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There's some new stretching research that I think you yoga geeks will find interesting! 🤓

You've probably heard the news by now that strength training through full ranges of motion has been shown to be just as effective as passive stretching for increasing flexibility.

I've personally written and talked about the research on this topic many times – and it's widely known in the evidence-based fitness and movement worlds.

(In other words, you know that claim that "strength training makes you tight"? This is an outdated myth that we can all let go of – phew! 😅)

With this as a background, there's a new study (just published in June) that sought to give us additional insight on this topic:

What new insights does this study provide?

While it's well-established that both stretching and full range of motion strength training improve flexibility, we still have a lot to learn about the details of this topic!

For example, it turns out that none of the previous studies matched two important variables when comparing static stretching to strength training:

training volume (how much time was spent performing each activity)

stretching intensity (how strong the stretch sensations were)

Without matching these variables, differences in training volume and/or stretching intensity could have influenced the outcomes in previous studies. These differences make it difficult to attribute changes in flexibility solely to the type of activity (stretching or strength training).

In this new study's research design, these variables were matched. 👍

This ensured that both the stretching and strength training groups received an equal stimulus in terms of time and intensity. And this allowed the researchers to better isolate the effects of each intervention on flexibility.

In other words, the new study's design provides a more accurate sense of whether stretching or strength training is more effective for flexibility gains.

In addition, by keeping the time and intensity variables consistent between groups, this research can help inform us on training dosages in our own yoga, movement, and strength practices.

That's definitely a win-win in my book!

So let's take a closer look at what happened in this study.

This study focused on hamstring and low back flexibility and strength.

There were 18 participants in this study. (This isn't a lot, but this was also the first study of its kind. Future research should include larger sample sizes.)

The participants were divided into three groups:

Group 1: Performed strength training through full range of motion for the hamstrings and low back muscles for 8 weeks

Group 2: Performed static stretching of the hamstrings and low back muscles for 8 weeks

Group 3: A control group

All participants' hamstring and low back flexibility and strength were measured and recorded before and after this 8-week period.

What did the strength training group do?

This group performed two strength training exercises with a "focus on an expansive ROM (range of motion)":

Exercise #1: Straight leg deadlifts – these strengthen the hamstrings in a stretched position and strengthen the low back muscles in a neutral-ish position:

Exercise #2: Jefferson curls – these strengthen the hamstrings and the low back muscles in stretched positions:

What did the stretching group do?

This group performed a seated forward fold that in the yoga world, we know as paschimottanasana. (But in this research study, it was called a “static sit & reach exercise”. 🙂)

This static stretch passively stretches the hamstrings and low back muscles:

How were training time and stretch intensity matched between the groups?

For training time, if the strength training group performed 1 set of 8 reps of an exercise with each rep lasting 4 seconds, this equaled 32 seconds of training time (8 x 4 = 32).

The stretching group matched this by holding a seated forward fold for 32 seconds.

Both groups performed between 4-8 sets of these time-matched exercises, three times a week over the 8-week period.

For stretch intensity, participants in both groups were instructed to stretch to an intensity level of 8/10 in their exercises.

What happened at the end of the 8 weeks?

At the end of the 8-week intervention, both the static stretching and the strength training groups showed significant improvements in flexibility 👍, but only the strength training group experienced notable gains in maximal strength.

To quote the researchers:

"The findings of the present study suggests that when ‘time’ is a limiting factor, resistance training [strength training] with a substantial ROM is a valid and efficient protocol since it increases both strength and flexibility."

What does this suggest about yoga?

First of all, I'm sure we all know that yoga is a practice that consists of more than static stretching (unless we're talking about a style like Yin Yoga).

So while these insights on static stretching would apply to the static stretching element of yoga, remember that we generally do a lot more than exclusively static stretching in our yoga practice!

Additionally, "flexibility" and/or "strength" as a singular goal is far from the only reason people practice yoga.

There are many reasons we might practice and love yoga, including

flexibility benefits (of course 🙂)
stress reduction
novel movement exploration
confidence in our body through reassuring movement
community connection
and so much more.

So while strength training through a full range of motion is an expedient way to gain both strength and flexibility, this does not diminish the value of practicing yoga.

I always strive to keep this bigger picture in mind while allowing insights from research to inform my approach to yoga and movement.

I hope this discussion of the latest study helps to support you in your approach to yoga and movement as well!