We all know it’s important to exercise, but do you actually know what is going on inside your body when you do a hard session at the gym or a long run? You may know you sweat, but do you know why? Why is your heart rate a sign of fitness?
We work out what’s happening inside your body when you’re working out.
Muscles
When you exercise your muscles require oxygen and this is delivered via your blood stream. The blood vessels in your working muscles dilate (get wider), increasing the flow of oxygenated blood.
These muscles are now able to extract three times the amount of oxygen from the blood than those at rest, consequently demanding about 85% of your blood's oxygen
Heart
When you exercise your heart pumps faster in order to reoxygenate your blood quicker and therefore provide your muscles with the oxygen they require. On average, your heart's blood flow is about four or five times greater during exercise than at rest.
It is your heart pumping quicker that in turn raises your heart rate. Your heart is a muscle and, like any muscle, it will grow stronger and will become more efficient the more you exercise.
Lungs
Unlike your heart, your lungs are not a muscle, so they do not grow. Their role is to suck oxygen from the air into your body so this can then be passed into your blood stream and taken to the vital working muscles. The fitter you are, the larger your lung capacity and the more oxygen in your blood.
As well as taking in oxygen, lungs are also vital to get rid of the unwanted by-products of deoxygenated (used) blood, such as lactic acid and carbon dioxide, through exhalation.
Adrenal glands
Your adrenal glands can be found near the kidneys. They release epinephrine, more commonly known as adrenaline. This raises your heart rate and desensitises your body to pain.
Skin
As the largest organ in your body, it is no wonder we all produce a lot of sweat when we’re exercising hard.
Sweat occurs when the capillaries in your muscles transfer warm blood to the sweat glands in your skin. As the sweat evaporates from your skin it keeps your body temperature down so you can continue working out.
Excessive sweating causes fluids and salts, such as sodium, chloride and potassium, to be lost, so it is essential to rehydrate with water during and after a work out. If you become too dehydrated your blood will thicken and each step will become more difficult. It's basically game over!
Brain
The role of your brain throughout any exercise session is to protect you from hurting yourself. If your temperature gets too high, it will make you feel unwell so you have to stop.
Your brain can also play mind games. It can make you have negative thoughts such as 'I can't do this anymore'. If this happens, you need to come back with a positive thought. You might have a mantra you use, a minimum time to beat, or a landmark to reach.
During exercise an opium-like substance is produced in the brain, which explains that natural high you feel post-workout. This is what makes you come back for more, time and time again!
Stomach
When you exercise digestion all but stops, caused by a restricted blood flow to non-working organs, such as the stomach, liver and kidneys, so your active muscles are prioritised.
For this reason it’s important to eat at least a couple of hours before you exercise in order to ensure your recent meal is fully digested, otherwise you could suffer a painful stitch.
Once you finish working out, the blood flow to your stomach restarts so it’s important to eat and drink as soon as possible. Nutrition is your body's best form of recovery, so include some carbohydrates to help replenish glycogen stores and protein to aid the repair of muscles.
As you finish your hard session, your body may have stopped moving on the outside, but your insides are still hard at work. It needs to replace glycogen stores, remove lactic acid, lower your heart and breathing rates and shut down the capillaries to your working muscles, while opening the ones to the rest of your body.