Alterations in muscle architecture and contractile properties in human sarcopenia

Background: Ageing is associated with muscle morphological and functional changes whereas in sarcopenia those changes severely affect the normal quality of life. The aim of this cross-sectional study was to evaluate relationship between architectural changes and contractile properties of the sarcopenic muscle and to validate ultrasound sarcopenia index in a diagnosed sarcopenic population. Methods: Sample consisted of 705 older adults (31.6% males) aged 73.16 ± 9.10 years from 11 Slovenian regions which were classified as non-sarcopenic and sarcopenic using a revised algorithm by European Working Group on Sarcopenia in Older People (EWGSOP2) and an algorithm by Sarcopenia Definition and Outcome Consortium (SDOC). Their proposed tests of muscle strength, muscle mass and physical performance were aquired. Muscle contractile properties were examined with tensiomyography (TMG) on vastus lateralis, biceps femoris and gastrocnemius medialis of the right leg. Additionally, on a subsample of 51 participants (47% males) aged 82.3 ± 8.2 years muscle architecture properties were assessed with ultrasonographic measurements of vastus lateralis. Muscle fascicle length (Lf) and thickness (Tm) at 35% of femur length were used to calculate Lf/Tm ratios known as ultrasound sarcopenia index (USI) as indices of muscle geometric proportion. Results: TMG-derived parameters (delay time, contraction time, radial displacement and contraction velocity) were different between non-sarcopenic and sarcopenic groups in all three assessed muscles. With EWGSOP2 classification, USI values were different (p =.008) between non-sarcopenic (n = 27; USI = 4.49 ± 1.06) and sarcopenic group (n = 12; USI = 5.41 ± 1.48). Similarly, both groups were also significantly different (p =.008) according to SDOC classification: non-sarcopenic (n = 19; USI = 4.29 ±.76) and sarcopenic group (n = 20; USI = 5.24 ± 1.47). USI was correlated with delay time (r =.388; p =.15), contraction time (r =.388; p=.015), contractile velocity (r= -.338; p=.035), and presented a trend for radial displacement (r = -.302; p =.062). Discussion: USI shows to be a reliable tool in distinguishing sarcopenic and non-sarcopenic muscles and thereforecould be used for sarcopenia diagnosis confirmation as they are non-invasive, novel and inexpensive muscle quality markers. Further, TMG-derived parameters were also correlated to USI values; however it needs to be further explored whether could be used for sarcopenia classification purposes. The study was funded by the Slovenian Research Agency (research core funding No. P5-0381 and J7-2605 – Validation of a new muscle quality marker for the diagnosis of sarcopenia). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.