How to use these training tools effectively

By Martin Punzalan | Photo by Paolo Candelo/Unsplash

Power and heart rate (HR) are the two primary metrics for tracking and measuring cycling performance. Although power meters are taking center stage these days, it does not imply that it is better than HR monitors. Both tools have their own merits and shortcomings, making it essential to understand how these are properly used, separately or together, in order to maximize its training benefits.

What’s so Great About Power?

HR and power measure workout intensity, the difference being the precision at which it is presented. Power output is consistent as far as strength and fitness is concerned, making it easier to control and quantify. Having a power meter eliminates the need to guess your exertion levels by feel. You will have a numerical prompt for knowing exactly how hard or how easy you are pedaling.

Heart rate on the other hand is easily altered and affected by several factors, making it trickier to rely on. Such factors include dehydration, fatigue, temperature, or even emotional states. There are also the concepts of HR lag (the time delay it takes to reach a target HR zone), cardiac drift (the gradual rise in HR when maintaining a long steady effort), and aerobic decoupling (when power drops and HR does not) that need to be understood in order to properly train using heart rate data.

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An example of cardiac drift graph on a 20 minute FTP test. It’s not very pronounced in this graph but notice how the heart rate line slightly tilts upwards moving to the right despite the power being relatively steady

Why HR is Still Essential?

Since endurance sports depend on the cardiovascular system, there are several things about endurance performance that only the heart can reveal. Heart rate is the body’s response to physical work exertions, which in this case is pedaling power. It reveals whether you are over or under training; why on certain days you feel like you have a personal tail wind pushing you forward or why on other days it seems like you are eternally riding against a headwind.

Reduced HR for the same power indicates improved fitness or a properly recovered body. Conversely, increased HR for the same or less power is a sign of fatigue or possible illness. This allows the athlete to plan training and racing schedules for optimal performance.

Which to Use and When

Depending on your training objectives, there are instances in which it is advantageous to focus on one device over the other.

For building endurance and base fitness, it is best to focus first on monitoring heart rate. Endurance sports coach Chris Carmichael recommends focusing on HR during offseason base periods by staying inside a specific HR zone while also trying for the most power you can reach. During pre-race build periods, observing HR also allows you to see whether you are overtraining and in need of more recovery.

Focusing on heart rate is also advisable during recovery sessions to ensure that the body is not working harder than it should. For improving power during peak race season, especially for cyclists, Carmichael recommends using power meters. Training for power requires short high-intensity interval to which the delayed response of HR might be unfavorable.

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The heart rate (thin red line) reaches its peak already at the end of the interval

Naturally, all these will entail establishing HR and power training zones first through a functional threshold power, heart rate, or lactate threshold test.

Why You Still Don’t Need a Power Meter

Power meters have its uses and advantages but it remains an expensive and inessential luxury. Short high-intensity intervals for which power meters are recommended are often about going as hard as you can. Even without a power meter, this is easily gauged by perceived effort alone.

Despite its drawbacks, HR monitors by itself is sufficiently reliable for intensity-based training. Just put in some extra effort to understand how it works. Also, given how conveniently affordable it is, there is no reason not to have one especially if you can already afford a power meter.

If you have the means to have one or both devices, then make the best out of these by not just riding and training with them but also learning how to interpret and understand the data it gathers. That or hire a knowledgeable coach to do it for you.