Numerous researchers have demonstrated that deliberate periods of training in a fasted state (reduced carbohydrate availability) can enhance aerobic adaptations as a result of endurance training. Whilst this has achieved a great deal of attention over recent years, and is an attractive strategy for a range of audiences, there are some very specific details often overlooked.
Whilst it does appear there are additional benefits with restricting carbohydrate intake at scheduled times during a training programme, this has to be carefully scheduled to reap any possible benefits. Carbohydrate intake during endurance exercise does improve performance – this is a well established theory however, increasing the capacity of your muscles to utilize fat as a fuel may also be beneficial.
The train-low, compete-high model suggests that CERTAIN sessions should be undertaken with reduced carbohydrate availability to maximize training adaptations. However, all competition is performed with high carbohydrate availability to maximize performance.
Training low can enhance adaptations within the muscle whereby they become more efficient at utilizing fat as an energy source. As a result, less carbohydrate is used during prolonged moderate steady state work and our muscles retain the capacity to produce high intensity work when needed due to the sparing effect on muscle glycogen stores.
During a race, we typically consume carbohydrate to maximize performance. It is therefore important we are able to still utilize this fuel source and not just rely on fat. Therefore, periods of training should also be undertaken with high carbohydrate availability where in-race strategies are employed. This means your muscles will retain the capacity to utilize both carbohydrate and fat as fuel.
One limitation to training low is the increased perception of effort and the potential for a reduced ability to perform high intensity work. Hormonal changes may also result in increased muscle protein breakdown and impaired immune function. Training low should therefore not be utilized as a long term training strategy.