Nutrient Timing: Updated Science for Cyclists, Triathletes, and Runners

By Chris Carmichael,
Founder and Head Coach of CTS

The timing of when and what you eat can have a big impact on cycling performance in training and competition, but there is a constant push-and-pull between keeping it simple and getting lost in the minutia. The more we know, the more we think we can manipulate, but we also have to be careful to step back and consider what we should do rather than just what we can do.

Depending on how long you’ve been a cyclist, triathlete, or runner, you have probably been exposed to the concept of nutrient timing in some shape or form. I first wrote about nutrient timing and periodized nutrition back in the early 2000s in “The Ultimate Ride” and “Chris Carmichael’s Food for Fitness”. In the nearly 20 years since, you’ve likely seen guidance about the timing of pre-workout and pre-race meals, or how much carbohydrate to consume during a workout, or how soon after training you should have a meal. All of those things have value, but they can each be their own rabbit hole, too.

Recommendations also change over time, as the science of performance nutrition evolves.  A recent review in the journal Nutrients by Shawn Arnt, Chair of the Department of Exercise Science at the University of South Carolina, and his colleagues, does a very good job of summarizing the current understanding of effective and practical performance nutrition strategies.

Glycogen ‘window’ vs. ‘garage door’

One of the key distinctions that Arnt’s team makes in the paper is that the classic ‘glycogen window’ or anabolic window would be better thought of as a ‘garage door’. If you’re unfamiliar with the concept entirely, this is the idea that the body is primed to rapidly replenish carbohydrate stores and maximize muscle protein synthesis immediately after exercise. It formed the basis of post-workout feeding strategies that focus on a high-carbohydrate, moderate-protein meal within 45-60 minutes after training or competition.

Nutrition science still supports the practice of consuming carbohydrate very soon after exercise, on the order of 1-1.5 grams of carbohydrate per kilogram of body weight per hour (g/kg/hr) beginning in the first 2 hours post-exercise and continuing through 4-6 hours post-exercise. However, it is also true that glycogen replenishment and muscle protein synthesis continue past this time period, and that in many cases glycogen stores will be completely replenished within 24 hours anyway, which has led some people to swing all the way to the viewpoint that the timing of nutrient intake after exercise doesn’t matter at all.

Arnt shares a perspective I think is particularly valuable for endurance athletes, and even more so for masters athletes and “super vets” (athletes older than 65 years). Rather than think of the small ‘glycogen window’ as meaningless, it should be thought of as a bonus. Yes, as long as your total daily energy intake is adequate to meet your expenditure needs (from exercise and activities of daily living), it’s likely that your carbohydrate stores will be fully replenished between the end of today’s ride and the start of a ride 24-48 hours from now. But there’s also no downside to eating within 45-60 minutes post-exercise, and there may be benefits beyond glycogen replenishment, so take advantage of the opportunity.

From a practical standpoint, based on the science and what real athletes will actually do day-to-day, here are some realistic guidelines and advice (albeit not an exhaustive list) for nutrient timing:

• Ensure total daily energy intake is adequate: This has to be the top priority. Total energy comes first, timing – and even composition – come after that.
• Eat between 1-4 hours before training: Even if you want to train with low carbohydrate availability, that’s not the same thing as low energy availability. Eating before training can also reduce muscle protein breakdown in the post-exercise period.
• Pre-exercise carbohydrate feeding will be increasingly beneficial when athletes have had limited recovery time after glycogen-depleting, high-intensity training or competitions. For masters athletes and “super vets”, ‘limited recovery time’ could extend to 24-48 hours or more.
• Consume 30-60 grams of carbohydrate per hour during rides longer than 75 minutes, up to 90 g/hr with mixed carbohydrate sources and adequate training of the gut.
• Following partially or completely glycogen-depleting exercise (>60 minutes high intensity, 2hrs+ moderate intensity), consume 1-1.5g carbohydrate per kg bodyweight within 60 minutes of exercise, along with 20-40 grams of protein. Athletes over 50, and particularly “super vets”, should aim closer to the 40g end of that protein range.
• The urgency, or potential benefit, of immediate post-exercise feeding of carbohydrate and protein is heightened after glycogen-depleting exercise bouts and when there is limited time between exercise bouts (‘limited time’ can be highly variable between individuals), but does not go to zero when the time between workouts is greater than 24 hours.
• Consume protein, in 20- to 40-gram doses, throughout the day, to achieve 1.6-2.0 grams/kg/day. This should include pre-sleep feeding in the evening, as recovery and muscle protein synthesis continues through the night.

References:

Arent SM, Cintineo HP, McFadden BA, Chandler AJ, Arent MA. Nutrient Timing: A Garage Door of Opportunity? Nutrients. 2020; 12(7):1948. https://doi.org/10.3390/nu12071948