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Is heart rate or power the best way to improve your bike performance?

Gadget showdown - a plus/minus look at bike training tech

Photo by: Kevin Mackinnon

Those of us who have been endurance junkies long enough can remember the first clunky heart rate monitors – big strap on devices that you could set ranges for to monitor your training. Around that same time (mid-80s), SRM was launching the first power meter, but that technology remained cost-prohibitive for most.

Heart rate monitors quickly became both easier to use and considerably less expensive – by the 90s most triathletes were gauging their training efforts by measuring their heart rate. As power meters became a more accessible piece of equipment, many triathletes started to use power as their primary means of measuring their effort during workouts and races. Now it’s not unusual to find athletes who don’t pay any attention to their HR data on the bike, electing to focus purely on their power output. Do those athletes have things right? Or is there still value to be had in training based on heart rate?

Heart rate vs power

At its simplest, your power meter is measuring how hard you are working on your bike (your power output) – how many watts you are putting into pushing the pedals. Your heart rate is a measurement of how your body is reacting to that effort.

So what are the advantages and disadvantages of each?

Heart Rate

Easy of use: Pretty much every training watch incorporates wrist-based heart rate monitoring these days. For most people, the data provided from the wrist-based monitors work pretty well, but for more accuracy (and for those who just can’t seem to get decent numbers from their wrist), adding a chest strap is an easy fix.

+ Expense: You likely already have one.
+ Set up and testing: A simple ramp test will provide you with some decent numbers to work with for your training zones, and many sport watches will also provide easy testing and monitoring to help you develop appropriate training levels.
+/ – Steady: Heart rate training works really well in steady state or easy training scenarios. There’s a lag between an effort ramping up and you seeing any changes in your heart rate (a positive component of training with a power meter – we’ll get to that momentarily), so you’ll get the most out of using your heart rate monitor when you’re setting it to maintain either an easy or steady-state effort for a longer period of time.
+ Overtraining warning: One sign of extending yourself too much in your training can be an elevated heart rate, both resting and during activity.
– Fluctuation based on conditions: Altitude, hydration levels, fatigue, temperature and how recently you’ve hammered down a cup of coffee (caffeine levels) can all affect your heart rate

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Power meter

+ Real-time measurement: Remember that lag we talked about with your heart rate? That doesn’t happen with your power meter.
+ Specificity of zones: Since you don’t have to wait for your heart rate to catch up, you can work through intervals at the exact level you’re trying to work on.
– Expense and set up: Yes, power meters have come down dramatically in price, but they’re still a lot more expensive than a heart rate monitor. Some can also be a bit tricky to set up, although that’s less and less of a factor these days.
+ Smart Trainers: If you don’t have a  power meter on your bike, you’ll be able to use your smart trainer to monitor your power data.
+ Pedalling analysis: In addition to getting feedback on how hard you’re working, many power meters will also provide you excellent feedback on how efficient your pedal stroke is.
+/ – Super accurate data: That real-time feedback can drive you nuts as you’ll see the numbers jump around a lot. You can set things up to monitor an average wattage for a period of time (an interval, for example) to make that a bit easier to read. To really get the most out of all the data you’ll be generating from your workouts, you might find you’ll need the help of an experienced coach.

Heart Rate Training Explained

The ultimate solution

As a coach I love to have the option to utilize both heart rate and power as a way to analyze training. I’m not a huge fan of using either as a racing tool – ideally through all the training we’ve done, my athletes can gauge their own effort on race day, rather than have to rely on what their watch or power meter is telling them.
So, in an ideal world, you’ll use a heart rate monitor to make sure you’re going easy enough on your easy days, and steady enough on your steady days. You’ll use your power meter to help get the most out of your specific interval and hard paced efforts.

And you’ll use all that information to teach your body exactly how hard it can go … without having to look at either on race day.

In addition to being the editor of Triathlon Magazine, Kevin Mackinnon was a former professional triathlete and has been a coach for over 35 years. 

This story originally appeared in the 2024 Triathlon Magazine Buyer’s Guide.