (Vc). Right leg vastus lateralis (VL) and biceps femoris (BF) were analyzed. Sarcopenia was defined using both European Working Group on Sarcopenia in Older People (EWGSOP2) and Sarcopenia Definition and Outcomes Consortium (SDOC) criteria. Regression models adjusted for age and sex were used to assess associations between TMG-derived contractile parameters and MFF. Age- and sex-adjusted models revealed associations between increased MFF and reduced Dm (R2 = 0.29, p = .003) and Vc (R2 = 0.32, p = .002) for the VL. SDOC-classified sarcopenic individuals showed increased VL MFF (27.2% vs. 22.5%, p = .019),while EWGSOP2 classified sarcopenia displayed no differences. The study reveals that increased MFF is associated with reduced muscle contractility in VL. MFF differs between sarcopenic and non-sarcopenic groups using only SDOC criteria. Since the TMG Dm increase is regularly found in atrophic muscles after bed rest, in sarcopenic muscle MFF explains lowering of the Dm, highlighting the TMG potential for early detection of changes in aging muscle.