How useful is wearing a heart rate monitor in CrossFit?
What does a heart rate monitor do?
A heart rate monitor provides you with feedback on how fast your heart is beating. Heart rate during exercise is often seen as an indicator of intensity and of cardiorespiratory health. A number of aspects are important to take into account when talking about using a heart rate monitor:
- Resting heart rate
This is your heart rate during rest. If your resting heart rate is low, it is plausible that the amount of physical and mental strain on your body are in balance and your cardiorespiratory system is in good shape. If your resting heart rate is elevated for more than 10 percent a few days in a row, it is plausible your body is overloaded and in need of rest. It might also be the case that your resting heart rate is low or high by nature, of you are on medication that affects your heart rate.
Furthermore, we need to mention the parasympathetic overtraining syndrome. This is a severe type of overtraining characterized by a heart rate that is very low during rest and barely increases during exercise. The dangerous part of this syndrome is that the symptoms can be misleading. Because your heart rate is low, you might think you are in good shape when in fact you are severely overtrained. Consequently, proper treatment often comes too late.
- Maximum heart rate
Maximum heart rate is often seen as an indicator of intensity and a reflection of cardiorespiratory health. More experienced athletes are often able to reach a higher maximum heart rate during training. But hereditary predisposition, illness and age can affect your maximum heart rate, among several other factors.
- Training recovery heart rate
This is the number of strokes your heart rate drops after the exercise. In general, the fitter you are, the faster you will flow back to the heart rate you had at the start of the exercise, and the faster you will recover from it.
Measuring (relative) intensity
CrossFit is constantly varied high intensity functional movements. Functional movements are characterized by large loads (force) over long distances (distance) quickly (time). The load and distance are the work you have to do, for example lift an 80 kg loaded barbell (load) from ground to overhead (distance). The intensity is determined by the time it takes you to lift.
In CrossFit intensity equals power, and power = (load x distance) / time. Power is the direct display of your work: 80 kg loaded barbell (load) for 10 reps from ground to overhead (total distance) in 90 seconds (time).
Calculating intensity (power) makes it possible to track and evaluate your progress based on measurable, observable and repeatable data from your workouts. More load, more reps, quicker.
In CrossFit we explicitly emphasize the importance of relative intensity. Working out at high intensity is key for results. This level of high intensity needs to be appropriate relative to your physical, mental and emotional tolerances. The idea is that we all have our own individual limits of capacity, yet if we all, despite our differences in fitness level, work near our individual limits of capacity, we will all have the same increased benefits from a workout. Therefore, it is not about your absolute output of a workout, but about the relative output: your results today compared to your results yesterday (CrossFit, nov 2019).
Why wear a heart rate monitor?
As mentioned above: intensity (or power) can be measured, but heart rate is not part of the math. Why is that?
A heart rate monitor measures your body’s response to the work. Heart rate is a direct response to variations in blood pressure, breathing rate and muscle contractions resulting from your effort and technique during the exercise.
Although a heart rate monitor is often used to measure intensity, it does actually not do that job. Heart rate is not an instant reflection of your work. It takes some time before your heart rate responses to your work. Therefore, your heart rate is a delayed reflection of your work and of intensity. You might recognize this: only after a few seconds of a 20 second sprint, your heart rate goes up and you start to breath heavier. A heart rate monitor monitors your response to the intensity, but not the intensity itself.
Furthermore, your heart rate can be influenced by several other factors besides your work. For example even thinking about the workout you’re about to do, can increase your heart rate. Also tense muscles, dehydration, fatigue, illness, medication, sugar and caffeine, hot temperature and humidity can increase your heart rate. Women have a higher heart rate than men. And older people have a lower heart rate, in general.
Therefore, a heart rate monitor does not measure your intensity, how much work you have done or if you’re making good progress based on measurable, observable and repeatable data (Mad Dogg Athletics, 2017).
Don’t throw it away yet
Nevertheless, don’t throw your heart rate monitor away yet because it is a perfect tool to measure power efficiency: how efficiently does your body responses to the work. For example, if you power output (load, distance, time) on a specific workout increases over time while your heart rate during that workout is lower, you are getting stronger and fitter. But if your power output stays the same over time while your heart rate is higher, you might be in a state of stress, under- rested, dehydration or improper nutrition. And if your power output decreases while your heart rate is higher, you might be overtrained or ill.
Therefore, training with a heart rate monitor can be useful. By registering your heart rate over a longer period of time (resting heart rate, maximum heart rate and training recovery heart rate) you can provide yourself with some additional feedback on how you are doing. Measuring power output and power efficiency can help to train more effectively and prevent overtraining.
Create your own health!©