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Posts Tagged ‘sports technology’

Altitude training fails to help Australian swim team

January 26th, 2012

A few months ago, I blogged about a placebo-controlled test of the “live high, train low” altitude training paradigm (here, and with a follow-up here). That test found no benefit to altitude training, which prompted some rather heated responses — including a comment from someone who works for an altitude tent company:

One bogus study cannot change the work that guys like David Martin and the Australia of Sport (AIS) have performed.

As it happens, the Australian Institute of Sport, working with Australia’s national swim team, has just published a massive new study of altitude training in the European Journal of Applied Physiology. They took 37 elite swimmers and divided them into three groups:

  1. “Classic” altitude training: three weeks in Sierra Nevada, Spain (2,320 m) or Flagstaff (2,135 m);
  2. LHTL, spending at least 14 hours a day for three weeks at simulated 3000 m at the Australian Institute of Sport in Canberra;
  3. a control group that didn’t go to altitude.

To assess the effects of altitude training, they looked at blood parameters like total hemoglobin mass, and measured race performances 1, 7, 14 and 28 days after returning from altitude, as well as assessing season-long performance profiles (including performance at the World Championships).

Let’s start with the good news. Unlike the previous study, this study did find a clear increase in total hemoglobin mass, of about 4%, in both altitude groups. Here’s the individual scatter:

But what about performance? There, the results weren’t so good:

Or in words:

Swimming performance was substantially impaired for up to 7 days following 3 weeks of either Classic or LHTL altitude training. Despite ~4% increases in tHb resulting from both Classic and LHTL altitude training, there were no clear beneficial performance effects in the 28 days following altitude… A season-long comparison of two tapered performances at major championships also did not reveal a benefit for athletes who completed mid-season altitude training despite the substantial physiological changes associated with the altitude.

So does this “prove” that altitude training doesn’t help endurance performance? Of course not. But it’s a pretty interesting data point. This is the Australian swim team — one of the world’s powerhouses — supported by the Australian Institute of Sport, who have done lots of research into altitude training, and believe in it enough to construct an altitude house on their campus. They understand how it’s supposed to be done, and they executed it effectively enough to produce hemoglobin changes… but still, they didn’t manage to improve performance. If anything, they got worse.

If you’re doing altitude training, are you confident that you’re doing it better than they are?

[UPDATE: Sam McGlone and Paulo Sousa raised an important point on Twitter: the swim distances that they tested in this study were 100 or 200m. That's pretty short - I don't know the numbers for swimming, but maybe 50% aerobic at most? Here's what the researchers say:

Based on the calculated aerobic contribution to energy production during competitive 100 and 200 m swimming races, the 3.8% increase in tHb we observed could elicit a 0.3–0.7% improvement in race time... Although improvements of this magnitude are equivalent to the smallest worthwhile change for swimming performance, detecting such changes can be difficult due to the variability associated with racing and the modest sample sizes available when targeting an elite athlete population.

Certainly something to keep in mind in interpreting this study.]

Is lactate threshold a reproducible measurement?

December 31st, 2011

I posted earlier this week about a study that found that the amount of lactate in your blood at threshold doesn’t predict endurance performance. This doesn’t mean that lactate measurements are useless, I pointed out:

It just means that a single lactate measurement in isolation is meaningless: you have to make repeated measurements and track your progress relative to your personal baseline, in order to eliminate the effects of individual variation.

Well, a new study in the British Journal of Sports Medicine actually calls that last statement into question. If you make repeated measurements of lactate threshold, are those measurements repeatable enough to detect small changes in fitness? Many, many studies have examined this question, with the general conclusion that “yes, they’re repeatable.” But most of these studies have only repeated the measurement twice or at most three times, which is hardly sufficient to look for variability.

So researchers from Massey University decided to run a study in which 11 fit subjects did at least six lactate tests each, to see how consistent the results were. The goal here was to make the measurements as identical as possible, so they strictly controlled diet, time of day, and training conditions, all which have been shown to influence lactate values. (Coaches: do you control these factors when you test your athletes?)

Of course, there are many different markers you can look for in lactate tests, so the researchers chose seven of the most common markers: Rest+1, 2.0 mmol/L, 4.0 mmol/L, D-max, nadir, lactate slope index, and visual turnpoint.

These results indicate that only the D-max marker has good reproducibility and that it alone can identify small but meaningful changes in training status with sufficient statistical power.

Expressed in terms of coefficient of variation (with is the standard deviation divided by the mean), the visual turnpoint was by far the worst, with a variation of 51.6%, while D-max has 3.8%. The other markers were between 5.9 and 12.6%. What does this mean in terms of cycling power? They run some numbers to show that even a fitness change corresponding to 70 watts (i.e. improving from 55 to 47 minutes in a 40 km time trial) wouldn’t be reliably detected by most lactate measures.

Tim Noakes, in his accompanying commentary, draws the following conclusions:

[T]hey conclude that unrealistically large changes in power output would have to occur before it can be claimed with certainty that training has produced a real change in an individual’s blood lactate concentrations during exercise. These findings should encourage sober reflection among that large group of exercise scientists who use blood lactate concentrations to guide athletes’ training.

I’m inclined to be a little less negative. After all, coaches and athletes can likely settle for somewhat less rigid definitions of what change can be considered “significant.” As long as they understand that the measurement is fallible and subject to variation, it might still be useful tool for monitoring fitness. (Is it useful for prescribing training paces? That’s a whole different question.)

Altitude babies and epigenetics

December 28th, 2011

Steve Magness has a fascinating post on his blog about a neat new study in the January issue of Journal of Applied Physiology. The researchers took a bunch of rats whose ancestors have been living at the Bolivian Institute for Altitude Biology, which is 3,600 metres above sea level. Half the rats were placed in a room with “enhanced oxygen” to mimic sea level from one day before birth to 15 days after birth; the other half simply grew up normally at 3,600 metres. Then the researchers followed the rats for the rest of their lives to see whether this “postnatal” exposure to low oxygen affected the rats’ development.

This study fits into the recent burst of research into epigenetics — the idea that early environmental influences can produce lasting changes in gene expression. And sure enough, there were significant differences between the rats who grew up at high altitude continuously (HACont) and those who got two weeks of sea-level oxygen (HApNorm):

As you can see, the high-altitude rats had higher hemoglobin and hematocrit long after the two-week exposure period (32 weeks is roughly middle-aged in rats). Among many other differences, the altitude babies also had a bigger heart, and used less oxygen. All of this sounds pretty good for endurance athletes — which is why Steve wrote:

I always joke with my friends that whenever I have kids, I’m going to stick them at altitude during pregnancy and right after just to develop super altitude adapted kids…

But there’s a caveat. Here’s the survival data for the two types of rat:

In fact, the researchers make the overall conclusion that low oxygen levels in the crucial weeks after birth are a bad thing:

We conclude that exposure to ambient hypoxia during postnatal development in [high altitude] rats has deleterious consequences on acclimatization to hypoxia as adults.

So you have to be careful what you wish for your kids. Either way, though, it’s clear that environment alone can produce profound, lifelong changes in physiology — producing group traits that we once might have mistakenly attributed to genetics.

Lactate at threshold doesn’t predict performance

December 27th, 2011

I was at a conference on fatigue a few months ago where one of the speakers was Mike Lambert, a well-known sports science researcher from Tim Noakes’s group at the University of Cape Town. One of the questions at the end of his talk was about the use of lactate monitoring; his answer was something along the lines of “We refuse to measure lactate, because we don’t believe it offers any useful predictive information.” As a result, the UCT sports science unit doesn’t do much work with certain teams like the South African swim team, because the swim coaches are convinced that lactate testing offers important feedback.

A new paper just published online in the European Journal of Applied Physiology reminded me of that discussion. Researchers in Austria performed a whole series of difference incremental and maximal tests on 62 volunteers to look for patterns. The basic finding was that the amount of lactate in the blood at “maximal lactate steady state” (MLSS: the point where you’re producing and clearing lactate at the same rate) isn’t correlated with how fast or fit you are.

This isn’t the first study to make this observation. But previous studies have used relatively homogeneous groups, which makes it hard to determine whether lactate levels really have an effect. With VO2max, for example, you can safely bet the someone with a VO2max of 75 will perform better on any endurance task than someone with a VO2max of 35. But if you take a group of people who all have VO2max clustered between 60 and 70, then VO2max becomes a very poor predictor of performance.

In this case, the study subjects ranged from sedentary (with 0 hours per week of sports or exercise) to very fit athletes training up to 24.5 hours per week. Their power output on the bike at MLSS ranged from 100 to 302 watts. But despite this wide range, it was still impossible to predict anyone’s power levels by looking at their lactate levels at MLSS.

So does this mean Lambert is right and lactate is useless? Not necessarily. It just means that a single lactate measurement in isolation is meaningless: you have to make repeated measurements and track your progress relative to your personal baseline, in order to eliminate the effects of individual variation.

More on altitude training research

December 1st, 2011

Yesterday’s post about Carsten Lundby’s altitude study sparked some fantastic discussion in the comments section, on Twitter, and over e-mail. I really appreciate everyone who took time to share their thoughts and expertise, and I’d just like to follow up with a few thoughts of my own.

When a study like this comes along that contradicts the “conventional wisdom,” there are many possible ways to respond. One good response is to look for flaws in the study, to figure out if there’s some logical reason that it contradicts previous findings. At the other end of the spectrum, there are responses like this one, from the comments section of the previous post:

This study has a lot of holes in it, especially since some of the “best” physiologists state that LHTL works. One bogus study cannot change the work that guys like David Martin and the Australia of Sport (AIS) have performed.

With all due respect, the study “has holes in it” if there’s a problem with its methodology or design, not just because someone says it does. One study certainly can refute the work that others have done if the new study is correct and the others are flawed. That’s how science works: it doesn’t care what your name is or where you work. (Speaking of which, it’s no coincidence that this particular commenter works for a company that manufactures and sells altitude tents!)

Another commenter asked about individual (rather than average) responses. This is an excellent question, since it has long been hypothesized that there are “responders” and “non-responders” to altitude training. Here are the individual responses in hemoglobin mass for the altitude group:

On the surface, this looks to be exactly what we see: five “significant” (above the dashed line, which represents the typical error level of the measuring apparatus) responders, three who got significantly worse, and two basically unchanged. But let’s look also at the placebo group:

Once again (though with fewer subjects), we have some individuals responding “significantly” in both directions to the placebo stimulus, and some staying unchanged. Though the small sample size makes comparisons difficult, the scatter of individual results looks pretty similar in both cases (and was statistically indistinguishable).

So what do we conclude from this study? As I said in the previous post, this was an exquisitely careful study with an excellent design. That means we can place very high confidence (relative to previous altitude studies) in its evaluation of the specific conditions it tested. And this is the rub. They held certain conditions constant, such as oxygen levels, time exposed to hypoxia, and training stimulus. But what if the training stimulus was inappropriate (too hard? too easy?). What if the athletes had insufficiently high iron (despite being given daily iron supplements)? What if being confined to their rooms for 16 hours a day caused negative adaptations?

These are all possibilities — and they’re all possibilities considered by the researchers themselves in their discussion in the paper. No one — not me, not the researchers — is saying “altitude training is a scam.” But what they (and I) are saying is that, if you take a fairly conventional live-high-train-low paradigm as executed in the study (4 weeks, 3,000m/1,000m, continuing essentially the same training plan that you were doing at sea level, etc.), don’t assume that you’re automatically going to get the results you’re looking for. There are clearly some other variables at play that need to be controlled. Elite coaches and athletes have some pretty strong ideas about what these additional variables are. And if I worked for an altitude tent company, I’d spend a little less time mouthing off about “bogus studies,” and a little more time trying to nail down exactly what those variables are.

A reality check for altitude tents and houses

November 29th, 2011

[UPDATE 11/30: Lots of great discussion of this post below and on Twitter. I've added a new post with some responses, more data, and further thoughts HERE.]

A recurring theme on this blog is that not all studies are created equal. The quality of the study design makes a huge difference in the amount of faith that we can place in the results. So it’s always a big pleasure to see awesomely painstaking studies like the new one in Journal of Applied Physiology by Carsten Lundby’s group in Zurich. The topic: the “live high, train low” (LHTL) paradigm used by endurance athletes, in which they spend as much time at high altitude as possible to stimulate adaptations to low oxygen, while descending to lower altitude each day for training so that their actual workout pace isn’t compromised by the lack of oxygen.

There have been a bunch of LHTL studies since the 1990s that found performance benefits — but it’s really difficult to exclude the possibility of placebo effect, since athletes know they’re supposed to get faster under the LHTL strategy (and, conversely, athletes who get stuck in the control group know they’re not supposed to get faster). But Lundby and his colleagues managed to put together a double-blinded, placebo-controlled study of LHTL. The main features:

  • 16 trained cyclists spent eight weeks at the Centre National de Ski Nordique in Premanon, France. For four of those weeks, they spent 16 hours a day confined to their altitude-controlled rooms. Ten of the subjects were kept at altitude (3,000 m), and six were at ambient (~1,000 m) altitude.
  • Neither the subjects nor the scientists taking the measurements knew which cyclists were “living high.” Questionnaires during and after the study showed that the subjects hadn’t been able to guess which group they were in.
  • On five occasions before, during and after the four weeks, the subjects underwent a whole series of performance and physiological tests.

So, after going to all this trouble, what were the results?

Hemoglobin mass, maximal O2-uptake in normoxia and at a simulated altitude of 2,500 m and mean power output in a simulated 26.15 km time-trial remained unchanged in both groups throughout the study. Exercise economy (i.e. O2-uptake measured at 200 Watt) did not change during the LHTL-intervention and was never significantly different between groups. In conclusion, four weeks of LHTL using 16 hours per day of normobaric hypoxia did not improve endurance performance or any of the measured associated physiological variables.

This is, frankly, a surprising result, and the paper goes into great detail discussing possible explanations and caveats — especially considering the study didn’t find the same physiological changes (like increased hemoglobin mass, which you’d expect would be placebo-proof) that previous studies have found. Two points worth noting:

(1) The subjects were very well-trained compared to previous studies, with VO2max around 70 ml/kg/min and high initial hemoglobin mass. It’s possible that the beneficial effects of LHTL show up only in less-trained subjects.

(2) There’s a difference between living at 3,000 m and living in a room or tent kept at oxygen levels comparable to 3,000 m: pressure. “Real-world” altitude has lower pressure as well as lower oxygen; this study lowered oxygen but not atmospheric pressure. Apparently a few recent studies have hinted at the possibility that pressure as well as oxygen could play a role in the body’s response to altitude, though this remains highly speculative.

As always, one new study doesn’t erase all previous studies, nor does it override the practical experience of elite athletes. But it suggests that we should think carefully about whether altitude really works the way we’ve been assuming it works. As the researchers conclude:

In summary, our study provides no indication for LHTL, using normobaric hypoxia, to improve time trial performance or VO2max of highly trained endurance cyclists more than conventional training. Given the considerable financial and logistic effort of performing a LHTL camp, this should be taken into consideration before recommending LHTL to elite endurance athletes.

 

Compression gear during interval workouts: a new possibility

November 19th, 2011

An interesting wrinkle in the debate over whether compression garments do anything during exercise to improve performance, from a new Australian study just posted in the Journal of Strength & Conditioning Research. The situation so far:

  • Every time you take a step while running, the flexing of your calf muscle operates something called the “calf muscle pump” — basically, your calf literally squeezes the blood vessels in your lower leg, helping to shoot oxygen-depleted blood back toward the heart.
  • Graduated compression of the lower leg (i.e. tighter at the ankle, looser at the knee) is thought to enhance the action of this calf muscle pump, by helping it to squeeze harder. This should reduce the load on your heart and speed the circulation of blood through your body, possibly enhancing performance.
  • One argument against the idea that compression garments boost performance is that, when you’re running hard, the action of the calf muscle pump is already maxed out, so adding more compression doesn’t help. You can’t squeeze more blood from a stone!

The new study put 25 rubgy players through a form of interval workout: basically 5:00 easy, 5:00 medium, 5:00 hard, 5:00 easy, 5:00 hard, 5:00 easy. They each did the test twice, once in running shorts and once in full-leg graduated compression bottoms. The researchers measured a bunch of variables (heart rate, oxygen consumption, lactate levels, blood pH) during each stage of the workout. There were basically only two elements where the data was significantly different between shorts and tights: in the fourth and sixth intervals (i.e. the easy recovery intervals), heart rate and lactate levels were both significantly lower in compression tights.

On the surface, this fits nicely with the ideas above. The tights don’t help when you’re running fast, since the calf muscle pump is maxed out; but during the easy recovery, the compression does help, resulting in lower lactate and heart rate — and, in theory, better performance on the subsequent hard section.

This is the problem, though: the study didn’t actually measure performance. The pace during each interval was predetermined, so we don’t know whether this difference in physiological parameters actually translates into better real-world performance. That’s a point that was highlighted in another Australian compression study that I blogged about back in August. That study also found physiological “improvements” from compression — but in that case, they also measured performance and found no difference. As the researchers wrote:

However, the magnitude of this improved venous flow through peripheral muscles appears trivial for athletes and coaches, as it did not improve [time-to-exhaustion] performance. This would suggest that any improvement in the clearance of waste products is insufficient to negate the development of fatigue.

Bottom line: I remain skeptical that wearing compression during a run will allow you to run faster. (Note that this is entirely separate from the question of whether wearing compression during and after a run will allow you to avoid or recover more quickly from muscle soreness, a claim that has somewhat better support.) This new study raises the intriguing possibility that compression might boost active recovery during interval workouts — but until it’s directly tested in a performance context, it’s just a hypothesis.

Power Balance bracelets in placebo-controlled experiment

October 28th, 2011

I’m embarrassed to even report on this study — but just in case there are still any Power Balance believers out there, researchers at the University of Texas at Tyler have just published a placebo-controlled, double-blind, counterbalanced test of strength, flexibility and balance, in the Journal of Strength & Conditioning Research. They compared Power Balance bracelets to the same bracelets with the “energy flow distributing Mylar hologram” removed, and to nothing at all. And, believe it or not, they found no differences. For example:

And for all those who still swear that, when the salesman put the bracelet on their wrist, they really did do better on the balance test, it’s worth noting the University of Wisconsin pilot study (cited in the Texas paper) that found that in balance and flexibility tests like the ones used by Power Balance salespeople, you always do better the second time you try it, due to learning effects. So if you try the test first with the bracelet on, then with the bracelet off, you’ll “prove” that the energy flow actually harms your balance. (Or maybe that just means you had the bracelet on backwards…)

Training changes your genetics (or rather, epigenetics)

October 11th, 2011

Just noticed this study published online ahead of print in the journal Drug Testing and Analytics, which suggests that both performance-enhancing drugs and hard training “may alter the expression of specific genes involved in muscle and bone metabolism by epigenetic mechanisms, such as DNA methylation and histone modifications.” Cool, huh? This is why the “genetics versus training” debate is so irreducibly complicated: training can effectively change your genetics.

Recognition of the potential role of epigenetics has been gaining traction over the past few years. Here’s how a review paper on the genetics of elite athletic performance in the Journal of Physiology put it a few months ago:

[F]uture research might determine to what extent the changes that environmental factors can induce in gene expression during critical periods of prenatal and postnatal development (i.e. through epigenetic mechanisms) explain why some individuals reach the elite athletic status. For instance, elite Kenyan runners, who have dominated most distance running events in the last two decades, undergo stringent training regimens since childhood (running ~20 km/day) at high altitude (~2000 m), which might lead to unique environment–gene interactions.

So what are these “epigenetic mechanisms”? This article from Scientific American explains the most common mechanism:

The best-studied form of epigenetic regulation is methylation, the addition of clusters of atoms made of carbon and hydrogen (methyl groups) to DNA. Depending on where they are placed, methyl groups direct the cell to ignore any genes present in a stretch of DNA.

The SciAm article focuses on evidence that overweight mothers may pass the tendency to be overweight on to their children. What’s crucial is that this “inherited” trait isn’t encoded in DNA — instead, it’s how the DNA’s instructions are carried out that is altered. For example, there’s preliminary evidence that children born to an overweight mother before she undergoes gastric bypass surgery are more likely to become overweight when they grow up than their siblings born after the surgery [EDIT: see this AP story or this study for details]. If this was a simple genetic inheritance (i.e. through DNA), the surgery wouldn’t make any difference to inherited traits. Instead, it appears to be an epigenetic phenomenon.

Anyway, this is a topic I’m hoping to learn more about. On the surface, it seems to be a vindication of the old saying “The harder I work, the more talented I get.” I certainly don’t discount the obvious role of genetics in shaping ultimate athletic potential (particularly when we’re talking about the extremes represented by world champions and world record holders), but I do think many people still underestimate how much their body — and even their gene expression — can adapt to the demands they put on it.

Toning shoes: a $25 million scam

September 30th, 2011

It has been a very long couple of days for me, packing up and moving out of my apartment, and getting ready to catch a trans-Pacific flight — so I was very happy to see some good news to brighten my evening. As Julie Deardorff of the Chicago Tribune notes, Reebok has apparently agreed to refund $25 million to consumers who bought their toning shoes because of misleading advertising claims:

According to the FTC complaint, Reebok falsely asserted specific numerical claims, saying, for example, that walking in EasyTone shoes had been proven to lead to 11 percent greater strength and tone in hamstring muscles than regular walking shoes.

Over the last year or two, I’ve had quite a few requests from readers (or disgusted skeptics) to write a column on the “science” (yes, those are sarcastic quote marks!) behind toning shoes. The problem is that it’s very hard to write a science-of-exercise column on something so devoid of science. (Or to look at it another way, it’s very easy, but the column ends up being two sentences long — and I get paid by the word!) :)

Anyway, as it turns out, there has been some critical scientific analysis of toning shoes: Christian Finn does a good job of summing up the topic here, including a link to a (non-peer-reviewed) study by some very well respected University of Wisconsin researchers that compared Reebok EasyTone, Skechers Shape-Ups and MBT shoes to ordinary running shoes, and found no worthwhile differences.

The one thing that surprises me is: why Reebok, in particular? Because ads for athletic apparel are generally so ridiculous and misleading that I’ve always assumed they just operate in a truth-free zone. Will similar suits follow against Skechers and other brands? Anyway, regardless of what follows, it’s always good to see the occasional victory for common sense. With PowerBalance earlier this year and now EasyTone, it’s been a pretty good year for the good guys.