Endurance athletes can improve their performance by occasionally training at low intensity with low glycogen stores. Called fasting morning workout or train low. This leads to an improved aerobic capacity and fat burning. Also in strength training and a combination of both workouts training low is performance enhancing.
A part of the energy available for sports performance comes from the stock of carbohydrates which is located in the muscles, in the form of glycogen. Depleted glycogen stores, therefore, has a negative effect on the sports performance. Prior to a race or heavy training, it is important to provide the body with enough glycogen. Regular use of low intensity workouts, for example, 1 time per week, with a depleted glycogen appears to lead to certain positive adaptations in the muscle. Recent studies have shown that endurance athletes will improve their performance. The available knowledge on the effects of training with depleted glycogen stores in endurance and power athletes is summarized here.
EFFECTS OF A SHORTAGE OF GLYCOGEN
When glycogen stores are low the body must switch to other energy stocks. The training with low-carbohydrate stocks leads to an increased oxidation of fat in the muscle during exercise. “Train Low” also ensures the production of new mitochondria. Mitochondria play an important role in the supply of energy with the aid of oxygen and are therefore of interest in aerobic sports performance. Recent studies show that performing a strength training just hours after a low intensity endurance training may enhance the desired effects of the endurance training
Whether power athletes also could improve their performance thanks to “train low” is not known. A shortage of glycogen in the muscles possibly comes together with a negative protein balance. Train low may inhibit therefore building up muscle tissue. In practice, athletes who applied “train low” and eat sufficient proteins and carbohydrates after training no negative effect was found on muscle growth.
It is likely that athletes would benefit from occasionally training at low intensity and almost depleted glycogen stores. Research shows that both fat burning, the aerobic capacity and performance improving occurs. If power athletes benefit by “training low” is not clear.
EXHAUSTED GLYCOGEN STORES
Research carried out by Jens Bangsbo (University of Copenhagen), shows that the regular training with partially depleted glycogen stores may lead to an increased capacity of the body to absorb and store carbohydrates. Also fat oxidation improves in athletes who train regularly this way. This is useful because even in high-intensity exercise (85% of VO2max) a part of the supplied energy originates from the oxidation of fat. It is important to be careful with heavy workouts as the glycogen is used up in the muscle. Intensive effort at an energy shortage can have negative effect on the immune systems of athletes and can significantly increase the chance of injury.