I learned about this from Jeff Nippard who just released a new video: https://www.youtube.com/watch?v=VuBhECs587w
Here’s the study he refers to: https://www.researchgate.net/publication/329644411_Interset_Stretching_vs_Traditional_Strength_Training_Effects_on_Muscle_Strength_and_Size_in_Untrained_Individuals
“Statistical significance when you pool the results together.”
Your thoughts are appreciated.
The study shows no significant differences for biceps, triceps or rectus femoris muscle groups. It does show a significant difference in the vastus lateralis muscle, and the “sum” of measures from four different sites favored the stretching group. Ultrasound isn’t the best/most accurate/reliable method to measure muscle hypertrophy, but it seems they did the best they could to optimize measurement with that modality.
Conversely, we have other evidence showing stretching pre-training to have harmful effects: Effect of the flexibility training performed immediately before resistance training on muscle hypertrophy, maximum strength and flexibility - PubMed , so we need to be cautious with our conclusions and implementation.
Mechanistically, it is interesting, and there has been some evidence on stretch-induced hypertrophy in animal models and in untrained / sedentary / bedbound individuals. Perhaps that’s enough tension to provide an effective mechanotransduction stimulus to initiate muscle hypertrophy. What would be better to know is whether it’s enough to augment the hypertrophy response in trained individuals who are regularly exposed to much higher degrees of mechanical tension. So this sort of study deserves replication in other populations before I’d recommend such a practice.