Power vs. Heart Rate: Which Metric is Better?

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Power vs. Heart Rate: Which Metric is Better?

You’re serious about your training and are ready to take it to the next level. You probably already have a heart rate monitor, and you’re seriously thinking about investing in a power meter. That’s good, because both metrics, when used together, are likely to improve your training even further. Each metric — beats per minute and wattage — is better in certain situations, so if you’re equipped with both heart-rate and power, you’ll be able to make the most of every workout.

THE STRENGTH OF HEART RATE TRAINING

Heart rate monitors are widely accessible and allow you to cross-reference performance data, such as power, against your physiological strain. Heart rate can help you notice changes in fitness and fatigue in a way that wattage cannot.

Newer riders will see a higher heart rate at a given wattage and even higher heart rates as they fatigue.

Highly trained endurance athletes will often see a lower heart rate for the same wattage and experience a depressed heart rate after several hard rides.

This change in your usual heart rate-to-power ratio is a great indicator of how your body is adapting to training and helps to let you know you need an off day.

Newer riders will see a higher heart rate at a given wattage, while highly trained athletes will often see a lower heart rate at that same power output. This change in your usual heart rate-to-power ratio is a great indicator of how your body is adapting to training and helps to let you know you need a day off soon.

Timing your recovery — how fast your heart rate drops after a hard workout or interval — can also be a good indicator of fitness. Keep track of how fast your heart rate drops to 60% of max heart rate after a ride to measure improvements in your fitness. If you do a 20-minute threshold test frequently, try pedaling at exactly 50 watts (or a low wattage for you) after you finish and see how fast you can get to 60% of max heart rate.

During intervals, you should keep your heart rate steady or increasing to be sure you are maintaining a steady or increasing load. Use this information as motivation to push hard even when things get hard. If heart rate drops in the last interval set a goal to focus on smooth pedaling through the whole last interval in your next workout.

WHERE POWER SHINES

Power can be a tremendous boost to your training. A power meter helps you see how and when you expend your energy. WIth a power meter, you can see the instantaneous results of your pedaling effort. In workouts you can practice keeping steady power (instead of coasting) to maximize your workout time — this is one of the first metrics I check with new coaching clients. For road rides, use power to help limit hard efforts on easy days and keep your output steady on endurance days.

Another place where power improves your workouts is during intervals. If you are doing a set of four-minute efforts, you can use the power from the first repetition to help guide your output for the next one — to hold it steady or increase it. The next time you do that same workout you can set appropriate levels to aim for and improve on.

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HOW POWER AND HEART RATE WORK TOGETHER

Power devices are expensive, subject to malfunction and read differently between units, so having a cross-reference like heart rate is helpful. I often test athletes’ aerobic ability by having them ride steady for 30 minutes or longer at 75–85% of max heart rate and see what the average wattage is. This is a relatively painless way to track your endurance progress using heart rate and power.

A big improvement when using power with heart rate is that you can see your wattage improve at a set heart rate, or distance, after months of training. If your average wattage for a given heart rate increases and/or the amount of drift over a longer ride decreases, this indicates your endurance — or your ability to maintain a steady state effort — is improving.

Heart rate will be higher when we are in hot conditions or higher altitudes, so you can use wattage to help guide your efforts — but be cautious as these extreme conditions drop our maximal outputs because our body is under more strain from the environment. Depending on your event and conditioning, you may be able to push your heart rate targets, but it’s wise to use heart rate early in a ride, or event, to avoid over pacing.  

When training, it doesn’t have to be either heart rate or power — the two work together nicely. Optimize your cycling by using both metrics to guide your training.

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  • Jeff Pedals

    Your heart rate will also be high most of the time on the bike if you are an overweight rider..such as myself. I’m always struggling to end up with my normal/dismal cumulative average speed of 11-12mph. So much so that I’m most always in my anaerobic zone during my rides. The only way I can get my heart rate down into fat burning level is to stop & sit down on a park bench for 4 minutes.

  • Alex Simmons

    If you have power, HR is at best redundant and you can lose the strap.