Figure 1. The effects of muscle glycogen on endurance capacity. Redrawn from Bergsrom et al., (1967).
Recently, arguably the best sport nutritionist of our generation, Professor Louise Burke (from the Australian Institute of Sport), performed an amazing study to test this hypothesis. In a brilliantly designed study, elite race walkers were given time to adapt to a high fat diet or a high carbohydrate diet and performed a maximum 50 km time trial. Despite achieving really high fat oxidation rates, the results again showed a significant performance advantage of carbohydrate over high fat diets. Given the historical data, combined with such well-designed and performed recent studies, I am more convinced than ever that if we want to maximise high-intensity performance we must start the event loaded with carbohydrates.
It would be wrong of me not to point out that in 2017 we are becoming increasingly aware of the performance benefits of performing some training sessions in a low carbohydrate state to promote adaptions to training. This style of eating is also seen as a good way for athletes to maintain muscle mass whilst dropping body fat (reducing carbohydrates allows protein to be consumed regularly to maintain muscle whilst still creating a calorie deficit) as recently demonstrated in some of our jockey research. Our recent work in Rugby has shown that some rugby players who eat a low carbohydrate diet in the 24 hours prior to a game, commence the match with lower muscle glycogen and end the game with glycogen levels that could affect performance. It is therefore more crucial than ever that athletes know how to load the day before performance to make sure they arrive at the start line loaded and ready to go. But how do we do this?
The original studies looking at carbohydrate loading described a method by which athletes performed a hard training session approximately 1-week prior to competition to initially deplete muscle glycogen. Training was then gradually tapered over the week with carbohydrate increasing daily up to about 10g of carbohydrate per kg of body weight. Whilst this strategy may well lead to the maximum carbohydrate stores, it is often not practical in sport given that on many occasions we do not have a full week to taper for performance. Fortunately, it has been shown that muscle glycogen concentrations can increase from 95 mmol/kg to 180 mmol/kg in as little as 24 hours providing that approximately 8g of carbohydrate per kg body mass are consumed and that some of this is in the form of high glycemic index carbohydrates . This is great news as this allows us to eat some of the foods that we may have been restricting during the week.
In reality, I often use between 6-8 g per kg body weight 24 hours pre-game to load my athletes, especially if they are not used to high carbohydrate diets. A typical diet giving these levels of carbohydrate may look a little like this:
Breakfast: Poached eggs on toast, with beans and a fruit smoothie (plus an extra banana)
Mid morning snack: Mint protein get buzzing bar
Lunch: Chicken with large portion of white rice, garlic bread. Fruit and Yoghurt. Large glass of fresh apple juice
Mid Afternoon Snack: Cherry protein get buzzing bar and smoothie.
Dinner: Cod with potato wedges (2 potatoes), mixed seasonal vegetables
Evening Snack: Greek Yoghurt with Muesli, pint of milk
So why not try it? The next time you have a big performance, see if this can be improved by a one day carbohydrate load. You may just find you achieve your personal equivalent of the sub 2 hour marathon. Good luck with your training and competition.
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