A reality check for altitude tents and houses

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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[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

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

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

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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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)

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

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

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

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.