Two New Studies on Static Stretching ... Are Completely Conflicting?
Recently I wrote a popular article on passive stretching referencing research that indicated this type of stretching reduced strength. In the article I concluded that passive stretching should be avoided prior to resistance exercise, but I also called for more information. I personally like this sort of stretching to improve sleep and figured if you’re doing it at night you’d be okay since I suspected the duration of this effect was short. But I was curious about how static stretching compared to dynamic stretching (stretching with constant movement). Not only is dynamic stretching a better warm up, but it may be a means of improving flexibility without the negative effects of passive stretching.
Well, ask and you shall receive. Not one, but two studies have been accepted by the Journal of Strength and Conditioning regarding the duration of effects of static stretching on performance, one of which compared it to dynamic stretching. When it rains it pours. Okay, enough old sayings, let’s get right to the nuts and bolts of these studies.
One study specifically measured the time needed to recover strength after static stretching and that’s it. The time was within ten minutes but longer than five. So, if you do any kind of light static or passive static stretching prior to exercise you should return to full strength within ten minutes. So my suggestion to stretch the night before was a good one. Further, the researchers suggest that the cause of the weakening effect is mechanical, meaning a relaxation of the associated tendons, which then lose their ability to store energy.
So far so good, and that’s a very cool result. The second study looked at the time to recover strength and also compared the results to dynamic stretching. They discovered, as I suspected, that dynamic stretching actually improved power, which researchers measured with various sprinting and jumping protocols. You have to love science. The other thing they discovered was that static stretching reduced performance for 24 hours after training.
Now, wait a minute. Static stretching reduces performance for five minutes ... or 24 hours. That’s a huge difference between these two studies. This is the sort of result that makes people question research, but a keen eye can help clear up some of the confusion.
In the first study, researchers only examined calf stretching and strength, and found a rapid recovery. In the second study, they looked at a complete lower body stretching protocol on sprinting and jumping. Note the differences here. The calf and Achilles are some of the toughest and most elastic parts of your skeletal muscle system, ideal for carrying your body for miles and miles of high impact. Sprinting and jumping are much more complex exercises than calf raises, and require a total body involvement. The weakening effect of static stretching seems to last longer with the larger muscles especially for complex activities.
As it stands, I suggest athletes should focus solely on dynamic stretching, which may have both warming effects and extended performance-improving effects. I still like passive stretching for sleep, and I think its full day weakening effects might be overstated a bit in the second study. However, it may be wise to keep your passive stretching to a minimum, using it sparingly to assist with sleep at night and when there is no complex workout the next day.
1. Takamasa Mizuno, et. al., “Stretching-induced deficit of maximal isometric torque is restored within 10 minutes,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0b013e3182964220
2. Monoem Haddad, et. al., “Static Stretching Can Impair Explosive Performance For At Least 24 Hours,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0b013e3182964836
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