The mechanical loading environment associated with eccentric exercise is one of the key stimuli to trigger sarcomerogenesis: It's a stretch to say eccentric exercise does not promote serial sarcomerogenesis

The addition of sarcomeres in series (sarcomerogenesis) in skeletal muscle has increasingly fascinated exercise scientists in recent years due to its potential to positively impact performance.1,2 In their new review article, Triggering sarcomerogenesis: Examining key stimuli and the role attributed to eccentric training-Historical, systematic, and meta-analytic review, Blazevich et al.3 provide a commendable overview of the history behind this area of research from the 1600s to present. They also provided a short meta-analysis of eccentric-biased exercise in animal models (which, due to methodological limitations, comprise most of this field to date) to bolster their overarching theme that eccentric exercise does not trigger sarcomerogenesis. They conclude explicitly that "Current evidence does not support eccentric training as an effective stimulus for sarcomerogenesis", with "a lack of effect of eccentric resistance training in animal models". Over the past 6 years, our research group has been investigating eccentric training-induced sarcomerogenesis in animal models, and based on experimental data from studies designed to optimize the serial sarcomerogenic response,4-8 we arrive at the opposite conclusion. Here we offer important context related to various interventions. We hope to demonstrate that the above-stated conclusion, while well-intentioned, forgoes several important considerations and can be misleading. In the review by Blazevich et al.,3 Fig. 7A includes data from all eccentric training studies in animals (downhill running and dynamometry with electrical muscle stimulation for all muscles investigated) and shows a significant effect (effect size (ES) = 0.51, p <0.001), going against their stated conclusion regarding eccentric loading and sarcomerogenesis.