Cardiovascular exercise is so called because of the effect that it has on your cardiovascular system which is your heart and blood vessels. It is defined as any physical activity that raises your heart rate. Normal resting heart rate or HR has a range and this is between 45 and 90 beats per minute. A value outside of this range, when at rest, is considered abnormal. If it is below the lower limit of normal this is termed bradycardia and if it is above the upper limit of normal this is termed a tachycardia.
There are numerous conditions that predispose to these abnormal values but the underlying problem is usually an abnormality of the conducting pathways in the heart itself.
A tachycardia when exercising, as opposed to a tachycardia at rest, is an entirely normal physiological response to exercise and of course it exists to pump more blood around the body to deliver more oxygen and nutrients to the cells that need it most i.e. the muscles. The volume of blood put out by the heart is called the cardiac output or CO and is measured in litres per minute. Each beat of the heart pushes out a certain volume and this is termed the stroke volume or SV. With an adult at rest this is usually about 80mls of blood per beat. Cardiac output is calculated by multiplying stroke volume by heart rate so you can see that an individual with a heart rate of 60 will have a cardiac output of almost 5 litres. If you want to increase the cardiac output you can do so by increasing both heart rate and stroke volume and in reality both are increased together and this can result in a doubling or even tripling of the cardiac output during strenuous exercise.
This increase is largely under automatic, i.e. subconscious, control by the sympathetic nervous system and is otherwise known as the “fight and flight” response. It is a normal homeostatic mechanism that has evolved to ensure that our bodies respond appropriately when we are faced with potential danger such as a predator. This almost certainly happened with a degree of regularity in primitive man but much less so now in everyday life. However it’s important that we still utilise this capability regularly in order to maintain that survival advantage and this is exactly the purpose of cardiovascular exercise. Regular exercise has been shown to have a very positive effect on general health and longevity. And of course the converse holds true as you would anticipate.
If you are overweight or already suffering from obesity then it’s only natural that you will find any form of exercise a challenge, even walking. But the good news is that even a brisk walk initially will raise your heart rate. As time goes on you will steadily lose weight and your exercise limit increases so you can walk faster and faster and then you will break into a jog and then into a run. So the answer is to start gently and to build up over time. The important thing is to push yourself a little bit further each and every day so that after half an hour you can feel your pulse increase, you are sweating and you are out of breath – that’s how you know you’ve done some good!
If walking and running aren’t for you it’s important that you find something that is, such as cycling, swimming or going to the gym. Ideally it should be done first thing in the morning whilst you are still fasting – don’t worry, your body has plenty of reserves and that’s exactly what you want it to use. Your immediate energy reserves are largely your liver and muscle glycogen stores that are replenished from the day before. If you’re trying to lose weight then it’s important to deplete these early in the day and this will happen with a good bout of exercise. This ensures that you get into uninterrupted fat burning for a good 6 hours before you start eating again. And it’s important that you do it every day for at least 30 minutes – no more excuses!