Theoretical elastic tensile behavior of muscle fiber bundles in traumatic loading events

• Published in: Clinical biomechanics (Bristol) Vol. 69; pp. 184 - 190
• Main Authors: Tamura, Atsutaka, Hongu, Jun-ichi, Matsumoto, Takeo
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2019
• Subjects: Elastic response; Muscle fiber bundle; Physical Medicine and Rehabilitation; Stress relaxation; Traumatic injury; Uniaxial stretch; Viscoelasticity; Viscoelasticity; Muscle fiber bundle; Uniaxial stretch; Stress relaxation; Elastic response; Traumatic injury
• ISSN: 0268-0033; 1879-1271; 1879-1271
• DOI: 10.1016/j.clinbiomech.2019.07.021

The mechanical characterization of skeletal muscle under high-rate loading regimes is important for predicting traumatic injuries due to traffic accidents and contact sports. However, it is difficult to perform dynamic mechanical tests at rates relevant to such rapid loading events. In the present study, a series of stress relaxation tests were conducted on rabbit hind-limb muscle fiber bundles using a custom tensile tester. Using relatively moderate loading conditions compared to those typically associated with traumatic injuries, the passive stress-decaying mechanical properties of muscle fiber bundles were characterized. In addition, stress relaxation responses to various ramp-hold stretches were theoretically predicted by a custom-built code. The results showed that the muscle fiber bundles exhibit greater stress relaxation at higher loading rates and greater stretch magnitudes. Based on these results, the data points representing the “elastic” stress–strain tensile behavior typical of traumatic injury were extrapolated using curve fitting. The theoretical model revealed rate-dependent characteristics of the muscle fiber bundles under traumatic loading conditions, which would result in tensile strengths of 300–500 kPa at the maximum engineering strain of 54%. This strength is on the order of magnitude as the maximum isometric stress of an active muscle contraction. The proposed numerical model is expected to serve as a powerful research tool to investigate injury mechanisms of the skeletal muscle. Moreover, the elastic response that was theoretically predicted here will be useful in the development of effective countermeasures to prevent traumatic injuries due to rapid loading events. •Rapidly stretched muscle fiber bundles showed 20% stress relaxation for 0.4 s after the ramp period.•Traumatic loading condition will theoretically lead to tensile strength of~400 kPa at 54% strain.•Predicted tensile strength was equivalent to the maximum isometric stress of muscle contraction.