Nutrition for Endurance During Training vs Race day

by Dr. Alex Harrison | Apr 18, 2021

Nutrition for endurance athletes during training vs race day

First, a crash course in endurance performance nutrition: 

  1. Pre-workout nutrition: Eat a carb rich, mixed meal 2-3 hours before training or racing.  Closer to to the session?  Less fiber and fat.  Farther from the session: more fiber and fat are tolerable. 
  2. Intra-workout carbs. 60-140 grams per hour is probably optimal for sessions/events >2 hrs.  Roughly half, per hour for shorter events.  Use between a 2:1 and 1:1 glucose:fructose ratio for best gut tolerance.
  3. Intra-workout sodium.  Target 300-1500mg per hour.  More sweat = more sodium need.
  4. Intra-workout hydration.  Target 500-1200mL per hour.  More sweat = more fluid need.  It doesn’t take much sweating to merit targeting the maximum fluid intake rate.

So that’s what to do to perform your best.  In training.  And in racing.  The end.  Wrong.  

Should training day nutrition really look like race day nutrition??

The most common pitfall among endurance athletes is NOT trying something new that might not work with their gut on race day.  Why?  

If you spend any time in groups of newer endurance athletes you’ll have heard a more experienced competitor repeat the wise adage “don’t do anything new on race day.”  

It’s great advice.  Heed it.  Most already do.  Most don’t do the basics right in the first place and it just bites them more on race day than in their shorter, less intense, training.

But let’s assume you’ve heard that before.

Let’s spend some time looking at the nuances of how and when to practice race nutrition strategy in training, or when there might be reasons for your training fueling to look very different from racing

First, here the most commonly cited reasons that training nutrition looks different than in racing:

  • Race >3 hours long, but all training is <2 hours, so “I don’t need to fuel.”

You’re right. You don’t NEED it. Here are some reasons that might be a poor rationale:

  1. You’ll perform better, fueled. Carb intake in training enhances performance if duration is >90 minutes, and for mortals, even as short as 45 minutes.
  2. You can improve adaptations to training with more intra-workout fueling. Your ability to burn carbs, the rate-limiting fuel for endurance activity, is linked to your glycogen storage and intra-workout fueling. More carbs now = more ability to burn carbs next time.
  3. When you decide to call on your carb-burning ability and your gut’s ability to tolerate high carb intake on race day, you’ll be better able to make use of higher carb intake if you’ve been regularly practicing it. Your gut and muscles adapt positively to it.
  • “My race is not for a while. “
  1. You should rehearse race-day nutrition on your hardest or longest workouts. These only come 1-2 days/week and it often takes dozens of trials to dial in fueling strategy.
  2. If seasons are changing, beverage needs may change, so it’s key to have the basics down pat, before heading into a season change, where beverage concentration and electrolyte content will need to be tweaked.
  3. Race-prep season is when you want to focus on nailing your training and maximizing recovery and adaptation, not fighting with fueling that gives you a rumbly tummy!
  • You’re not that serious, that fit, or that fast!

Wrong! >98% of you reading this article, are capable of burning 300-400kcal per hour in endurance activity. The less fit you are, the more carbs you’ll burn as a percentage of your kcal expenditure. Replace them! Most of us will fall well short of being able to consume what we expend because gut tolerances are lower than our ability to expend energy.

  • Fear of weight gain.

In my experience as a diet coach to >500 endurance athletes over the past several years, those who fuel their workouts most optimally, tend to lose weight the easiest. Those who don’t fuel well tend to suffer from binges that derail weight loss goals or cause unintentional weight gain.

  • Fear of sugar.

Sugar is used a LOT differently during training than during rest. There are no insulin or inflammation concerns with high intra-workout carb consumption. Muscle sensitivity to carbs is increased 100-fold during and immediately after endurance exercise. Elevated blood sugar during training is the goal!

Here are some better reasons that your training nutrition might look different from your race day: 

  1. Time in short supply.  Time taken to prep would take away from time spent training, sleeping, working, or time spent with loved ones, and is outweighed by those losses.  This only applies if training less than ~5 hr/wk.  If training >5 hr/wk, take a few minutes from training time to fuel.

  2. Your race is <90 minutes.  If this is the case, then you should probably be consuming more intra-carbs on training days than in racing because of the slight tradeoffs in performance coming from the  effort of carrying and consuming anything while racing.  You’ll probably have a few sessions >90 minutes in training, where higher-than-race carb intake rates are optimal.

  3. Your event lasts >8 hours and you never get to train longer than 4-5 hours.  If this is the case, there may come a point in your race where you are forced to consume slightly more dilute solutions of carbs and sodium for your gut to tolerate the consumption while you’re in an inevitably dehydrated state.  The goal should be to maintain hydration as long as possible in both training and racing, but it’s often possible to target higher carb consumption rates in training sessions lasting 3-5 hours, compared to 8+ hour events.  There is no sense in making training sessions suboptimal simply to practice the consumption of more dilute fluids.

  4. You are forced into training before work, but you’ll race after breakfast.  In this case, your pre-workout meal may consist of just a few swigs of your intra-workout beverage right before you hop into the workout, whereas on race day, it may make sense to have a solid meal before racing, if the race starts later in the morning.  If that is the case, it will behoove you to move mountains in your schedule to get at least a few days of training in while trialing the pre-race meal before some of your longest or hardest training sessions.

  5. Weight loss is a primary goal, and satiety is an issue.  In some cases, limiting intra-workout carb fueling to the minimums listed in the Table of Intra-workout Carb Needs Per Hour of Training shown at the beginning of the article, or even slightly below, during the easiest and/or shortest of endurance training sessions, can be a reasonable strategy for increasing food volume and improving satiety during fat loss diet phases.  Use this approach as a last resort and monitor closely for hypoglycemia symptoms.

Race like you train, but first, train like you want to race.  Perfect practice makes perfect.  And when perfection falls apart, you’ll have had loads of similar training experiences to draw upon, come race day.