People are getting a little too excited about a surprising new study that suggests stretching can improve strength.
Furthermore, it does so in both sides (more on the stretched side, though).
Since I know people (especially stretching enthusiasts) are probably going to take the results of this one study and run with them, I am going to write this quick article to throw a stick in their bicycle spokes.
Hopefully this gets around before it’s too late.
The results are not that surprising – and still don’t really support the use of stretching for anything other than specific flexibility goals.
The study in question:
This study was just published last month in the Journal of Strength and Conditioning Research 1. The researchers wondered if stretching a muscle on one side would have an effect on the other side.
Untrained individuals were divided into two groups: 13 of them in a ‘treatment’ (stretching) group, and 12 in a ‘control’ (do nothing) group. The ‘stretch group’ had to stretch their right calf under supervision (to ensure it was done right), for 30 seconds, 4 times, and with 30 second rests. They did this three times a week. They measured strength and range of motion (flexibility) in both sides before and after the study. The study lasted 10 weeks.
At the end of the study, the control group had no changes. The stretch group had an 8% increase in range of motion in the stretched calf… but the opposite side had a 1% decrease – which is kinda funny. However, the strength of the stretched calf increased by 29%, and the opposite side increased by 11% (a ‘cross-education effect’).
The researchers actually did this project to study the ‘cross-education’ effect (they make this somewhat clear in their introduction), which is indeed super-duper interesting – it’s not clear what causes this cross-over (which I’ve mentioned before here), so it’s a cool thing to study.
This study doesn’t suggest strength gains are ‘more’ of a neurological phenomenon than a morphological (size, shape, etc.) one. It’s already well known that strength increases have a neurological contribution, but changes in morphology are more important in the long run. 2
However, one thing that has gotten people so interested in this study is the finding that stretching lead to a significant increase in strength.
Why is this so interesting?
Well, those of us who are nerdy about exercise science know that stretching has gotten a lot of bad press. I myself have torn down stretching – quite a bit. Go to the ‘Exercise and Training’ section of this site, and scroll down to ‘Stretching’ to see my stretching articles.
Basically, yes, it’s good for increasing flexibility. Sport specific ‘dynamic’ stretching might prevent injuries and can help with some athletic tasks when performed as part of a warm-up. But overall, stretching doesn’t improve some important factors of sports performance (including strength), it doesn’t prevent injuries, and doesn’t significantly reduce post exercise soreness. Not a lot of bang for your buck!
But then along comes this study – apparently proving us all wrong about being less than impressed with the effects of stretching.
But here’s the thing about this study…
or… a few things…
When it comes to strength, a recent systematic review huh? did a ‘meta analysis’ on 104 studies on stretching and its effects on strength 3. It demonstrated that only a few studies ever showed an increase in strength after stretching, with the overall results typically showing a 5% decrease in strength with stretching greater than 45 seconds.
However, those are the immediate effects. Maybe stretching has different long term effects? I mean, if we studied a muscle immediately after resistance training, we wouldn’t be too surprised to find its strength severely diminished, would we? But we know that after recovery, the muscles will be stronger.
Muscles strengthen as an adaptation to applying tension, – causing micro damage, etc., etc. Stretching could certainly (and probably does) do that to a certain extent – it definitely applies a significant force to the muscle. Also, it should be noted that the stretch was performed using body-weight – the ‘curb’ stretch – like this, but with hands also against the wall. That’s not just a stretch guys.
Also, keep in mind that this new study used ‘untrained’ participants – which really means people who are not very physically active, if at all. Still, these were young (early 20’s) people, who were not necessarily ‘unhealthy’. Therefore, the slightest exercise stimulus is probably going to have a more pronounced effect on these people.
So, in physically sedentary (but young, and not necessarily unhealthy) people, applying tension (by stretching applied by body-weight, in this case) three times a week for 10 weeks improved strength in the muscles stretched.
So is this really that surprising? I think not.
Compared to what?
This brings us to another problem – compared to what?
The control group did -NOTHING- in fact, the researchers went to great lengths – making them keep a journal, and even checking sign-in sheets of local gyms – to make sure the study participants didn’t do any other physical exercise or stretching.
Although it’s interesting to see that stretching did do something – and this may lead to more interesting research in the future – this doesn’t give us much of a leg to stand on for making recommendations. For instance, how would this have been different if there were three groups? 1. stretching, 2. resistance exercise, and 3. controls.
A study did exactly that last year… 4
Researchers at the University of North Dakota published a study that had three groups of “untrained adults”: 1. full-range resistance training, 2. static stretching, and 3. a “do nothing” control group, and looked at the effects on flexibility and strength. For increasing flexibility, resistance training had roughly the same (if not greater) improvements in flexibility as the stretching group. For strength, yes, static stretching increased it. But not nearly as well as resistance training. Another interesting detail (although not “statistically significant” huh?) is that stretching increased strength in the quadriceps a little, but slightly decreased it in the hamstrings.
So there it is. Make of this what you will.
Let’s not forget that both these interesting studies were done on “untrained” individuals. Therefore, it’s very difficult to know how any of this stuff will affect people who exercise regularly, especially elite athletes. It’s very likely that stretching wouldn’t do a damn thing to increase strength in athletes. Furthermore, in people who need extreme flexibility in their sports – resistance training probably isn’t going to cut it. You still probably have to stretch your groin hard to get those splits.
The results of this new study STILL don’t imply that stretching:
- can replace strength training,
- prevents injuries, or
- is ‘necessary’ for anything other than increasing flexibility.
What is cool about this study is it adds to the idea that if you are inactive, doing anything will increase your general level of fitness – and hopefully health.
Stretching enthusiasts will take this new article and run with it – claiming how stretching does it all – and is good for your ‘holistic’ health. Whatever.
There are already many established benefits of strength training, and very few for stretching. So personally, if I had to choose one due to time constraints, it would be resistance exercise.
However, I am currently stretching the hell out of my groin and hamstrings so I can do better flares in my b-boying. Because that’s what stretching is for. Flexibility.