How does exercising affect your hormones?

Monica,

There have been volumes and volumes of books written on this topic. I think if you want an answer of a better quality, you should specify what hormones you're interested in.

Personal trainers are required to have a limited and basic understanding of the relationship between certain hormones and exercise. I'll share my knowledge with you. I'm going to pull out my Essentials to Exercise Science book and my ACE personal trainer manual for a reference, so a lot of what you'll be reading will be some version of what an ACE certified personal trainer should know concerning the relationship between exercise and hormones.

Understand that hormones are released into your bloodstream, and are not released locally. Hormones will only act at specific sites (receptors) within your body an on specific tissues (we'll deal with this at the cellular level for now), although there are some hormones that will act at a number of sites and on a number of tissues. All you really need to know is that hormones are very specific in what they do.

Once a hormone has binded to a receptor at a cell, it can send messages to the cell and tell it, and effectively the body as a whole, to perform a specific function. Think of the hormones as managers who are telling an employee what to do. Hormones are limited in what they can tell the body to do, however. One or possibly a few bodily functions or adaptations to exercise can be regulated by a specific hormone.

In other words, a hormone is very specific in what it can do *I'm driving this point home because there are A LOT of different physical adaptations that your body must go through when exercising*. An exception might be Growth Hormone, but I'll get to that later. For now, let's address epinephrine and norepinephrine, vasopressin, testosterone, and then we'll finish off with growth hormone.

Have you ever wondered why your heart rate increases and slows down?

Epinephrine and Norepinephrine are responsible for regulating cardiac output.

During exercise, your brain will release epinephrine and norepinephrine because it has been told that the body needs to adjust to the new demands that must be met. This means that heart rate needs to increase so that your body can support itself and work as efficiently as possible. I could go into more about this, but to understand it, this should be sufficient. Epinephrine (aka adrenaline) causes constriction of the blood vessels. This is why it's good for people who experience anaphylaxis after a bee sting. People who are alergic to bees may swell in the throat, then the swelling blocks the airway. Think of the blood vessels here as dilated and wide open, which is not always a good thing. Administering epinephrine to person going into anaphylaxis will reduce the swelling so the person can breathe.

When your heart rate increases, it's safe to say that epinephrine was more than likely the culprit in conjunction with Norepinephrine.

Norepinephrine is responsible for keeping your blood vessels under tension. This is the cause of the increase in blood pressure that is experienced during exercise, along with the constricting effect that epinephrine has on blood vessels. These effects make the heart work harder, which is a good thing. The amount of these hormones secreted is dependent upon the level of activity. The amount of hormones has a direct effect on how fast your heart will beat. Your body needs time to adjust to this change, however. It takes your body 3 to 4 minutes on average to adjust the new oxygen demands when you're exercising. Many people don't understand this, and as a consequence, they give up on things like running before they've had a chance to adapt to the new demands. It also works the other way around, you need 3 to 4 minutes on average to adjust to the new oxygen demands when you're stopping aerobic exercise, like running. People who stop abruptly after intense aerobic exercise can find themselves light-headed and they may even black out due to excess oxygen. Always do a proper warm up and cool down to ease your body into these changes when doing aerobic exercise.

The two hormones epinephrine and norepinephrine are also responsible for breaking down glycogen from the liver into glucose in the blood stream. More glucose is needed during bouts of physical activity.

Vasopressin is released by the brain in order to reduce urinary excretion of water. This is to counteract the excretion of water by sweat when you exercise. (so you don't dehydrate) Vasopressin also plays an important part in keeping your blood plasma levels in a certain range, so if you're too hydrated, vasopressin will cause an increase in urine production so that your body can bring the plasma level in your blood to a specific range that is ideal for exercise. This matters because the level of plasma in your blood has an effect on your ability to maintain a proper electrolyte balance during exercise (so you don't cramp or experience other things that happen when you lose too many electrolytes, which we won't get into right now).

Aldosterone is released by the adrenal cortex (it's an area with some hormones that sits atop your kidneys, this isn't really important). Aldosterone helps your body to limit sodium excretion. It's important for your body to conserve sodium so that it can maintain a good electrolyte balance. Sodium is not the cause here, just to be clear. There is a web of things when you're looking at this. Think of it like this... if your body gets rid of sodium, it may need it later depending on how long you exercise. There are many functions that require sodium in the body, and we won't go into it right now because we'd be here all day.

Cortisol is also secreted from the adrenal cortex (again, not really important) and has the ability to control maintain blood glucose during prolonged bouts of exercise. Cortisol does this by telling the body to start breaking down proteins and triglycerides. Cortisol is more or less THE stress hormone, though there are others. If you have exercised too much or you haven't allowed your body proper time to rest, expect an increase in Cortisol. How Cortisol affects the body gets into explaining the HPA axis (not too hard to understand), and there are a number of differrent things that Cortisol affects, not all of those things are physical in nature, there is a big psychological component that is related to Cortisol.

Testosterone has been considered the holy grail of muscle building. Testosterone blood serum levels can be increased during heavy strength and weight training. The hormone promotes protein synthesis. Testosterone will also support production of new red blood cells and more of them, which leads to an increased ability to utilize oxygen more effectively, which leads to more usage and more efficient usage of glucose, which leads to less difficulty when performing strenuous exercise, which leads to you pushing yourself harder. This is why it is often abused by athletes in an attempt to enhance performance. The mechanisms behind all that involve many, many steps. Beware, testosterone users! the hormone is subject to aromatization which means that testosterone is eventually converted into estrogen. Both men an women have both hormones, and a balance is needed for a number of reasons, healthy sexual function being the main one. Estrogen has a number of effects on the body. Estrogen is good for supporting bone formation and bone maintenance. It is also important in protecting neurons. (Males continue to make estrogen via aromatization of testosterone, whereas women don't make estrogen after menopause. Ever wonde why most Alzheimer's patients are women?)

Growth Hormone is a chain of 191 amino acids. These amino acids, when grouped together can instruct the body to perform specific functions. For instance, protein synthesis and cell transport. There has been and there continues to be a lot of research in this area. Certain chains in the hormone have been isolated and identified for their specific properties and actions in the body (the list is extensive, actually). What you need to know is that Growth Hormone is secreted in response to exercise.

There you have it. Just a little bit about a very small number of hormones that can be affected by exercise. There are a number of exercise physiologists on this site that can be of more assistance. I hope I haven't left you with more questions than anwers, and I hope this was easy enough to understand. Please know that there are MANY hormones that are affected by exercise, and without knowing what specific hormones you are interested in, it's impossible to tell you what you're looking for.

I hit the main ones here. Testosterone, Cortisol, and Growth Hormone are usually the big three that people are interested in.

I welcome any feedback from my peers. Know that a lot of this information came from the ACE manuals, and some of it is from my understanding of the topic and research into these areas. I am not a professional exercise physiologist, however.

I hope this helped!