Abstract
Tendons must be able to withstand the forces generated by muscles and not fail. Accordingly, a previous comparative analysis across species has shown that tendon strength (i.e., failure stress) increases for larger species. In addition, the elastic modulus increases proportionally to the strength, demonstrating that the two properties co-vary. However, some species may need specially adapted tendons to support high performance motor activities, such as sprinting and jumping. Our objective was to determine if the tendons of kangaroo rats (k-rat), small bipedal animals that can jump as high as ten times their hip height, are an exception to the linear relationship between elastic modulus and strength. We measured and compared the material properties of tendons from k-rat ankle extensor muscles to those of similarly sized white rats. The elastic moduli of k-rat and rat tendons were not different, but k-rat tendon failure stresses were much larger than the rat values (nearly 2 times larger), as were toughness (over 2.5 times larger) and ultimate strain (over 1.5 times longer). These results support the hypothesis that the tendons from k-rats are specially adapted for high motor performance, and k-rat tendon could be a novel model for improving tissue engineered tendon replacements.
Highlights
Tendons must be able to withstand the forces generated by muscles and not fail
A meta-analysis of 50 studies, with tendons from mammalian species ranging from mice to cows, showed that tendon mechanical properties uniformly vary with body size[5]
All results are presented as mean ± standard error of the mean (SEM) of data from ten animals each of k-rats and rats
Summary
Tendons must be able to withstand the forces generated by muscles and not fail. a previous comparative analysis across species has shown that tendon strength (i.e., failure stress) increases for larger species. The elastic moduli of k-rat and rat tendons were not different, but k-rat tendon failure stresses were much larger than the rat values (nearly 2 times larger), as were toughness (over 2.5 times larger) and ultimate strain (over 1.5 times longer) These results support the hypothesis that the tendons from k-rats are specially adapted for high motor performance, and k-rat tendon could be a novel model for improving tissue engineered tendon replacements. The linear relationship between elastic modulus and ultimate stress is robust (R2 = 0.785) across 11 mammalian species despite differences in study methodology, the muscles attached to the tendons, and tendon modifications due to age, injury, genetic alterations, or in vivo mechanical interventions (i.e., disuse, vibration, strength training)[5]. Species with highly specialized motor function, such as kangaroo rats, were not included in the meta-analysis, as their tendons have not been studied previously
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