If you wear a smartwatch or fitness tracker, you probably already have access to a constant stream of data about your heart health.
In addition to basic heart rate monitoring, smartwatches and fitness trackers can also measure and track heart rate zones, heart rate variability, and heart rate trends.
This information can be powerful for your health and fitness if you’re willing to experiment with different intensity levels during exercise—and if you understand the limitations of the data.
To make the data useful, Kathryn Larson, a cardiologist at the Mayo Clinic’s Sports Cardiology Clinic in Rochester, Minnesota, asks patients about their health and fitness goals. “The discussion changes a lot based on what that patient or athlete wants to do with that data,” she said.
For people looking to develop an exercise habit, heart rate data can be a great tool for understanding how their fitness levels change over time. For more experienced athletes, heart rate zone training can help improve speed and endurance.
How to measure your heart rate
To measure your heart rate without a wearable device, find your heart rate on your neck or wrist. Count the number of hits you detect in 15 seconds and multiply that number by four.
Your resting heart rate is the number of times your heart beats per minute when you are not exercising. Your maximum heart rate, which can be roughly calculated based on your age, is a measure of how fast your heart beats during intense exercise.
Most fitness trackers, GPS running watches and Apple Watches measure heart rate using a small light to measure changes in the blood flowing through the vessels in your wrist throughout the day. Chest strap monitors can be slightly more accurate than watches, but are usually only worn during exercise.
A healthy resting heart rate is usually between 60 and 100 beats per minute, although there can be a lot of individual variation. Athletes and people with high levels of fitness often have a lower resting heart rate.
The basics of heart rate zone training
Zone training involves structuring your exercise plan around five heart rate zones that range from a relaxed effort to your maximum intensity. Training in this way can help you design workouts that target specific goals, such as building endurance or improving performance.
Each zone is based on a percentage of your maximum heart rate: in zone one, for example, you should reach 50 to 60 percent of your maximum heart rate, while zone five requires 90 to 100 percent of your maximum heart rate. Many fitness trackers can estimate your heart rate zones and tell you which zone you are in during exercise. But you can also replicate zone training based on your own sense of effort.
“The best way to really understand the zones is by understanding the effort and the goal,” said Dr. Tamana Singh, a cardiologist and co-director of the Sports Cardiology Center at the Cleveland Clinic, adding that different levels of exercise intensity trigger different physiological processes. in the body.
First zone it should be easy, comparable to warming up or cooling down. You should be able to “sing a song or recite a Shakespeare sonnet without interruption,” Dr. Singh said.
Zone two it should be a bit more challenging. You should be able to carry on a conversation, but you may need a breath here and there, Dr. Singh said. Training in zone two is key to building endurance and developing your aerobic capacity. During endurance sports such as running and cycling, the majority of your training time should be spent in this area.
Zone three it’s not as sustained as zone two, and you may feel the need to take more breaks between calls, Dr. Singh said. Many runners refer to this level of effort as “pace.”
Area four is what runners and cyclists would call a threshold workout, “something you could probably do for maybe 45 minutes or an hour max,” Dr. Singh said.
zone five, your maximum, all-out effort is an intensity that Dr. Singh considers a “red line.” There is no room for conversation as your body works on building its ability to function on less oxygen.
Athletes in sports such as swimming, running, and cycling typically spend most of their training time in zones one, two, and three to build aerobic fitness and endurance, with limited time in four and five based on individual goals.
Many factors—stress, weather, and sleep, for example—can affect your heart rate, so it’s important to consider your own sense of exertion along with your heart rate readings. If you’re interested in experimenting with a structured zone training plan, programs like Orangetheory and Peloton also offer heart rate-based workouts.
Heart rate variability
Many wearables also calculate the user’s heart rate variability, or HRV. The measurement tracks how your heart rate naturally varies from beat to beat and can generally be used to track how recovered or tired you are between workouts.
Numbers that are higher than your own baseline usually indicate a healthier cardiovascular system that is well recovered. (Most fitness trackers and smartwatches can calculate your baseline for you after they’ve collected enough data.) Lower numbers, especially after a hard workout, may indicate that your body still needs more time to recover. But, like other measures of heart rate, HRV can also vary based on factors unrelated to exercise, including illness and alcohol consumption.
Many doctors say there is not yet enough data on HRV to use as a basis for health or training decisions. Dr. Seth Martin, a cardiologist at Johns Hopkins Medicine, said he found the number “interesting but not as applicable” as other heart rate data.
The fine print
While heart rate data can provide useful clues about your health, experts caution against relying too much on the data.
“Any device will sometimes detect things accurately, and sometimes it can be unreliable,” Dr. Larson said, adding that any abnormalities that might cause concern should be a sign to talk to your doctor.
Using a talk test—trying to hold a conversation, even just to yourself, while exercising—can be just as helpful as checking your heart rate. And paying attention to how recovered or tired you feel can be just as helpful as tracking HRV.
Dr. Larson said some patients may be overwhelmed by the data. In those cases, she urges them to look at the big picture: “How much does this data actually help, or how much does it distract us from the bigger issues?”
