Non Animal Testing Database

Intraoperative measurement of isometric contractile properties in muscle

Shirley Ryan AbilityLab, Chicago, USA
The isometric contractile properties of skeletal muscle are one of the classic structure-function relationships in biology, allowing extrapolation of the mechanical properties of a single fiber to the properties of the whole muscle based on the optimal fiber length and physiological cross-sectional area (PCSA) of the muscle. The aim of the present study was to measure the properties and function of human gracilis muscle directly in situ to validate this relationship. The authors used a surgical technique in which a human gracilis muscle is transferred from the thigh to the arm to restore flexion of the elbow after brachial plexus injury. During this procedure, the force-length relationship of the gracilis muscle in situ and its properties ex vivo were measured directly. The optimal fiber length of each subject was calculated based on the length-tension properties of the muscle. The PCSA of each subject was calculated from the muscle volume and the optimal fiber length. Using these experimental data, the authors determined a human muscle fiber-specific tension of 171 kPa. Furthermore, the average optimal fiber length of the gracilis was 12.9 cm. With this subject-specific fiber length, excellent agreement was found between the experimental and theoretical curves of active length and tension. However, these fiber lengths were only about half of the optimal fascicle length of 23 cm previously reported based on other preclinical research. Thus, the long gracilis muscle in humans appears to be species-specific, consisting of relatively short, parallel fibers.
Direct intraoperative measurement of isometric contractile properties in living human muscle
Richard L. Lieber
Added on: 04-26-2023
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