Ask anybody in the gym flogging their guts out on a running machine why they are doing it, and most will respond that it is to improve their cardiovascular system. In chapter 6, I will explain why, according to research, endless hours on the treadmill are just not necessary. But first, let’s start with a basic understanding of what cardio or cardiovascular really is.
Our cardiovascular system refers to the way our heart and blood vessels transport approximately five litres (eight pints) of blood around our body - all day, every day. Cardiovascular originates from Greek ‘kardia’, meaning heart, and ‘vasculum’ from Latin for ‘small vessel’, which relates to the blood vessels. Driven by the heart (which is not much bigger than our fist), blood is used as a vehicle to transport nutrients, oxygen and hormones to every part of the body. Our arteries carry blood away from the heart and our veins bring it back. The heart has a left side (left ventricle) and a right side (right ventricle). The left ventricle pumps blood out of the heart. People that are sedentary tend to have a smaller left ventricle than those who exercise. Put simply, those who exercise regularly can turn their low-powered engine from a Mini into a Ferrari. Obviously, the more powerful the engine, the better it deals with stress, such as going up inclines.
Let’s assume we are now taking regular exercise, and our heart has increased in size and power, the next thing we want is our transport system, (a.k.a. our arteries), to enlarge, so that pressure doesn’t build up. If we can become less stressed, and therefore more relaxed, then our arteries won’t be uptight and our blood pressure will therefore drop. Both sprinting and weightlifting are what we call interval training, which helps the heart to grow strong and arteries to become more elastic. In contrast, we now understand that - despite what was originally believed - the endurance sports we were encouraged to do, such as running (the very activity that was first called aerobic), do not help strengthen the heart after all and instead completely stress out our hormones and immune system. Sorry joggers, but it’s true.