Archive

Archive for February, 2010

CRM: The charity runners controversy

February 25th, 2010

The March issue of Canadian Running magazine is on newsstands now (including my Science of Running column). It includes an interesting look by Kevin Mackinnon at the sometimes controversial topic of charity runners in big marathons. Mackinnon makes the case that charity runners are responsible for a major boom in road running participation that started in the late 1990s:

The development of large marathons in the 1980s saw the number of participants double over a 10-year period. A decade later participation had doubled again, which, according to many marathon experts, was because of the steady growth of charity running groups…

“It was the fall 1994 marathon debut by Oprah Winfrey that caused another ripple in marathon participation,” [Dave Watt, executive director of the American Running Association,] says. “… As the 90s came to a close, women’s participation numbers in the marathon had doubled from the late 80s. At the turn of the 21st century, the marathon added a new twist: the charity runner.”

Mackinnon also gives a brief nod to some of the criticism the charity runners have attracted, mentioning the Jean’s Marines scandal from 2006, and some more general complaints:

Critics say that the increased cost of taking care of charity runners – for example, having to keep race courses open longer for slower athletes – inevitably gets passed down to the rest of the competitors in the field. Since so many charity competitors tend to be beginners, more experienced runners complain that these rookies display a lack of runner’s etiquette. There’s also a feeling amongst more serious marathon competitors that the charity runners aren’t truly involved in the sport – once they achieve their goal, they move on to another challenge or simply stop running altogether.

To me, none of these criticisms hold any water. Having more runners at races is fantastic, and mobilizing people to raise money for charities is also fantastic. My only quibble, on a personal level, is when people use these programs to earn themselves free or subsidized trips to run races in exotic locations like the Caribbean — paid for, in effect, by the donations they’ve raised from friends. To me, if you want to visit New Orleans and run a race, the money to fund that trip shouldn’t come from the same hat that you’re passing around to solicit donations for a worthy cause. (Or least be honest and say, “Would you like to donate $20, $10 of which will go to cancer research and $10 of which go towards my plane ticket and hotel room.”)

To reiterate, I think these programs are a great idea for charities, because even if they have to allocate some money towards travel costs, they still end up with more money than if they just sent out a bunch of junk mail asking for donations. I’m just calling on individual runners to do their own accounting to make sure their personal contribution exceeds the benefits they’re taking. (And if you can’t afford to fly yourself to the Cayman Islands, run something a little closer to home.)

I know this can be a touchy topic — so please do let me know if you think I’m not being fair or if I’m missing the point.

How fast you eat affects appetite hormones

February 24th, 2010

Nice little nugget in the New York Times on the common claim that eating slowly makes you feel more full:

Researchers have found evidence over the years that when people wolf their food, they end up consuming more calories than they would at a slower pace. One reason is the effect of quicker ingestion on hormones.

In particular, they cite a new study in the Journal of Clinical Endocrinology & Metabolism, in which volunteers ate a bowl of ice cream in either five minutes or half an hour. Sure enough, those who ate (drank?) their ice cream in half an hour had higher levels of a pair of gut hormones that signal when you’re full, and they also felt more full.

Nothing too surprising here, but it’s always nice when you see a study that backs up folk wisdom.

Pool running: oxygen use and max HR change as you get better at it

February 23rd, 2010

Pool running is very different from running on land. Aside from the crushing boredom, there’s also the fact that your heart rate stays lower for a given effort, and your VO2max is lower. This has been demonstrated in lots of studies, and is typically attributed to:

(1) an increase in central blood volume, as a result of the hydrostatic pressure causing a higher stroke volume and therefore lower heart rate for a similar cardiac output; (2) the thermal effect of water, since water temperatures below thermoneutral (33–35 C) reduce heart rate and increase stroke volume; (3) less muscle activity during deep water running because of the possible reduction of muscle activity of the weight-bearing muscles.

But even though most people agree about that, pool-running studies have produced conflicting results about exactly how much lower VO2max gets, what happens to your ventilatory threshold, how perceived exertion changes, and so on. According to a new study in the Journal of Sports Sciences (from which the above quote is taken), this may be because there’s a steep learning curve associated with pool running.

The study, by researchers in the U.K., South Africa and Brazil, compared 10 runners who had at least two months of pool-running training with a certified instructor with seven runners without pool-running experience. They had both groups perform VO2max tests and run at threshold, both on land and in the water. (The testing in the water was as problematic as you might guess, and the machines apparently broke down three times and data from four subjects had to be discarded.)

Going from land to water, the novices dropped the max heart rate from 186 to 172 and their VO2max from 55.1 to 44.3. In comparison, the experts went from 186 to 177 and from 53.8 to 48.3. In other words, they were able to work harder once they’d mastered pool running — probably, the authors speculate, because they’d learned to recruit more muscles.

Practical applications? Well, if you’re trying pool running for the first time, expect it to feel really hard and yet strangely unsatisfying as a workout. But be reassured that if you stick with it, you’ll be getting a better and better workout for the same effort.

How does air pollution affect marathon times?

February 21st, 2010

There are a couple of different ways you could pitch a new study on air pollution and marathon performance from the March issue of Medicine & Science and Sports & Exercise. The good news is that levels of six key pollutants almost never exceed EPA guidelines during seven major U.S. marathons (Boston, Chicago, New York, Twin Cities, Grandma’s, California International and Los Angeles). And when you compare top times to pollution levels, there’s no correlation in all but one case.

Or you could do it the other way around: Danger! Elevated levels of particulate matter smaller than 10 micrometers (PM10) make women run more slowly, even when levels are well below EPA guidelines!

The study is by Linsey Marr of Virginia Tech and Matthew Ely of the US Army Research Institute of Environmental Medicine. It looks back at marathon results from the past 28 years (or as long as available) and digs up accurate pollution readings for the races. To assess performance levels, they look at the top three men and women’s times as a percentage of the existing course record. They also use the results of a previous study to subtract out the variation due to temperature, humidity and solar radiation.

The main finding is that major marathons have pretty good air quality, even in big cities. They’re held on weekend mornings, so they avoid the rush-hour car pollution, and they’re generally early enough in the morning that they avoid the secondary pollutants like ozone which are produced by intense solar radiation.

Despite that fact, it wouldn’t have been a big shock to find that higher pollutant levels — even below the usual thresholds — were associated with slower times. After all, as the authors note:

An athlete running at 70% of maximal oxygen uptake for the length of a marathon (~3 h) inhales the same volume of air as a sedentary person would in 2 d. In addition to the elevated ventilation rate, the switch from nasal to mouth breathing and an increased airflow velocity carry pollutants deeper into the lungs and further amplify the runner’s dose of pollutants.

In the end, though, the only correlation that showed up was between PM10 and women’s (but not men’s) times. This isn’t the first study to find that women may be more sensitive to certain pollutants than men. The theory is that their narrower larynx openings lead to greater turbulence in their airways, which results in greater deposition of pollutant particles.

For what it’s worth, the Beijing Olympics — whose high pollution levels stimulated this study in the first place — had PM10 levels well above the highest levels included in this study. Could this have been a factor in the result?

It is interesting to note that despite relatively high PM10 concentrations of 87 [micrograms/m3] on race day, the men’s marathon winner set a new Olympic record. In addition, the average of the top three men’s finishing times was faster than the preexisting record. During the women’s marathon, PM10 concentrations averaged 62 [micrograms/m3], and the top three women were 2.6% slower than the Olympics marathon record.

The science of home-field advantage

February 18th, 2010

In celebration of a couple of Canadian gold medals in Vancouver, this week’s Jockology looks at the science behind home-field advantage:

The biggest edge gold medalists Maëlle Ricker and Alexandre Bilodeau had over their Olympic opponents may have been from their brain chemistry rather than the roar of Canadian spectators at Cypress Mountain.

A series of studies over the past decade has debunked the long-held theory that home advantage stems primarily from external factors such as an enthusiastic crowd, a familiar venue, travel-weary opponents and officials whose calls are swayed by the crowd. While these factors can play a role, a more basic biological imperative may be at work, as athletes display an evolutionarily driven desire to protect their territory. [read on...]

There are a bunch of interesting studies on the topic, which dissect the role of crowds, stadiums, refs and so on. There’s a sidebar to the piece that doesn’t appear in the online version (not sure if it’s in the paper version), so I’ll reproduce it here:

Can fans influence the game?
A new study shows that sports teams have a “home advantage” even if there’s no one in the stands. But that doesn’t mean crowds don’t have an impact. A 2002 study in the journal Psychology of Sport & Exercise asked qualified soccer referees to make calls on games they watched on video, with the sound either turned on or off. The refs who could hear crowd noise called 15 per cent fewer fouls against the home team than those watching in silence.

Have we reached the limits of sports performance?

February 17th, 2010

Further to yesterday’s post about the incredible amount of work ski technicians do to squeeze an extra half-second out of downhill skis, a reader sent me this link to an article in the L.A. Times titled “Have Olympic athletes done all they can?”:

Some scientists say so. Papers published in the last few years indicate that human performance has already peaked, and the only way to improve is with technology — or cheating.

The article takes a look at the various biomechanical and statistical arguments suggesting that world records aren’t going to progress much further. There are, of course, some holes we can poke in those studies. For instance:

A French researcher who analyzed a century’s worth of world records concluded in a recent paper that the peak of athletic achievement was reached in 1988. Eleven world records were broken that year in track and field. Seven of them still stand.

It’s hard to believe anyone could write this with a straight face. Of the seven records still standing from 1988, four of them were set by women from Eastern Bloc countries with well-established state doping programs, and two were by Florence Griffith-Joyner. If the year 1988 represented the “peak” of anything, it was unfettered doping, not human performance. Not coincidentally, that was the year Ben Johnson was busted, and authorities, however reluctantly, started tightening doping controls.

But to be honest, I think poking these sorts of holes in the article is missing the broader point. Are we reaching a regime of diminishing returns in terms of performance? Of course! In 1900, the world record for the men’s mile was 4:12.75; 100 years later, it was 3:43.13. Unless we expect to be running two-minute miles in 300 years, it’s obvious that the curve has to gradually flatten out.

Does this mean we’re reaching “The Limit” of human performance in the mile? This is where I think the conceptual framework of the L.A. Times article is a little shaky. There is no limit, there’s just statistics. The farther we push towards the extreme edge of the distribution, the less likely we are to find an outlier with even better characteristics, and the smaller the margin of improvement will be. But the distribution never just stops. Even if Usain Bolt turns out to be a once-in-five-generations talent, there’s still the possibility, 10 generations from now, of someone just like him but with, say, slightly quicker reaction time.

Training and technology are the two other X-factors. In a sport like swimming, if you reinvent the swimsuit, you’re essentially moving the finish line. Is Michael Phelps better than Ian Thorpe? I have no idea, because they’re competing under different circumstances. To me, the resulting debate is less interesting, because we end up discussing the rules and bylaws of sport rather than human performance (which is why, as I argued here, I think sports governing bodies should be reactionary and conservative in their approach).

As for training, it’s impossible to separate training from talent. (One major aspect of talent, after all, is having an abnormally large response to training.) It’s advances in training, far more than track surfaces and better shoes, that separate today’s milers from Roger Bannister. Have we optimized the science of training? Far from it, though we’ve certainly picked most of the low-hanging fruit.

So if the message of the Times piece is that humans have reached their “peak,” I think they need to revisit their statistics. If it’s that athletes, especially in “mature” sports, will improve less frequently and by smaller margins than in the past — well then, yeah. Of course.

Tuning the perfect ski for Olympic competition

February 17th, 2010

From a nice, detail-packed two-part post at Wired’s Playbook blog about how Matthew Schiller, the head technician for the U.S. Ski Team, prepares ski bases and edges for downhill competition, a lovely kicker that sums up the technological arms race:

After all this work, the endless coats of wax, the scraping and filing and polishing — what’s the difference between a perfect ski and one that’s totally missed the mark?

About half a second, according to Schiller.

Months and years of work to find a half a second? That’s the Olympics, and not just for the athletes.

The “fat-burning” zone for weight loss and performance

February 17th, 2010

I exchanged a few e-mails last week with Canadian Running blogger Rebecca Gardiner about weight loss and exercise. It’s a hot topic these days, thanks to Matt Fitzgerald’s recent book Racing Weight and the subsequent media coverage, including this piece by Gina Kolata in the New York Times.

But if you have a little time to spare and you’re looking for a well-informed scientist’s perspective on weight loss, I’d recommend taking a look at Ross Tucker’s series at the Science of Sport blog. (Here’s part 1, part 2A, part 2B, and part 3. The series has been stalled for a few weeks, but may resume soon.) He gives a very basic explanation of the essential facts about losing weight, keeping it simple while acknowledging the complexity that lurks behind many of the statements.

In particular, he takes aim in part 3 at one of my favourite pet peeves, the “fat-burning zone” that encourages people to take it easy during cardio workouts. It’s true, he notes, that you burn about 80% fat (and 20% carbohydrate) when you exercise at low intensity, and those ratios are reversed at high intensity.

So, what you’re probably thinking is that theory that low intensity exercise is better if you want to burn fat is correct. Well, think again. It is true that at low intensity, when you walk, most of your energy comes from fat, and that as you increase the intensity, less and less comes from fat.

But what is missing in this picture is the TOTAL amount of energy.

It turns out that you burn about 50% more fat per hour at moderate intensity than you do at low intensity. So the rationale for a low-intensity fat-burning zone is spurious, unless you have time to exercise for several hours a day. But really, the most important message comes later in the same post, and I hope people don’t miss it:

[P]erhaps most significantly, the key is still to create a calorie deficit, which means that you need not worry too much about whether your energy use is coming from fat or carbs – the key is to create that deficit, because in the long run, the energy will have to be provided and you will achieve similar results regardless.

Another point Tucker makes is that it’s really hard to provide general-purpose weight-loss advice, because there are so many different things that can be going on physiologically. He advises consulting a dietitian to get personalized advice if you’re struggling to lose weight. The corollary that I’d add is that anyone who tells you they have The One True Answer to your weight-loss problems without knowing in detail about your history is kidding themselves.

Is hiring a personal trainer worth it?

February 15th, 2010

Hiring someone to tell you what exercises to do seems like a reasonable proposition — after all, there’s a big difference between a well-planned exercise program and just puttering around the gym. But what about after you’ve learned the details of the program: is it still worth paying someone to come and watch you work out?

According to a new study in the Journal of Strength and Conditioning Research, yes. (And yes, I’m aware that JSCR is the official organ of the National Strength and Conditioning Association, which may have a vested interest in promoting this idea.)

The study, by researchers at the University of Brasilia in Brazil, builds on previous studies that have found that people doing weight training build more muscle and gain more strength when they’re supervised than when they’re on their own. In this case, the study compared 124 untrained young men, and had them undertake an 11-week training program with either a coach for every five athletes or a coach for every 25 athletes. Sure enough, the more highly supervised athletes gained significantly more strength in bench press and knee extensor exercises.

As the paper explains, personal trainers “may help to control important training variables such as load, rest intervals, and exercise technique and to provide motivation and psychological reinforcement,” so it’s hard to nail down exactly what’s happening. But the data provide some interesting insights.

One initially confusing fact is that the total volume of weight lifted was pretty much the same between the two groups. On closer examination, what happens is that the less-supervised group picks a slightly lighter weight and lifts three sets in a nice, controlled manner. The heavily supervised group picks a more ambitious target, reaches failure during the third set, and has to stop a few reps earlier. Total volume is the same, but the guys reaching failure get bigger training benefits.

I certainly don’t discount the effect of knowledge and supervision (e.g. to ensure correct form, especially in inexperienced exercisers), but my interpretation is that motivation is the key differentiator between the two groups. I think most people would agree intuitively that personal trainers can help people push harder than they would otherwise. But for those who can’t or don’t want to spring the cash, it seems to me that a good training partner can help serve a similar role — especially if you’re close to the same abilities, and you don’t want to have to re-rack the weights between each set!

If heel-striking is so unnatural, why do apes do it?

February 14th, 2010

In the wake of Dan Lieberman’s foray into the barefoot running debate, there’s an interesting counterpoint in the newest Journal of Experimental Biology from David Carrier of the University of Utah — the man who anticipated Lieberman’s 2004 “endurance running” evolutionary hypothesis by 20 years.

muybridge-walkingIn a nutshell, Carrier’s paper points out that heel-striking — a.k.a. “the devil,” as far as Lieberman is concerned — actually has advantages in some contexts. As the Utah press release puts it:

Humans, other great apes and bears are among the few animals that step first on the heel when walking, and then roll onto the ball of the foot and toes. Now, a University of Utah study shows the advantage: Compared with heel-first walking, it takes 53 percent more energy to walk on the balls of your feet, and 83 percent more energy to walk on your toes. [...]

Economical walking would have helped early human hunter-gatherers find food, he says. Yet, because other great apes also are heel-first walkers, it means the trait evolved before our common ancestors descended from the trees, [Carrier says].

The main point of the paper is that it’s curious that our foot anatomy is adapted to heel-strike while walking (i.e. we have a big, prominent heel), unlike most other mammals. But it’s a trait we share with all the other great apes, so it’s not something that was only created by the advent of thick-heeled modern shoes. As both Carrier and Lieberman have argued, many of our anatomical features seem to have evolved precisely to favour endurance running — but our heels, in contrast, seem better suited walking. This isn’t that surprising, the authors argue, given that both running and walking were likely essential to early hunter-gatherers.

Ultimately, none of this conflicts with the arguments put forth by Lieberman. Even if it’s natural to heel-strike while walking, the evidence suggests that early humans didn’t heel-strike while running. (Though the new study confirms earlier findings that there’s no difference in efficiency between heel-foot and fore-foot striking for running.) But as the barefoot running debate heats up, it’s interesting to note that heel striking has an evolutionary origin.