I see the idea of stretching between sets often revisited, with the supposed benefits and detriments f doing so hotly debated. One thing for sure: it’s understood that stretching stimulates the facia, a thin sheath of fibrous tissue that encloses a muscle or other organ.
So let’s take a look at how the fascia is stressed both during weight lifting and in fascial training.
Weight lifting places a load (stress) on the muscle as the muscle changes length. This is the stimulus behind the hypertrophy (muscle growth) and is the core principle behind getting bigger and stronger. What’s not always considered is that while the muscles are stressed under a load, the fascia is not very affected.
In order to apply stress and activate the fascia structures we have to do something different. This is where the stretching component comes in, but more specifically a loaded stretching component. While under a load and in the end of range position, the muscle fibers are predominately stressed. To stress the fascia, the lifter needs to include an active muscle contraction at the end range position. The idea here is in order to stress the fascia, the lifter needs to combine a stretch position with an isometric muscle contraction.
But why would you want to stress the fascia?
In short, stress applied to the fascia can impact the properties of muscle fibers by influencing the release of growth factors and cytokines which contribute to hypertrophy. Here’s a good post on bodybuilding.com about regarding intra-set stretching.
So let’s review:
- During a normal workout, the fascia isn’t stressed significantly
- Including an isometric contraction in a stretch position we can stress fascia
- Stressing fascia can increase the release of local growth factors which contribute to hypertrophy
- By incorporating fascial stretching into a workout you can increase the rate of hypertrophy by stimulating fascia to release growth factors
However, this all still remains in theoretical realm. There is no actual evidence that supports fascia stretching contributes to hypertrophy. So far, stretch studies in humans have shown no hypertrophy benefits. Some isolated studies have shown stretching may slightly augment the response to resistance training, but the effect seems to be limited to only untrained individuals. It often proposed that performing resistance exercises though a full range of motion could provide the same stimulus.
On an associated topic, it’s often cautioned that stretching before lifting can reduce strength levels, defusing any benefits gained by intra-set stretching. Here’s a study that shows stretching reduces strength during the workout. If strength is reduced, then load and volume are likely reduced, which, in turn, could have negative affects on the progress of hypertrophy.
So what’s the take-away? Based on current knowledge:
- Stretching before lifting can negatively affect strength levels
- Stretching during lifting (intra-set stretching) doesn’t seem to have any confirmed benefit
- Working though a full range of motion likely provides comparable effects as intra-set stretching