Axial Strain Measurements in Skeletal Muscle at Various Strain Rates

• Published in: Journal of biomechanical engineering 1995-08, Vol.117 (3), p.262-265
• Main Authors: Best, T. M, McElhaney, J. H, Garrett, W. E, Myers, B. S
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biomechanical Phenomena; Biomechanics. Biorheology; Fundamental and applied biological sciences. Psychology; Muscle, Skeletal - physiopathology; Rabbits; Sprains and Strains - physiopathology; Tissues, organs and organisms biophysics
• ISSN: 0148-0731; 1528-8951
• DOI: 10.1115/1.2794179

A noncontact optical system using high speed image analysis to measure local tissue deformations and axial strains along skeletal muscle is described. The spatial resolution of the system was 20 pixels/cm and the accuracy was ±0.125mm. In order to minimize the error associated with discrete data used to characterize a continuous strain field, the displacement data were fitted with a third order polynomial and the fitted data differentiated to measure surface strains using a Lagrangian finite strain formulation. The distribution of axial strain along the muscle-tendon unit was nonuniform and rate dependent. Despite a variation in local strain distribution with strain rate, the maximum axial strain, Exx = 0.614 ± 0.045 mm/mm, was rate insensitive and occurred at the failure site for all tests. The frequency response of the video system (1000 Hz) and the measurement of a continuous strain field along the entire length of the structure improve upon previous noncontact optical systems for measurement of surface strains in soft tissues.