WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
By Dr. Mercola
Exercise has been a game-changer for me since I first started with it in 1968. My consistent commitment to exercise the last 50 years has improved my health to a level that would not have been possible through diet alone. Integrating some kind of exercise program into your life is the only way to be optimally healthy. After years of doing cardio, I am now a passionate fan of high intensity interval training (HIIT). Not only does HIIT shorten the time of my workouts, but it also elevates my heart rate and strengthens my heart muscle.
This year I have been doing a deep dive in molecular biology and have learned that exercise is responsible for increasing PGC-1alpha, which is a transcriptional coactivator that regulates the genes involved in energy metabolism, and more importantly is responsible for increasing your mitochondria in a process called mitochondrial biogenesis.
Beyond PGC-1alpha exercise also activates other transcriptional activators Nrf2 and FOXO3a, which are both responsible for improving your response to oxidative stress by increasing superoxide dismutase, catalase and glutathione. I used to believe that diet was responsible for 80 percent of your health and exercise 20 percent but I suspect it is much closer to a 60/40 split.
I have painfully learned that chronic cardio is not ideal and that high intensity but brief exertional efforts offer superior metabolic benefits in a shorter time. In order to achieve these benefits it is important to know how to calculate your maximum heart rate (MHR).
Accuracy is important because certain high intensity benefits can only be realized when your heart rate is elevated for specific intervals. Overestimating your heartbeat by even 20 beats per minute can make a big difference in the quality of your workout. Let's take a closer look at how and why you should exercise in your target heart rate zone.
Understanding Your Heart Rate and What Affects It
Most healthy adults have a resting heart rate (RHR) of 60 to 100 beats per minute. Due to their smaller bodies and heart size, infants and children have higher heart rates than adults. The "normal" range for your adult RHR remains consistent as you age. For best results, you can determine your RHR when you are sitting or lying down and when you are calm, relaxed and in good health.
If you have a low RHR — anything under 60 beats per minute — it may be a sign of health and not necessarily an indication of a medical problem. Generally speaking, lower RHRs can be a sign of better cardiovascular function and more efficient heart function. If you are a fit, well-conditioned athlete, you may have a RHR as low as 40 beats per minute.1 According to the American Heart Association, the following factors have been shown to affect your heart rate:2
- Air temperature: Changes in air temperature and humidity can raise your heart rate by five to 10 beats per minute because your heart has to pump a little more blood to accommodate the weather
- Body position: Typically, your pulse is the same when you are resting, sitting or standing, but it will elevate temporarily when you move from sitting to standing (it will soon level off again)
- Body size: If you're very obese, you may have a higher resting pulse than a person of a smaller size, but it is unlikely you will have a heart rate more than 100
- Emotions: For sure your emotions can raise your heart rate; particularly if you're stressed or anxious, those feelings will be reflected in your pulse
- Medication use: Medications can either raise or lower your pulse; antidepressants, beta blockers and opioid painkillers tend to slow your pulse, while too much thyroid medication will quicken it
Higher Heart Rate Is Associated With Increased Incidence of Heart Attack
While having a heart rate between 60 and 100 beats per minute is considered "normal," research suggests maintaining a heart rate at the lower end of the spectrum will be better for you. A large U.S. cohort study involving 15,680 participants with a mean age of 54 years enrolled in the Atherosclerosis Risk in Communities Study suggests a higher heart rate is associated with a greater incidence of:3
During the research, which began in 1987, participant heart rates were recorded at baseline and during follow-up visits about every three years for the next 28 years. Increases in time-updated heart rate — defined as the most recent heart rate value measured prior to an event (or the end of study) — and change in heart rate from the preceding visit were both associated with death, incident heart failure, incident heart attack and stroke.
Specifically, with respect to their time-updated heart rate, participants faced a 14 percent greater risk of all-cause mortality for every five beats per minute their heart rate increased prior to an event (e.g., a heart attack or stroke).
Similarly, they faced a 12 percent greater risk of all-cause mortality for every five-beats-per-minute increase noted for the change in heart rate measurement. Due to the serious health risks associated with higher RHRs and increases in your heart rate over time, the study authors recommend measuring and tracking your RHR at regular intervals.
Other Heart-Related Troubles That May Affect Your Ability to Exercise
Chronotropic incompetence (CI) is a condition marked by your heart's inability to increase its rate in proportion to the output that is needed, as in the case of exercise. One pair of researchers suggest CI is "an independent predictor of major adverse cardiovascular events and mortality. It is present in up to one-third of patients with heart failure and contributes to their prominent exertional symptoms and reduced quality of life."4
Not only is it a sign of trouble when your heart can't meet the demands for increased output with respect to exercise and other tasks, but you also face an increased risk of early death if your heart is consistently unable to return to its resting rate after periods of exertion. Research suggests a generalized decrease in vagal activity can be a risk factor for death.
To test the hypothesis, a six-year study5 involving more than 2,400 adults with a mean age of 57 years, who did not have a history of heart failure, coronary revascularization or pacemakers, found participants with abnormal values for heart-rate recovery were twice as likely to die than those with normal heart-rate recovery cycles. The study authors stated, "A delayed decrease in the heart rate during the first minute after graded exercise, which may be a reflection of decreased vagal activity, is a powerful predictor of overall mortality."6
How to Determine Your Maximum Heart Rate
To maximize the quality and effectiveness of your workouts, you need to determine your heart's maximum capacity for exercise. There are several methods for calculating your MHR. First, you can use the "old-school" method, which involves subtracting your age from 220. If you are a 25-year-old, your MHR would be 195. Some experts believe this method to be inaccurate, especially as you advance beyond age 50.7 You can further personalize your number by testing your heart rate during intense exercise using one of two methods:
1. MHR: Declan Connolly, Ph.D., exercise physiologist and coauthor of the book, "Heart Rate Training: Increase Endurance, Raise Lactate Threshold, and Boost Power," suggests getting your heart rate up as high as you can. He says:8
"A simple test I have proposed over the years is going out onto an outdoor track, jogging 400 meters (1/4 mile) as a light warm-up, then running [the same distance] as fast as you can. Repeat that entire sequence two more times, for a total of six laps — three jogging and three fast [running]. Check your heart rate right after the third set. Whatever that number is after the last lap is a good indication of your MHR."
If you are not able to run for whatever reason or may be prone to injury from running, you can complete this exercise on a stationary bike or other machine using the same set structure and time sequence. If you need help, consult a personal trainer.
2. Heart rate reserve (HRR): Dr. Bryant Walrod, team physician at Ohio State University, suggests a different technique that involves first calculating your MHR using this formula: 208 minus (0.7 x your age).9
In this scenario, if you are 25 years old, your target maximum is 190.5 beats per minute. Says Waldrod, "This formula tends to be more accurate as you get older." Next, you need to find your RHR by either using a heart rate monitor or counting your heartbeats for 60 seconds when you are sitting down and feeling relaxed.
Finally, use those two numbers to calculate your HRR as follows: MHR minus RHR = HRR. "As you get fitter, your RHR will drop," noted Waldrod. "If you're consistent, your RHR will change, so check in with that number at least annually."10 Fans of HRR suggest it provides a better target heart rate to achieve optimum levels of exertion based on both your maximum and RHR.
Four Options for Measuring Your Heart Rate
Your pulse is an exact measure of your heart rate because your heart's rhythmic contractions cause increases in your arterial blood pressure that create a noticeable pulse. Although there are 12 places on your body to feel a pulse, the two places known to provide the easiest and most reliable reading are your radial artery (on the inside of your forearm) and your carotid artery (on the side of your neck a short distance from your Adam's apple). Below are four options to measure your heart rate:
- Manual reading: Sit down and relax for a few minutes and then use two fingers to gently compress either your carotid or radial artery while counting the beats for 60 seconds. This is your heart rate (beats per minute). For accurate results, avoid using your thumb because it has its own pulse, which may confuse the measurement.
- Electrocardiogram (ECG or EKG): This is a painless test used to record the electrical activity of your heart using small electrode patches attached to your chest, arms and legs. An ECG is the most reliable measurement of your heart rate.
- Wearable heart rate monitors: As mentioned in the featured video, wearable devices such as chest straps that are wirelessly connected to an exercise machine, fitness tracker or smartwatch are also handy tools to measure your heart rate, especially during intense exercise.
- Pulse Oximetry: These are devices that you wear on your fingertip that tell you the oxygen saturation of your blood but nearly all of the devices also display your heart rate.
Due to the simplicity of their design, smartwatches have inherent limitations but they are still a useful tool to achieve real-time heart-rate data, just be sure to put it in airplane mode. Most certainly, during periods of intense exercise, it will be easier to track your heart rate using an electronic device versus trying to take manual measurements. Accuracy is important when tracking your heart rate because reaching your specific zones is the key to achieving maximum calorie and fat burning during your workouts.
The Importance of Getting in the Zone During Exercise
For exercise to be effective, you need to know your heart rate and work out to the degree that your body "gets in the zone" (your heart rate zone) and stays there for a defined period of time. In this case, the zone can be one of three levels and each one provides different potential benefits for your workout. You can use either your calculated MHR or your HRR to determine the following numbers:
- Aerobic/low intensity: 50 to 75 percent of MHR or HRR
- Anaerobic/moderate intensity: 75 to 85 percent of MHR or HRR
- Anaerobic/high intensity: 85-plus percent of MHR or HRR
Once again, if you are 25 years old, you have a low intensity range of 95 to 143, a moderate intensity range of 143 to 162 and a high intensity range of 162 and above. The low intensity range is consistent with conventional cardio exercise that is usually performed in 30- to 60-minute segments. Moderate intensity exercise is characterized by bursts or intervals lasting one to three minutes. High intensity work takes places in the shorter bursts or intervals lasting just 10 to 45 seconds.
After years of doing mostly cardio, I am now a passionate advocate for peak fitness, which is my favorite form of HIIT. I love peak fitness because it pushes my heart to near-maximum effort. If you are unfamiliar with this type of workout, check out my "What Is Peak Fitness? infographic." Additionally you will increase nitric oxide production, which has enormous cardiovascular benefits. Another option is to join a club focused on getting your heart into the high intensity zone.
Heart Rate-Based Exercise May Have You Seeing Orange
If you are a fan of heart-rate based exercise but may not be motivated to do it on your own, you may want to check out Orangetheory Fitness (OTF),11,12 a franchised fitness studio with 1,000 locations around the globe and upward of 623,000 members.
The first OTF studio opened in Fort Lauderdale, Florida, in 2010 and the hallmark of the franchise is the focus on heart-rate monitoring for the purpose of achieving what they call "afterburn," the ability to burn calories long after your workout ends — assuming you reached a sufficiently high level of intensity, near your MHR.
Because tracking your heart rate through five defined target zones is the cornerstone of an OTF workout, calculating your MHR is one of the first activities you'll do. From there, your MHR will guide all of your workouts, which change daily.
During a typical 60-minute OTF session, you will perform various exercises and use several different tools and machines, including rowers and treadmills, as well as varied levels of effort, to maximize your heart rate. All exercises can be customized to individual needs and all activities and interval work, including reps and timing, are displayed on monitors.
No matter what your approach to exercise, I cannot stress enough the importance of tracking your heart rate and paying attention to your target heart rate zone to give yourself and your heart the best workout possible. I also highly recommend core work, strength training and stretching, as well as achieving 10,000 to 15,000 steps a day. After all, getting regular exercise — particularly specific workouts that hit the three intensity zones — is one activity you must embrace if you want to take control of your health.