How heart rate zones work in endurance training

We’ve written extensively about the training zones in endurance sports and their importance for the training process, here, on our blog. In this article, we’ll talk a bit more about the heart rate zones — which are equally important in endurance sports — and how we can integrate them into a training plan.

How does the Ergophysiologist calculate an athlete’s heart rate zones?

To define an athlete’s heart rate zones, the Ergophysiologist performs an ergometric test, using an oscilloscope. Usually, the athlete takes the test, either on a treadmill or out in the field. One of the most common tests for finding an athlete’s heart rate zones is progressively increasing the exercise intensity. 

How does this test work? The athlete starts executing an exercise, instructed by the Ergophysiologist. Every few minutes (the sequence is also determined by the Ergophysiologist), they gradually increase the speed — or watts — depending on the sport. The scientist continues increasing the intensity, up to the point where the athlete is unable to maintain it. 

Throughout this test, the Ergophysiologist keeps recording the athlete’s heart rate. Naturally, the heart rate increases with the gradual increase of intensity. This happens until the test is complete, when the athlete has reached their limit. That’s how the athlete’s maximum heart rate is defined.

Afterward, the Ergophysiologist collects the athlete’s heart rate data and specifies their heart rate zones, based on this freshly collected scientific data. Each zone serves a different purpose in the training process. So, let’s see what these heart rate zones are, how coaches incorporate them into the training plan, and what happens in each one, physiologically.

What are the 5 heart rate zones and what happens in each one?

When it comes to their athletes’ heart-rate-based workouts, coaches typically use the 5 training zone model to create their training plan. What do these zones describe? And what happens in the athlete’s body when training in each one of these heart rate zones? Read on, to be in the know!

1st heart rate zone: 50-60% of HRmax

The first zone is a low-intensity zone — bordering on the first threshold —  where the body mainly uses aerobic metabolism. It’s mainly used for warming up. That is, before the athlete jumps into the main part of their training or recovery session. However, it’s also used for recovery, between two steps of intense interval training. Or for an entire recovery workout, lasting up to 40 minutes. 

In this zone, coaches integrate long-term training (> 2 hours) for base building. This improves the overall heart system, by enabling the heart to send more blood throughout the body, with each pulse. As a result, the athlete’s heart rate decreases.

2nd heart rate zone: 60-70% of HRmax

The second heart rate zone is also of mild intensity, and coaches allocate it immediately after the first threshold. That’s another zone coaches integrate in long-term endurance training (> 90 min) for base building or fitness training (30-90 min). What’s more, long-term training in the second zone improves the athlete’s musculoskeletal system.

Training in this zone increases the number of mitochondria in the cells; which is essential for the endurance athlete to improve overall speed and endurance. Also, the body learns to use fat for energy production. 

3rd heart rate zone: 70-80% of HRmax

During training in this heart rate zone — which is of moderate intensity — athletes start to feel out of their comfort zone. But they don’t need much exertion to complete their training successfully. Therefore, coaches mainly integrate it into long interval sessions, but also medium-distance workouts. 

Physiologically speaking, this zone helps the body create mitochondria in the cells and develop a capillary network; which, in turn, helps transport oxygen to working muscles, more efficiently. Consequently, muscle economy greatly improves. It’s also worth mentioning that this zone is where most athletes locate their race pace. Especially when preparing for endurance races, like half marathons, marathons, or half-distance triathlons.

4th heart rate zone: 80-90% of HRmax

This is one of the two demanding heart rate zones in the 5-zone model, requiring high levels of energy from athletes. For this reason, it will also require proper recovery time until the next workout in this zone is scheduled. Keep in mind that only coaches can add workouts in this zone in a training plan. It’s potentially dangerous for athletes to decide to train in this zone, by themselves. 

The fourth zone is located after the second threshold, where there’s an increase in lactic acid. That’s why coaches prefer to use it for short interval training (4-5 min) in their athletes’ plans. 

What are the physiological adaptations that take place in the body, when training in this zone? Well, the musculoskeletal system certainly improves, but the body can also eliminate the presence of acid much faster. To elaborate on the latter, the accumulation of lactic acid will be slower in the body. Hence, it will be able to endure higher intensities. By extension, the VO2max increases, as well.

5th heart rate zone: 90-100% of HRmax

Finally, the fifth zone — the most demanding of all the heart rate zones — is where athletes reach up to 100% of their heart rate. That’s why this zone is used for short break training or sprint intervals. 

In this zone, we find a sharp increase in lactic acid in the body, due to the high energy requirements of the muscles to maintain the workout intensity. The physiological benefits of this zone include improvements in maximum speed, as well as the VO2max — for the same reasons we mentioned earlier.

Following your zones, to success

Generally speaking, most athletes will train in all zones, depending on their needs and goals, and under their coach’s guidance. By monitoring their athletes’ heart rate zone training, coaches can help them:

  • Avoid pushing too hard, ending up injuring themselves
  • Give it all they’ve got, where — and when — it’s safe to do so
  • Bounce back faster, after intensive training sessions

All in all, heart rate zones help athletes keep their focus and be consistent in their training. And, we all know how important consistency is for a successful race. Right?

How heart rate zones work in endurance training was last modified: September 28th, 2022 by Marilena Kokkinou