Published: 8/6/2024
Author: Michael S OConnor
Your heart rate is how many times your heart beats in 60 seconds (typically expressed as beats per minute [bpm]) and will increase and decrease as you go through your day. Typical behavior is that you heart rate will be low during periods of being sedentary and higher during periods of activity. Heart rate is also dependent on an individuals biological sex. For the purpose of this article, we will be explaining heart rate as a way to gauge effort during exercise as well as for recovery.
Resting Heart Rate (HRrest)
Your resting heart rate is the average beats per minute measured when a person is awake and has been inactive and relaxed for several minutes. A lower resting heart rate typically indicates better heart health and cardiovascular fitness. The normal range for resting heart rate for adults is 60 to 100 bpm (Laskowski) with some well conditioned adults sitting as low as in the 40 bpm range. Resting heart rate is often correlated with mortality. In the Copenhagen City Heart Study, a heart rate of 65 bpm rather than 80 bpm was associated with 4.6 years longer life expectancy in men and 3.6 years in women (Jensen).
Maximum Heart Rate (HRmax)
Maximum, or maximal, heart rate (HRmax) is the highest heart rate one can theoretically attain during exercise and is a key metric in determining the target heart rate (THR), i.e. training zones, one would use in order to achieve various training objectives. Although, knowing your heart rate is not required to engage in cardio-based exercise, it does provide a method by which more accurate feedback can be obtained thus allowing the individual to adjust their exercise plans with greater accuracy. It also important to note that ones maximal heart rate decreases as we age.
There are two methods by which one can determine their HRmax. The most common, and easiest, is using an age based formula, typically referred to as “age predicted maximal heart rate” (APMHR) in order to calculate HRmax. Two of the more popular APMHR formulas are the Fox equation and Tanaka equation. The second method is to use “graded exercise testing” (GXT) such as a VO2 max test on a treadmill or bike. Out of the two methods, the latter has shown to provide considerably more accurate results.
Calculating HRmax Using Age Predicted Maximal Heart Rate (APMHR)
It is important to understand that any age predicted formula to calculate maximal heart rate is an approximation among general populations. There are too many variables including genetics, body mass index, pre-existing medical conditions, medications, altitude, and specific activity, which are not able to be taken into account when calculating an APMHR. That does not mean that APMHR formulas are not effective for training, only that consideration needs to be given when using them. For example, the Fox equation, which is the most popular APMHR formula used, and is used even today in clinical settings, has a standard deviation of between 10 and 12 bpm (Shookster). Even with that noted, and after doing considerable research, I have reached the conclusion that the Fox equation is still the best APMHR formula to use when addressing the general population.
To calculate HRmax using the Fox equation
- 220 – age = maximum heart rate (HRmax)
To calculate HRmax using the Tanaka equation
- 208 – (0.7 x age) = maximum heart rate (HRmax)
So at age 57, my maximum heart rate using the Fox equation would be 163 bpm, while using the Tanaka equation my maximum heart rate is 168.1 bpm, a difference of 5.1 bpm. Given that I’m a conditioned individual, I’m inclined to start using the Tanka number vs. Fox, simply because I believe that the Fox has me estimated low for HRmax1.
Heart Rate Reserve (HRreserve)
Heart rate reserve is the difference between your maximum heart rate (HRmax) and your resting heart rate (HRrest). Heart rate reserve (HRreserve) is one way to measure cardiovascular fitness and another method by which target heart rate (THR) can be determined. It is calculated by subtracting your resting heart rate (HRrest) from you maximum heart rate (HRmax). A high heart rate reserve is the result of a low resting heart rate and indicative of good cardiovascular fitness.
To calculate your target heart rate (THR) using heart rate reserve (HRreserve) use the following formula, aka Karvonen formula, based on desired intensity (Scheid).
- moderate-intensity exercise is estimated to be 40–59% of your HRreserve target heart rate
- vigorous-intensity exercise is 60–89% of your HRreserve target heart rate
- THR = (HRreserve x % intensity) + HRrest
Examples
- My HRrest: 48 bpm (as of 8/1/2024 via Apple Health app)
- My HRmax: 168 bpm (using Tanaka at age 57)
- My HRreserve: 120 bpm (HRmax minus HRrest)
- If I want to exercise to a moderate-intensity of 45%, my equation would look like this
- THR = (120 x .45) + 48
- THR = (54) + 48
- THR = 102 bpm
- If I want to exercise to a vigorous-intensity of 85%, which is a pretty standard THR for training, my equation would look like this
- THR = (120 x .85) + 48
- THR = (102) + 48
- THR = 150 bpm
So you are probably asking, if I already have HRmax around which to set my target heart rate (THR), why should I care about using Heart Rate Reserve to set my THR? Because HRreserve takes into account both an individuals HRmax and their HRrest, it is considered to be a more accurate measurement around which to set target heart rate zones.
Target Heart Rate Training2
Target heart rate training provides a method by which one can effectively manage their workouts using their specific heart rate referenced to heart rate zones. Heart rate zones are traditionally broken up into 5 zones3, with each zone serving a unique purpose related to workout effort (e.g. endurance, strength, recovery, speed, etc.) and the associated energy sources that are used by the body to fuel the workout. This approach allows an individual to design a training program around their objectives, gauge the intensity of their workout, and train more efficiently while avoiding overtraining.
The chart below was developed in order to demonstrate how the phrases “moderate-intensity exercise” and “vigorous-intensity exercise” align with the traditional heart rate zones as well their associated heart rates. It is important to note that the traditional heart rate zone table uses maximum heart rate (HRmax) to determine the zone. The American College of Sports Medicine (ACSM) in it’s use of “moderate-intensity” and “vigorous-intensity” phrasing related to exercise, established in 2021 that moderate-intensity exercise using HRmax had a target heart rate range of 65% – 75% (Liguori), which corresponds to the bottom half of zone 2 and the top half of zone 3, and that vigorous-intensity exercise using HRmax had a target heart rate range of 76% – 96% (Liguori), which corresponds to the bottom half of zone 3 and the top half of zone 5. [Dashed red line denotes HRmax intensity with it’s associated heart rate zone(s)]
The ACSM also established the following target heart rate ranges related to using HRreserve. Moderate-intensity exercise using HRreserve had a target heart rate range of 40% – 59%, which corresponds to zone 0 and zone 1, and the vigorous-intensity exercise using HRreserve had a target heart rate range of 60% – 89%, which corresponds to zone 2 thru zone 4. [Dash orange line denotes HRreserve intensity with it’s associated heart rate zone(s)]
At first glance when reviewing the heart rate percentages between HRmax and HRreserve in the table, it appears that there is quite the discrepancy between the two calculations; however, when the calculations are run (see below) that discrepancy is +/- 3 bpm at best.
Using my own data, I calculated the following:
Moderate Intensity – Top of Range
HRmax, using Fox, would result in a maximum heart rate of 163 bpm. Using the top end of the moderate-intensity exercise heart rate, which is 75%, we come away with a target heart rate (THR) of 122 bpm. [163 HRmax x .75]
HRreserve provides a heart rate reserve of 120 bpm. Using the top end of the moderate-intensity exercise heart rate, which is 59%, we come away with a target heart rate (THR) of 119 bpm. [(120 HRreserve x .59) + 48 HRrest]4
Vigorous Intensity – Top of Range
HRmax, using Fox, would result in a maximum heart rate of 163 bpm. Using the top end of the moderate-intensity exercise heart rate, which is 96%, we come away with a target heart rate (THR) of 156 bpm. [163 HRmax x .95]
HRreserve provides a heart rate reserve of 120 bpm. Using the top end of the moderate-intensity exercise heart rate, which is 59%, we come away with a target heart rate (THR) of 155 bpm. [(120 HRreserve x .89) + 48 HRrest]4
Another example of how to use target heart rate, let’s suppose that I want to train in zone 2 for a given period of time during a cycling workout. I would perform the following steps.
- Determine the target heart rate range for zone 2, which is 60% to 69% of HRmax
- Calculate heart rate for the lower end of the range. (120 HRreserve x .6) + 48 HRrest = 120 bpm4
- Calculate heart rate for the higher end of the range. (120 HRreserve x .69) + 48 HRrest = 130.8 bpm4
- In order to train in zone 2, I would need to keep my heart rate between 120 bpm and 131 bpm for a given period of time.
Target heart rate training is a great way to quantify your effort so you can clearly see where you are making progress (or not) in your workouts. As your body becomes more conditioned to a particular effort, your heart rate will adapt meaning that for you to reach a certain heart rate it will become easier and also means you will be able to push harder in your workouts to achieve desired outcomes.
Peak Heart Rate (HRpeak)
Not to be confused with maximal heart rate (HRmax), peak heart rate is the maximum heart rate an individual reaches during an exercise session and typically occurs right at the end of an exercise session before cooldown.
Heart Rate Recovery (HRrecovery)
Heart rate recovery (HRrecovery) is how quickly your heart returns to normal after you stop exercising. It is measured by taking the difference between your peak heart rate (HRpeak), usually captured at the end of your exercise push and just before cooldown, and your heart rate one minute post exercise push during cooldown (active rest5). This is referred to as the “fast phase” of heart rate recovery.
The recovery rate for the average person is a drop of 15 to 25 beats during the first minute (nasm). The higher the number the better cardiovascularly conditioned the individual.
Heart Rate Variability (HRV)
Heart rate variability (HRV) is the measure of variation in time between each successive heart beat and is measured in milliseconds (ms). Although far too thorough of a topic to discuss in this article, I did feel compelled to mention this measurement, especially as it relates to recovery from workout and overall determining how well the body is adapting to stress. More about HRV will be written in a future article.
Notes
1This is my perception and is not based in fact. At this time there is no clear evidence to establish which one of the methods is more reflective of my true HRmax. Only after performing a graded exercise test will I know which number is more accurate.
2What should be a straight forward question asking “What target heart rate percentage ranges should one use for moderate-intensity exercise and vigorous-intensity?” has been anything but straight forward when it has come to finding a reliable answer. There are inconsistencies abound based on sources using either outdated information or just applying information incorrectly, thus making it extremely challenging to know what information is accurate. This holds true for what one might consider to be more trusted resources like Mayo Clinic, Cleveland Clinic, Harvard, etc. To combat these inconsistencies I looked for two things prior to publishing. First, could I find definitive, updated, information and second, if definitive and updated information was not available, was there at least general consensus among reputable sources that the information could be considered reliable.
3You will notice in the chart that I listed a Zone 0. There has been some discussion and traction gaining for a sixth zone designed around recovery and reducing muscle soreness. Some examples of zone 0 exercise include yoga, Pilates, stretching, and walking.
4Note that the HRmax used to calculate HRreserve was derived using the Tanaka equation.
5Active rest, as it is referred here, is the portion of the cooldown phase where your intensity drops considerably. For example in a cycling session, active rest would refer to lowering the intensity by dropping the pedal resistance (lower gear), whereas in a running session, active rest would refer to as either a slight jog or a walk.
Works Cited
Laskowski, Edward R, MD. “What’s a normal resting heart rate?” Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/fitness/expert-answers/heart-rate/faq-20057979 Accessed August 1, 2024
Jensen, Magnus T. “Resting heart rate and relation to disease and longevity: past, present and future.” Scandinavian Journal of Clinical and Laboratory Investigation vol. 79,1-2 (2019): 108-116. https://pubmed.ncbi.nlm.nih.gov/30761923/ Accessed August 1, 2024
Shookster, Daniel et al. “Accuracy of Commonly Used Age-Predicted Maximal Heart Rate Equations.” International journal of exercise science vol. 13,7 1242-1250. 1 Sep. 2020 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7523886/ Accessed August 1, 2024
Liguori, Gary, PHD., FACSM, ACSM-CEP, “ACSM’S Guideline for Exercise Testing and Prescription” American College of Sports Medicine 11th Edition. 2022. https://www.acsm.org/education-resources/books/guidelines-exercise-testing-prescription Accessed August 5, 2024
Scheid, Jennifer L. Ph.D.; O’Donnell, Emma Ph.D. “Revisiting Heart Rate Target Zones Through the Lens of Wearable Technology” ACSM’s Health & Fitness Journal 23(3):p 21-26, 5/6 2019. https://journals.lww.com/acsm-healthfitness/fulltext/2019/05000/revisiting_heart_rate_target_zones_through_the.8.aspx Accessed August 5, 2024
NASM. “Pump Up Your Heart Smarts” National Academy of Sports Medicine https://blog.nasm.org/fitness/pump-up-your-heart-smarts Accessed August 5, 2024
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