Max Heart Rate and Training Zones
This is no medical advice. Although moderate to strenuous workouts are generally considered healthy, everything depends on you and your situation. A trial at the Mayo Clinic with middle-aged, obese participants concluded that higher intensity workouts have the highest chance of increasing cardiorespiratory fitness while still being medically safe. Nevertheless, if you think you are not healthy, see a doctor. If you are over 40 years old and have not worked out in the last couple of years, go see a doctor before starting a new fitness regime. The same is true if you are on any kind of medication.
People just starting cardiovascular training (cardio for short) often need guidance. How much is too much, how much is too little? The most often recommended aids for finding one’s right training intensity are heart rate zones and perceived exertion. However, it is as easy for beginners to get their heart rate zones wrong, as it is easy to overestimate one’s exertion. So the best approach is to use both. They complement each other perfectly. Finding one’s individual heart rate zones depends on knowing one’s maximum heart rate (maxHR). Chances are however that one underestimates one’s maxHR, as it is highly individual and changes over the years.
The most often cited formula for estimating maxHR is
220 - age in years, although its origin is surprisingly hard to find and does not come from original research. A better way to estimate maxHR is the result of the HUNT fitness study which tested 3,320 participants aged 19–89 years:
211 - 0.64 * age. However, there is still a standard error of nearly 11 beats per minute to take into account. That means that the ‘calculated’ maxHR is still only an estimation and should be verified, if possible. The simplest verification is checking with perceived exertion. If one is running in Zone 2 (moderate exercise) one should be breathing harder but still be able to hold a short conversation. If one can still sing an opera, one is not in Zone 2. If one can only speak a short sentence before gulping for air, one is not in Zone 2.
The best way to find one’s maxHR is by doing a test. How this test is done depends on the type of activity, but most often consists of repeatedly doing more and more challenging intervals until one has reached maxHR. This endeavour is decidedly unfunny, especially for beginners who are unsure of what their body can provide or not do. During the final stage, one reaches Zone 5, is unable to speak at all and feels completely out of breath. This exertion can only be maintained for a short amount of time. To complicate things, maxHR is different for different activities.
Different studies have shown that one’s individual maxHR depends on the sport one undertakes. The difference between running and biking can be over five beats/min for example. The difference between swimming and running is a further 20 % higher. This difference, while being significantly lower than the standard error in the above maxHR-formula, is still enough to shift one’s heart rate zones notably.
Heart rate zones or training zones give an estimate of the way an individual training will contribute to one’s fitness and body composition. Training in lower zones allows the body to burn more fat in relation to burning sugar and increases one’s aerobic base. Training in higher zones and especially interval training like Tabata will increase one’s lactate tolerance and increase the body’s capability to use oxygen and therefore to spend more energy. A balanced cardio training plan will consider all training zones with an emphasis on the lower zones.
Most literature speaks of five heart rate zones and calculates them as percentages of the maximum heart rate:
A notable exception is the Mayo Clinic which is contend saying that 50 to 70 % maxHR equals moderate activity (somewhat hard) and everything above is vigorous activity (challenging). Calculating heart rate zones from maxHR alone has one great weakness. It ignores a person’s level of fitness.
As the maxHR is non-negotiable the only way for the heart to get more blood pumping in the same amount of time (e.g. get fitter) is to increase its volume and therefore its capacity for circulating blood. The reverse conclusion being that a larger heart has to do less beating if the body is at rest. While the ability to pump blood increases, the resting heart rate (restHR) decreases. This is a desired effect. Extremely fit rowers can have a restHR of less than 40 beats/min. A lot of fitness trackers can measure restHR. Alternatively one can take one’s pulse in the morning, right after waking up. The difference between maxHR and restHR is called the heart rate reserve (reserveHR).
Martti Karvonen was the first to factor the reserveHR into his recommendation for training intensity zones. He calculates a target heart rate with the formula
reserveHR * intensityFactor + restHR and states that the intensity factor for intensive training should be 0.8 and for moderate training 0.6. Most fitness trackers can calculate heart rate zones using maxHR or reserveHR but use the same percentages for the zones. As the Karvonen-formula renders different results with increasing fitness it should be better suited for calculating heart rate zones than the simpler maxHR method. As before, perceived exertion can be used to check if the training zones fit.
- Start by estimating maximum heart rate using a modern formula.
- Calculate your training zones.
- Check for matching perceived exertion.
- Find out your real maximum heart rate and your resting heart rate.
- Refine your training zone calculation.
Photo by SwapnIl Dwivedi