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Power Meters vs. Heart Rate Monitors

Should you train using a power meter or a heart rate monitor?

The discussion has gone on for decades, and both technologies have improved and become more accessible. So which of these training tools should you use?

The short answer is “both.” Okay, let’s end the article here and go for a ride, m-kay?

Ah, if it were that easy. Using power as a metric and using heart rate as a metric are very similar, but they tell you different things as well. A simplistic explanation might be that a power meter measures your output on the bike, while a heartrate monitor measures your input to the bike. Heart rate lags and takes a while to catch up with your effort, but power measurement is immediate.

Before proceeding, you should realize that even if you’re a novice, using the information you get from either a power meter or a heart rate monitor will probably improve your riding. The first electronic training tool I had 35 years ago was a crude bicycle computer called a Pacer 2000, which sat on my stem, as big as an iPad mini 2. It goaded me into trying to maintain a high average speed, and hit a higher top speed. Electronic gadgets, even used peripherally, can help you, much as almost any diet will cause you to (temporarily) lose weight. But to really take advantage of the data made available to you, you must intelligently parse the information and apply it to your training. And today we have the greatest electronic training devices ever.

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If you’re a casual rider, you may prefer the freedom from gadgetry. Many retired racers I know don’t use any electronics on the bike, and they usually measure their rides in hours, not miles. I was an early adopter of heart rate training, and I spent time in the lab on a bike to find out my AT (anaerobic threshold) and VO2 max. (Nice to have a friend who ran the cardiology department of a big hospital.) Other than experienced racers around me, I never used a coach, but I’ve logged every ride, my heart rate activity, and miles (214,744 so far) since 1983. I did intervals and twenty minute time trials on the trainer, holding my heart rate just below my AT. Although I had no knowledgeable plan, I found that the sustained intensity improved my fitness greatly. This was before the proliferation of power meters, and I found a heart rate monitor to be necessary.

The more serious you are about your training and racing, the more essential a power meter becomes. Most pro riders use power meters and have their activities on the bike analyzed by their coach. That said, you should really use a power meter in conjunction with a heart rate monitor. If you have a training goal of riding for an hour at 240 watts, your heart monitor will offer you valuable information. If 240 watts for an hour usually requires a 165 bpm heart rate, but you can’t elevate your pulse over 150 bpm on that day, you may be overtrained. If your heart rate goes to 178 bpm when your AT is 174, you won’t be able to complete the effort, and your heart rate will tell you why. Another example of how intertwined heart rate and power are, if you are in need of rest from training, you can tell that by a higher than normal resting pulse.

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In my opinion, if you’re serious about your training and racing, you need both a power meter and a heart rate monitor, and you may also need two more things…

Consider a coach. And consider getting tested in a performance lab.

Your coach doesn’t have to be an “in person” coach. Most cycling coaches monitor your workouts digitally and make tweaks to your training plan based upon your data. A good coach will understand your particular parameters and goals, and your abilities, and they’ll write you a custom program. And being tested in a performance lab is a good idea. You must determine that you are healthy enough to train at high heart rates, you should know your lactate and anaerobic thresholds, and you should know your VO2 max. I determined my own AT using the Conconi Method and my results were about the same as those rendered in the lab. At the time, my numbers told me I could maintain a 172 bpm heart rate for an hour, more than long enough to ride a sub-60 minute 40k time trial. Of course, there are variables. Your AT might be lower because of cold temperature, fatigue, or elevation. Cars develop more power at sea level than at high elevations because the atmosphere is denser and more air is entering the throttle body, and therefore more fuel can be shoved through the fuel injectors for that ideal 14.7:1 air-to-fuel ratio. These variables due to conditions are things a power meter won’t tell you as well as a heart rate monitor.

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If you want to determine your AT on your own, the Conconi Method is a relatively easy and foolproof method. Warm up well on a trainer (not rollers), and then ride the trainer at a steady 15 mph with a constant cadence. Every minute, increase your speed 1 mph (or you can increase by 25 watts a minute), maintaining a consistent cadence, and write down your heart rate at the end of each minute. (Have someone with a clipboard and a watch writing this down.) Your heart rate will increase steadily until you reach the “point of deflection.” At this point, your heart rate will spike, meaning you have gone anaerobic. Note your heartbeat at the knee of the curve, and that’s approximately what your Anaerobic Threshold is.

We’re taught in business not to collect data unless we intend to use it, and it’s the same with power and heart rate. An experienced coach can really help interpret your numbers and get you to raise your FTP (Functional Threshold Power) from, say, 200 watts to 300 watts. As you improve, your heart rate under load and at rest will change, too. You’ll be pumping more wattage into your cottage at a lower heart rate the more fit you become (efficiency), and your resting heart rate will be lower.

If you want to improve as a cyclist and get better results, consider using heart rate, power, and a coach. Oh, and ride your bike. That probably helps the most.

Written by Paul Scarpelli

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One Response to “Power Meters vs. Heart Rate Monitors”

  1. Stuart J. Holt on 24 Feb 2017 at 7:27 am

    Excellent article, learned these things years ago from
    The Sarge and Nelson R. After he returned
    a from the OTC, also from my personal
    Mafiosi, Dom Ori and Alberto B. My first
    electronic device was that Pacer 2000 that
    you pictured above.

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