Carbohydrates Around Training
Introduction
This is where supplement marketing has invested most: intra-workout drinks, post-workout loading, replenishment windows. It's also where the answer changes most depending on who's asking.
For most people training once a day, the answer is disappointing. For a few specific cases, it matters a great deal.
Carbohydrate timing matters when recovery time is short. If you have twenty-four hours, it barely matters.
What carbohydrates do
They're the fuel for intense work. They're stored as glycogen in muscle and liver, and that reserve is what sustains high-intensity efforts.
Two consequences that organize everything else:
At low intensity, they matter little. Walking, easy jogging or comfortable cycling run well on fat as the main fuel.
At high intensity, they matter a lot. Heavy sets, intervals, team sports: there glycogen is limiting and there's no substitute.
How much per day
It depends on how much you train, and the working ranges are:
- Light activity: 3 to 5 g per kilo of body weight.
- Moderate training, an hour daily: 5 to 7 g/kg.
- High-volume endurance: 6 to 10 g/kg.
For an 80 kg person training strength four times a week, that's about 400 to 560 grams daily — considerably more than someone trying to "eat carefully" usually consumes.
Does timing matter?
Here's the question that interests people, and the honest answer is: for most, little.
If you train once a day, eat enough carbohydrate in total and have twenty-four hours until your next session, your stores refill without you doing anything special. Distribution within the day is a minor optimization.
Timing does matter in three specific situations:
1. Two sessions less than eight hours apart. There rapid replenishment is real and useful: carbohydrate immediately after the first session, in quantity.
2. Long endurance sessions. Beyond 60-90 minutes, taking carbohydrate during the effort consistently improves performance: 30 to 60 grams per hour. Beyond 2.5 hours you can reach 90 g/h by combining different sugar types, which are absorbed through different pathways.
3. Training fasted or far from your last meal. If you've gone many hours without eating, having some carbohydrate beforehand improves the quality of an intense session.
Outside those cases, the meals you already eat before and after do the job.
Before training
What matters more than composition is digestive tolerance. Practical rules:
- Three or four hours before: a normal meal, with carbohydrate, protein and some fat.
- One or two hours before: something lighter and low in fibre and fat.
- Less than an hour before: only if it suits you; something small and easy to digest.
And most importantly: don't try anything new before an important session or a race.
After training
The famous replenishment window exists and is far wider than it was sold. If you're training again within a few hours, eating carbohydrate soon speeds glycogen replenishment. If your next session is tomorrow, eating within the following hours is perfectly sufficient.
Put differently: if you aren't an athlete doing double sessions, the meal you were going to have anyway does the job.
Low-carbohydrate diets and training
This deserves an honest paragraph because it generates plenty of debate.
For low-intensity work and general health, low-carbohydrate diets work well, and for many people they're sustainable and enjoyable.
For high-intensity work, the evidence is less favourable: studies on very low-carbohydrate diets in athletes show impairment in intense efforts, and Burke and colleagues' work additionally found worse movement economy in elite race walkers after adapting to a very low-carbohydrate diet, despite improved fat oxidation.
The practical conclusion: if you train heavy strength or do intervals, restricting carbohydrate heavily will cost you performance.
Common mistakes
Optimizing timing before total. The inverted order, as with protein.
Taking sports drinks in one-hour sessions. Unnecessary, and calories you probably didn't want.
Habitually training heavy on low stores. It lowers performance and, over time, results.
Confusing low-carb with good for everything. It depends entirely on what kind of training you do.
Eating lots of fibre or fat right before. The most frequent cause of digestive trouble mid-session.
Conclusion
For someone training once a day, the daily total of carbohydrate governs, not the clock. Timing gains importance with two close sessions, in efforts beyond an hour, and when you train far from your last meal.
Check one thing this week: if your intense sessions feel flat, calculate how many grams of carbohydrate you eat daily and compare against the 5 to 7 per kilo range. It's quite common for the performance problem blamed on the program to be, simply, training on a half-empty tank.
References
- Burke, L. M., Hawley, J. A., Wong, S. H. S., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(S1).
- Burke, L. M., et al. (2017). Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of Physiology, 595(9).
- Jeukendrup, A. E. (2014). A step towards personalized sports nutrition: Carbohydrate intake during exercise. Sports Medicine, 44(S1).
- Kerksick, C. M., et al. (2017). ISSN position stand: Nutrient timing. Journal of the International Society of Sports Nutrition, 14.
- Areta, J. L., et al. (2013). Timing and distribution of protein ingestion during prolonged recovery from resistance exercise. The Journal of Physiology, 591(9).