220 – 50 = 170bpm (maximum heart rate)

170 – 65 = 105bpm (heart rate reserve)

(105 x 0.7) + 65 = 139bpm

Using the Karvonen formula this person’s target heart rate works out as 139bpm. To create a ‘zone’ you might want to subtract i.e. 129 to 139bpm

Using the traditional 220 – age formula this same person would have a target heart rate of 119bpm, which is considerably lower (220 – 50 x 0.7). It’s worth noting that the Karvonen formula nearly always calculates a higher target heart rate than 220 – age.

Here is a rough guide to different heart rate zones and the adaptations they elicit…

Recovery Zone - 60% to 70%
Active recovery training should fall into this zone (ideally to the lower end). It’s also useful for very early pre-season and closed season cross training when the body needs to recover and replenish.

Aerobic Zone - 70% to 80%
Exercising in this zone will help to develop your aerobic system and in particular your ability to transport and utilize oxygen. Continuous or long, slow distance endurance training should fall under in this heart rate zone.

Anaerobic Zone – 80% to 90%
Training in this zone will help to improve your body’s ability to deal with lactic acid. It may also help to increase your lactate threshold.

It is important to remember that the heart rate reserve method of prescribing exercise intensity is by no means flawless. Firstly, estimating a person's maximal heart has been shown to have inaccuracies compared to laboratory testing (2) - where exercise intensity is increased until a plateau in heart rate is found.

Secondly, the heart rate reserve tells us nothing about a person's lactate or anaerobic threshold. By recording heart rate data along side the point at which lactate threshold is thought to occur, a far more effective training plan can be devised.