When a single kilo on the bar or a hundredth of a second on the clock can mean the difference between first and second place, we want to be able to tease out the effects of every aspect of preparation. Of particular interest is stretching and whether or not it should be a part of athletes’ warm-up routines.
For ages, we’ve been told to start our training sessions off with some light aerobic activity followed by static stretching and sports-specific drills . In addition to increasing range of motion, static stretching is supposed to reduce muscle soreness, bulletproof the body against injury, and even enhance performance .
Since the turn of the century, however, these purported benefits have come under fire . The reviews on injury reduction are mixed , and apart from anecdotal evidence, the idea that stretching reduces soreness is pretty much a farce . Most damning for the static stretching enthusiast, though, are the investigations into the effects of static stretching on strength and power.
Hundreds of studies have examined the effects of acute static stretching on performance measures such as one-rep max strength, isometric torque production, jumping, sprinting, throwing, etc. Most – but not all – actually report static-stretch induced performance impairments resulting from a combination of neural and muscular factors .
In fact, meta-analytic estimates from a pool of 104 studies reveal a very likely negative effect of static stretching on explosive muscle performance (2.0 ± 0.8% reduction in performance); a likely negative effect on maximal muscle strength (5.4 ± 1.2% reduction); and a negative, though inconclusive, effect on muscle power (1.9 ± 2.1% reduction) . Making these results broadly applicable are the facts that the observed impairments are independent of age, sex, and training status , as well as contraction type, muscle group, and movement velocity .
The static stretching diehard will be quick to point out two loopholes. For one, the duration of stretches utilized in many studies are irrelevant from a practical standpoint (often upwards of 90 seconds, whereas most folks hold stretches for less than 20 seconds ). In addition, there have been plenty of studies that report no performance impairment. Indeed, these studies must not be neglected, as they shed light on conditions and tasks for which performance may not be impaired and pre-activity stretching can be practiced without reservation .
The topic of stretch duration certainly warrants further discussion. A dose-response relationship exists such that as the duration of the stretch increases, the magnitude  and duration  of performance impairments also increase. In other words, the longer you hold the stretch, the more your subsequent performance suffers. And depending on the duration of the hold, wear-off time can be anywhere from 15 minutes  to up to 2 hours .
All this begs the question: Is there some threshold stretch duration below which performance may not be affected? A recent review paper actually determined this threshold to be 45 seconds . However, a subsequent – and more mathematically rigorous – meta-analysis reported impairments even for such short stretch durations .
Another likely contributing factor to conflicting reports is poor study design. Lack of randomization , control , reliability analysis , standardization of stretch intensity , and blinding  is rampant in the stretching scientific literature. (When someone figures out how to blind a subject as to whether or not they’ve stretched, please let me know!)
In addition, it’s important to remember that laboratory studies don’t always translate perfectly to the real world, especially when dealing with an issue as complex as athletic performance . In order to determine the effects of acute static stretching in the lab, studies often look at it in isolation instead of as a part of a comprehensive warm-up . All told, the link between a lab measurement like isokinetic torque production and sport performance is tenuous at best.
Nevertheless, if the weight on the bar or the time on the clock means everything to you, then you must avoid performance impairment at all costs. In this case, static stretching should be reserved for post-activity or a separate session altogether (for its chronic benefits) with dynamic stretching, as shown in the video below, used in its place.
Dynamic stretching is broadly classified as the controlled movement of a joint through its active range of motion . Not only does dynamic stretching induce small gains in range of motion, but it may also actually enhance performance through post-activation potentiation, increased body temperature and heart rate, and enhanced neuromuscular control and activation . Perhaps most interestingly, dynamic stretching has even been shown in some cases to reverse the negative effects of static stretching .
There are, of course, a few mitigating factors when it comes to the above recommendation to avoid pre-activity static stretching. From a practical standpoint, the magnitude of performance impairment tends to be pretty small . If you are average Joe/Jane who doesn’t care how much weight you lift, how fast you run, or how far you throw, go ahead and static stretch away. Moreover, if you’ve always static stretched, like the way it makes you feel both mentally  and physically, and have a firm belief in its benefits – the scientific evidence be damned – then suddenly eliminating it may indeed have a negative effect on your performance .
Finally, if your activity has positional requirements that you simply cannot attain without acute static stretching (think Olympic weightlifting, hockey goaltending, gymnastics, etc.) , then there are a few precautions you can take to reduce impairments. For one thing, perform your static stretching well prior to the activity (at least 15 minutes). Hold stretches for no longer than 45 seconds, and do not push to the point of discomfort . Finally, always follow up static stretching with dynamic stretching.
For another spin on the information presented above, check out my podcast on the acute effects of static and dynamic stretching:
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