How does running improve fitness?

This article aims to explain some of what happens to your body and how running training might work for your physical fitness. It will also improve your mind, of course, but we'll save that for another article (see runsmarter).

If you were to take a look around your local gym you would see various machines and exercises for various areas of the body. Many are designed to increase strength in certain muscles and can require fast, controlled or explosive movements. They often take less time and fewer repetitions than the number of foot contacts we make with the ground when we run.  Running, along with other endurance activities, also make many of our muscles stronger but none more so than the heart. Endurance is about sustained exercise with repetition and this combination makes for a healthy heart. When we run our muscles ask for more oxygen and we ask our heart to pump more oxygen carrying blood to them. Our heart then increases the number of beats per minute and pushes out more blood with each stroke than it would otherwise. Cardiac output is increased.

Over time your heart adapts and finds it easier to pump out more blood with each stroke, your heart rate comes down, as it doesn't need to beat as often to send the blood around the body, and then running feels easier as your heart is working at a lower rate than it previously did. We can relate this to a car that has a top speed of 120mph. It can maintain a speed of 80mph with much less strain or wear and tear for a longer time than a car which has a top speed of 80mph. The first car is working in its "comfort zone" whereas the second car is working to the limit of its capacity. Through running you can increase the capacity of, not only your heart, but your lungs and muscles which replaces your 600cc engine with a 2L engine and this will help you to run further at a comfortable pace or to run your usual distance faster!

Oxygen rich blood travels to your muscles via a network of  blood vessels. Tiny capillaries feed the cells in the muscles where they extract oxygen and nutrients and send back carbon dioxide and waste products. Running strengthens the heart, increases the number of capillaries in the body, increases the number of red blood cells and the capacity of the muscles to use the oxygen when it gets to them. The oxygen is then utilised to create a series of reactions needed to release fat or glycogen to be used as energy.

The rate at which you can use the oxygen for the purpose of creating energy is called Vo2 Max. It may be useful to have your Vo2 max measured and have some advice on how you to increase it. London Metropolitan University offer this service as do other universities around the country. Once seen as the preserve of elite athletes the benefits are now being discovered by more club and recreational runners. Elite runners often have a Vo2 max of around 80 whereas sedentary folk are more likely to be around 35.

Running in your "comfort zone" means running aerobically or with oxygen. If you run at the limit of your aerobic capacity or you tip over the limit you will be running without oxygen, or anaerobically. You are able to do this for short periods of time. The anaerobic energy system is explored in more detail in our runstronger section.

So, there you have it, running makes the heart stronger and more efficient through your muscles demanding a good supply of oxygen and energy. It also supplies more oxygen to the brain to make you more alert and healthy but that's another story!