Drinking during exercise: maybe you don’t need as much as you thought

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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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My column in today’s Globe takes on a pretty controversial topic: how much water can you afford to lose as sweat before your performance suffers? I gave a little preview of one of the studies in a blog entry a few weeks ago, but this article is a much more detailed look at some recent research suggesting that the amount of weight you lose during exercise doesn’t necessarily correspond to the amount of water you lose:

Here’s a riddle posed recently by South African scientists: A group of soldiers undertook a gruelling 14.6-kilometre march during which they lost an average of 1.3 kilograms. But sophisticated measurements with isotope tracers showed the total amount in water in their bodies actually increased by 0.53 kilograms. Where did this “extra” water appear from?

Groups such as the American College of Sports Medicine have long advocated weighing yourself before and after exercise to determine how much fluid you lost. A litre of water weighs exactly one kilogram – so by this calculation, if you’re a kilogram lighter, that means you sweated out one litre more fluid than you replaced by drinking. Lose more than about 2 per cent of your starting weight, the ACSM warns, and your performance will suffer due to dehydration.

But the South African study, published in the British Journal of Sports Medicine by researchers at the University of Pretoria, adds fuel to a simmering debate about whether weight loss during exercise corresponds to water loss. They argue that some of the weight loss is from the energy stores you burn, and that your body has “hidden” stores of water that are released during exercise – which may mean we need to rethink how we approach hydration. [READ THE REST OF THE ARTICLE…]

The print version of the article is accompanied by a fantastic graphic by Trish McAlaster that breaks down the various ways your body gains and loses water during a marathon. So far it’s not available online (I’m hoping it will be posted later), but it you have a copy of the paper around, check it out.

Treadmills make you walk slower but work harder and feel worse

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 bit of an unusual study from Brazil just published online in Medicine & Science in Sports & Exercise. Basically they asked 34 young adults to go for a 20-minute walk either on a treadmill or outdoors on a 400-metre track, at whatever pace they would “feel happy to do regularly.” The results: they chose to walk significantly faster on the track than on the treadmill — but their percent of VO2max and their perceived exertion was higher on the treadmill, despite the slower speed. In addition, their “affective valence was more positive” (i.e. they were happier) on the track.

The goal of the study was to figure how to convince more people to exercise (and in that sense, it was somewhat unsuccessful because the volunteers chose paces that were too slow to elicit significant fitness gains), and to figure out whether recommendations formulated in the lab can be applied to normal outdoor conditions.

Leaving aside the psychology (which is certainly interesting — I know I’m happier outside than on a treadmill!), the fact that people walked more slowly but worked harder on the treadmill is odd. This wasn’t a biomechanics study, but it seems like more ammunition for those who say that movement on a treadmill is fundamentally different from overground — a debate that’s been dragging on for a long time now. I still don’t really understand why it should be different (other than wind resistance, which wouldn’t explain the current results), but apparently this is one of those deep mysteries…

Beta-alanine: a boost for anaerobic power… and finishing sprint?

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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In general, I’m not a big fan of performance-boosting supplements, in part because of some vague notions of “the spirit of sport” and in part because the vast majority of them are expensive placebos. But one of the sessions at the sports nutrition conference in Canberra earlier this week made a strong case that beta-alanine now has enough evidence to join the very, very short list of supplements with solid performance-enhancing science behind them (e.g. caffeine, creatine). The first important study of beta-alanine was only in 2006, but there have been 27 more studies since them, according to Trent Stellingwerff, a researcher at the Nestle Research Centre in Switzerland who also works with Canadian Olympic teams.

(Sorry for the delay in reporting on the sports nutrition conference — really busy week! There’s lots more to come, which I’ll post over the next few weeks.)

Basically, beta-alanine works just like baking soda to buffer pH, but does it from inside the muscle rather than outside (and, happily, doesn’t cause diarrhea). The actual buffering agent is something called carnosine, which is present in meat. When you eat meat, the carnosine is split into its two constituent amino acids (beta-alanine and histidine), which are absorbed into your muscles and recombine to form carnosine again. The rate-limiting step is the absorption of beta-alanine into your muscles, so if you take some extra beta-alanine you end up with more carnosine.

So when does this work? The sweet spot is thought to be exercise lasting between 60 seconds and 10 minutes. Studies dating way back to the 80s showed that sprinters have twice as much carnosine in their muscles as marathoners do. More recently, a Belgian study measured baseline carnosine levels in a group of rowers (i.e. without supplementation) and found that higher carnosine levels correlated to higher performance. Supplementing with beta-alanine then led to a 4.3-second improvement over ~6 minutes for the rowers.

The dosing details: unlike baking soda, it’s not a one-shot deal. Trent suggests that taking 3-6 g/day for four to eight weeks will increase muscle carnosine content by 40-50%. It then stays high for quite a while, so you can expect to continue seeing a performance boost up to a month after stopping supplementation.

For endurance athletes, there are a couple of potentially interesting wrinkles. A 2009 study in the Journal of Applied Physiology (Van Thienen et al.) found that cyclists on beta-alanine performed better in a 30-second all-out sprint at the end of a 110-minute time trial. So the buffering might help with the anaerobic demands of a finishing sprint even during a very long race, though this is just one study so far.

The other thing to consider is whether beta-alanine could help endurance athletes sustain higher levels of intense training — after all, interval sessions often include intense running within that 60s-10min sweet spot. Stellingwerff, who coaches a bunch of athletes including his wife, a 4:05 1,500m runner, gave one piece of practical advice. He said for a workout like 10x400m, athletes on beta-alanine tend to feel really good in intervals 1, 2, 3 and 4 — in fact, they sometimes feel too good and wreck the rest of the workout, so that intervals 7, 8, 9 and 10 get really ugly.

Anyway, food for thought. But as Trent pointed out, there’s no point even thinking about these kinds of supplements if you haven’t already taken care of the far more important basics of good diet and recovery and so on.

Swelling helps healing, so are ice and NSAIDs bad?

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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Lots more to come from the sports nutrition conference in Canberra, but first I just wanted to quickly put up a link to my article in today’s Globe about new research suggesting that swelling may help injuries heal faster:

Every weekend athlete knows the RICE rule for dealing with minor sprains and strains: rest, ice, compression and elevation, with the latter three tactics aimed at minimizing inflammation.

But a study published last month by researchers at the Cleveland Clinic adds to growing evidence that swelling actually plays a key role in healing soft-tissue injuries. The result is a classic tradeoff between short-term and long-term benefits: reducing swelling with ice or anti-inflammatory drugs may ease your pain now, but slow down your ultimate return to full strength.

“This whole discovery has really thrown into question all of our traditional approaches to treating injuries,” says Greg Wells, a University of Toronto exercise physiologist who works with national-team athletes at the Canadian Sport Centre. [READ THE WHOLE ARTICLE…]

Maximizing carbohydrate absorption during exercise

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)

***

Great first day at the International Sport Nutrition Conference in Canberra. Several interesting sessions that I’ll post about in days to come. For now, since I have just a few minutes before dinner, a few notes about Asker Jeukendrup‘s session, which he called “Carbohydrate: boring old or exciting new?”

In the “boring old” category, he took aim at the ACSM’s position stand, which states:

For longer events, consuming 0.7 g carbohydrates/kg body weight/h (approximately 30-60 g/h) has been shown unequivocally to extend endurance performance.

Now, it’s well known that if you take a drink with glucose in it, the fastest you can possibly make use of it is at a rate of about 0.8-1.0 g/min, no matter how much carb you have. The rate-limiting step is absorption from the intestine, which doesn’t depend at all on how big or small you are, so the guidelines shouldn’t be expressed “per kg body weight” — it should just be 30-60 g/hr (with the high end corresponding to the 1.0 g/min which is the fastest we can make use of glucose).

However, there are ways around this rate-limiting step. Over the last five or six years, Jeukendrup’s group has done a long series of studies on combining glucose and fructose. On its own, fructose is absorbed slower that glucose. But it’s transported across the intestinal wall by a different mechanism, so you can have both glucose and fructose being absorbed at the same time. Add them together, and you can get about 1.7 g/min that the body actually makes use of.  (And this is, indeed, the formulation used in Power Bar’s “C2 Max carb mix” bars and gels.) So Jeukendrup suggests that ultra-endurance athletes should aim for closer to 90 g/hr of carbs, and he showed some data from Ironman triathlete Chrissie Wellington, who does precisely that (and who just set a new Ironman world record in Arizona).

Does this apply to everybody? Well, it’s not such a big deal for shorter events. He offered these loose guidelines (which I copied down quickly — if I made any mistakes, I’ll correct them when I get the official proceedings):

  • less than 45 min: no carbs needed (but he later noted that some new studies are now showing that “mouth rinsing” with carbs can have an effect with exercise bouts as short as 30 min)
  • 45-75 min: mouth rinsing, with any type of carb
  • 1-2 hr: up to 30 g/hr, any type of carb
  • 2-3 hr: up to 60g/hr, carbs that are oxidized rapidly like glucose or maltodextrin
  • more than 2.5 hrs: up to 90g/hr, MUST be a combination of carbs that are absorbed via different mechanisms (e.g. glucose or maltodextrine combined with fructose in a 2:1 ratio)

Anyway, that’s a quick overview of some of the take-home messages he offered. There was lots of discussion afterwards, so if you have any questions about any this stuff, feel free to post ’em in the comments section and I’ll answer if I can.