Train low, compete high

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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One of the most interesting developments in sports nutrition over the last few years is the “train low, compete high” concept — the idea that purposely doing some of your training when your glycogen stores (the main form in which your body stores carbohydrate for exercise) are low can boost your performance when you eventually compete fully loaded. An initial study in 2005 found that subjects doing half their training in the “low” state ended up with higher glycogen levels and longer time-to-exhaustion. But there were some questions about how well those results would translate to real-life — for example, whether trained athletes would experience same effects as the untrained volunteers in that experiment.

A new study [LINK FIXED] from Asker Jeukendrup’s group at the University of Birmingham, just posted online at Medicine & Science in Sports & Exercise, tackles some of these questions, with interesting results. The set-up was two groups of seven cyclists, training six days a week for three weeks. Both groups alternated 90-minute aerobic sessions with intense interval sessions of 8 x 5:00 with 1:00 rest. The control group did the sessions on alternate days, while the “low” group trained just three days a week, starting with the aerobic session to deplete glycogen, then doing the intervals an hour later without refuelling.

As hypothesized, the “low” group learned to burn more fat instead of carbohydrate — a physiological strategy that some experts think might allow your body to last longer before running out of glycogen. On the other hand, there was no difference in time-trial performance at the end of the study. You might think this means that the strategy was ineffective, but there’s an added wrinkle: not surprisingly, the “low” group managed a much feebler effort in their interval sessions (since they were so depleted), but still managed to improve by the same amount on the time trial. This means that the key variable in a training session isn’t how fast you go, but rather what stimulus signal you’re sending to convince your body to adapt.

In this regard [the authors write], we suggest that the additional “stress” of training with low glycogen compensates for a slight reduction in physical performance during training.

There was also a penalty to pay for the increased fat burning: the “low” group didn’t increase their carbohydrate-burning abilities as much as the control group:

This also suggests that training with low muscle glycogen may be counterproductive for athletes who compete in high intensity events where CHO oxidation plays a significant role in performance, and that this type of training may be more suited to preparation for ultra-endurance activities.

For now, it’s a case of “more studies needed” — although there’s no doubt that coaches and athletes are already experimenting with these ideas. It may be that trial and error will sort out some useful approaches before we really understand why they work.

[An unrelated note: I’m heading out on a hiking trip tomorrow morning, so I’m unlikely to be able to update the blog for the coming week. Next weekend, I’ll be watching the Sydney triathlon — the first stop on this year’s world championships series, and the first race on this course since Simon Whitfield’s immortal gold-medal performance in 2000. Can’t wait!]

Canadian Running magazine: Jan.-Feb. issue

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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A belated note that the Jan.-Feb. issue of Canadian Running magazine is on newsstands now. My top picks for this issue: a hilarious back-page essay by Canadian miling legend Harvey Mitro on runners’ obsession with stopping their watches, and an interesting piece by nutrionist Matthew Kadey on which foods it’s worth paying more for, and which you can skimp on. (For example, he argues in favour of dark poultry meat — a policy I’ve long advocated in order to save $1.19 at Swiss Chalet!)

And, of course, there’s my regular Science of Running column, tackling hyponatremia, deep-water pool-running, “dynamic compression” technology, and other topics.

Artificial sweeteners can’t fool your subconscious brain

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Here’s a mystery: Why is obesity still such a problem in the age of the magic zero-calorie sweetener? New Scientist has a great article on the latest brain-scanning research, which offers some hints about how these sweeteners may fool us on a conscious level, but don’t manage to trick our unconscious minds. These new studies suggest that “zero-calorie” options may really just lead to “deferred calories” that make us consume more than a full-sugar version would have.

For many years, there have been hints that people who drank sugar-free sodas ended up gaining more weight than those who didn’t. (Travis Saunders described some of this evidence at Obesity Panacea last year.) Guido Frank at the University of Colorado is one of the researchers whose studies help explain this. He fed drinks containing either sucrose (sugar) or sucralose (artificial sweetener) to subjects, who were unable to tell the difference between the two. However:

Sucrose produced stronger activation in the “reward” areas of the brain that light up in response to pleasurable activities such as eating and drinking. Sucralose didn’t activate these areas as strongly… Frank suggests that sucralose activates brain areas that register pleasant taste, but not strongly enough to cause satiation. “That might drive you to eat something sweet or something calorific later on,” he says.

This is still a developing area of research, but it seems highly likely that there’s no (calorie-)free lunch. You can’t have sweetness without (eventually) paying a caloric cost.

The obvious question, then, is whether you’re better off drinking diet soda or full-sugar soda. I’ll join with Travis Saunders in suggesting that you keep consumption of either to a minimum (though, as with most “bad” foods, it should be fine in moderation). But if I’m choosing between the two, now that I know that the overall caloric hit will be about the same for regular and diet soda, I’d rather drink the real thing.

[Thanks to Selam for the tip!]

The American Dietetic Association’s new position on nutrient supplementation

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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I’ve written a bunch about supplements recently, but bear with me for one more quick post. The American Dietetic Association just released its new position stand on “nutrient supplementation.” (The full text is available here.) A few interesting nuggets in there — for one, they note that supplement sales in the U.S. totalled an astounding $23.7 billion in 2007. About half of Americans take dietary supplements, and in particular about a third take a multivitamin/mineral (MVM). However you slice it, that’s a lot of money.

The basic gist of the position stand is as follows:

It is the position of the American Dietetic Association that the best nutrition-based strategy for promoting optimal health and reducing the risk of
chronic disease is to wisely choose a wide variety of nutrient-rich foods. Additional nutrients from supplements can help some people meet their nutrition needs as specified by science-based nutrition standards such as the Dietary Reference Intakes.

Pretty basic stuff. As you read further, it gets a little more forceful:

Although MVM supplementation can be effective in helping meet recommended levels of some nutrients, evidence has not proven them to be effective
in preventing chronic disease
. A study published in 2009 from the Women’s Health Initiative found no association between MVM supplementation and cancer or cardiovascular disease risk or total mortality in postmenopausal women…

They then do a pretty good job of summing up the evidence for and against various health claims, like vitamin B-12 and cognitive function, vitamin D and bone health and so on. If you’re taking vitamins, it’s worth a look to see what they have to say about the benefits you’re looking for (though it’s a far from comprehensive list).

The bottom line for me (as I ranted in a recent comment) is that supplements offer many people a false sense of security with, in many cases, very little evidence to back them up. Eating enough fruits and vegetables is a real challenge — one that I certainly struggle with, especially at this time of year — but I’m not sure it’s helpful to convince ourselves that coming up short doesn’t matter because we’re taking some pills that will compensate.

Jockology: vitamin C may slow muscle recovery and inhibit fitness gains

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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This week’s Jockology column delves into the highly controversial body of research on antioxidants and exercise:

The question

How do antioxidants affect my workout?

The answer

Sales of orange juice are soaring as people seek flu protection from vitamin C, The Globe and Mail reported last month.

Old habits die hard, and our faith in the power of antioxidants is deeply entrenched. Over the past few years, a vast series of studies involving hundreds of thousands of subjects have failed to find any health benefits from antioxidant supplements.

Now, a handful of studies suggest that popping these pills may even block some of the benefits of exercise, and even slow down post-workout muscle recovery. [read on…]

Not to spoil the ending, but to me this research is yet another reason to focus on meeting nutritional needs by eating good foods (in this case, fruits and vegetables) rather than by swallowing pills.