Most endurance athletes are familiar with cortisol, a catabolic hormone. In other words, it breaks down muscle tissue. Cortisol has a pretty bad image, especially among the endurance athletes. Yet it plays a vital role in helping athletes perform.
Cortisol is all about energy. Meeting the body’s demand for energy is the number 1 focus of the cell’s metabolic machine. Cortisol is particularly important and sometimes your muscle’s requirement for energy exceed your cell’s capacity to create it. Under normal metabolic conditions, your muscles use a combination of glycogen, which is stored in the muscle. When glycogen stores begin to be depleted during extended endurance exercise, your body begins metabolizing fat stores and then begins to break down muscle protein and convert it to energy. Think of cortisol as a controller of energy needs. During extended exercise, cortisol levels are elevated. Elevated cortisol activates the breakdown of fat and protein into energy. So the primary function of cortisol is to marshal energy sources wherever they are so that working muscles can operate at peak capacity. This is the good part about cortisol.
The bad part about cortisol: it does not operate as an on/off switch. When you stop exercising, cortisol levels remain high. Thus, breakdown of muscle protein continues, which has negative consequences on recovery. The greater the muscle protein breakdown, the greater the soreness and the longer the recovery. That’s why consumption of a recovery drink is so important. A recovery drink containing carbohydrate and protein not only facilitates the replenishment of muscle glycogen, and turns on the cellular pathways which rebuild and repair muscle protein, but also modulates or reduces cortisol levels.
The ugly part of cortisol has to do with its impact on the immune system and on appetite. High cortisol levels have a negative effect on immune response. Many endurance athletes are familiar with the overtraining syndrome. When athletes train very hard at high volume on consecutive days, they become more susceptible to colds. So this is the good, bad, and ugly about cortisol. The best part is you can modulate the bad and ugly parts of cortisol. With the right recovery nutrition and by being careful to listen to your body and not overtrain.