Cortisol Levels During Exercise

Although it has been somewhat vilified by some diet pill manufacturers, cortisol is a naturally fluctuating hormone that is vital to promoting normal energy levels in the body. Generally speaking, cortisol should rise during training then fall again shortly after. When cortisol fails to respond properly to a training stimulus, the body can have difficulty burning fat or retaining muscle.

Cortisol Definition

• Cortisol is a stress hormone that is produced by the adrenal glands. The adrenals are two tiny glands that sit atop your kidneys and are responsible for producing a variety of hormones, such as aldosterone and testosterone in limited amounts. Cortisol production fluctuates based on the time of day; in a typical individual, cortisol levels are highest in the morning and taper off by evening.

Cortisol's Purpose

• Cortisol is a energy-mobilizing hormone that is released under two conditions. First, cortisol is naturally released according to the daily cyclical pattern outlined above. Second, cortisol is produced in response to stressful situations where the body believes that it will require a sufficient reserve of energy to survive. This can occur during situations involving physiological or psychological stress, such as during exercise or when preparing for a big meeting.

Cortisol and Exercise

• During training, cortisol is released to break down existing tissue for energy. Cortisol production signals the process of catabolism, which is a negative energy balance whereby muscle tissue is being broken down faster than it is being created. Upon cessation of the training stimulus, cortisol should fall back to its original baseline level, appropriate to the time of day. Where it fails to do so, problems can arise.

Excessively Elevated Cortisol

• Where cortisol remains elevated despite the cessation of exercise or a stressful event, the body will continue to break down muscle tissue needlessly, essentially filling the bloodstream with energy that will never be used. When the body realizes its mistake, that "floating" energy is then stored again as fat, which is why cortisol is often mistakenly referred to as a fat-storage hormone. Additionally, if this problem continues for a long period of time, it can lead to adrenal fatigue, a condition whereby the adrenal are no longer able to keep up with the cortisol demands of the body.

Elevated Cortisol Side Effects

• While it is difficult to retain lean mass in the presence of elevated cortisol levels, it becomes even harder upon consideration of the following. Testosterone---the body's primary muscle-building hormone---and cortisol levels are inversely related, as they are both made from the same raw materials. Thus, where cortisol is excessively high, testosterone levels will be correspondingly low. This can make it difficult to build new muscle tissue and can also have the unwanted effect of decreasing your sex drive.