Sports drinks don’t help for one-hour exercise (unless you’ve been fasting)

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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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If you’re running a marathon or cycling for several hours, you need to ingest some carbohydrates during the session to maintain your performance. If you’re sprinting for 100 metres, on the other hand, you can leave the buffet belt at home. Where things get murky is the middle ground, for sessions lasting about an hour: several decades of research have produced lots of conflicting results. A study in the April issue of the Journal of Sports Sciences, by researchers from Loughborough University in Britain, offers some new insight.

The basics: 10 trained runners did two trials in which they ran as far as they could in one hour (they used a neat treadmill that automatically speeds up if you move towards the front of the belt, and slows down if you lag towards the rear, so it was a freely paced trial). In both cases, they ate a high-carbohydrate meal three hours before the run. They drank either a sports drink containing 6.4% carbohydrates or a placebo before and during the run. The results: no difference whatsoever in performance, blood glucose, lactate, respiration, carbohydrate burning, perceived exertion, or anything else they measured.

What’s interesting is that the same group published a similar paper last year, where the only difference is that the runners were fasted before the trial instead of having a meal three hours prior. In that case, the sports drink group significantly outperformed the placebo group.

So it seems pretty clear: you only need supplemental carbs for a one-hour exercise bout if you haven’t topped up your carb supplies beforehand. There are two ways your body stores glycogen: in your muscles (which is then used exclusively by your muscles), and in your liver (which feeds glucose into your bloodstream to fuel your heart and brain and keep blood sugar levels stable). When you sleep overnight, your muscle glycogen stays relatively stable, but your liver glycogen drops by more than 50 percent (because your brain and heart are still running all night). So the researchers believe that, if you don’t have a pre-exercise meal, the sports drink is needed to make up for your depleted liver glycogen stores.

Practically speaking, this means you don’t need to worry about carbs during short exercise bouts in the afternoon or evening, since you’ll have had a meal or two. In the morning, though, you need to make sure your liver glycogen is restocked, even for a short one-hour run. You can do that by getting up early enough to eat beforehand — or, apparently, by consuming some carbs immediately before and during your session.

One other interesting note from the paper. They discuss the performance boost that comes from “rinsing and spitting” with a sports drink, which some researchers have suggested could explain why sports drinks sometimes help with short exercise sessions even when muscle glycogen stores are full. Interestingly, a couple of recent papers suggest that the same conditions also apply in this case: you get benefit from rinse-and-spit if you’ve fasted beforehand, but no benefit if you had a pre-exercise meal. That suggests that your brain is monitoring levels of carbohydrate throughout your body, and only responds positively to the carb stimulus if your body actually needs it:

Although speculative, the idea of central monitoring of whole-body carbohydrate status, which in turn influences the self-selection of exercise intensity, is worthy of further investigation.

Off-the-bike running form changes economy in triathletes

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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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Interesting article [LINK FIXED] on what intense biking does to your running form, by researchers at the Australian Institute of Sport and the University of Queensland, coming up in a future issue of the Journal of Science and Medicine in Sport. There has been quite a bit of prior research on what happens when you run off the bike, generally showing that your running economy is worse than it would otherwise be — in other words, tired as you are, you also have to burn more energy to run at a given pace than you normally do. Various reasons for this have been proposed: you’re dehydrated, your breathing muscles are tired, you’re burning a higher proportion of fat because your carbohydrate stores are depleted. But it may also have something to do with running form, thanks to changes in neuromuscular control. That’s what this study set out to investigate, by having a group of 17 moderately trained triathletes do a pair of runs with and without a 45-minute high-intensity bike ride beforehand.

Unfortunately, the results don’t reveal any universal truths about what triathletes do wrong off the bike — but there are some interesting findings. First of all, everybody was different: some people had changes in running form, others didn’t; some had better running economy, others had worse. Crunching the data, the researchers find that the people whose running economy got worse had some things in common. When running after biking, these people tended to extend their knee and dorsiflex their ankle at the moment of ground contact a bit more than when they ran fresh. That makes them more likely to have a jarring heel strike, which wastes a bit of energy. Basically, when they start running after biking, they’re overstriding.

I’m not sure this really says much about fancy concepts like “neuromuscular fatigue,” but it does offer a useful warning about a pitfall that about half the subjects in the study fell into. Yes, you’re tired when you come off the bike, but overstriding isn’t going to get you to the finish line any sooner. (And one thing the researchers note is that their subjects were not elite triathletes, so this advice may be most relevant to less-experienced age-groupers.)

Thinking good (or bad) thoughts increases endurance

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 new study from Harvard University suggests that it’s good to be a good guy, but better to be a bad guy:

Study participants who did good deeds — or even just imagined themselves helping others — were better able to perform a subsequent task of physical endurance. The research, published in the journal Social Psychological and Personality Science, shows a similar or even greater boost in physical strength following dastardly deeds.

The researcher,  a psychology grad student named Kurt Gray, calls the effect “moral transformation.” It suggests that we may have cause and effect backwards, he says: It’s not that people who do great things have incredible strength and willpower; instead, people who attempt great things gain strength and willpower by making the attempt.

So what does this mean for exercisers? Well, I haven’t been able to dig up a copy of the original paper, so I’m relying on a press release whose details are somewhat sketchy:

Gray’s findings are based on two studies. In the first, participants were given a dollar and told either to keep it or to donate it to charity; they were then asked to hold up a 5 lb. weight for as long as they could. Those who donated to charity could hold the weight up for almost 10 seconds longer, on average.

In a second study, participants held a weight while writing fictional stories of themselves either helping another, harming another, or doing something that had no impact on others. As before, those who thought about doing good were significantly stronger than those whose actions didn’t benefit other people.

But surprisingly, the would-be malefactors were even stronger than those who envisioned doing good deeds.

So it doesn’t sound like this will be a magic ticket to unlimited strength and endurance. Still, it might be worth keeping the power of mental imagery in mind next time you’re working out — you might combine the power of evil thoughts with the ergogenic effects of swearing for maximum effect.

Pickle juice stops muscle cramps

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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)

***

No, really, this is a serious blog entry. There’s an article in the May issue of Medicine & Science in Sports & Exercise by researchers at Brigham Young University called “Reflex Inhibition of Electrically Induced Muscle Cramps in Hypohydrated Humans,” and that’s what it says:

The most significant and novel observation of this study was that ingesting small volumes (73.9 +/- 2.7 mL) of pickle juice alleviated electrically induced muscle cramps in mildly hypohydrated (3%) humans. Pickle juice required approximately 85 s to alleviate muscle cramps (cramp duration after ingestion ranged from 12 to 219 s). Although this was much longer than the purported claims of pickle juice’s efficacy, it still relieved a cramp 45% (85 vs 153 s) faster than when no fluid was consumed. In contrast, ingesting similar volumes of deionized water had no therapeutic effect on cramp duration (cramp duration after ingestion ranged from 71 to 246 s).

What’s interesting about this is not so much the promise of a “cure” for muscle cramps. (There are some reasons to think that downing a bunch of vinegar and salt probably isn’t a great habit, for one thing.) Instead, it’s how it stops cramps that is intriguing and suggests that conventional thinking on cramps may be mistaken.

The pickle juice cure has been around for at least a decade (it was described in a 2000 article in the Journal of Athletic Training), and most people assumed that it had something to do with all the electrolytes. But the authors of this new study aren’t convinced. First of all, the amount of electrolyte in 73 mL of pickle juice has a negligible effect on concentrations in the body. Second, the 85 seconds it took (on average) to relieve the cramps is far too short for the pickle juice to exit the stomach, be absorbed by the small intestines, and reach the relevant part of the body. Earlier studies have found that it takes at least 30 minutes for small volumes of pickle juice to leave the stomach.

Instead, the researchers suggest that the pickle juice acts on neural reflexes — a plausible suggestion, given that earlier experiments have found that vinegar can provoke reflexes and affect neurotransmitter levels. This fits with an alternate theory that cramps have nothing to do with dehydration or electrolyte loss, first proposed in the 1990s by Martin Schwellnus of the University of Cape Town:

Schwellnus et al. proposed that [cramps] were due to neuromuscular fatigue. Neuromuscular fatigue is thought to create an imbalance between muscle spindle and Golgi tendon organ activity, resulting in increased alpha motor neuron excitability. Thus, if [cramps] are caused by an imbalance between excitatory and inhibitory stimuli at the alpha motor neuron pool, pickle juice ingestion may cause an increase in inhibition from supraspinal sources, thereby resulting in cramp alleviation.

If you’re interested in the details of Schwellnus’s theory and the controversies surrounding muscle cramps, the Science of Sport blog did a good series on it back in 2007 (Part 1, Part 2, Part 3 and Part 4). It’s interesting stuff — and now, courtesy of pickle juice, there’s some new evidence.

How many calories does sitting on an exercise ball burn?

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)

***

In the comments section of an earlier post that mentioned the potential caloric benefits of standing as opposed to sitting, Peter asked how sitting on an exercise ball stacks up. The news is good. A 2008 study in the European Journal of Applied Physiology by researchers at the University of Buffalo compared energy use during clerical tasks while sitting in an office chair, sitting on an exercise ball, or standing up. Subjects burned 4.1 calories more per hour (a 6% boost) when they were either standing or sitting on the exercise ball compared to sitting in the regular office chair. There was no difference between standing up and sitting on the exercise ball. The numbers are consistent with a 2006 study that found a 3.9 calorie per hour (5.6%) boost for exercise balls, with effects that persisted for at least a week.

Presumably, this enhanced calorie gain has the same benefits as standing — that it doesn’t trigger your appetite hormones to make you compensate. On the other hand, some back experts are still cautious about the effects of sitting on exercise balls all day. Stuart McGill of the University of Waterloo, for instance, did a study in 2006 with the following conclusions:

The results of this study suggest that prolonged sitting on a dynamic, unstable seat surface does not significantly affect the magnitudes of muscle activation, spine posture, spine loads or overall spine stability. Sitting on a ball appears to spread out the contact area possibly resulting in uncomfortable soft tissue compression perhaps explaining the reported discomfort.

So, as long as your back doesn’t start bothering you, the exercise ball seems like a reasonable choice. And you don’t have to worry about your productivity, at least according to the University of Buffalo study: in 20 minutes, the men in the study typed 551.8 words on the exercise ball, 535.6 words while standing up, and 519.2 words while sitting in the office chair. (The women were much consistent, at 700.3, 697.8 and 702.5 respectively.)