How to Work out the Target Heart Rate Zone

The Karvonen Formula and Improving Aerobic Fitness During Exercise

Nov 28, 2008 Sharon Kirby

The target heart rate zone is the heart rate range considered to be most favourable for improving aerobic fitness. This range can be worked out using a simple formula.

Regularly exercising within the target heart rate zone improves aerobic fitness, and has important long term health benefits. The Karvonen formula is a calculation that takes into account maximum heart rate, and resting heart rate, to determine the upper and lower limits of the target heart rate zone.

How to Work Out the Target Heart Rate Zone

The Karvonen formula can be used to estimate target heart rate zone if a more accurate heart rate test is unavailable. Firstly, the person’s age is taken away from the figure 220 to get the estimated maximum heart rate. Maximum heart rate minus resting heart rate gives the heart rate reserve. The lower limit of the target heart rate zone is 60% of heart rate reserve plus resting heart rate, while the upper limit is 85% of heart rate reserve plus resting heart rate.

(Please note: this formula should only be used as a rough guide, and is not without criticism.)

The Karvonen Formula

220 - (age) = estimated maximum heart rate (MHR)
MHR - resting heart rate (RHR) = heart rate reserve (HRR)
HRR x 60% + RHR = lower limit of target heart rate zone
HRR x 85% + RHR = upper limit of target heart rate zone

To get the resting heart rate, take the pulse by pressing the first two fingers gently against an artery in the wrist or neck for ten seconds, and multiply by six to get the number of beats per minute. Alternatively, use a heart rate monitor. To obtain resting heart rate, the pulse should be taken for a full sixty seconds before getting out of bed in the morning.

Improve Aerobic Fitness by Exercising in the Target Heart Rate Zone

When exercising in the target heart rate zone, the body is working aerobically (with oxygen), using large muscle groups. Aerobic exercise includes activities such as running, cycling, brisk walking, dancing and swimming. During exercise at this level, breathing becomes more rapid and there is a noticeable increase in body temperature and heart rate. It should be possible to stay in the target heart rate zone for twenty minutes or more without fatiguing.

Regular aerobic training (three to five times per week with each session lasting twenty to thirty minutes) makes the heart stronger and more efficient at pumping blood around the body, and improves the ability of the lungs to release oxygen into the bloodstream. Thus, the body becomes more efficient at transporting oxygen to the working muscles. Activities that require physical exertion become easier, and the duration for which they can be performed increases due to enhanced physical conditioning.

The Health Benefits of Exercising Within the Target Heart Rate Zone

There are many reasons to find the motivation to exercise within the target heart rate zone. Exercising at this level burns fat and aids weight loss, reduces the risk of obesity and its related health effects, and helps to prevent coronary heart disease. Aerobic exercise also helps to ease depression and improve mood.

If a person has been sedentary for a while, or has any health concerns, it may be necessary for him or her to start exercising at a lower intensity (perhaps 50%) and build up gradually as fitness improves. A medical expert can help determine a suitable heart rate training zone. It is important to exercise at a level that suits the individual.

Resources:

McArdle, W.D., Katch, K.I. and V.L. Katch. Exercise Physiology: Energy, Nutrition and Human Performance, 6th Ed. London: Lippincott Williams and Wilkins, 2007, 490-491

The copyright of the article How to Work out the Target Heart Rate Zone in Fitness is owned by Sharon Kirby. Permission to republish How to Work out the Target Heart Rate Zone in print or online must be granted by the author in writing.

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