Race day versus training: why your fuelling needs to change
The same effort at the same pace requires a different fuelling approach on race day.
The way you fuel a training session and the way you fuel a race are not the same. Getting this wrong is one of the most common causes of race-day GI distress, and one of the most preventable.
The physiological difference
Race effort produces a substantially higher sympathetic nervous system response than training. Adrenaline, cortisol, and other stress hormones increase gut motility, reduce gastric emptying speed, and redirect blood away from the digestive system. The same 60g per hour that absorbed comfortably on a long training run may cause cramping at race pace, not because your plan is wrong, but because your gut is operating under different conditions.
Research by Camilleri et al. shows that even pre-race anxiety increases intestinal permeability and alters motility patterns before the start gun fires. The gut is responding to the stress of the event, not just the physical effort of exercise.
What changes on race day
- //Pre-race loading matters more. The window to load carbohydrate into glycogen storage and get caffeine into circulation is narrow. Mistiming it costs you when you most need performance.
- //Intake timing is less flexible. In training you can adjust on the go. On race day, the sympathetic response makes the gut less tolerant of ad-hoc changes.
- //The stakes of GI distress are higher. A bad session in training is just a bad session. A GI crisis at mile 18 has no recovery.
In training: optimise for adaptation
The goal in training is gut adaptation. Higher relative intake during sessions, even at doses beyond your race day plan, trains the intestinal transporters and builds the absorption capacity you need when it counts. Training runs are where you stress-test the protocol, not just execute it.
Race simulation sessions
This is why concept//fuel treats race simulation interval sessions differently from standard interval training. A race simulation effort triggers enough of the sympathetic response to merit race-level fuelling and a full intake schedule. Use these sessions to test your race day protocol, not to discover it for the first time on the start line.
Build your race day routine in training, at race intensity, with the same products you plan to use. Your stomach needs the rehearsal as much as your legs do.
Camilleri et al. (2012) Gut; de Oliveira et al. (2014) J Int Soc Sports Nutr; Peters et al. (2000) Eur J Appl Physiol.
Put it into practice
Apply this to your own training.