Multiscale Passive Mechanical Characterization of Rodent Skeletal Muscle

Purpose: To experimentally measure selected passive properties of skeletal muscle at three different scales (macroscopic scale: whole muscle, microscopic scale: single skinned fiber, and submicron scale: single myofibril) within the same animal model (mice), and to compare a primarily slow-twitch fiber muscle (soleus) and a primarily fast-twitch fiber muscle (extensor digitorum longus, EDL) for each scale.Methods: Healthy 3 months old wild-type C57BL6 mice were used. To characterize each scale, soleus (N = 11), EDL (N = 9), slow fibers (N = 17), fast fibers (N = 16), and myofibrils from soleus (N = 11) and EDL (N = 11) were harvested. Passive mechanical (ramp, relaxation) tests were applied at each scale to compare the passive properties (Young's modulus, static and dynamic stresses) within a given scale, across scales and between muscle types.Results: The soleus and EDL showed significant passive mechanical differences at the macroscopic scale while no variation was observed between both tissues at the microscopic and submicron scales. The results highlight the importance of the scale that is used to mechanically characterize a multiscale tissue. Conclusion: The present work will allow for a better understanding of the multiscale passive mechanical properties for two muscles with vastly differing physiological and metabolic properties. This study provides referent data to the body of literature that can be built upon in future work.@2023 AGBM. Published by Elsevier Masson SAS. All rights reserved.

Automated summary

The study aimed to compare the passive mechanical properties of soleus and extensor digitorum longus muscles at different scales in a mouse model. Results showed significant differences in passive mechanical properties at the macroscopic scale, highlighting the importance of scale in tissue characterization. This research contributes referent data for future studies on multiscale passive mechanical properties of muscles.