Being aware of your working heart rate - the rate your heart beats at when exercising - it an important factor in achieving your health and fitness goals.

To work your heart and lungs most efficiently and to burn fat you need to work at between 65% and 85% of your maximum heart rate. (MHR) this range is known as you optimum training zone .

To calculate your maximum heart rate, subtract your age from 220. So if you are 40, your MHR is 180 beats per minute.

Your optimum training zone is therefore between 65%x180 ie 117 and 85%x180 ie 153 . So when exercising you should try to keep heart rate in this range.

If you train above this range, you begin to exercise anaerobically and your body won't be able to sustain this for long.

The best way to monitor your heart rate is to wear a heart rate monitor. These simple devices vary in price, and some are very affordable.

The chart below shows the optimum training   zones for various age ranges.