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Keyword: ‘stretching’

Dynamic stretching doesn’t hurt (or help) running performance

January 24th, 2012

Back in 2010, researchers at Florida State published a study showing that trained distance runner became about 5% less efficient and covered 3% less distance in a time trial if they did static stretching before the run. This was significant because, after a long series of studies showing that stretching compromises strength and power, it was one of the first to look at endurance performance.

Now the same researchers have published another study, in the current issue of Journal of Strength & Conditioning Research, this time looking at “dynamic” stretching instead of static stretching. Other than the stretching routine, the protocol is exactly the same. The runners spend 15 minutes stretching (or sitting quietly, during the control condition), then run for 30 minutes at 65% VO2max for a running economy measurement, then run as far as they can in the next 30 minutes.

This time, stretching had no significant effect on the distance covered in the time trial: stretchers covered 6.1 +/- 1.3 km, non-stretchers covered 6.3 +/- 1.1 km. On the other hand, the dynamic stretching did increase range of motion in the sit-and-reach test just as much as static stretching (from 32.3 to 37.6 cm). So the basic conclusion: if you’re really into stretching before a run, dynamic stretching will allow you to work on your flexibility without hurting your running performance.

One subtlety, which you pick up if you look at the individual results:

The dynamic warm-up routine takes a fair amount of energy (more details on that below). So you might wonder: for the less fit runners in the group, is it possible that they’re just tired out? The researchers do allude to this possibility:

[I]t is interesting to note that our top 2 performance runners both increased their performance under the dynamic stretching condition with the top runner seeing the largest increase in distance covered in the dynamic stretching condition of 0.2 km. Furthermore, the 2 runners in our study who covered the shortest distance performed better during the nonstretching control condition with the worst performance runner seeing the largest decline in performance after the stretching condition (i.e., 0.6 km). It is possible that elite endurance runners need a warm-up protocol of greater intensity and duration than do recreationally trained runners.

Looking back at the data, it actually looks to me like the top runner was better in the non-stretching condition, but maybe that’s just an artifact of the line thickness they used in the graph. Either way, the differences are pretty small in all cases. To me, the moral of the story is: if you’re an endurance athlete, you may have many reasons for why and how you stretch, but “going faster” shouldn’t be one of them.

As an addendum, here’s the stretching routine the study used:

A total of 10 different movements were used and completed in 15 minutes by performing 2 sets of 4 repetitions of each movement. The dynamic stretching movements were performed in the following order:

(a) Toe and Heel Walks: In these exercises, the subjects walked on their toes for 4 steps followed by walking on their heels for 4 steps to stretch the entire calf complex.

(b) Hip Series: The subjects performed a dynamic stretch of the hip flexors and extensors by placing their hands on a wall with their arms fully extended so that their body was at a 45 angle. In this position, each subject lifted his leg off the ground while bringing the knee to the chest and stepping over a hurdle placed laterally before returning to the starting position.

(c) Hand Walks: The subjects stretched their calves and hamstrings by beginning in a pushup position and walking their feet as close to their hands while keeping their heels flat. As soon as the subjects’ heels came off the ground, they walked with their hands back to a pushup position.

After the hand walks, the subjects performed a series of walking lunges, including (d) rear lunges, (e) lateral lunges, (f ) forward lunges, (g) a knee pull to a lunge, and (h) an ankle pull to a lunge to focus on the quadriceps and gluteus maximus.

(i) Walking Groiners: The subjects began this movement in a pushup position and then brought 1 foot next to the same side hand as to perform a groiner. Instead of holding this position, the subjects walked their hands out to return to the starting position before performing the action on the opposite leg.

(j) Frankensteins: The subjects stood with their feet together and their arms extended straight out in front of them so that their arms were parallel to the ground. While walking, the subjects were instructed to kick 1 leg up to touch the opposite hand to focus on the hamstrings. Every time a step was taken, a kick was made.


Yoga vs. stretching for lower back pain

October 31st, 2011

I tend to post a lot about studies that find no benefits from traditional static stretching. Does that mean stretching has no benefits? No — it just means that the benefits are hard to quantify. So to be fair and balanced, I figured I should mention this recent study from the Archives of Internal Medicine, which suggests that stretching may be helpful for lower back pain (press releases here and here).

The study was actually designed to test whether yoga helps back pain. They compared a 12-week yoga program to 12 weeks of stretching (chosen to have a similar level of physical exertion), or 12 weeks reading a self-care book. Both yoga and stretching were better than reading the book at improving pain and function; there were no differences between yoga and stretching.

Now, I can’t help pointing out that the study isn’t immune to placebo effects. The assessments of pain and function were done with telephone interviews, and relied on subjective reports from the patients. And let’s be honest: the suckers who were randomized into the “self-care book” group knew darn well that they got the short end of the stick! So I don’t view this as strong evidence of a mechanistic relationship between stretching and back pain (i.e. that the back pain is caused by tightness in some specific muscle, and stretching releases the pressure to eliminate the pain). But that’s kind of beside the point. The stretching made people feel better — and for a very simple, low-cost, low-risk, uninvasive intervention (unlike, say, surgery), that’s a good enough outcome.

Stretching doesn’t prevent or reduce muscle soreness

October 18th, 2011

[UPDATE: Welcome Reddit Running and Running Times folks! In answer to the question on the Running Times homepage, 11 of the 12 studies in this review used static stretching, while one used PNF stretching.]

The British Journal of Sports Medicine just published an analysis of the most recent Cochrane Review on stretching to prevent or reduce muscle soreness. The title says is all: “Stretching before or after exercise does not reduce delayed-onset muscle soreness.” This isn’t a surprise — while the exact mechanism that leads to DOMS is still up for debate, it’s pretty clear that it involves microscopic damage to muscle fibres and the subsequent repair process. Once those muscle fibres are damaged, no amount of post-exercise stretching can magically undamage them!

The analysis incorporated 12 studies, including one very large randomized trial with 2,377 participants. There was no difference between pre-exercise and post-exercise stretching in the effect on soreness. Of the 12 studies, 11 used static stretching and one used PNF stretching. Here’s a forest plot of some of the results, from the BJSM summary:

As the Cochrane Review notes, people generally stretch for one of three reasons:

  1. reduce the risk of injury;
  2. enhance athletic performance;
  3. reduce soreness after exercise.

There’s plenty of evidence that the second point is misguided: stretching actually seems to harm athletic performance in many contexts. Now this Cochrane Review reaffirms that the third point is misguided too — and the BJSM reviewers make it clear that, in their opinion, this isn’t one of those tentative findings that might be modified by future research:

The best available evidence indicates that stretching does not reduce muscle soreness. These findings were consistent across settings (laboratory vs field studies), types and intensity of stretching, populations (athletic or untrained adults of both genders) and study quality. As such, they are unlikely to be changed by further studies.

That leaves the first point — reducing injury. There’s still a little wiggle room here. Numerous studies have failed to find any reduction in injuries following stretching, but it’s certainly a complicated topic. In particular, I’m open to the possibility that individually tailored stretching targeted at specific areas of weakness, inflexibility or imbalance could help people avoid or treat certain injuries.


Static stretching before cycling makes you less efficient

September 19th, 2011

I wrote a few months ago about an Italian study showing that static stretching hurts cycling performance — that was the first study I’d seen about stretching and cycling, joining a whole bunch of studies showing that stretching hurts speed, power and endurance in running. Now researchers at Cal State Fullerton have backed up that initial result with a slightly different study, published in the Journal of Strength & Conditioning Research, that reaches basically the same conclusion.

The study was very simple: 10 highly trained cyclists (5 men, 5 women) did two 30-minute rides at 65% VO2max pace, while the researchers measured economy (i.e. how much oxygen they needed to maintain the pace), perceived exertion, and heart rate. Before one of the rides, they did a standard 16-minute static stretching routine. Here are the results for oxygen use (squares indicate the non-stretching trial):

Pretty straightforward: after stretching, it took more oxygen to maintain the same pace. Note that the difference was statistically significant only at the five-minute mark, not for the rest of the data points, indicating that the effect gradually wears off. Perceived exertion was the same in both trials — so the volunteers felt the same, but their bodies were working less efficiently.

Why does this happen? The researchers write that the results “may be explained through either muscle mechanics or neural factors or a combination of the two.” Then they spend a few pages going through all the various muscle-related theories and the various brain/nerve-related theories. The short answer is that no one knows. One of the previous neural studies they mentioned was interesting, and I wasn’t familiar with it:

Cramer et al. (4) proposed neural factors, such as decreased muscle activation or altered reflex sensitivity, might be the primary mechanism underlying the stretching-induced decreases in force. After stretching only one leg, they reported the same pattern of stretch-induced decrease in both stretched and un-stretched limbs...

That’s pretty cool! It certainly suggests that, whatever is going on in the muscles, there’s also something going on in the nervous system. Bottom line is simple — and by now, should be no surprise: don’t static stretch before workouts or races. It hinders performance.

Static stretching lowers cycling effiency and time-to-exhaustion

June 22nd, 2011

What we know so far: static stretching seems to cause a decline in maximal power, strength and speed, as well as hurting running economy in endurance runners. What a new study in the Scandinavian Journal of Medicine & Science in Sports reveals: stretching is bad for cyclists too — possibly even worse than it is for runners.

The authors of the study, from the University of Milan, argue that the performance-damping effects of stretching may be more obvious in endurance cycling than in running. The reason is that type II muscle fibres (a.k.a. fast twitch) are affected more than type I muscle fibres (slow twitch) by stretching. When you’re running at below-threshold paces, your leg muscles are only applying about 20% of their maximal force, so they can rely mainly on type I fibres. Cycling, on the other hand, requires a greater proportion of maximal force: about 60% of max force at 85% VO2max, according to the paper. As a result, cyclists recruit a higher proportion of type II fibres, and are thus more vulnerable to stretching-induced weakness.

That’s all fine in theory — but what do the experiments say? The researchers did a series of tests of VO2max, mechanical efficiency, time to exhaustion (with the power set at 85% of power at VO2max, so that exhaustion took about 30 minutes), and so on. Here are the efficiency results, with open circles corresponding to no stretching and closed circles corresponding to 30-minute pre-exercise stretching routine:

On average, efficiency was about 4% lower after stretching. The time to exhaustion was decreased by 26% after stretching (22:57 vs. 31:12).

I’ve been explaining the reduction in running economy caused by stretching by talking about the legs as a set of springs that store energy (and do so less efficiently when they’ve been stretched). But these results suggest that the effects of stretching on the muscle fibres themselves (and perhaps on neuromuscular signalling pathways) are just as important, since cycling doesn’t rely on that springy-legs effect.

Anyway, this is, as always, just one study — but probably worth keeping in mind if you do a lot of static stretching before cycling.


Muscle cramps risk factors: tapering, stretching and pacing

March 22nd, 2011
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I’ve written a few times now about the “new” theory of muscle cramping advanced by Martin Schwellnus of the University of Cape Town and his colleagues, most recently last month. In a nutshell, he argues that muscle cramps have nothing to do with dehydration or electrolyte depletion, but result from “altered neuromuscular control” (for an more detailed explanation, see this article).

Schwellnus and his colleagues have just published a new study online at the British Journal of Sports Medicine — a prospective study of 49 runners at the 2009 56K Two Oceans marathon. And it produced some very interesting results. Twenty of the runners reported cramps during or within six hours after the race, compared to 29 non-crampers. The two groups were statistically identical in many important respects: age, weight, height, BMI, sex, training history, recent and all-time personal best times, finishing times during the race. But they differed in a few key areas:

  • Pacing: Even though the two groups had similar best times and similar pre-race goals, the group that ended up cramping split the halfway mark 13 minutes faster than the non-crampers on average (144 minutes versus 157 minutes).
  • Tapering: In the three days prior to the race, the crampers trained 1.1 hours on average, while the non-crampers trained 0.6 hours on average. This despite the fact that the non-crampers actually did marginally more training overall in the final week (31.8 km versus 26.5 km).
  • Muscle damage: Perhaps related to the inadequate taper, the eventual crampers had higher levels of creatine kinase before the race, indicating the presence of muscle damage. They were also more likely to report soreness in their hamstrings.
  • Stretching: 92.9% of the crampers reported stretching before exercise, while just 54.6% of the non-crampers reported stretching. Of course, this could simply be because those prone to cramp are more likely to stretch.

Does this settle the cramping debate? Nope, but it should provide a little more fuel for the fire!

Dynamic stretching trumps static stretching for kicking a soccer ball

March 4th, 2011

A pretty straightforward study from researchers in Malaysia, just posted in Journal of Strength and Conditioning Research. They took 18 professional soccer players and analyzed their kick on three separate days, after a warm-up that incorporated static stretching, dynamic stretching, or no stretching. Their range of motion during the kick was 1.67 degrees worse after static stretching and 8.38 degrees better after dynamic stretching compared to the no-stretch condition, a difference that was significant with p<0.01. Since higher range of motion correlates with greater angular velocity in the kick, the researchers conclude that dynamic stretching is better than static stretching for soccer players.

Here’s how they describe the dynamic stretches used:

Subjects performed the dynamic stretches… for 30 seconds at a rate of approximately 1 stretch cycle per second… The dynamic stretches used involve the Quadriceps femoris (quadriceps); Lateral lunge (adductors); Hip extensors (gluteals); Hamstrings (hamstrings); and Plantar flexors (gastrocnemius) described in Yamaguchi and Ishii.

Err, thanks for that. Fortunately, Yamaguchi and Ishii actually have a pretty helpful description:


Pre-run stretching doesn’t affect injury rate

August 23rd, 2010
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In the “I didn’t know they did research” department, U.S.A. Track and Field just released the results of a study on pre-run stretching. They recruited 1,400 runners through their website for a randomized, prospective study in which half the volunteers stretched before running and the other half didn’t. Over the next three months, 16% of the runners got injured, with no difference whatsoever between the stretching and non-stretching groups.

You can’t read too much into a volunteer, self-reported study like this, but if you drill a little further into the data, there are some interesting wrinkles. Age, sex, weekly mileage, flexibility and level of competition all had no effect on injury rates. High BMI and previous history of injury, on the other hand, both led to a higher probability of injury.

Most interestingly, people who normally stretch before runs but were assigned to the non-stretching group actually doubled their risk of injury. There’s not really enough detail in the study to understand why this happened, but it underscores an important message that applies not only stretching, but to other hot topics like running shoes: If you’re running happily without injury problems, don’t change what you’re doing!

Jockology: some (but not all) pre-run stretching slows you down

March 18th, 2010

I posted last month about a new study on how static stretching before your run makes you slower and less efficient. To find out more about the study, I got in touch with the lead author, FSU’s Jacob Wilson. The result is this week’s Jockology column:

For years, researchers have been finding that the more flexible you are, the less efficiently you run – a message that tradition-bound runners have been reluctant to hear. Now, research to be published later this year in The Journal of Strength and Conditioning Research makes it clear that some (but not all) prerun stretching makes you slower. [read the whole article]

The most significant new piece of news in the article is that Wilson and his colleagues have just finished a follow-up study, in which they used the exact same protocol to study dynamic stretching. They’re still completing the analysis, but the results appear to show no significant decrease in performance for pre-run dynamic stretching. This means that you can still get your flexibility fix before a run without compromising performance — you just need to use dynamic stretches instead of static ones. (Some examples, with illustrations, are provided in the Jockology article.)

Drilling deeper into the dynamic stretching data, Wilson said it appeared that the most experienced runners weren’t affected by the pre-run stretches. Less experienced and less fit runners, on the other hand, still saw a bit of performance decline, probably because the unfamiliar stretches fatigued them a bit. So make sure you practice these stretches before trying them in a race situation. (This last stuff is very preliminary, so it may not be statistically significant — we’ll have to wait until the study is published to see.)

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Stretching is still bad even if you follow it with more warm-up

March 9th, 2010
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I’m a little more than a year late in reporting on this paper, but I just stumbled across it while researching another story, and thought it was interesting. As I discussed in a recent post, there’s a
lot of evidence emerging these days that stretching has some acute negative effects. When I wrote about this topic in the Globe back in 2008, one of the researchers I spoke to basically said (and I paraphrase): “The studies all show that pre-game stretching makes you weaker and slower, but athletes don’t really care. So the best thing you can do is encourage them to stretch early in their warm-up, and then do some more dynamic activity afterwards to help ‘shake out’ the negative effects of stretching before game time.”

So the paper I just found, from the January 2009 issue of the European Journal of Applied Physiology, tackles this very question:

Recently, it has been suggested that the published research, testing after an acute bout of stretching, does not reflect current practice where individuals follow up a bout of stretching with further activity. Therefore, the aim of this study was to investigate the use of stretching followed by a secondary bout of movement.

Basically, the subjects did a five-minute warm-up on the treadmill; then did a vertical jump test; then either did nothing, static stretching, or dynamic exercises; then did another jump test; then they all did another set of warm-up exercises (i.e. high knees, skip-steps, side-stepping, cross-overs and zig-zag running); then did another series of jump tests after 10, 20 and 30 minutes.

The results: after the first stage, the static stretching group jumped lower, while the dynamic exercise group jumped higher. After the second part of the warm-up, the static stretchers still jumped significantly lower than both the dynamic group and the controls. So you can’t just “shake out” the negative effects of stretching (at least with this particular protocol): once you’ve done it, you’re stuck with the effects for an hour or two.

UPDATE (a few minutes later): Okay, as I dig more, I find more studies on this topic. For example, this November 2009 study, titled “Negative effect of static stretching restored when combined with a sport specific warm-up component,” which reaches the opposite conclusion. Clearly, this debate is far from settled.