By Chris Beardsley
Chris Beardsley graduated from Durham University with a Masters Degree in 2001. He since contributed to the fields of sports science and sports medicine by working alongside researchers from Team GB boxing, the School of Sport and Recreation at Auckland University of Technology, the Faculty of Sport at the University of Ljubljana, the Department of Sport at Staffordshire University, and the College of Health Solutions at Arizona State University. He is also a Director at Strength and Conditioning Research Limited
Surprising new research has shown that static stretching can increase muscle size (if not strength), even when the stretch is totally passive and involves no muscle activation at all. The key seems to be a fairly intense stretch, with progressively greater loading each workout.
Even though this comes as a surprise to many, there were already clues in the research, as rodent models had found that passive stretching could produce increases in p70S6K phosphorylation, which is part of the mTOR anabolic signaling pathway.
Such studies tend to show that active contractions and passive stretch can both cause increases in anabolic signaling activity, but that combined active and passive mechanical loading together are additive, and can produce the greatest changes.
This is probably why studies comparing strength training at long and short muscle lengths (such as full and partial squats) have typically reported greater hypertrophy in the groups training at long muscle lengths.
After all, the muscle contractions at the longer muscle lengths combine the active and passive mechanical loading to produce a greater hypertrophic stimulus.
Even so, this does not indicate that static stretching is always valuable for hypertrophy when performed at any time.
Although many bodybuilders use intense static stretching between sets of strength training, this may actually reduce hypertrophy by decreasing workout volume.
After all, strength training will always be the primary stimulus for hypertrophy, and if the static stretching has an adverse effect on the number of reps that can be performed in a workout, then it will be unhelpful overall.
This suggests that if static stretching is to be used in addition to strength training to increase muscle growth, then it should be performed at the end of a workout and not either beforehand or in between sets of strength training.