We can effectively use the heart rate to quantify work being done during a cardio session. It’s a tool that can be used to build fitness, measure progress, and increase exercise safety. Heart rate is closely correlated with oxygen consumption and how much work the muscles are doing.
The basic tenets are:
Max Heart Rate is based on age, gender, and training level.
Working in a percentage, or “zone” of your max heart rate allows you to see your training intensity. i.e. cardio, fat burn, intense, etc.
The difference between your resting heart rate and maximum heart rate is known as your Heart Rate Reserve (HRR), and is what you’ll be working in when you’re doing your cardio.
Doing “cardio” involves sustaining an elevated heart rate (in your HRR) through exercise for a period of time, which is also directly correlated with intensity. This means that the more intense the exercise, the shorter you can sustain it, and vice versa.
Walking, hiking, rowing, elliptical, or biking at low speed. Usually in the “fitness/fat burn zone”, and around 2 on RPE scale (see below for explanation of RPE scale).
Jogging or running, rowing, elliptical, or biking at moderate speed. Usually in the “cardio/endurance zone” and around 3 on RPE scale.
Sprinting, rowing, elliptical, or biking very intensely. Usually in the “hardcore training/max effort zone”, or 4-5 on RPE scale
Note: Many sports are a mix of intensities. Example: basketball involves sprinting, jumping, jogging, and walking at different points during a game, as does soccer. Sports like American football and volleyball involve a short quick burst of activity followed by short rest periods of inactivity or light walking. Athletes should thus train to make adaptions tailored to their own unique sport.
RPE (Rating of Perceived Exertion) scale:
0: Sitting quietly, standing in place.
1: Very low speed walk, “leisurely stroll”
2: Normal paced walk, described as “easy or light”
3: Moderate intensity, can keep short conversation. Described as “good pace”. Example: jogging 8-11 minute mile pace
4: Fast paced or hard effort. Can say a few words, “described as hard or intense” Example: Running at 5-7 minute mile pace
5: All out intensity, full speed sprint, described as “extremely hard or intense”
Note: The RPE of any given exercise will vary based in the individual. This has to do with many factors including fitness levels, amount of lean mass or fat mass, gender, age, size, and genetics. The RPE provides a good reference, but the scale should be tailored to the individual. Example: A person who can run a 4:00 minute mile might feel that that a 8:00 minute mile pace is around a 2 because they are so well trained. On the opposite end, someone who is untrained may feel a slow jog is a 4 because they have not made adaptations to training yet.
Max HR is correlated with age as you can see above (Age Predicted Maximum Heart Rate). The “zone” you’re working in is correlated with your maximum HR.
Measuring heart rate can be done with the actual cardio machine you’re using (if it has this technology), or with wearable tech heart rate monitors. It can also be done by finding and pressing down gently on the radial artery of the wrist or the carotid artery of the neck to feel the pulse. You can count the beats for 60 seconds, 30 seconds times 2, or 15 seconds times 4.
Note: it may be tough to manually measure heart rate during a cardio session. Technology is your friend in this case.
What Zone Should I work in?
This depends on your goals. If you just want to burn a bit of calories and do something light and low impact, aim for the fitness/fat burn zone. If you’re looking to build up a good cardio and endurance base, work in the cardio/endurance zone. HIIT type cardio makes use of a couple of different zones, depending on the type. It all comes down to personal preference, how much time you have for training, your injury history, and what you’re trying to achieve.