Monitoring heart rate during cycling training can be a valuable tool for optimizing performance and achieving fitness goals. By understanding how your heart responds to different intensities and durations of exercise, you can tailor your workouts more effectively, prevent overtraining, and track improvements over time. In this guide, we’ll explore the basics of using heart rate monitoring in cycling training and how to integrate it into your regimen for maximum benefit.

Understanding heart rate

Heart rate has seen a decrease in popularity over the past decade. As the power meter has become available for everyone, cyclist have become obsessed with watts, because that’s more proportionate with increased speed and performance. However, heart rate is still extremely important in a large part of your workouts and as a recovery metric.

We all know that our heart rate increases as we increase exercise intensity. That’s because when you increase exercise intensity, your muscles require more oxygen to produce energy. To meet this demand, your heart pumps more blood to deliver oxygen and nutrients to the muscles and remove waste products, like carbon dioxide and hydrogen ions. You might think having a higher heart rate means you can transport more enrgy and remove more waste products, but heart rate is not all that matters in this equation.

Cardiac output

Cardiac output is a more precise measure of an athletes ability to transport blood around the body. Cardiac output is the volume of blood pumped by the heart per minute and is calculated by multiplying the heart rate (beats per minute) by stroke volume (volume of blood ejected from the heart with each beat).

• Heart Rate (HR): This is the number of times the heart beats per minute. It’s influenced by factors like exercise, stress, hormones, and temperature.

• Stroke Volume (SV): This refers to the volume of blood ejected from the left ventricle of the heart with each contraction (systole). Stroke volume is influenced by factors such as preload (volume of blood in the ventricles before contraction), contractility (strength of heart muscle contraction), and afterload (resistance against which the heart must pump blood).

Cardiac output can be increased by either increasing heart rate, stroke volume, or both. During exercise, both heart rate and stroke volume typically increase to meet the increased demand for oxygen and nutrients by the muscles.

Finding your heart rate zones

Establishing your max heart rate and heart rate zones is necessary to be able to train by heart rate. As a rule of thumb you can take 220 minus your age for men and 206 – (0.88 times you age) for women, to find your max heart rate. However, there’s individual variability, so finding your true values is advisable.

Finding max heart rate just requires you to do an all out effort over a few minutes. You should do it in a fresh and rested condition, as tiredness can lower your overall heart rate.

The other relevant values are your heart at lactate threshold 1 and 2 (LT1 & LT2) . The most precise way of getting these values are by performing a lactate test, but these are hard to do at home and requires a lactate meter. You can also hae them performed in a lab. The good thing is, your heart rate zones won’t change much over time, so it might be worth the effort and price for you.

Another way of establishing these at home is to find the effort where your start to notice your breathing. You can still have a conversation, but it will not be as easy as when sitting on the couch. That’s your LT1 heart rate. It should be around 70% of your max heart rate.

LT2 is the maximal effort you can sustain over a longer period of around an hour. If you go above LT2, you will generally fatigue in less than 10 minutes, and higher above it will of course yield a shorter duration. So the way to find your LT2 heart rate is to simply do an hour of max steady effort. Then take your average heart rate of the test and use that as your LT2 heart rate. This test is by no means easy. Setting out slightly too fast can turn out as a big difference in the last 20 minutes. So you should start out conservatively. And going hard for an hour is just tough.

When to use heart rate in training

The best workout to use heart rate as your key metric is the long slow ride. Also known as zone 2 rides among most cyclists based on coggan’s model. The best zone model for long slow distance is however the 3 zone lactate model.

The key to long slow rides is staying below that first lactate threshold (LT1), as this is the point where we increase the stress on our body when we go above it. The idea with the long slow ride is to spur endurance adaptations without increasing training stress.

It’s important on this ride to keep riding at a steady pace. Going harder and easier to get an average is bad execution of this workout, and defeats the purpose of reducing stress while targeting specific adaptations. Going harder for a short duration will increase your lactate levels, which can take up to 15 minutes to get back to the desired level, depending on your ability to clear lactate. Therefore, staying below that turnpoint is more important than powering up a short hill.

Taking lactate tests while riding this long slow ride is troublesome at best. Therefore, heart rate is a better metric, since that’s another metric measuring the effort inside our body, but we can read it on our head unit all the time. Power is not a good metric for this type of ride, as it only measures an external output. It says nothing about what’s going on inside the body. As the ride goes on, you will eventually experience cardiac drift, where your power will drop for the same heart rate, or your heart rate will increase while holding the power.

You saw above how to find your LT1 heart rate, so now you just need to find the length of the ride. That totally depends on your fitness level and how long you usually ride. Try to progress the length over time. When you go further into the ride before experiencing cardiac drift, you can extend your duration. Or if you don’t have a power meter, you can simply go by feeling. Once a 3 hour ride gets easy, try to extend to 3.5 and so on.

Another workout where heart rate can be useful is threshold workouts. Those with the intensity just below LT2, or around FTP. Power is the better measure for setting your intensity. But keeping heart rate below your LT2 heart rate threshold is also great for adjusting to your level and freshness on the day. If you have a bad day with higher heart rate, dial back the effort a bit to keep the stress in check. Remember zones are never static and can change from day to day.

Heart rate in racing

Heart rate is pretty useless as a metric in racing. In my experience, heart rate is always a lot different on race days due to adrenaline. Heart rate is also slow to respond to changes in effort. Typically there are many intense and short efforts, where heart rate won’t show you anything meaningful. Therefore, I advise to remove it from your race screen on your head unit, unless you are riding a time trial, long gravel or gran fondo event, or is riding a triathlon. It is a bigger risk of holding you back, because you might think an effort is too intense when you take a look at your heart rate, because it’s much higher than you usually see. But in reality the effort might not be harder, it’s just the excitement of the race.

Using heart rate as a recovery score metric

Heart rate is one of the best metrics for judging your recovery and ability to train. Tracking your resting heart rate every day when you wake up will give you an indication of how rested you are. If your heart rate is higher than usual, consider if you should take an easier session or a rest day.

When on the bike, it’s actually the other way around. If you are unrecovered, your high rate won’t be able to get as high as normal. This is tricky, because it might seem like you have a good day, and have responded positively to your training by increasing wattage compared to heart rate. But it could be the other way around. Of course, if you haven’t trained hard and come into the session fully rested, and your heart rate is still low, it can just be day to day variability. But if you’ve had some hard days, keep an eye on the heart rate, and be ready to cut a day short or dial down the intensity if your heart rate doesn’t come up.