Why Is My Heart Rate High on Easy Runs?

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Easy runs are part of an effective training routine. If you’ve been doing them for a while, and you’ve been monitoring your metrics while you run, you may be wondering, “Why is my heart rate high on easy runs?”

The truth is, many runners aren’t sure where their heart rate should be during an easy run. You may even be thinking you’re doing an easy run, but you’re actually going a bit more intensely than you realize!

But, a high heart rate on easy runs can happen. In this article, we’ll dive into what exactly an easy run is and how to make sure you’re running at the right level of exertion. Then we’ll look at some possible causes for a higher heart rate during an easy run.

How to Figure Out Your Baseline Heart Rate

Training according to your heart rate can be a valuable tool to help you train more efficiently while preserving energy.

Fortunately, smartwatches and health trackers have helped to remove most of the guesswork, as your heart rate directly reflects the effort of your workout.

But, this can also create uncertainty, especially when your heart rate is high on an easy run. Heart rates vary from one runner to the next, making it difficult to pinpoint what a “normal heart rate” is while running.

To help you determine your baseline heart rate, you can use the range based on a percentage of your maximum heart rate.

The most common formula is to subtract your age from 220. For example, a 30-year-old’s max HR would be 190, while a 50-year-old’s would be 170.

According to the CDC, you should stay within 64 to 76 percent of your maximum heart rate for a moderate-intensity run.

For vigorous activity, like a tempo run, your heart range should be between 70 and 85 percent of your maximum heart range.

At most, you’ll want to run at 90 to 100 percent of your max heart rate for short bursts only.

So What Is an Easy Run?

Understanding the pace of an easy run can be difficult, as it varies from person to person. You may find that some authority running sites talk about an easy run being 1 to 2 minutes slower than your race pace—5k or marathon.

However, this calculation can be flawed. Your heart rate during an easy run should fall below your aerobic threshold, and 1 minute below your race pace may still be going too hard. On the other hand, 2 minutes below your race pace may be frustratingly slow.

The best way to ensure you’re running at an easy pace is to disregard any information about your pace and focus instead on your heart rate and perceived effort.

During an easy run, your heart rate should be between 50 and 70 percent of your max heart rate. This is still quite a wide range, so you should pair this with a perceived effort of 3 to 5 out of 10.

You’ve hit the right pace when you:

  • You have a heart rate in the 50 to 70% range of your max heart rate
  • You have a perceived effort of 3 to 5 out of 10
  • You still feel relaxed and comfortable while running
  • You can hold a conversation easily without huffing and puffing
  • You feel that your run is sustainable and easy to finish

It’s best to do your easy runs on flat, non-challenging terrain to keep your muscles and your heart rate light and easy.

Possible Reasons Your Heart Rate Is High on Easy Runs

Since your heart rate can rise on easy and long runs for various reasons, it is helpful to understand the causes of these fluctuations.

You’re On Tricky Terrain

Changes in terrain, including hills, sand, grass, or lots of turns, will cause your muscles to work harder as you run. But your body will also recruit other muscles—accessory muscles—to help propel you forward, increasing your effort.

This causes your heart to work harder to get oxygen-rich blood to these muscles, increasing your heart rate.

This may make it more challenging to stick to an easy pace.

You’re Dehydrated

When you become dehydrated, the amount of blood circulating through your body decreases.

To compensate for the reduced blood volume, your heart will speed up as it tries to deliver the blood to your muscles fast enough.

A higher-than-normal heart rate is one of the early, common signs of dehydration.

High Heat or Humidity

Running in hot conditions causes your body temperature to rise, while the humidity can prevent your sweat from evaporating quickly.

Your body works harder as it tries to cool down, placing more strain on your heart, causing your heart rate to increase.

High heat can also cause you to sweat more, leading to dehydration.

Stress Levels

Outside of your running, daily life can increase your stress levels. Although running does release endorphins and relieves stress, if you begin your run in a stressed state, your heart rate may already be high due to increased cortisol and adrenaline levels.

Exercise will help lower cortisol and adrenaline levels, but your heart rate may still be higher than usual even after it’s down a little.

Lack of Sleep

When you haven’t slept enough, your adrenaline and cortisol levels rise. Just like increased stress levels, this can cause your heart rate to rise as your heart beats faster.

This is especially true if you’ve been short on sleep for many nights in a row. One late night may not have a big impact, but multiple late nights where you don’t get the necessary sleep will have a negative effect on your body.

You’re Anemic

The iron in your body helps the blood to transport oxygen. When your iron levels are low—you’re anemic—this function is impaired, which means your muscles aren’t getting enough oxygen-rich blood when you exercise.

Your heart then needs to work harder to increase the oxygen levels in your muscles, which contributes to a higher heart rate.

Anemia is more common in women than in men, but it can happen to any runner for various reasons.

Long-Term COVID-19 Symptoms

If you’ve had COVID-19 in the past few months, the effects can linger for an unusually long time after you were sick.

While you may feel good, your heart rate may be higher than it used to be as your activity levels increase. This is due to your body still recovering from the virus.

You’ve Had a Lot of Caffeine

Ingesting caffeine increases the body’s adrenaline levels. There’s no way to pinpoint what “a lot” really means, as it varies from person to person.

In general, exceeding 400 milligrams of caffeine per day can lead to side effects like a fuzzy head, headache, jitteriness, and heart palpitations.

You can find caffeine in your morning coffee, tea, pre-workout, and among other supplements, so it can be relatively easy to ingest too much of it before your run.

This is one of the common reasons your heart rate may be higher than you expect during a run.

You’re At a High Altitude

When you’re at a high altitude, the air is thinner. This creates less oxygen available for you to inhale, so you tend to breathe harder and faster to try and get more oxygen.

Your heart will also work harder to try and circulate oxygen to the muscles so you can exercise effectively, which could elevate your heart rate.

You’re Pregnant

When you’re nourishing your own body and a baby, some of the oxygen in your bloodstream goes towards your baby.

An elevated heart rate—20 to 25 percent—can be normal during pregnancy. It may rise even higher than when you’re running, as your heart is working harder to provide adequate oxygen for you and the baby.

You’re On Medication

Some medications—such as antidepressants, asthma medicine, and ADHD drugs—can increase heart rate.

While you may not notice it during everyday activities, it might become more apparent when you run.

You’re Not Running As Easy As You Thought

Your perceived effort may be higher than you realize. Even if you’re running alone, you should be able to speak out loud without getting short of breath.

If your breathing is labored or you can’t say more than a sentence without needing to pause and breathe, you’re probably running too hard.

This is why using perceived effort and heart rate zones is the best metric for ensuring you’re running at a proper, easy pace.

Your HRM Is Inaccurate

Many runners use a wrist-based heart rate monitor that’s built into their smartwatch. However, these are notorious for being inaccurate.

The positioning on your wrist, how tight or loose it is, your skin tone, tattoos, how much hair you have, or even how much you’re sweating can influence the reading you get with a wrist-based HRM.

If you don’t have a chest strap or an armband, you can double-check your heart rate by taking your pulse on your neck for 10 seconds. Multiply this by 6 to get your per-minute rate and compare this to your HRM.

You should note that the HRM handles on a treadmill are almost always incorrect. We advise investing in a chest or arm heart rate monitor if you’re using these.

Ways to Lower Heart Rate While Running

Once you understand the possible reasons behind your heart rate being high on easy runs, you can take steps to lower it while you’re running.

Increase Gradually

Increasing your intensity, speed, or distance too rapidly can cause your heart rate to rise as your heart works harder to provide oxygen-rich blood to the muscles.

To avoid this, increase slowly, especially if you’re starting again after a break. Try to increase by 5 to 10 percent per week, in either distance, pace, or intensity.

Stay Hydrated

In cold and hot weather, dehydration can set in faster than you may realize. Ensure that you’re sufficiently hydrated during your run.

If you don’t like carrying a water bottle, you can invest in a hydration pack, which will allow you to stay hydrated without worrying about holding a bottle.

You should take small sips every few minutes. Your mouth should never feel dry as you’re running.

You can also add electrolyte tablets to your water to help keep your nutrient balance correct, as an imbalance may also lead to a high heart rate on easy runs.

Take Recovery Seriously

Make sure that you’re resting for enough time between your runs. You should ensure that you get 7 to 9 hours of good quality sleep every night.

Other actions you may want to consider to help you recover faster are eating a healthy diet, using compression gear to increase circulation, and doing gentle stretching.

Avoid Overtraining

Overtraining can lead to fatigue during your run, which causes your heart rate to spike as your body works harder.

Avoid this by training in your heart rate zones. This will help you get a good combination of high-intensity and low to moderate-intensity exercise, so you don’t push yourself too hard.

Keep Yourself Cool

Keeping yourself cool during your run will help prevent your body temperature from rising enough to disrupt your heart rate.

You can consider buying a cooling vest, taking a cold compress, or taking ice with you. However, this may be impractical.

You may want to keep a cooler in your car with ice and run a loop that requires you to pass by your car every so often where you can cool off with a cold compress on the back of your neck.

If you’re on a trail run, splashing your face and the back of your neck every time you run past a stream can help keep your body temperature from rising and increasing your heart rate.

Calm Your Breathing

Rapid breathing can cause an increase in heart rate. Focusing on slowing your breathing down and taking deep breaths at a measured pace can help to bring your heart rate back to a normal level. This is also an excellent time to focus on a mantra.

Slow Down

If your heart rate is rising during an easy run, slow down. You may not be running as easily as you think, and slowing down can help lower your heart rate and make you feel better.

Try to take hills and rough terrain more slowly instead of increasing your intensity. Or you can alternate between running and walking for short periods.

Pay Attention to Your Body

Rather than paying attention to your pace, you should be considering how your body feels. If your heart is pumping harder than it should be, slow down and consider the possible reasons.

If you’re feeling good, then there’s no reason you shouldn’t continue. But if you’re worried about your heart rate, considering the underlying causes and rectifying them could be the best thing for you.

When Should I Worry?

Although a slightly elevated heart rate is more common than you may realize, there may be cause for concern in some cases.

If your increased heart rate occurs along with any of these symptoms, you should stop running and seek medical attention:

  • Dizziness
  • Lightheadedness
  • Nausea
  • Vomiting
  • Chest pain
  • Chest tightness
  • Irregular heartbeat
  • Shortness of breath
  • Diarrhea
  • Unexplained weight loss

These symptoms may indicate an underlying cardiovascular problem. If you experience these while on a run, you should stop immediately and contact an ambulance.

If you have experienced these before, make an appointment with your doctor before you run again to find out if there are any issues you should be aware of.

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AUTHOR

Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.