Practice, practice, practice. I can't tell you how many athletes arrive to a long distance race without confidence in their fueling and hydration plan. A precise balance of carbs, fluids and electrolytes are needed to delay the onset of fatigue by sparing liver glycogen, maintaining blood glucose concentrations and off-setting excessive fluid losses from sweating. You can't 'fake it 'til you make it' when it comes to fueling during a long distance event. It's not uncommon for athletes to underfuel/hydrate in training and then overcomplicate fueling strategies on race day due to fear of running out of energy. Whereas too little of an energy intake (carbs, calories) is detrimental to performance, not having a well-practiced nutrition plan may result in GI issues, or more serious health complications. It seems obvious that if you are going to do something on race day, you should repeatedly do it in training, but far too often is this not the case. Rushed and busy...
3x Author, Board Certified Sports Dietitian, Master of Science in Exercise Physiology, 22 x Ironman finisher, 3x XTRI finisher, 6xIM World Championship finisher, Triathlon Coach, 32-year Vegetarian. Trimarnicoach.com