Powermeter vs Heart Rate Monitor

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I receive a lot of questions about why your would train with a powermeter vs a heart rate monitor.  They’re all great questions and they make me stop to think before I go on praising the greatness of having a powermeter and how it’s revolutionized my training.  I think powermeters are a great thing and are well worth their money if used correctly.  However, if you buy a powermeter and do no baseline testing, observe your power while you’re riding without any references or targets, and download your data onto your PC without any analysis, in my opinion a powermeter will be useless to your training progression.  Sure you might be able to gauge if the average wattage of a ride was more or less than the last one, but that’s a hindsight analysis and it does nothing for the specificity of your training as it’s meant to.  A HR monitor can basically give you the same data if you’re looking to gauge the difficulty of a ride at the end.

The main benefit of a powermeter is that you can measure your efforts and gauge them without question.  A powermeter is measuring the bicycle’s “output“. If you are targeting some intervals and want to be sure that you’re hitting the correct zones, then a powermeter is the way to go.  Another benefit of the powermeter is that it allows you to figure out your limits and lets you know how to pace yourself.  For example, if you know you can push 500 watts for 1 minute in training, then you probably won’t be able to push it for much longer in a race.  The powermeter also tells you exactly what’s happening to your power output when you blow up after a hard effort.  You’d be surprised how difficult a simple 200 watts feels after you’ve blown yourself up with a massive effort of a large wattage.

A HR monitor is measuring your body’s “input” to the bike. There will be a lag response time between your “output” and your HR rising to it’s target zone.  A powermeter is particularly useful during shorter intervals (under a couple minutes) when your HR spends much of the interval rising to the zone you’re targeting.  You’ll very likely be going too hard at first when trying to get your HR up, and then the rest of the interval you’ll be so tired out you’ll actually be pushing very little power (but your HR will remain high).   When you use a powermeter, you’ll notice that you’ll push a certain wattage and it will feel easy at first.  As the interval goes on it will progressively feel harder, but the power will remain constant and HR will rise.  As your form progresses, you’ll notice that you’ll be able to push a higher wattage at a certain heartrate.  This is when you know your training is working.

Heart rate drift means that your HR is not always the same on different days or even on the same day. On a day that you’re tired you won’t be able to get your HR up, but your power will be in the correct zone that you’re aiming for.   You start noticing this phenomenon when you use a powermeter and HR monitor together. See a post I did earlier about how you can tell if you’re overtraining by measuring your heart rate.

All that said, I believe a powermeter is only effective if you are using it in conjunction with a prescribed training plan from a coach who knows what he’s doing with power.  Even better if you pick up this book and figure it all out yourself.   The next best thing can to having a personal coach can be found here (not a paid product plug!).  These are designed by Hunter Allen who has heaps of experience in coaching athletes using power.

If you are not overly methodical about your training (which I’m not saying is a bad thing), then I think a powermeter is a waste of money.  I am not using my powermeter the way its intended to be used at the moment and I’m unfortunately just wearing it out (it’s just an expensive speedometer right now) .   Using only a HR monitor can give you a good indication if you are tired or feeling good, where you are in your limits, and can gauge the difficulty of a ride.  If this is all you’re looking for then a HR monitor will suit your needs.  The majority of cyclists out there can get by just fine and even excel without a fancy powermeter.

Am I a better cyclist because of owning one? Perhaps at certain times when I’m serious about my training towards a certain race(s). Do I love using it and enjoy my training more because of it? Certainly.

Feel free to agree or disagree. I’d be interested in hearing other points of view on this.

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