(English) Episode 280-Deep range eccentric training grows longer muscles

This study investigated how an eight-week eccentric training program affects muscle structure and mechanical properties in the human gastrocnemius medialis. Researchers compared two groups of active young adults, with one performing exercises at long-muscle lengths and the other at short-muscle lengths. The results showed that only the group training at long-muscle lengths experienced a significant increase in muscle fascicle length, specifically in positions where the muscle was not under tension. Importantly, these structural changes occurred without altering muscle stiffness or other passive mechanical properties of the muscle-tendon unit. The findings suggest that fascicle lengthening from eccentric exercise is likely driven by the addition of sarcomeres in series rather than changes in connective tissue. Consequently, the range of motion used during training is a critical factor for inducing specific architectural adaptations in skeletal muscle.(Bizet B, Nordez A, Tallio T, Lacourpaille L, Cattagni T, Colard J, et al. Eight weeks of eccentric training at long-muscle length increases fascicle length independently of adaptations in passive mechanical properties. J Appl Physiol [Internet]. 2025;138(4):939–49. Available from: http://dx.doi.org/10.1152/japplphysiol.00859.2024)