When you exercise, your heart rate increases to meet the extra demand for oxygen that exercise places on it. More intense exercise causes a greater rise in heart rate since your body needs more oxygen as exercise intensity increases. Without a rise in heart rate, you wouldn’t be able to sustain exercise due to inadequate oxygen delivery.
Some people wear a heart rate monitor to track their heart rate during a workout. Most do this to ensure they’re exercising hard enough to get the cardiovascular benefits. If your heart rate stays below a certain threshold level when you work out, your aerobic capacity won’t improve since the intensity is too low. Aerobic capacity is a measure of stamina and endurance and improvements in aerobic capacity are one reason you feel less winded when you work out after training for a few months. Higher aerobic capacity is also linked with a reduction in mortality.
Maximum Heart Rate: How It’s Measure and What It Means
But what happens if your heart rate climbs too high during exercise and how do you know what too high is? There’s a term called maximum heart rate, referring to how fast your heart beats when maximumly stressed. There are a number of ways to measure or estimate maximum heart rate. The most reliable way is to do a maximum exercise stress test.
For a maximum stress test, a technician asks you to walk briskly on a treadmill while the incline gradually increases to make the exercise harder as they monitor your heart rate. Your heart rate will continue to rise as the challenge increases, but at some point, it reaches a plateau where it stops going up, despite the intensity increasing. This heart rate is your maximum heart rate.
Since not everyone can rush out and get maximum exercise stress test, there are formulas for estimating maximum heart rate with varying degrees of accuracy. The most common formula is to subtract your age from 220. Although studies now show this isn’t the most accurate formula, it’s the simplest and most practical and gives a reasonable estimate of maximum heart rate.
Once you have your calculated maximum heart rate, based on your age, you can use it to monitor exercise intensity. For example, moderate intensity exercise corresponds with 50 to 70% of your maximum heart rate. If you’re doing a high-intensity or HIIT workout, your heart rate should be between 70 and 90% of your maximum heart rate.
What If Your Heart Rate Rises Above Your Target Zone?
You might wonder if it’s dangerous for your heart rate to exceed your target heart rate. For example, what if your heart rate goes above 90% of your maximum heart rate, your designated upper limit, during a high-intensity training session? If you have a healthy heart, going above the upper range of your target heart rate shouldn’t cause problems. However, exercising above your target heart rate zone consistently can be a sign that you’re pushing harder than you need to and is an indicator you can slow down a bit. Doing this often also increases the risk of overreaching and overtraining by pushing yourself hard without allowing enough time to recover.
Also, if you have uncontrolled hypertension or underlying cardiovascular disease, you may put yourself at risk when you exceed your target heart rate zone. Plus, your target zones may be different if you have health problems or take certain medications. So, check with your health care provider about how vigorously you should exercise and what your target heart rates should be.
Keep this in mind too. The formulas available to calculate maximum heart rate are only estimates. Your maximum heart rate could be higher or lower than what the 220 minus age formula tells you that it is. Target heart rate zones are only guides. They aren’t written in stone. There will always be some variability based on the individual.
Should You Wear a Heart Rate Monitor
Wearing a heart rate monitor is one of the best ways to monitor your exercise intensity and ensure you’re exercising safely. Heart rate monitors (HRMs) measure the pulse in your wrist or neck. They use an optical sensor to detect changes in blood volume as it flows through your veins. These changes occur when your heart beats, which causes blood to move more slowly through your body when it contracts (systole) and more quickly when it relaxes (diastole).
The heart rate monitor calculates your heart rate by measuring these changes over time. Heart rate monitors are helpful for all ages and fitness levels, but they’re especially useful for people with health conditions like high blood pressure.
A heart rate monitor can track your heart rate and calories burned. The best ones also have features that allow you to set a target heart rate zone, so you know when to speed up or slow down. Then you can use a heart rate monitor to determine how close you are to your target heart rate and whether you’ve exceeded it. Heart rate monitors are great for all ages and fitness levels, but they’re especially useful for people with health conditions like high blood pressure.
Be sure to listen to your body. The most common signs you’re pushing too hard:
- You’re breathing too hard. If you’re huffing, puffing, gasping for air and unable to say more than a word or two at a time, it’s time to slow down.
- You feel dizzy or lightheaded. If you experience these symptoms, it could be a sign your blood pressure is dropping too low, or you’re dehydrated.
- You feel sick to your stomach. If this happens after a long run or intense workout, it could be caused by dehydration or low blood sugar levels.
- Your muscles hurt more than usual when you exercise or after your workouts
- You’re getting more injuries than usual.
- You’re exhausted after your workouts, and it persists for hours after a workout.
The Bottom Line
If your heart rate is too high during exercise, you may be pushing too hard. However, a healthy heart can tolerate a heart rate outside of the training zone. But if you have health issues, it’s important to follow your healthcare provider’s advice on how hard to exercise and monitor your heart rate closely.
References:
- Deborah Riebe, Jonathan K Ehrman, Gary Liguori, Meir Magal. Chapter 6 General Principles of Exercise Prescription. In: ACSM’s Guidelines for Exercise Testing and Prescription. 10th Ed. Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia, PA: 2018, 143-179.
- Target Heart Rate and Estimated Maximum Heart Rate. Published 2022. Accessed August 14, 2022. https://www.cdc.gov/physicalactivity/basics/measuring/heartrate.htm
- “Target Heart Rates Chart | American Heart Association.” 09 Mar. 2021, https://www.heart.org/en/healthy-living/fitness/fitness-basics/target-heart-rates.
- “Intrinsic aerobic exercise capacity linked to longevity.” 30 Sept. 2011, https://www.sciencedaily.com/releases/2011/09/110930102806.htm.
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