# Maximum heart rate

The HRmax calculator determines your maximal heart rate based on age and sex. This can be useful for your personal exercise training, and is of great importance for exercise stress testing to uncover cardiovascular disease. Maximum heart rate is largely determined by genetics, not fitness level, hence we recommend testing yourself to find your exact HRmax.

Correct HRmax of great clinical significance
Maximum heart rate (HRmax) is an important tool in uncovering cardiovascular disease. During stress testing, age-expected maximum heart rate is used as a guideline for when the test should be concluded. The traditional formula for determining HRmax – age subtracted from 220bpm – can underestimate HRmax by up to 40 bpm in seniors, and starts becoming inaccurate already at an age of 30-40 years. Consequently, the load may be too low during testing, and the underlying cardiovascular disease is not discovered. Therefore, it is of great clinical relevance to have a means of accurately estimating HRmax.

Figure 1. Individual values and regression calculation (Source: Nes et al. 2012)

Our new formula, 211 – 0.64*age, is based on the maximum heart rates measured in 3320 healthy adults between 19-89 years old, who participated in the HUNT Fitness study. The researchers found that variation within age groups was fairly large, with a standard deviation of approx. 11 beats/min. Genetics contribute more to maximum heart rate than physical fitness, hence peers in the same age group may have disparate maximum heart rate values. Therefore, we recommend that you test yourself to find your exact HRmax, even though our formula gives a better estimate than the old one.

A simple way of finding your maximal heart rate is to push yourself to exhaustion while wearing a heart rate monitor. First, it is important to warm up thoroughly so you start sweating. Do two intervals, each 4 min long. During the intervals you should be too short of breath to talk, and intersperse them with 3 min active rest. Start the third interval, but 2 minutes in, run as fast as you can until you're too exhausted to continue. Your HRmax will be the highest heart rate you reach, based on the assumption that the heart reaches a plateau at which it cannot beat any faster, regardless of how much you increase the workload.

HRmax and beta blockers
People on beta blockers will have a reduced maximum heart rate. This is because beta blockers bind to adrenaline receptors and block access for adrenaline molecules. Adrenaline causes the heart to pump both harder and faster, hence beta blockers reduce the maximum heart rate. The magnitude of the reduction depends on the dosage, hence we recommend that you test yourself to find an exact HRmax.

Use HRmax to give your heart a workout
4x4 interval training uses HRmax to exercise the heart, and can be adapted to different activities such as running, biking and swimming according to personal preference:

• Start with a 10 min warm-up at approx. 60% of HRmax to get you sweating
• Do 4 intervals, each 4 min long, interspersed by 3 min active rest
• Your heart rate should be at 90-95% of HRmax during intervals, so you become short of breath
• Your heart rate should be approx. 70% of HRmax during active rest (e.g. light jog), since this is the zone where the body most efficiently clears lactic acid
• End with a 10 min cool-down with lighter activity after the last interval

Send us an e-mail:
cerg-post@medisin.ntnu.no

Send us regular mail:
NTNU, Fakultet for medisin og helsevitenskap
Institutt for sirkulasjon og bildediagnostikk
Postboks 8905
7491 Trondheim

Visit us:
St. Olavs Hospital
Prinsesse Kristinas gt. 3
Akutten og Hjerte-lunge-senteret, 3. etg.
7006 Trondheim