Slushies: the new weapon for exercising in heat

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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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Reading up on Australian sports research for an upcoming magazine story, I came across this little nugget about dealing with competition in hot conditions. The Aussies have been leaders in research on “pre-cooling” to lower body temperature before starting extended exercise in the heat. They introduced ice vests at the 1996 Olympics (which have since become widely used commercial products), and in 2004 brought big bathtubs full of ice-water to the Athens Olympic venues, actually immersing their endurance athletes shortly before their competitions.

I can’t imagine the pre-race ice bath becoming a really widespread phenomenon, for many reasons including logistical ones. But for the Beijing Olympics in 2008, the Aussies unveiled a new idea: slushies! As Louise Burke, head of sports nutrition at the Australian Institute of Sport, explained at a conference in Switzerland last fall, ingesting crushed-ice drinks cools the athletes internally — not just with the coolness of the ice, but with the energy of the phase transition as it melts. In tests, the Aussies found their athletes lowered their body temperature by about one degree Celsius by drinking the slushies (which were filled with “a mix of carbohydrates, electrolytes, and ice with other secret ingredients“). So the Australian Olympic team brought seven slushie machines to Beijing.

Other interesting points from Burke’s talk in Switzerland: The ice baths actually lowered body temperature more than the slushies, but this turned out to be a negative. In cycling time-trial tests, the athletes felt so good after the ice baths that their internal pace regulation was messed up, so they started too fast and paid for it late in the race. The slushie-fed athletes, on the other hand, started a little slower but ultimately performed better.

And the other reason the Aussies introduced slushies in 2008? They wanted to have something new, Burke says, to elicit a placebo response in their athletes.

Dynamic compression: even better than compression socks?

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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normatecBack in April, when I wrote a Jockology column on compression garments, I was surprised to find out that there’s pretty good evidence that these things can actually work. “Graduated” compression socks, for instance, squeeze tightest at the bottom of the leg and gradually loosen, forcing blood back towards the heart. But regular socks have nothing on these super-fancy recovery boots that U.S. marathoner superstar Ryan Hall is now using. The picture to the right was posted on Twitter by Hall’s wife earlier this month after they started using NormaTec MVP compression boots, in this case to help recover after a long tempo run.

Basically, these things squeeze the legs with a “peristaltic pulse” that moves from the bottom of the leg towards the top, pushing blood back towards the heart. The makers refer to it as “dynamic compression” instead of the “static compression” offered by simple leggings. The idea sounds reasonable — if you believe in compression socks, then it seems like these might do the job better.

But is there any evidence, or research into how well they work? I couldn’t find any in a quick search, but I’ve e-mailed the company to see if they have anything to offer. I’ll report back when I hear from them.

Keeping current on fitness research

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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You could describe the primary motivation for this blog as “evidence-based exercise” — the idea that it’s worth trying to verify whether the things we do in the gym actually produce the results we expect when they’re tested under controlled conditions. There’s a huge amount of exercise research coming out of research labs around the world on a regular basis. The problem is that very little of it reaches the general public (or even many fitness professionals). I spend time flipping through the contents of at least half a dozen journals where this research appears on a regular basis, but it’s hard to keep up with it all.

So it’s always nice to see other people pushing the same agenda. A friend recently tipped me off about Research Review Service – Fitness, which is run by Shawn Thistle, a Toronto-area chiropractor and trainer. The idea is that he and a team of other fitness professionals comb the literature and pick out important papers, then summarize and critique them. The main target audience, it seems, is personal trainers, coaches and health/rehab professionals (it’s a subscription service that costs $99). The papers they review focus on nutrition, rehabilitation, sport-specific training, sports injuries and strength & conditioning. Some sample reviews are here.

Anyway, if I were going to see a trainer or a physiotherapist or someone like that, it would make me very happy to think they were interested in using a service like this to stay current on the relevant literature — so I figured I’d share it for anyone out there who may be interested.

Aerobic exercise makes you smarter than weightlifting

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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A nice post by Gretchen Reynolds at the NYT Well blog goes beyond the usual “exercise makes you smarter” to investigate what kind of exercise, exactly, boosts IQ most effectively. Key result from one study:

The students were noticeably quicker and more accurate on the retest after they ran compared with [lifting weights or sitting quietly], and they continued to perform better when tested after the cool down. “There seems to be something different about aerobic exercise,” Charles Hillman, an associate professor in the department of kinesiology at the University of Illinois and an author of the study, says.

And a result from a more recent study:

[T]hey allowed one group of mice to run inside their rodent wheels, an activity most mice enjoy, while requiring the other group to push harder on minitreadmills at a speed and duration controlled by the scientists. They then tested both groups again to track their learning skills and memory. Both groups of mice performed admirably in the water maze, bettering their performances from the earlier trial. But only the treadmill runners were better in the avoidance task, a skill that, according to brain scientists, demands a more complicated cognitive response.

So, at first glance, it looks like aerobic exercise has the edge, and the harder the better. This jibes with a study I wrote about in July showing that aerobic exercise developed better blood vessels that got more oxygen to aging brains. On the other hand, if you push too hard during a marathon, your memory actually gets worse — temporarily.

Pool running: does it use the same muscles as running on land?

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)

***

Pool running: two words that strike fear into the heart of injured runners everywhere. It’s the ultimate cross-training and rehab exercise, because it has zero impact and is thought to most closely emulate the motion of running. There have been plenty of studies on the cardiorespiratory effects of pool running — anyone who has tried it will tell you that you have to work harder to get your heart rate to its usual levels (and to avoid stabbing yourself in the eye out of sheer boredom). But there has been surprisingly little study of how your muscles actually get used in pool running.

Researchers from the University of Nevada, Las Vegas have finally performed such a study. They took a group of seven runners, wired them up with electrodes on various parts of their legs, and had them run at various intensities first on a treadmill, then in the pool (wearing drysuits to keep from zapping themselves). The results: tibialis anterior (shin) and gastrocnemius (calf) activations were way lower in the pool than on land. Rectus femoris (quad) and biceps femoris (hamstring) activation was a little more ambiguous: it tended to be a bit lower in the pool, but the patterns were different (because the stride is so different) and they overlapped a bit.

So what can we take away from this? Not a huge amount — as the researchers point out in their paper, there are a lot of methodological limitations to measuring EMG signals from someone in a dry suit. Also, the stride pattern in pool running is hard to control (the subjects in this case were asked to use the “high-knee” style of pool running rather than the “cross-country skiing” style). If anything, we can say that the lower legs get significantly less stimulation from pool running, so when you do return to dry land, you might want to take extra care looking for aches and pains in your calves and shins. In the end, no one is doing pool running because they think it’s the same as running — and for now, it’s probably the next best thing (unless you have an Alter-G treadmill).