Contraction type dependence of serial sarcomere addition following resistance training
Longitudinal muscle growth occurs through the addition of sarcomeres in series, a process termed serial sarcomerogenesis. To investigate contraction mode dependence of sarcomerogenesis in Sprague-Dawley rats (n=36, 14 to18 weeks, ~468g), we compared the effects of isometric, eccentric, and concentric training (4 to 6 weeks; 3 times/week) on morphological and mechanical adaptations of the plantar…
Serial sarcomerogenesis, the process of adding sarcomeres in series during longitudinal muscle growth, was examined in relation to different contraction modes in Sprague-Dawley rats (n=36, aged 14 to 18 weeks, weighing approximately 468g). The researchers investigated the impact of isometric, eccentric, and concentric training (lasting 4 to 6 weeks, performed three times per week) on the morphological and mechanical adaptations of the plantar flexors.
Isometric training was executed at a joint angle corresponding to the plateau near the descending limb of the force length relationship. Eccentric contractions commenced at a shorter muscle length and gradually lengthened to the identical joint position. Conversely, concentric contractions began at the lengthened position and subsequently actively shortened. Due to the rapid regulation of serial sarcomere number, the 4- and 6-week timepoints were combined.
Despite a significant increase in force output across all training modes (+16%; p < 0.05), no such enhancement was observed for the sarcomere addition. Consequently, these findings underscore the mechanical loading environment associated with isometric and eccentric training as a crucial factor driving serial sarcomerogenesis.
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