Читать книгу Eating for Sport - Shelly Meltzer - Страница 22

Lactate or lactic acid is often blamed for the burning feeling associated with fatigue and exhaustion during or just after maximal exercise and has also taken the blame for cramps, stitches, and for post-exercise muscle soreness. This is not the case and it is now widely accepted that the culprits are the production of hydrogen ions and the rise in muscle acidity. Supplements sold on the premise that lactate is a limiting factor in exercise therefore have no value (see p103).

Lactate, in fact, is a very important source of fuel. It is one of the products of glycolysis (the breakdown of glycogen). It is produced and used by the muscles. Its rate of production increases as the exercise intensity increases and as more carbohydrate is used as a fuel. Lactate from the muscle is either taken up by the liver and converted and stored as glycogen (via gluconeogenesis) or the lactate formed in the muscle can be shuttled to adjacent muscle fibres to be used as fuel to sustain exercise. It is thus not a useless byproduct of glycolysis, but is possibly an important metabolic fuel used by the muscles, especially during exercise (see also Manipulating the Fuel Mix p30).

Lactate is not the only factor responsible for fatigue. Studies have shown that fatigued runners can have varying blood lactate levels.