Why Is My Heart Rate So High When I Run?

11 factors that can affect your heart rate while exercising.

Whether you are a runner who focuses explicitly on heart rate training or simply notes your running heart rate when you check your running watch at the end of a workout, there can be times when you notice that you have a high heart rate, even on easy runs.

You may even notice that your resting heart rate is higher than your normal heart rate at rest or that your heart rate takes longer to come down after your workout and return to baseline.

For many runners experiencing the same thing, it brings up the question, “Why is my heart rate so high when I run?”

If your heart rate on easy runs is high or you are having difficulty keeping it in the target heart rate zone, there might be issues with your recovery, training plan, or running pace, among others.

In this guide, we will briefly discuss heart rate training and target heart rate zones for easy runs and give you the most common causes of a higher heart rate during easy runs to help answer your question, “Why is my heart rate so high when I run?”

A lady checking her pulse wearing running gear in the woods

Is My Heart Rate High When Exercising?

Before discussing the most common causes of an elevated resting heart rate or elevated running heart rate on easy runs, let’s briefly discuss heart rate training and the expected average heart rate for easy runs.

Heart rate training uses different target heart rate training zones based on a percentage of your maximum heart rate.

Easy runs are designed to be low-intensity workouts that provide the cardio benefits of running while not stressing your cardiovascular system as much as high-intensity workouts such as tempo runs and interval training.

For this reason, your average heart rate on easy runs should fall within zone 2 of the heart rate zones if you are healthy, running at an easy pace, and reining in your effort level so that you feel comfortable.

Therefore, the normal heart rate for an easy run should be between 60 and 70% of your age-predicted max heart rate.

If you review your heart rate data after an easy run, or you look at your average resting heart rate overnight with a wearable fitness tracker and notice that you have a high resting heart rate or an elevated heart rate while running easy, it is important to troubleshoot the issue.

The body sends us signals about our health and recovery through biometrics such as heart rate and heart rate variability.

An elevated heart rate can indicate certain underlying issues with your training, recovery status, or overall health, and research suggests1Nauman, J., Janszky, I., Vatten, L. J., & Wisløff, U. (2011). Temporal Changes in Resting Heart Rate and Deaths From Ischemic Heart Disease. JAMA306(23), 2579–2587. https://doi.org/10.1001/jama.2011.1826 that a higher resting heart rate is associated with an increased risk of adverse cardiovascular events and all-cause mortality. 

According to the American Heart Association,2American Heart Association. (2015, July 31). All about Heart Rate (pulse). American Heart Association; American Heart Association. https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure/all-about-heart-rate-pulse the normal resting heart rate for adults is typically between 60 and 100 beats per minute (bpm). However, runners and other endurance athletes usually have a lower resting heart rate due to cardiovascular adaptations from consistent training.3Farrell, C., & Turgeon, D. R. (2021). Normal Versus Chronic Adaptations To Aerobic Exercise. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK572066/

a lady running next to snowy mountains

Why Is My Heart Rate So High When I Run?

Here are the most common causes of unexpected heart rate increases either in terms of your resting heart rate or particularly when you have a high heart rate when running:

#1: Running Too Fast

Easy runs should be run at an easy pace, where you can comfortably hold a conversation and seemingly run for a long time without stopping.

As a running coach, I notice that beginners and experienced runners alike often run too fast on easy runs and then only glance down at their heart rate monitor towards the end of the workout to notice that they were pushing too hard.

Particularly if you have just done a hard workout the day before or are recovering from a long run or race, you may need to slow down your running pace to keep your easy run heart rate in zone 2. 

In other words, don’t worry about pace, but focus on your heart rate and effort level.

#2: Stress

Physical, mental, and emotional stress can all trigger the sympathetic nervous system or the “fight-or-flight” response. 

Activation of the sympathetic nervous system increases heart rate and respiration rate. Acute or chronic stress can cause an elevated heart rate at rest or while running.

the silhouette of two people running against a white and blue background

#3: Lack of Sleep

Sleep is vital for recovery, so a lack of sleep increases resting heart rate4Corliss, J. (2021, January 29). How Does Sleep Affect Your Heart rate? Harvard Health Blog; Harvard Health Publishing. https://www.health.harvard.edu/blog/how-does-sleep-affect-your-heart-rate-2021012921846 and running heart rate due to incomplete recovery and elevated cortisol levels.5Hirotsu, C., Tufik, S., & Andersen, M. L. (2015). Interactions between sleep, stress, and metabolism: From physiological to pathological conditions. Sleep Science8(3), 143–152. https://doi.org/10.1016/j.slsci.2015.09.002

#4: Temperature and Environmental Conditions

When running in the heat or humid weather, your heart has to work harder to cool your body down. The heart beats faster to bring more blood to the skin’s surface and produce sweat to lower your core body temperature. 

Therefore, your easy run heart rate can be higher on hot days even when your perceived exertion or effort level feels the same as it does on a cooler day.

Running at altitude can also increase your average heart rate6Grover, R. F., Weil, J. V., & Reeves, J. T. (1986). Cardiovascular adaptation to exercise at high altitude. Exercise and Sport Sciences Reviews14, 269–302. https://pubmed.ncbi.nlm.nih.gov/3525187/ because the oxygen availability in the atmosphere is lower. Therefore, your heart has to pump faster to maintain sufficient cardiac output as less oxygen is transported through the circulatory system.

#5: Fever or Illness 

In much the same way that your heart rate increases running in the heat to increase cutaneous blood flow to cool your body down, if you have a fever, you will also notice that your heart rate is high relative to your normal heart rate because your heart has to work harder to cool you down.

Similarly, if you are sick or getting sick, your immune system is working hard to fend off the illness, which can increase your heart rate running and at rest.

a lady wearing running gear drinking water in a rocky desert environment

#6: Hydration Status

Dehydration can increase your resting heart rate7The Heart Foundation . (2019, April 26). The Importance of Water – The Heart Foundation. The Heart Foundation. https://theheartfoundation.org/2019/03/08/the-importance-of-water/ or running heart rate because as your body water drops, your blood plasma level decreases. 

When less blood is pumping through your circulatory system, your heart has to pump faster to maintain the same cardiac output. 

#7: Cardiac Drift

Just as dehydration can cause a higher heart rate due to the strain on the cardiovascular system, cardiac drift8Souissi, A., Haddad, M., Dergaa, I., Ben Saad, H., & Chamari, K. (2021). A new perspective on cardiovascular drift during prolonged exercise. Life Sciences287, 120109. https://doi.org/10.1016/j.lfs.2021.120109 is one of the most common causes of an elevated heart rate on long runs, even when you are maintaining the same easy pace or level of perceived exertion throughout the duration of the run.

As you sweat and blood plasma volume drops, your heart rate increases to maintain the same cardiac output and provide ample blood flow and oxygen to your working muscles.

This is why staying well hydrated on long runs is critical, especially when running in the heat, as sweat rate increases in hot weather.

#8: Medications

Certain prescription and over-the-counter medications can affect your resting and exercise heart rates. 

For example, beta-blockers usually cause decreases in heart rate, while certain stimulants and psychoactive medications may increase your normal heart rate.

a man running in nature checking his watch

#9: Caffeine Intake

Caffeine is a stimulant because it competitively binds with adenosine receptors in the brain.

Drinking coffee, having caffeinated energy gels, or taking other forms of caffeine before running can artificially elevate your heart rate relative to your pace.

For example, if you can normally run at a 10-minute pace in zone 2 but have a big cup of coffee 30 minutes before running, you may find that the same easy pace that normally keeps your heart rate below 70% of your maximum heart rate is now causing your heart rate to be closer to 75-78%.

#10: Poor Fitness Level

Beginners will notice that their heart rate decreases at the same easy pace as their fitness level improves. 

Adaptations to the cardiovascular system improve efficiency and will decrease your submaximal heart rate over time.

a lady sleeping

#11: Overtraining

Beginners and competitive runners who follow an aggressive training plan or push too hard during workouts without building in ample recovery time may start to notice an elevated heart rate at rest and while running.

This is the beginning of overtraining syndrome.9Kreher, J. B., & Schwartz, J. B. (2012). Overtraining Syndrome. Sports Health: A Multidisciplinary Approach4(2), 128–138. https://doi.org/10.1177/1941738111434406

Chronic overtraining can leave the body in incomplete recovery, reflected in a higher resting heart rate and high heart rate running at a slow pace.

If your high heart rate is accompanied by palpitations, heart arrhythmias, chest pain, high blood pressure, or dizziness or simply is not resolving, you must see a cardiologist and get a medical workup. 

Looking to calculate your heart rate training zones? Check out this next guide:

References

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Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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