Monitoring your heart rate while you run is an excellent way to measure the effort and intensity of your daily runs. There are four prescribed zones when it comes to heart rate training. To calculate heart rate for these zones, you first must establish your maximum heart rate (MHR).
You can do that via age-based formulas, such as the Gelish equation, or you can do a treadmill stress test in a lab for the most accurate reading.
- Zone 1: Easy effort done at 60-70% of your max heart rate. Warm-ups, cool-downs, and easy recovery runs can be done at this effort.
- Zone 2: Here you’ll be operating at 70-80% of your max effort. The majority of runs should be done at this pace, as it’s how you build fitness and endurance without overdoing it.
- Zone 3: A harder effort done around 81-90%, this heart rate zone is reserved for speed workouts, intervals, and threshold runs. You’ll probably feel the lactic buildup towards the end of these workouts.
- Zone 4: The highest heart rate zone, Zone 4 is equivalent to race pace. You’re operating at your highest effort for a shorter amount of time before you have to stop.
However, going off of heart rate isn’t always a perfect science. There are many factors, both internal and external, that can impact your heart rate. This is why many runners choose to focus on pace or perceived effort, and use heart rate as a secondary tool to guide their training.
Top Reasons Your Heart Rate Might be High on Easy Runs
If your heart rate is higher than normal on your easy runs, there’s no need to panic right away. It’s normal for any of the below factors to increase your heart rate on an easy run. What’s important is paying attention to your heart rate over a longer period of time to monitor trends, so you can catch things like symptoms of overtraining and fatigue.
If you’re frustrated and asking yourself, why is my heart rate high on easy runs?, it could be for any of the following reasons:
High Altitude
Going from sea level to altitude is guaranteed to change your breathing and your heart rate. With less oxygen available, your body has to work harder to take more breaths and get the same amount of oxygen you would at lower altitudes. A recovery run that felt easy at sea level might feel slightly difficult at altitude, which means you’ll need to slow down your pace to adjust accordingly.
Heat and Humidity
Anecdotally speaking, running in high heat and humidity never feels the best. Studies show that for every degree your body’s temperature rises, your heart beats about 10 beats faster. The humidity also means that sweat doesn’t evaporate quickly off your body, which further increases your heart rate, as your body isn’t able to cool down as fast.
Lack of Sleep
Sleep is the number one thing you can do to help your body recover, boost its immune system, and repair damaged muscle and tissue. Lack of sleep can negatively impact your recovery and overall training, especially if it’s a chronic issue.
Poor sleep quality means you’re not spending enough time in your deep and REM sleep stages. Deep sleep (also known as “slow wave sleep”) is a critical sleep stage that allows your body to build muscle, repair tissue, fight illness, and more. REM allows your body to solidify memories and learning, and recharge the brain.
If you’re not getting enough sleep, or you have interrupted sleep that takes you out of critical sleep stages, your body will be tired and your heart rate will be higher on your easy runs.
Stress
People underestimate how much stress can impact exercise and performance. While a little bit of daily stress is normal, exposure to high-stress situations at work, at home, or in your personal life can leave you feeling drained and on edge.
When you’re stressed, your body releases adrenaline, which causes your breathing and heart rate to increase and creates the fight or flight response in your brain. Stress can also increase cortisol levels in your body. Cortisol is a stress hormone that affects nearly every organ in the system–nervous, immune, cardiovascular, reproductive, and respiratory.
Cardiac Drift
Cardiovascular drift describes the physiological phenomenon whereby the heart rate progressively increases over the course of exercise. This can happen during long runs when you’re running at a steady, comfortable pace. Many runners assume that if they run the same pace, their heart rate will stay the same.
However, research has shown that the heart rate can naturally increase by up to 20 beats per minute. This is normal, and it just means that your body is naturally increasing its core temperature, which elevates heart rate.
Hills, Trails, and New Terrain
If you’re used to running on the roads, switching it up on rougher terrain will easily cause your heart rate to increase on an easy run. Technical maneuvers and constant ups and downs will take more energy out of your body.
Additionally, running hilly courses will naturally increase your heart rate, even if you’re taking it easy up a steep incline.
Overtraining
If your heart rate is chronically high on easy runs, you may want to figure out if you have additional symptoms of overtraining. Overtraining symptoms include:
- Elevated resting heart rate
- Increased perceived effort on easy runs and workouts
- Irritability
- Loss of appetite
- Heavy legs, even at an easy pace
- Taking longer to recover from workouts
- Decline in performance and pace
- More prone to injuries
Overtraining is a chronic condition caused by a lack of recovery. If your body is not getting enough nutrition, sleep, and hydration following exercise, and if you tend to overdo the mileage, you could be at a risk for overtraining.
However, don’t hit the panic button too soon. If your heart rate is high on some easy runs, that doesn’t mean you are overtrained. It could be any of the aforementioned causes. Pay attention to your heart rate over time, and if you bounce back in a few days, chances are your body just needed some additional rest.
Taking Your Easy Runs Easy
Monitoring heart rate while you run is an excellent way to get precise measurements on the cardiovascular loads on your body, and can be done through chest straps or wrist-based wearables. At the end of the day, your easy runs should be exactly that: easy.
If you’re wondering why is my heart rate high on easy runs and you feel out of breath, tired, or get any lactic buildup, you are going too fast and need to slow down the pace to a perceived easy effort.
