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4 surprising new insights into fuels for endurance sports

4 surprising new insights into fuels for endurance sports

4 surprising new insights into fuels for endurance sports

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In sports science, there is sometimes a disconnect between those who conduct research in laboratories and those who work directly with the field’s elite athletes—”on the face of coal,” as sports nutritionist Louise Burke puts it. Both groups have valuable perspectives, but I find that the best advice comes from those who have managed to bridge both sides of the divide.

In this regard, I attended a presentation by Jennifer Sigo at a recent conference in Toronto. Sygo currently works as a nutritionist for the Canadian track and field and gymnastics teams, as well as the Toronto Raptors basketball team. On the side, she is working towards her PhD at Manchester Metropolitan University, based on her work with gymnasts. Her talk focused on sports nutrition for endurance athletes, and included some ideas and perspectives I had not encountered before. Here are some of the highlights that stuck in my mind:

Ask for carbs

I’ll start with the less surprising message from Sygo’s talk: Endurance athletes need carbohydrates, and lots of them. I’ve covered the research indicating that low-carb diets do not improve performance in Olympic-distance endurance events like the marathon, while recognizing that ultramarathoners may choose to make different trade-offs. She noted that elite marathon runners get about 85 percent of their calories from carbohydrates, with most coming from glycogen stored in the muscles and the remainder from glucose in the bloodstream.

To keep your carb tanks stocked full, I shared some specific carbohydrate intake goals that I use with elite runners for various distances:

  • The day before a 10k, fill your muscles with glycogen by aiming for 7 to 12 grams of carbohydrates per kilogram of body weight (g/kg). On race day, take 1 to 4 g/kg between one and four hours before the race. If you weigh 155 pounds, that’s between 70 and 280 grams of carbohydrates—a pretty wide range that reflects individual variation in how well people handle a meal before a workout. For reference, a breakfast of 1/2 cup of oats, 1 cup of berries, and 1 cup of fruit juice gives you 100 grams of carbohydrates.
  • For a half marathon, take a similar approach, and then—one I haven’t considered—top up your carb stores with a gel or sports drink. After, after your warm up. She also suggested considering eating some carbs during the race, or at least rinsing and spitting out some sports drinks to get brain benefits. I don’t usually think about intra-race nutrition for this short race, but then again Jeffrey Kamworour drank sports drinks at the aid stations when he broke the half-marathon world record a few years ago.
  • For a marathon, increase your pre-race loading to 10 to 12 g/kg 36 hours before the race. That’s a huge amount, which you’ll probably achieve just by drinking some juice or a sports drink on top of carbohydrate-rich meals. Power it up in the morning, and again after your warm-up, then aim for between 30 and 90 grams of carbs per hour during the race. (I will add that some professional cyclists – and scientists – are now pushing closer to 120g/hr, but I’m not sure how well that translates to running.)

No need to develop on vegetables

Yes, this letter surprised me — but read on to see what it means. One of the big trends in sports nutrition over the past decade has been the idea that rather than just eating the same things every day, you should adjust your intake to match your expenditure. Sygo showed slides from the Athlete’s Plate, a concept developed at the University of Colorado Colorado Springs in conjunction with the United States Olympic Committee that provides visual guidelines for how to eat during light, medium and heavy training periods. You can see the three panels here.

On the easy training plate, vegetables and fruits take up half of the plate. On a hard training board, vegetables only take up a quarter of the board (even though the fruit has been moved off the board, since there’s no room for it!). The point is not that vegetables are bad. Quite the opposite: it is necessary. But if you’re training hard, your calorie needs are at a high level, and you can’t rely on vegetables alone, or even mostly vegetables, to get you there. They are simply not calorie-dense enough, and their high fiber content makes them very filling and cumbersome to eat.

A common trap, Sego noted, is the “too much salad”—a frequent sight when health-conscious endurance athletes gather. It feels like you’re overeating, but if you’re not careful it won’t have as many calories as your stomach tells you to. Given the growing understanding of the negative (often unintended) aspects of lack of fuel, it’s worth considering calorie density. Grains and fats are good choices, along with more subtle modifications. For example, the easy training plate includes only fresh fruit; Stewed and dried fruits are added to mild and solid dishes.

Getting rid of dead weight

There’s no exact way to say this: You have one to two pounds of fecal matter in your colon, and getting rid of it before a competition might give you an infinitesimal advantage. One technique that athletes in weight-sensitive sports have long used is a temporary low-residue diet — the “residue” is the undigested fiber, bacteria, and water left over after you’ve digested the good stuff. In practice, this means cutting back on fiber for a few days.

Researchers at Liverpool John Moores University in Britain tested this approach in a study published earlier this year. 19 volunteers reduced their daily 30 grams of fiber to less than 10 for four consecutive days, while maintaining the same total caloric content and macronutrient distribution at each meal. The result: an average weight loss of 1.3 pounds, mostly assumed to be poop. The other outcome: firmer stools and half as often, although 18 of the 19 volunteers said they were willing to repeat the intervention.

There are other reasons you might be interested in following a low-residue diet before a race. A few years ago, professional cyclist Mike Woods told me he went on a low-fiber “five-year-old” diet before races, not to lose weight but to reduce digestive upset. For most of us, losing a pound won’t be worth it. Even for the elites, Segou noted, it is marginal. She broached the subject with a triathlete recently, but she didn’t get far before the athlete cut her short with a version of: I’ll do anything to win, but not that.

Pump up your iron

Sygo is not a complement motivator. She points to four relevant, evidence-backed ergogenic aids for track athletes: beta-alanine, sodium bicarbonate, creatine, and caffeine. Only the last one has been shown to work reliably for long-distance events. (This is consistent with a recent IOC consensus statement, although they also included nitrates on their list.) She also pointed out some key parameters that should be monitored on an ongoing basis: vitamin D, vitamin B12 – and iron.

The risk of low iron is a familiar topic for endurance athletes. I’ve written before about thresholds to watch out for and how to raise your levels. Sygo’s goal is similar or maybe a little higher: She suggests aiming for ferritin levels of at least 30 μg/L in women and 50 μg/L in men. For hemoglobin, she suggests a goal of at least 130 g/L for both men and women. The usual lower limit for hemoglobin in healthy women is slightly lower, but it’s not clear if this is truly optimal, or just reflects the fact that women tend to have lower (and possibly suboptimal) hemoglobin levels primarily because of menstruation.

One particular challenge for athletes is that strenuous exercise produces elevated levels of a hormone called hepcidin, which interferes with iron absorption for up to six hours after training. As a result, Sygo suggests taking the supplement away from training time, ideally on an empty stomach, with Vitamin C to aid absorption. She also pointed to another development: US Army researchers recently showed that, in addition to being triggered by the exercise itself, hepcidin is more activated if you don’t get enough calories to replace what you burn. This is another reason to avoid fuel shortages.

I must stress that I carefully selected the parts of Sygo’s presentation that I found most interesting or unusual. In practice, it is the big picture that matters more than the small details. However, getting the right sports nutrition takes a lot of trial and error, because everyone is different. You’ll need to experiment to see which techniques work best for you, and that definitely means practicing whatever training you want to try in competition. And in the end, it’s the basics that matter most: Eating a healthy, balanced, calorically adequate diet will do more for your performance and health than expending a pound of poop.


For more race science, join me Twitter And Facebook, sign up for our email newsletter, and check out my book Endurance: The mind, body, and limits of human performance are strangely resilient.



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