Four key training zones

Zone three: aerobic zone

This zone refers to an exercise intensity producing a heart rate of between 70% and 85% of maximum. It’s the most popular intensity of exercise used to develop general fitness. For most people, it’s the hardest work rate that they can maintain for long periods of time and – because it won’t usually result in any significant increase in lactic acid levels – is also known as the aerobic zone. Training in Zone Three intensity will improve endurance and familiarise the body with exercise at a high intensity.

Lactic acid
Build up of lactic acid occurs in the muscles when the body’s exercising faster than the heart can pump oxygen-rich blood to the muscles – this means the muscles are working anaerobically or without enough oxygen. Anaerobic exercise can only occur for short periods of time. The build up of lactic acid prevents the muscles from working properly and – unless it’s cleared away by a proper cool down after exercise – it can cause them to ache afterwards. 

Zone four: the high performance zone

High intensity exercise pushes the heart rate to between 85% and its maximum. The training in Zone Four will start to become much more anaerobic – with the accompanying build up of lactic acid – and can only be done for relatively short periods. Exercising in this zone is definitely hard work – breathing is heavy and the working muscles will quickly tire. This zone is generally only to be recommended for those who are already very fit, and even then only as a small proportion of their overall training programme. Doing too much training in this zone is a common problem for many top athletes. Too much High Performance Zone training will result in excessive fatigue, staleness, and the problem often referred to as ‘over-training’.

Measuring target heart rate

If you want to plan your exercise programme by the four key training zones, you first need to estimate your maximum heart rate. Then you need to work out what target heart rate you should be exercising at to achieve your goals – whether they’re to lose weight, maintain fitness or improve endurance.

To see if you’re achieving your target heart rate, you need to measure your heart rate. A rough method is to take your pulse rate either during – or more possibly immediately after – exercise. The ‘pulse’ of blood through the arteries and veins is directly related to the beating of the heart. But, taking your pulse from the two most common sites – either the carotid artery in the neck, or radial artery in the wrist – are prone to error if you try to take it yourself, especially during or after exercise. Add to this that even the most unfit person will experience a rapid decrease in pulse rate after exercise has finished – a pulse taken just 30 seconds after exercise can give a false indication of the pulse rate during the exercise itself.

The most accurate and reliable way of checking heart rates during exercise is to invest in a personal heart rate monitor. There are many different models available, all of which involve wearing a light-weight chest strap and a ‘wrist watch’ display. These easily enable you to keep a check on your heart rate while exercising – prices range from around £50 to £300.