In the last feature we examined some of the overwhelming wealth of scientific data that demonstrates the need to consume sufficient levels of dietary carbohydrate in order to maintain optimal exercise performance. The evidence suggested that 60-75% of daily energy should come from carbohydrates, ensuring that carbs burnt during exercise are replaced daily. However, this is a high amount of carbohydrate to consume from your normal diet. So in order to fulfil these targets, and to enhance performance during exercise, an additional strategy should be considered.
Clearly the nutrition strategy adopted whilst you are exercising will be related to the frequency, intensity, duration, and goals of your exercise. If you are training 15-20 hours per week in order to be competitive during a sport like cycling, the information may be of more value than if you are doing four moderate intensity rides per week, but the underlying issues are still the same. Preparation for training will impact both the quality of the session and speed of recovery. Furthermore, for those individuals who are undertaking prolonged sessions (over 90 minutes) training nutrition will actually increase the likelihood of the session being completed effectively.
In the ideal situation, the importance of training is not related to the intensity or duration of the session, but more importantly the recovery from the session. The faster, you recover, the better you are able to train tomorrow. There is little purpose going out on a hard chaingang today, if you are unable to walk properly for the next three days. Thus, the impact of training nutrition should be considered as it will enhance your recovery from a training session. There will another article on recovery very soon.
In order to ensure both muscle and liver stores of glycogen are full, it is essential to eat prior to exercise. This intake must be well timed, as it may otherwise impair the ability to work. The recommendations are that a normal sized meal should be consumed about four hours prior to training. Ideally this should be a high carb meal, with moderate protein and low fat. If you are training or competing in the morning this will not be possible (unless you eat at 4am), so a high carb meal should be consumed the night prior to exercising.
About two hours prior to exercise a light carbo-hydrate snack should then be consumed. This should consist of either food that is easy to digest, or can be a high carb sports bar or energy drink. Any solid food intake after this time can impair performance.
In the two hours prior to exercise fluid taken in should be predominantly water, or have a low energy level. Then immediately prior to the start of the session a volume of fluid sufficient to fill the stomach comfortably (200-400ml) should be consumed. This can contain carbohydrate in a 5-10% solution (10-40g CHO).
If the exercise session is due to last less than one hour, further intake of fluid and carbohydrate is not essential, but may help offset some of the dehydration and glycogen depletion that will occur, and so would be recommended.
Where you are looking to exercise for more than one hour, small regular feedings of fluid containing carbohydrate are essential (100-150ml of fluid every 10-15 mins). Ideally, you should aim to replace all sweat loss (although this may not actually be practical or physically possible), and the drinks should replace about 0.5 and 1g of carbohydrate per Kg of body mass per hour (remember you actually can burn carbohydrate during aerobic exercise at 5g per minute, and faster during anaerobic exercise).
Care needs to be taken, as it is possible to overload on fluid intake, and especially when exercising in an upright position, where your body weight is not supported. In these sports maximum rates of fluid absorption are 600ml per hour. Whilst you may find it difficult to adopt the strategy of eating before exercise, or you find it uncomfortable to drink during exercise, eating for recovery should not be overlooked.
This Article first appeared in London Sport Magazine London Sport Magazine
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