During any type of cardio workout, your heart rate increases above resting levels. Indeed, the whole purpose of aerobic exercise is to elevate your heart rate in order to strengthen your heart and lungs and improve the efficiency of the cardiovascular system.
Today, whether you run or work out at a gym for exercise, it’s common to use a heart rate monitor and fitness tracker to monitor your heart rate zones while training.
But, how long should you have an elevated heart rate after exercise? Does a prolonged elevated heart rate after exercise point to heart problems or heart conditions such as cardiovascular disease?
In this guide, we will discuss what causes an elevated heart rate after exercise and what you can do if you notice you are experiencing one yourself.
Why Do I Have An Elevated Heart Rate After Exercise?
Physical activity increases your heart rate because your muscles need much more oxygen and nutrients than what is available at normal resting heart rate levels.
The main reason your heart rate is elevated after exercise is that your heart has yet to return to resting levels after you have exerted yourself.
In order to supply this oxygen, the heart has to beat faster to pump more blood per minute.
In general, the fitter you are and the healthier your cardiovascular functioning, the faster your heart rate will drop back down to resting levels after being at your maximum heart rate or moderate-intensity exercise rate.
Heart rate recovery is a metric that encapsulates the heart’s ability to recover after exertion and return to resting levels. This metric is taken after the first minute of rest after finishing your workout.
How Can I Lower My Heart Rate After Exercise?
Here are some things you can do to help your heart rate slow down and recover faster after high-intensity exercise.
#1: Cool Down
Doing a low-intensity cool down after your exercise program will help guide your elevated heart rate bpm back down to resting heart rate levels.
#2: Reduce Your Intensity
In general, beginners or those who have jumped back into a fitness routine after several weeks or months of inactivity tend to be most affected by a prolonged elevated heart rate after exercise.
It takes time for the cardiovascular system to adapt to the increased workload imposed by aerobic exercise, such that even workouts that are seemingly easy or low-intensity for well-conditioned athletes will result in a very high heart rate during the workout for a beginner.
Your VO2 max, or aerobic capacity, is a measure of how well your body can take in (via the lungs), deliver (via the heart and blood vessels), and extract and use (via the mitochondria in the muscle fibers) oxygen to create usable cellular energy.
Untrained individuals and beginners have a much lower VO2 max than trained athletes consistently performing aerobic workouts.
Aerobic training and HIIT workouts improve your VO2 max over time by improving all aspects of the oxygen intake, delivery, extraction, and utilization process.
The lungs become stronger, capable of taking in more oxygenated air per breath, known as the tidal volume. The heart muscle becomes stronger, and the chamber size of the ventricles can increase.
Cardiac output, Q, refers to the total amount of blood pumped by the heart per minute.
It is the product of your heart rate, the number of times your heart beats per minute, times the stroke volume, which is the amount of blood ejected out of the heart and pumped per beat.
Thus, the equation for cardiac output is Q = HR x SV.
Like any muscle in the body, the heart becomes stronger through consistent training. Aerobic workouts strengthen the cardiac muscle fibers and improve the heart’s ability to contract forcefully with each beat.
Simultaneously, adaptations to the heart muscle itself, including an increase in chamber volume, and adaptations to the cardiovascular system1Romero, S. A., Minson, C. T., & Halliwill, J. R. (2017). The Cardiovascular System after Exercise. Journal of Applied Physiology, 122(4), 925–932. https://doi.org/10.1152/japplphysiol.00802.2016 in general, such as an increase in your blood plasma volume, enable the heart to pump out a greater volume of blood per beat (an increase in stroke volume).
You will notice over time that your heart rate does not get as high when performing submaximal exercise at a given intensity as it once did as you become more conditioned.
This occurs mainly because the stroke volume of your heart has increased.
Back to the equation for cardiac output, if stroke volume increases, your heart does not have to beat as many times per minute to sustain the same cardiac output as it did when the stroke volume was significantly smaller.
Furthermore, as your fitness increases, that last factor of the VO2 max also improves—the ability of your muscles to extract and utilize oxygen. This decreases the “Q,” or the requirement imposed on your heart to meet the muscles’ needs.
Consistent aerobic training helps build new capillaries, the smallest blood vessels intimately interwoven with your skeletal muscles.
This allows for better delivery of oxygen- and nutrient-rich blood flow to your working muscles during exercise. It’s like adding new roadways. Supply delivery becomes faster and more efficient.
Simultaneously, the muscle fibers develop additional mitochondria, the specialized organelles that help extract oxygen from the blood and create usable cellular energy in the form of ATP.
The greater your muscles’ mitochondrial density, the more oxygen they can take up and use to create the energy you need to fuel your workouts.
Therefore, with a greater number of capillaries and mitochondria, oxygen delivery and utilization efficiency improves, further reducing the need for the heart to beat as fast during exercise.
Each beat that the heart does make not only provides more blood because stroke volume has increased, but it also better reaches the muscles (due to increased capillary density) and is extracted and used more efficiently.
Thus, this improves cardiovascular efficiency and reduces your heart rate during exercise as you become more aerobically trained and conditioned.
Ultimately, this allows you to exercise at a higher workload than you previously could when you are trying to hit the same heart rate, or you can match the previous workload, and your heart rate will be significantly lower than when you first started training.
These same cardiovascular adaptations help your heart rate return to resting levels quickly after exercise once you become fit.
The recovery process after physical exertion requires a brief period of increased circulation to shuttle away metabolic waste products built up in your muscles during the energy generation process and deliver nutrients to help repair and refuel your muscles.
When your aerobic capacity is high and your cardiovascular system is well-conditioned, this process goes quickly, so your heart rate recovery is good.2Cornelissen, V. A., Verheyden, B., Aubert, A. E., & Fagard, R. H. (2009). Effects of aerobic training intensity on resting, exercise and post-exercise blood pressure, heart rate and heart-rate variability. Journal of Human Hypertension, 24(3), 175–182. https://doi.org/10.1038/jhh.2009.51
However, when you have just begun a workout program or are trying to regain fitness after an extended period off, the stress on your heart and muscles imposed by your workout will be much more impactful, and it will take longer for your body to recover.
Additionally, the entire oxygen intake, delivery, extraction, and utilization process is less efficient, further extending the process.
Therefore, if you’re in poor shape, it’s common to have a high heart rate after exercise, and you will also likely see that your elevated heart rate is prolonged.
Although high-intensity cardio workouts are a great way to strengthen your heart and lungs and improve your cardiovascular health, beginners often jump into a fitness routine or take on workouts that are a bit too ambitious or vigorous for their current fitness level.
If you are new to working out or returning to a fitness routine after extended time off, consider dropping the intensity of your workouts a notch or two until your fitness progresses.
#3: Drink More Water
Drinking more water and staying hydrated during your workout will help keep your plasma volume stable. As you become dehydrated, your plasma volume drops, which means that less blood pumps through your body to reach your muscles.
Recalling the concept of cardiac output, when your stroke volume decreases (which happens if you have less blood pumped per heat), your heart rate has to increase in order to maintain the cardiac output your muscles need to fuel your exercise and recovery.
#4: Check In With Your Doctor
If you have been working out consistently for several months and are still habitually experiencing a prolonged elevated heart rate after exercise, it’s a good idea to check in with your doctor.
An abnormal or poor heart rate recovery can be indicative of underlying cardiovascular issues and can increase your risk for future heart disease.
Although the American Heart Association stresses not to “obsess” over heart rate values,3Watch your heart rate, but don’t obsess about it. (n.d.). Www.heart.org. https://www.heart.org/en/news/2021/02/10/watch-your-heart-rate-but-dont-obsess-about-it a poor heart rate recovery or an elevated rate after exercise that lasts for several minutes can be associated with certain disease states.4Jolly, M. A., Brennan, D. M., & Cho, L. (2011). Impact of Exercise on Heart Rate Recovery. Circulation, 124(14), 1520–1526. https://doi.org/10.1161/circulationaha.110.005009
It might be that you are dealing with an underlying medical condition that should be treated in one way or another. You can visit your healthcare provider or cardiologist to keep on top of your heart health and discuss any risk factors.
They may have you take a stress test to decipher the underlying issue, whether it be overtraining, an arrhythmia, or dehydration.
To measure your heart rate recovery and better understand what your target heart rate should be, check out this next guide:
