It’s no secret: Runners love fancy running gear, and if you’ve been itching for a good reason to invest in a new fancy watch that will track and measure everything you might need to hit your next PR, heart rate training just might be the excuse you’ve been looking for.
“Heart rate training allows you to monitor your effort, to keep the easy days easy, the hard days hard, and the tempo sessions in the right ‘effort,’” says Terra Castro, the Owner and Founder of Detroit Body Garage. Without heart rate data, “many people spend time in this ‘gray zone,’ not getting the full benefit of the training effect,” she says. “Plus, heart rate training is also a way to make sure you aren’t overtraining and are recovering well.”
But in order to execute heart rate training properly, you have to get to know your different heart rate zones and specifically, your maximum heart rate, the highest heart rate you can attain during exercise. The catch, of course, is that knowing your estimated maximum heart rate can be a little elusive to pin down.
The most common way to find your maximum heart rate is by using one of the many age-based equations. The most well-known of these is the Fox formula. It is the very simple:
220 - age = Maximum Heart Rate (MHR)
This means that for a 30-year-old runner, the estimated maximum heart rate would be 190. Then, heart rate zones can be determined by calculating a given percentage of the 190 MHR.
The trouble with the Fox formula is that it’s not the most accurate measure as numerous variables impact MHR including genetics, the specific activity (MHR varies between running and cycling due to the involvement of upper body musculature), medications, body size, altitude, and yes—even age. Runners of the same age can have drastically different max heart rates depending on how well-trained they are.
Because of this, there are at least six possible formulas, all claiming bragging rights for being the “most accurate” for predicting maximal heart rate. Of course, researchers are doing their best to validate the different formulas, but that gets tricky, too. For instance, a 2011 study published in the Journal of Strength and Conditioning Researchdetermined that in college-aged subjects, the Gellish2 and Fairburn equations seemed to be the most accurate options. That said, the American College of Sports Medicine recommends formulas with a standard deviation of seven beats per minute such as Gellish and Tanaka equations.
But there’s still a problem for the general public when it comes to using these formulas—they’re still just a rough estimate of MHR because differences between individuals can vary widely. For instance, a longitudinal study published in 2010 in the Journal of Medicine and Science in Sport and Exercise found that the older a person is, and the higher the person’s body mass index (BMI), the less likely it is for age-predicted maximal heart rates (like all of the formulas above) to be accurate. So studies that look at healthy, college-aged subjects, or trained athletes, or really, anyone under 50 years old, may not be good predictors for other people in the general population.
So what are you to do? It never hurts to get an estimate of what your heart rate max might be based on any of the above formulas. But from there, just start paying attention to where your heart rate tracks during workouts to see if the estimates feel accurate. “The heart rate tolerance is specific to each individual and is best determined by experience,” says William O. Roberts, M.D., M.S., professor in the Department of Family Medicine and Community Health at the University of Minnesota. “The role of MHR for runners is to provide a guide for training. The closer you are to your MHR during your workouts and races, the shorter the duration of exercise that you’ll be able to maintain at that pace. So, if you can maintain a rate of 160 during your workouts and races, your MHR is well above that.”
To properly utilize heart rate training, you need an easy way to track your heart rate. Of course, you can always go “old school,” use a timer, and place your fingers on your pulse to check beats per minute during your workouts, but that can get challenging when your heart rate soars, and you’re trying to count beats while huffing and puffing. Fortunately, chest straps and wrist watches make measuring your HR instantly easier.
Just about any GPS-tracking watch will also track heart rate with at least moderate accuracy, but if you’re looking for the most accurate option available, studies show you’ll be best-served by opting for a chest-strap monitor.
According to a 2017 study comparing chest strap and wrist-based heart rate monitors, the Polar H7 (currently available as the H10) was the most accurate of the seven products tested. Of course, there are many options on the market that haven’t been tested with this type of scientifically-validated approach, but of those that have been studied, these products consistently achieve the most accurate results:
Once you’ve selected a heart rate monitor, the trick is putting the information you glean from the watch or strap to use. After calculating your estimated MHR, determine your different heart rate zones by multiplying your MHR by the percentage for each zone. For example, if you wanted to find 55 percent of your maximum, you multiple your MHR by 0.55.
This will give you ranges of beats per minute for each percentage of maximum heart rate. Then pre-determine the zone you want to work in during each running routine. As you run, you can check your heart rate monitor to make sure you’re staying in the desired zone.
And luckily, there are apps that help manage this type of training for you. “I love using Garmin Connect Software and Strava,” says Castro. “I can plug my zones into my Garmin and track the time spent in each zone as well as track my overall progress toward my goal with specific data.”
Just remember, because heart rate maximums using age-predicted formulas are estimates, you may need to adjust your zones over time based on your own results and how each run feels. For instance, if you calculate your 90-percent zone (a near all-out effort) to be 175, but you’re able to maintain 175 beats per minute comfortably for several minutes, your estimated maximal heart rate has probably been underestimated. You may need to adjust your zones based on perceived effort at each level of intensity as time goes on and as you adapt to training.