During Event Nutrition Strategies
A number of research studies have conclusively shown that eating or drinking carbohydrate during exercise longer than 60 minutes in duration will improve performance. In athletes that train in the morning after not eating overnight and depleting their liver carbohydrate stores (this provides the energy needed by your body overnight), such a practice is strongly recommended. The longer the event, the more important eating or drinking carbohydrate becomes to maintain the blood glucose levels and improve performance. For athletes who have not carbohydrate loaded, consumed a pre-exercise meal or are dieting to lose fat weight, taking in carbohydrates during exercise is even more important.
Research has also shown that the maximum rate at which carbohydrate can be used as a fuel is 60 grams of carbohydrate per hour of exercise (approximately 0.7 gm carbohydrate/kg body weight/hour). This is the reason why sports drinks that contain 6 grams of carbohydrate per 100 ml (what we call 6%) are suggested consumed at 250 ml every 15 minutes or one litre per hour – this delivers 60 grams of carbohydrate. Taking any more carbohydrate in has been shown to lead to gut upsets and slow fluid uptake in the gut, not a good thing when fluids might be crucial.
If carbohydrate is the priority during an event, then a high GI food or drink with high GI food makes sense. If not, then sports bars, gels or fluids that deliver the optimal amount of carbohydrate (30-60grams/hourr) are suggested. The higher the exercise intensity, the greater the carbohydrate intake need. The form of carbohydrate does not appear to be important so sucrose, glucose, maltodextrins, are suggested but research suggests avoid fructose (and thus fruits) during exercise as this sugar has been linked to gut upsets and slower glucose release.
Thus, in summary, the following guidelines are suggested for during exercise nutrition:
- Start shortly after starting exercise (15-20 minutes)
- Focus on glucose with a mixture of other sugars
- Sports drink or gels with water (to get 4-8 grams with 100 ml water) are optimal
- The higher the intensity, the greater the amount of carbohydrate needed
- Maintain fluids at 150-350 ml/hour depending on fluid losses.