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How many carbs do you need to max out your muscle stores?

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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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My column in today’s Globe and Mail takes a look at some recent field research on carbo-loading the day before a marathon:

[…] To find out whether this revised advice works in practice, researchers in Britain followed 257 London Marathon participants for five weeks prior to the race, collecting data about their training and eating patterns. The runners had an average age of 39 and an average finishing time of 4 1/2 hours. The results were published in the International Journal of Sports Medicine.

Sure enough, day-before carbohydrate consumption mattered. Runners who ate more than seven grams of carbohydrate for every kilogram of body weight (g/kg) ran 13.4 per cent faster than a comparable group of runners who ate fewer carbohydrates but were otherwise identical in terms of age, body mass index, training and marathon experience. Surprisingly, the amount of carbohydrate consumed during the marathon didn’t matter as much. [READ THE WHOLE ARTICLE HERE]

Most people don’t realize what an enormous amount of carbohydrate you have to take in to maximize your glycogen stores — which is why only 12% of the runners in the study hit the 7 g/kg threshold. Trish McAlaster did a nice job with an accompanying graphic showing just how much you’d need to eat and drink to hit 5 g/kg (the average in the study), 7 g/kg, or 10 g/kg (which is the amount suggested for elite athletes). Note that I’m not suggesting you should actually eat four plates of plain pasta for dinner — this is just to put the amounts in context!

[CORRECTION: Reader Mike LaChapelle just pointed out that the math doesn’t add up in the graphic. The “threshold” lunch should include 500 ml of sports drink. That being said, I should clarify that I’m not recommending these menus as exactly what you should eat; it’s aimed at giving a sense of the quantities involved. In real life, I’d go for more variety, and include things like fruit and vegetables!]

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The ideal warm-up for swimmers

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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What type of warm-up optimizes swim performance? A new study from the University of Alabama, just posted in the Journal of Strength and Conditioning Research, ran a simple test with 16 NCAA swimmers. Each of them performed three 50-yard sprints, on separate days, with three different warm-ups:

  1. No warm-up.
  2. A short warm-up consisting of 50 yards of 40% of max effort followed by 50 yards at 90% of max effort.
  3. The swimmer’s individual usual warm-up, which averaged a total of about 1,300 metres for the group.

The results:

Mean 50-yd time was significantly faster (p = 0.01) following regular WU (24.95 ± 1.53 sec) when compared to short WU (25.26 ± 1.61 sec).

But take a look at the individual results for the three conditions:

The researchers raise a very, very important point that is often neglected in sports studies:

It is important to note that swimmers compete individually and not as a “group mean”. Therefore, for swimming, it is important competitively to determine how each individual swimmer responds to different warm-ups.

So yes, the “normal” warm-up was indeed best on average. But 19% of the swimmers actually had their best time after the short warm-up, and 37% had their best time after no warm-up at all, compared to a relatively modest 44% — less than half! — who performed best after the regular warm-up.

Now, let’s not get carried away with this result. This was a small study, and the swimmers only did one 50-yard swim under each condition. It’s unlikely that no warm-up at all is really optimal. But it’s certainly worth investigating whether a shorter warm-up might do just as well, particularly for swimmers competing in multiple rounds of multiple events over a short period of time. And more generally, athletes and coaches should be open to the idea that different athletes respond differently to routines like warm-up. Maybe there’s an athlete in your group who would do better with an unorthodox warm-up. It’s worth doing some experimentation.

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Exercise only preserves the muscles you actually use

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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It was great to see the big response to the MRI pics I posted a couple of days ago showing the well-preserved leg muscles of a 70-year-old triathlete. Very striking stuff. But let me now offer the following caveat:

This is a figure from a new study from the University of Western Ontario, just posted at Medicine & Science in Sports & Exercise. They analyzed the biceps brachii (arm muscles) of nine young runners (average age 27), nine old non-runners (70), and nine lifelong masters runners (67). They measured the number of functional motor units (i.e. group of muscle fibres activated by a single motor neuron), which typically declines with age. As you can see, the two old groups were pretty much the same, far below the young group.

In contrast, the same researchers studied leg muscles (tibialis anterior) in a similar group of volunteers last year (as I blogged about here) — in that case, the older runners did preserve the number of motor units. What this tells us is that exercise, on its own, doesn’t preserve all the muscles in your body: in the words of the researchers, there’s no “whole body neuroprotective effect,” or at least none that shows up in this relatively small study. It just preserves the muscles you’re using on a regular basis. So that’s still good news for triathletes, but maybe not as good for runners and cyclists!

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The neurochemical reality of placebos

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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The New Yorker had a great look at the placebo effect last month (unfortunately the full text isn’t available online), focusing on the work of Harvard’s Ted Kaptchuk. He’s the guy who did the study last year that found that placebos can be effective even when patients are aware that they’re receiving a placebo instead of “real medicine.” His hope is that doctors will learn to harness the placebo effect more effectively, and understand that it’s a real physical effect, not just in your head.

To that end, one of the most interesting nuggets in the article was a description of one of the classic placebo studies, from UCSF back in 1978. People recovering from dental surgery were given either morphine or a saline placebo; as expected, some patients responded to the placebo (their pain diminished) while others didn’t (their pain got worse).

What happened next, however, fundamentally reshaped the field. The researchers dismissed the subjects who had received morphine and then divided the remaining participants into those who responded to the placebo and those who didn’t. Then they introduced Naloxone into patients’ I.V. drips. Naloxone was developed to counteract overdoses of heroin and morphine. It works essentially by latching onto, and thus locking up, key opioid receptors in the central nervous system. The endorphins that we secrete attach themselves to the same receptors in the same way, so Naloxone blocks them, too. The researchers theorized that, if endorphins had caused the placebo effect, Naloxone would negate their impact, and it did. The Naloxone caused those who responded positively to the placebos to experience a sharp increase in pain; the drug had no effect on the people who did not respond to the placebo. The study was the first to provide solid evidence that the chemistry behind the placebo effect could be understood — and altered.

In other words, placebo responders were dulling their pain via exactly the same route as morphine recipients. It was a “real” effect. In the realm of sports science, that’s something to bear in mind when we read yet another report showing that some supposedly performance-enhancing substance doesn’t outperform placebos in a controlled trial.

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Dathan Ritzenhein after his fourth place Trials marathon

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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At the U.S. Olympic Marathon Trials, where the top three book tickets to London, fourth is the loneliest place. Here’s my post-race interview with an emotional Dathan Ritzenhein:

He ran a new personal best of 2:09:55, breaking 2:10 for the first time and capping a remarkable comeback from a seemingly never-ending string of injuries. But silver linings don’t matter when you finish fourth at the Olympic Trials – and for Dathan Ritzenhein, the frustration of being hobbled yet again by leg cramps could mark the end of his marathon career.

“It’s the same thing that’s happened in other marathons,” Ritzenhein said after the race, struggling to contain his emotions. “Maybe I’m forcing it. Everybody wants me to be a marathoner. And I want to be a marathoner. But right now maybe it’s not in the cards.” […]

Read the whole interview here.