You will often see the words appropriate attached to exercise or diet when health advice is given. The appropriate amount of exercise will be different for each person, so in this article I will share with you some knowledge about how your body uses energy so you can calculate how to work at your maximum aerobic capacity (MAC). MAC is important because too little exercise will not provide the health benefits and too much can leave you prone to injury or inflammation.

On a cellular level we have 2 sources of fuel for energy production in our muscles, fat or sugar in the form of glucose. For any sort of long-term exercise, over 10 minutes, your muscles rely on burning fat as fuel and this is known as aerobic exercise. For short term exercise like sprinting or high intensity training (HIT), spinning or weight lifting the muscles rely on sugar for fuel and is known as anaerobic exercise, you are only able to do these things in short bursts and will then need to rest.

All health benefits come from aerobic exercise, it may seem obvious but the only way to develop aerobic fitness is to do aerobic exercise.  An important thing to know is that if you start an exercise regime which is largely anaerobic (spinning, HIT etc.) you CANNOT develop your aerobic fitness.

For anyone starting out on a new fitness regime or returning to exercise after a period off it is essential that you spend time developing your AEROBIC fitness before you do any other forms of exercise.

So how do we know when we are moving from aerobic capacity to anaerobic? The best method is to use a heart rate monitor and use this simple formula:

180–Age = Heart rate in beats per minute (BPM) = Maximum Aerobic Capacity (MAC)

Using this formula my MAC is 135 bpm, which means that if I exercise just under this threshold I will be exercising at the most efficient aerobic capacity that I can. The great thing is that it doesn’t matter how you exercise whether it is swimming, walking, running or cycling the rule is the same. Over this level you entering anaerobic exercise, which is not what you want, and you are more prone to injury when you exercise like this (Maffetone, 2000).

The above formula is a very simple scientific method but if using a heart rate monitor seems a bit much for you then there is an even simpler way to gauge when you are close to your MAC. That is to pay attention to your breathing. If you are exercising and you get to the point where you are having to start breathing through your mouth to get more air in you are above your MAC, when you stay breathing through your nose you will be exercising within your aerobic capacity.

For many of us especially those over 40, walking will generally be enough to keep your heart rate close to your MAC. If you are new or returning to exercise time is more important than distance start slowly with 10 mins of exercise daily and build up over a number of weeks to 45-60 minutes every day.