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Posts Tagged ‘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.

Inflexibility is genetically determined and makes you fast

July 30th, 2011

Last year I blogged about some cool findings from the University of Cape Town on a gene called COL5A1, a certain variant of which seems to predispose people to be (a) inflexible and (b) efficient distance runners. That initial study looked at participants in the South African Ironman triathlon; the same research group now has a new study in press at the International Journal of Sports Physiology and Performance looking at 72 runners in the 56km Two Oceans ultra-marathon.

The results confirm the previous findings: runners with the “TT” variant of the COL5A1 genotype ran faster (5:41 versus 6:05 on average), and that group was also overrepresented in the “fast and inflexible” quadrant of subjects. The genotype accounted for about 7% of performance variance.

It’s worth emphasizing that the effect of this gene is still quite small overall — there are so many genes that affect performance that any one gene is unlikely to have a large effect. As the paper puts it:

[T]he magnitude of the effect of the COL5A1 gene on endurance running performance was calculated as being “moderate” in this study. Due to the polygenic nature of the endurance phenotype3, it is highly unlikely that a single gene would have any greater magnitude of effect.

There are plenty of other questions that remain to be answered — for instance, does this genotype allow you to directly run faster, or does it (for example) make you more injury resistant so that you can train more? This study apparently represents just one part of a larger cohort being studied, so perhaps there will be further insights before long.

Tendon length, joint flexibility and running economy

July 22nd, 2011

We already know that pre-exercise stretching makes you less efficient at running and cycling. But is it the stretching that’s bad (e.g. by temporarily interfering with the signals from your brain to your muscles), or is flexibility itself a potential problem? For running (though not cycling), your legs function like springs, storing energy with each stride then releasing it in the next stride. If you’re too flexible, the thinking goes, those floppy springs will be less efficient at storing energy.

A new study from the University of Alabama at Birmingham in next month’s issue of Medicine & Science in Sports & Exercise takes a look at this question. They took 21 male recreational runners and measured a bunch of physical traits, then measured their running economy to look for correlations. The key traits they measured were tendon length (Achilles, patellar and quadriceps) and joint flexibility (knee and ankle). They expected that longer tendons would be a good thing: they can store more elastic energy simply because they’re longer. On the other hand, they expected greater joint flexibility to be a bad thing (as far as running economy goes). And that’s exactly what they found:

In conclusion, lower limb tendon length, especially Achilles tendon length, is associated with improved running economy in male recreational distance runners. In addition, plantar flexion and knee extension flexibility are negatively related to running economy.

I don’t think the finding about longer tendons being more efficient means that we should aim to do lots of stretching (after workouts, perhaps) to lengthen tendons. Instead, I think that’s likely just something that’s genetic: some people (including a lot of Kenyans, it seems) have long, thin tendons, and they’re more likely to be efficient runners. But I’m not sure if that’s the correct conclusion. We don’t know whether a couple of years of dedicated stretching to lengthen tendons would have increased or decreased economy, and this study has nothing to say about the question. One problem is that stretching to lengthen tendons will also increased plantar flexion and knee extension, which hurt running economy — so it may be a case of one step forward, two steps back.

I’d also like to point out the contrast between these results and the cycling study I blogged about last month. The two studies seem to point to completely different mechanisms by which stretching could impact endurance performance. This study suggests that stiff musculo-tendon complexes are good for storing energy; the cycling study (which doesn’t involve this stored-energy effect) suggests that stretching does something to the muscle fibres or neuromuscular signalling. So it’s not a simple picture.

Finally, we should bear in mind that running (or cycling) economy isn’t the whole picture. Many athletes — particularly recreational ones — would happily accept a 0.5% decline in economy if it reduced their chances of injury by 50%. I personally don’t think that the evidence for stretching and injury prevention is convincing, but it’s important to remember that we’re balancing different desired outcomes in making training decisions.

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.

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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:

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Dynamic warm-up restores power lost in cold temperatures

November 11th, 2010

I ran a trail race last weekend that involved a waist-high creek crossing through pretty cold water. Climbing the long uphill after the creek, my legs were suddenly dead — I felt like I could barely get my feet a few inches off the ground. So I sympathize with the volunteers in this study, published online ahead of print in the Journal of Strength and Conditioning Research by researchers at the University of Connecticut.

The researchers used vertical jump to measure leg power in a group of NCAA D1 athletes, with three main purposes: (1) to see how much power would increase after a dynamic warm-up, (2) to see how much power would decrease if the subjects were pre-cooled by standing waist-high in 12 C water, and (3) to see if the dynamic warm-up could off-set the negative effects of cooling — something that would be of interest to athletes who compete in cold temperatures.

Everything was pretty much as expected. The dynamic warm-up increased jump power by 5%, and the cold water decreased jump power by 21%. When the subjects did a dynamic warm-up after cold-water immersion, they regained 70% of the lost power — not perfect, but still good to know.

Leaving aside all this cold-water stuff, the main reason I’m posting this is highlight the ever-stronger consensus that dynamic warm-up is the way to go. As the researchers note in their introduction:

Traditionally, static stretching exercises have been used by many coaches to prepare athletes for sporting activity. However, studies have shown that static and proprioceptive neuromuscular facilitation (PNF) stretching may negatively impact jump performance and power output. Dynamic warm-up exercises now appear to be preferred after many studies have compared the 2 modes and demonstrated dynamic exercises to be much more effective.

So what does that mean in practical terms? Well, here’s the dynamic routine the researchers used:

Continuous warm-up 1 (20 yds)
1. Arm circles forward X 1: walking forward on the toes while circling the arms forward with the arms parallel to the ground
2. Backward heel walk w/arm circles backward X 1: walking backward on the heels while circling the arms backward with arms parallel to the ground
3. High knee walk: walking forward and pulling the knee up to the chest with both arms, alternates as you walk
4. High knee skip: skipping forward and bringing the knee up so that the quadricep is parallel to the ground
5. High knee run: running while focusing on bringing the knees up so that the quadricep is parallel to the ground
6. Butt kicks: running while bringing the heel to the glutes
7. Tin soldiers: walking forward and kicking a single leg up in front while keeping the knee locked in extension (alternates)
8. One leg SLDL walk forward X 1: walking forward with straight legs, lean forward on 1 leg and reach for the foot with the opposite hand
9. 1 Leg SLDL Walk Backward X 1: walking backward with straight legs, lean forward on 1 leg and reach for the foot with the opposite hand
10. Backward skip: moving backward and skipping at the same time
11. Backward run: running backward and extending the rear foot behind you
12. Back peddle: moving backward while shuffling the feet and keeping them low to the ground
13. Overhead lunge walk: hands on the head while doing walking lunges forward
14. Inchworm: starting in the push-up position, walk the feet into the hands; then walk the hands out to the push-up position

Pre-run stretching doesn’t affect injury rate

August 23rd, 2010

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!

The science of proper warm-up

May 19th, 2010

Gina Kolata has an article in the New York Times on whether warming up improves performance that’s worth a read. Overall, her message seems to be that there’s very little evidence about whether warming up helps or hurts performance, or does nothing. To reach this conclusion, she relies largely on a recent review by Andrea Franklin at Bloomberg University of Pennsylvania, which begins with this statement:

The value of warming-up is a worthy research problem because it is not known whether warming-up benefits, harms, or has no effect on individuals.

I agree that there’s lots of research that needs to be done — for example, there have been several interesting recent studies looking at the effects of dynamic warm-up activities as opposed to traditional static stretches, but more is needed to identify what works best for different activities and what the mechanisms are. But I think it’s a little melodramatic to claim that we have no idea whether warming up helps. Even Franklin describes her analysis of 32 “high-quality” studies as follows:

Warm-up was shown to improve performance in 79% of the criterions [sic] examined. This analysis has shown that performance improvements can be demonstrated after completion of adequate warm-up activities, and there is little evidence to suggest that warming-up is detrimental to sports participants.

That seems to be quite a bit more positive than the opening sentence, to say the least. There’s still lots to learn about warm-ups, but let’s not exaggerate our ignorance.

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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