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Archive for February, 2011

Do running shoes reduce injuries?

February 27th, 2011

This week’s Jockology column is now posted on the Globe and Mail website. It takes on a topic that’s reasonably familiar to readers of this blog: whether the “right” running shoes will reduce your risk of getting injured:

[...] “I was completely convinced that impact is something bad, and pronation is something bad, and I wanted to show that,” recalls Benno Nigg, a biomechanics researcher and co-director of the University of Calgary’s Human Performance Lab, who helped shape the original theory of pronation.

The initial studies were promising. Specialized running shoes, designed to address different degrees of under- or overpronation, could indeed reduce the impact forces shooting up through the legs of runners in lab testing. In the United States, sales of these high-tech shoes jumped from 25 million pairs in 1988 to 40 million in 2009, and growth was similar in Canada.

But there was just one problem: Running injuries didn’t disappear…[READ THE REST OF THE ARTICLE]

I also spoke to Michael Ryan, the researcher whose UBC/Nike randomized trial of different shoe types made a huge splash last year:

“We were a bit nervous, because … if you see someone who is highly pronated, putting them in a neutral shoe may be a recipe for causing more pain,” acknowledges Michael Ryan, the study’s lead author, who is now a postdoctoral researcher at the University of Wisconsin.

He needn’t have worried…

In terms of practical advice, the article ran with a sidebar that doesn’t appear to be posted online, so I’ll add it here:

Picking a running shoe
Shoe researchers Benno Nigg and Michael Ryan agree that comfort is a good starting point for picking a running shoe. Some other factors to consider:

  • You can only assess comfort by actually running in the shoe. Many running stores will allow you to run around the block or on a treadmill.
  • Don’t ignore fit in favour of fancy shoe features. Find a brand and/or model that fits the specific characteristics of your foot, such as width.
  • Dr. Ryan’s research suggests that heavier, bulkier shoes may be associated with more injuries. So all else being equal, choose a lighter shoe.
  • If you’re making a radical switch (trying minimalist shoes for the first time, for example), take it slow. Expect to spend four to six months adjusting to the new shoes.
  • If you’re currently running successfully in a certain type of shoe, stick with it!

Metabolism rises for 14 hours after hard exercise

February 27th, 2011

Pretty cool study from David Nieman’s group at Appalachian State, just published online at Medicine & Science in Sports & Exercise. We’ve all heard the various theories about how exercise pumps up your metabolism so you’re burning extra calories throughout the day. The only problem is that attempts to measure this have produced all sorts of conflicting results, primarily because it’s such a pain to measure. You have to hook people up to complicated metabolic measuring equipment over and over, control for whatever random activities they do throughout the day, and so on.

This new study has two big strengths. One is a fancy, newly built “metabolic chamber” — basically a tiny room where everything that goes in and out is strictly controlled, including oxygen and carbon dioxide. Measuring the amounts of oxygen and CO2 going in and out (along with exact knowledge of the food going in and human wastes going out) allows the researchers to calculate exactly how many calories the subjects burn while they’re in the room.

And the second strength is that they were pretty hard-ass about the study protocol. The subjects (10 healthy young men) spent two 24-hour periods in the metabolic chamber: one where they did basically nothing, and the other where they did nothing except one 45-minute cycling session at about 70% VO2max:

At 8:00 am, subjects were sealed in the chamber and asked to stay in a seated position unless they needed to use the restroom or perform other necessary daily activities (e.g. washing hands, brushing teeth, etc.). Breakfast was served through an air lock passage at 9:00 am. On rest days, subjects remained in a seated position from breakfast until 12:30 pm when they were asked to get up and stretch for 2 minutes. On both rest and exercise days starting at 12:30 pm, subjects were asked to get up and stretch for 2 minutes every hour until 6:30 pm… Subjects were asked to remain in the seated position until 8:00 pm, at which point they were able to relax and lay down but not go to sleep. Bed time was at 10:30 pm, and subjects were asked to lie down even if they were not sleeping.

Hard core! Anyway, getting (finally) to the point: exercise boosted metabolism for the next 14 hours, burning an extra 190 calories in addition to the 519 calories burned by cycling (i.e. 37 percent extra). Note that it was vigorous exercise, which the researchers believe is important — some of the earlier studies that didn’t find any metabolic boost used more leisurely protocols (e.g. 50% VO2max). Here’s what the data looked like:

How much will I slow down in my late 30s?

February 26th, 2011

While I’m clearing out my mailbag… I got a question from a 800-metre runner in his mid 30s asking about how quickly he should expect his (and his competitors’) times to decline. It’s an interesting question that can be approached in a number of different ways — age-group records, which obviously depend on outliers; population-level cross-sectional studies; individual longitudinal studies — and all give different answers.

I cover this in a fair amount of detail in my book, but a couple brief points: numerous studies over the past three decades have found that cross-sectional declines tend to be steeper than longitudinal declines. That makes sense: the cross-sectional data gets weaker and weaker as you get to higher ages because there are more injuries and fewer people interested. (The latter factor is interesting in its own right: there’s evidence, albeit in mice, that the “impulse to exercise” declines with age. So it’s not just that people get busy or bored with competition, they may also have less intrinsic drive to compete.) Anyway, the point is: if you remain healthy and continue training at the same relative intensity (big “ifs” in both cases), you should expect to be able to beat the “average” decline represented by data like age-graded tables.

Speaking of which, here’s some data. The WMA age-graded table expect that you don’t start slowing down at all until you hit 35. At that point, the decline until your 40 appears to be linear. For comparison, I’ve plotted the times put up by the inimitable Johnny “Twilight Zone” Gray:

Gray was obviously a one-of-a-kind performer in many respects. The question is: was he a freak because he was still capable of running 1:45 as a 39-year-old? Or was he a freak because he was still interesting and willing to train at the level required to run 1:45 when he was 39? How many other 1:42 guys could have done the same if they’d tried? We don’t really know the answer to these questions, but the general feeling among researchers that I’ve spoken with is that the fundamental physical decline is much less steep than we previously believed. It’s more about training and motivation (and, of course, injuries).

Alcohol-free beer as a recovery drink: better than what?

February 26th, 2011

Way back in October, I got an e-mail from Glenn, a running coach at Concordia University in Montreal, wondering whether alcohol-free beer might make a good post-workout recovery drink. He made a pretty convincing case for it, and I promised to look into it and get back to him with my take…

Fast forward to February (with his e-mail still in my to-do list), and there’s a big flurry of articles about Bavarian brewer Erdlinger’s “Alkoholfrei” beer being promoted as a sports recovery drink:

Promoted as a “sports and fitness drink,” Erdinger began targeting athletes in 2001 in Europe with an advertising campaign featuring a pair of triathletes. Its popularity quickly grew in Europe, where it’s often distributed for free in the finishing area of sporting events.

Sure enough, if you go to the Alkoholfrei website (“100% regeneration”), they have profiles of all the triathletes and biathletes that they sponsor.

So is it justified? Well, it depends on what you’re comparing it to. Most of the articles I’ve seen line it up against sports drinks — the equivalent of classic Gatorade. And actually, in that context, it doesn’t do too badly. It’s a drink with some carbohydrates in it, and not much else. But is anyone really recommending that athletes should pound some Gatorade after their workouts? In fact, as Glenn pointed out in his e-mail to me, a better comparison would be with chocolate milk, which is often touted as an “ideal recovery drink” because it contains protein in a roughly 1:4 ratio with the carbs it contains.

Here’s how some of these options stack up, in grams per 100 mL:

Carbs Protein Fat Calories
Alkoholfrei 5.3 0.4 0 25
low-fat choc milk 10.4 3.2 1.0 63
Original Gatorade 5.8 0 0 21
Gatorade Recover 2.9 3.3 0 25

Now, there are some other details like electrolytes, and Alkoholfrei likes to point out that it has vitamin B12 and so on — but to me, these are irrelevant details. When you’re recovering after a workout, you need fluid, carbohydrate and protein. If you get that, it’s highly unlikely that you’re NOT going to get the electrolytes you need.

So the verdict: Alkoholfrei looks a lot like plain old Gatorade — primarily carbs, though it does have a bit of protein. As a recovery drink, it’s not bad, as long as you’re also eating some food to give you some protein. But it’s not “complete” in the way chocolate milk is hyped to be. I guess the conclusion is sort of like those breakfast cereal commercials: alcohol-free beer is “part of a complete, balanced post-workout recovery protocol.”

(Last thought: of course, calories matter too — and that depends on how vigorous your workout was. Unless it’s a particularly vigorous workout, you really don’t need any recovery food/drink at all beyond whatever meal is coming up next — or at least, you certainly don’t need 500 mL of chocolate milk or three alcohol-free beers!)

[Thanks again to Glenn for putting the topic on my radar.]

Running halts mitochondrial aging (and hair loss!) in mice

February 23rd, 2011

Scientists don’t know exactly why or how we get old, but they have a few theories. One of them is that mutations in mitochondrial DNA gradually accumulate until body systems stop working properly — a theory supported by the premature aging observed in mice genetically engineered to rapidly accumulate mutations in mitochondrial DNA. Yesterday, McMaster University researcher Mark Tarnopolsky‘s group published a paper in the Proceedings of the National Academy of Sciences in which these fast-aging mice ran on a treadmill — with extremely encouraging results:

[T]hose who had endurance exercise training three times a week looked as young as healthy mice while their sedentary siblings were balding, greying, physically inactive, socially isolated and less fertile. [press release here]

Sounds pretty good… and the changes weren’t just on the outside. In the exercising mice, their brains didn’t shrink, their muscles didn’t waste, their hearts didn’t weaken, they didn’t die prematurely, and so on and so on. Of course, mutations in mitochondrial DNA were still accumulating — but the basic cellular response to endurance training is that you increase the amount of mitochondria in your cells, so the researchers suspect that having lots of healthy mitochondria made the mice less susceptible to problems stemming from the mutations.

This isn’t the only theory about aging. Telomere length is another idea that has received a lot of attention recently, for example — but that too seems to respond dramatically to endurance exercise. Of course, conflicts of interest should be reported in studies like this: Tarnopolsky is a highly accomplished ultra-runner! :)

Platelet-rich plasma doesn’t work for rotator cuff (shoulder) tendons

February 22nd, 2011

Yet another salvo in the ongoing debate about whether platelet-rich plasma (PRP) therapy — sometimes known as “blood spinning” — is a miracle tendon healer or an expensive placebo. At an American Orthopaedic Society for Sports Medicine conference in San Diego, researchers presented the results of a new study of PRP for rotator cuff tendon repair — and the results weren’t encouraging.

The study involved 79 patients who all received standard surgical rotator cuff repair and post-operation rehab; half of them were randomized to receive a form of PRP treatment. There were “no real differences” between the groups:

“In fact, this preliminary analysis suggests that the PRFM [the form of PRP used in the study], as used in this study, may have a negative effect on healing. However, this data should be viewed as preliminary, and further study is required” said study author Scott Rodeo, MD, of New York City’s Hospital for Special Surgery.

Right now it’s just a conference presentation; the study will presumably be published eventually, at which point we’ll get some more details on the design and specific results of the study. But the scientists still seem optimistic:

Researchers think there may be several reasons for a lack of response in healing, including variability in the way platelets are recovered, platelet activation and the mechanisms for the way the PRFM reacts with the tendon cells. The study was also unable to document the number of platelets actually delivered to patients who received the PRFM…

“Additional research needs to be performed to figure out the mechanisms for why PRP is successful in healing certain areas of the body and not others…” said Rodeo.

I’m not really sure which areas of the body he’s talking about. I only know of one properly controlled clinical trial that came to a positive conclusion, on tennis elbow — but even that study was subject to criticism. So far PRP is one of those ideas that makes perfect sense in theory, but hasn’t yet proven itself in practice.

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More about stride length, rate, and “cruise control” for runners

February 20th, 2011

I posted last week about a newly invented “cruise control” device for runners, which controls pace by cueing stride frequency with a metronome. That ignited an interesting discussion about how we change pace while running: do we take quicker strides, longer strides, or a combination of both?

For starters, Pete Larson send me a paper with some nice clear data that shows how the two factors interact (at least in one physically active group of 24 men and nine women between 18 and 34 years old):

The x-axis runs from 0 to 12 m/s, so the data runs from 2.5 to just over 9 m/s, which is 6:40/km to under 2:00/km — i.e. sprinting). Sure enough, stride length is a much bigger factor than stride frequency at typical jogging/running speeds, but the frequency curve is never perfectly flat.

I also exchanged a few e-mails with Max Donelan, one of the co-inventors of the cruise control, who explained a little more about how the device works and what sort of interactions between stride rate, length and running speed they saw in their testing. His answers were very interesting and well-explained, so with his permission I’m going to post them here rather than trying to summarize them. One of the most interesting points, I think, is that when his metronome cues runners to increase their stride rate, they also automatically increase stride length to arrive at the pace they’d naturally associate with the new cadence. Makes sense, but that hadn’t occurred to me.

Q: I’m also curious (as you saw in my blog entry) about how effective cadence is at controlling pace.

A: We have tested a number of subjects running at a range of speeds. It is absolutely true that some runners increase speed predominantly by increasing stride length. In fact, I would say that most runners that we have tested increase stride length more than frequency. However, all the runners we have tested also increase their frequency when they increase speed. We have yet to find a runner that only increases stride length or only increases stride frequency. For our purposes, it doesn’t matter whether people increase speed predominantly with increasing stride length as long as the relationship between speed and frequency is not perfectly flat (and we have yet to find a subject like that).

Of equal importance is a second phenomenon which is less intuitive. When someone is running at a particular cadence and you ask them to match a faster cadence, they not only increase their stride frequency but also their stride length.They alter both frequency and length to converge on the speed that they normally prefer at the new cadence. For example, a 10% increase in frequency might yield a 40% increase in length to get a 54% increase in speed. This allows us to use frequency to have control authority over speed.

Q: What sort of testing did you do?

A: We initially determined how frequency and length change with increases in speed by having subjects run at different steady state speeds on a treadmill. We carefully calibrated the treadmill speed and we measured step frequency with pressure sensitive foot switches. Stride length is simply speed divided by stride frequency.

To study how runners change both speed and step length when you give them an increase in cadence to match, we had them run overground with a metronome beeping in their ear. After a few minutes, the metronome frequency would rapidly increase to a new frequency. Subjects were instructed to match the beat. They were free to choose whatever speed they liked and, in principle, they could have stayed at the same speed. We measured step frequency with the same pressure sensitive foot switches. We measure and record overground running speed using a high-end GPS designed for quantifying acceleration in race cars.

We test our cruise control algorithm also during running overground. When we implement cruise control, we get runners within 0.5% of their desired average speed. This compares well with recreational athletes who average an 8% error, and collegiate runners who average a 4% error:

Green et al. Pacing accuracy in collegiate and recreational runners. Eur J Appl Physiol (2010) vol. 108 (3) pp. 567-572 http://dx.doi.org/10.1007/s00421-009-1257-5

For the recreational runners, an 8% error means that they will only be within 4 minutes of their target time for a 50 min 10 K. Running 4 minutes too fast may mean a surprisingly fast personal best, but it may also mean crashing and burning.

Very interesting stuff — both from a practical point of view (i.e. the cruise control), and for understanding more about how we run. Thanks to both Max and Pete for their contributions.

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What do we actually KNOW about running injuries?

February 20th, 2011

I’m a couple of weeks behind the curve on this, but I just wanted to highlight an excellent post by Pete Larson of Runblogger. He recently attended a conference/course on running injuries taught primarily by Blaise Dubois, and took the opportunity to write up a succinct list of 16 things we know about running injuries, ranging from the very basic to the fairly technical.

Part of the reason I liked it so much was that it was very balanced — not promoting big shoes, little shoes, or no shoes as the panacea that will cure everything. In fact, his fourth point is:

Most running injuries are overuse injuries that can be attributed to stubborn and obsessive runners doing too much too soon. In doing this, runners exceed their body’s stress threshold and something gives. The end result is an injury.

Just for kicks, though, I’ll quibble with one point. He writes:

One of the things that also came through loud and clear is that barefoot running is our default. It is how we evolved, and modern shoes are a change from that default. Thus, the burden of proof should be to prove that we are better off running in big, bulky shoes. People often seem to think that the notion that we should run in a way that emulates the barefoot gait is radical (whether actually barefoot or in minimal shoes), but in reality it’s what our species has done for nearly 2 million years prior to about 1970.

I understand the point, of course. But let me make a competing point: in the U.S. alone, according to Running USA, there were 25.559 million people who ran at least 50 times in 2009. Some 10.29 million of them finished a road race. They bought a total of 39.76 million pairs of running shoes. How many of those people went barefoot, or in minimalist shoes? I really don’t know — I wish I had the data. But I think it’s fair to say that the overwhelming majority of people who have grown up in a modern, western, convenience-filled, concrete-covered society and have taken up running without having relied on it as a primary form of transport throughout their childhood have done so wearing conventional running shoes. Does that mean barefooting or minimalism or forefoot striking is bad? Definitely not. But since we don’t have any answers yet, let’s be circumspect about applying the “burden of proof.”

Anyway, I’m just quibbling here. Pete’s post is great, and a must-read for anyone interested in the topic!

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Carbo-loading with a “hyperglycemic-hyperinsulinemic glucose clamp”

February 19th, 2011

In search of the ultimate carbo-loading protocol, I stumbled across a paper in the European Journal of Applied Physiology that was posted online a few weeks ago. Researchers at Liverpool John Moores University in Britain investigated the use of a “hyperglycemic-hyperinsulinemic glucose clamp” as a sort of super-accelerated way of stuffing your muscles full of glycogen (the form in which carbs are stored in the body).

What the heck does that mean, you ask? Basically, the subjects spent two hours the day before the big exercise test, lying around with needles stuck in their arm delivering elevated levels of glucose and insulin. (The “clamp” means they picked a specific level of blood sugar and infused exactly enough glucose to maintain the subjects at that level for the two hours.) Glucose is carbohydrate, and insulin is one of the signals that initiates the storage of carbohydrate in your muscles, so the subjects were able to pack about 198 grams of carbohydrate into storage during the two-hour protocol.

The next day, the subjects did a 90-minute steady-state bike ride following by a 16K time trial — and sure enough, the clamp improved time-trial performance by 3.3% (49 seconds over ~24 minutes) compared to when the subjects received a placebo saline infusion. So yes, you can carbo-load in two hours the day before a race without any special dietary or training intervention (though it doesn’t show whether this method is better or worse than standard carbo-loading protocols). Of course, this really doesn’t have much practical significance. I suppose you could imagine Tour de France riders having the resources and incentive to undertake a protocol like this, but insulin is banned by WADA. (Oh wait…)

The most interesting part of the paper is buried near the very end, and it’s written very confusingly — it sounds very much as if the paper’s peer reviewers have insisted on a bunch of caveats and rephrasings, which wouldn’t be surprising as the topic is Tim Noakes’s highly controversial “central governor” theory. It relates to a somewhat confusing quirk in the data:

[D]espite the evidence of alterations in substrate availability (higher glucose and insulin), the patterns of substrate oxidation were no different.

In other words, carbo-loading makes more carbohydrate available, but it doesn’t seem to change how much carbohydrate (versus fat) is actually burned. A number of other studies have found similar anomalies, which has made some researchers question whether we really understand why carbo-loading works to improve performance:

The essence of this theory, supported by appropriate findings, is that muscle glycogen may have a signalling function that influences pacing strategy. Subjects who start exercise with elevated levels of muscle glycogen would be able to exercise at a higher pace due to signalling between muscle and the brain than when in a glycogen depleted state.

In this picture, carbo-loading is just another version of the carbohydrate mouth wash, whose function is to convince your brain that you have enough fuel. It’s hard to imagine that this is always the limiting factor, but it’s an interesting area of research.

New explanations for runner’s high

February 17th, 2011

Gretchen Reynolds has an article in the New York Times about recent research into the origins of “runner’s high,” suggesting that endocannabinoids rather than endorphins might be responsible — in other words, the body’s internal version of marijuana instead of morphine:

But perhaps the most telling experiment was published last year by researchers in France who had bred mice with no functioning endocannabinoid receptors. Mice usually love to run, but the genetically modified animals, given free access to running wheels, ran about half as much as usual.

Reynolds is usually an excellent reporter, but I was a bit disappointed in the lack of context offered in this article. She dismisses the role of endorphins as follows:

Endorphins, however, are composed of relatively large molecules, “which are unable to pass the blood-brain barrier,” said Matthew Hill, a postdoctoral fellow at Rockefeller University in New York. Finding endorphins in the bloodstream after exercise could not, in other words, constitute proof that the substance was having an effect on the mind.

This is true, but German researchers published a study back in 2008 that was very widely reported (including in the Times by Reynolds’s colleague Gina Kolata) that directly measured the increase of endorphins in the brain after a two-hour run. Both Reynolds and Hill are undoubtedly familiar with this study, so it seems disingenuous to pretend that we don’t know anything about the link between exercise and endorphins in the brain.

Ultimately, the runner’s high is such a nebulous, ill-defined thing, meaning different things to different people, that it’s probably a combination of several different effects — endorphins, endocannabinoids, and perhaps other factors, including some straightforward psychological ones. So it seems silly to dismiss the “old” theory in favour of a new one when there’s no reason the two can’t coexist.

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