Heart Rate Monitor vs. Power Meter

I have conversations about heart rate monitors and power meters a lot. People always want to know, “Should I train with a heart rate monitor or a power meter? Is a power meter really worth it? What’s the difference between the two? Is one more effective than the other? Do I really need both?” The questions go on and on. Let’s address some of these questions once and for all.

Heart Rate Based Training Benefits

Technology has advanced so quickly that heart rate is already considered to be a little bit of an ‘old school’ training approach. Just because something is old though, doesn’t mean it is outdated. Heart rate monitors are pretty cheap and therefore much more widely available to the general public. If you are fairly new to cycling or not yet sure if you want to really commit to a full training plan, then a heart rate monitor is a great place to start. You can get your feet wet and see if you really enjoy completing structured workouts and then advance upward to a powermeter if you want.

Heart rate monitors definitely have their own unique set of benefits. Heart rate gives us a window into what is happening inside your body during a workout. In fact, when we are trying to train a specific physiological system such as the aerobic system or the anaerobic system, heart rate is actually the variable that will tell us if we are meeting the demand that we need in order to inspire adaptations. For example, if you can push 300 watts but are only at 60% of your max heart rate, then you are not achieving the goal of VO2 intervals for the day. On the other hand, if you are pushing 300 watts, but are at 90% max heart rate, then you wouldn’t be achieving the goal of an aerobic ride. In this way, heart rate really shows us what our effort level is during a workout. In fact, when we set power zones for aerobic, threshold, and anaerobic efforts, those power zones generally have a heart rate attached to them as well.

Heart Rate Based Training Limitations

All of the above sounds pretty good and that’s why heart rate metrics can provide the metrics needed for a great training plan. At the same time though, heart rate monitors have some major limitations as well.

Heart rate is a highly subjective metric. That means that heart rate can be influenced by caffeine, stress, heat, hydration, age, sleep, etc. This can make training highly variable as well. If you become overly nervous or stressed about a workout, your heart rate may spike and you’ll appear to hitting your goal targets, but the reality is, your heart rate is only high because of your anxiety levels and not because your body is actually working hard. The same can apply on race day. “My heart rate was through the roof, but I wasn’t going anywhere.” That phrase is usually stated when anxiety or stress got the best of us. This can be a very confusing situation when we don’t have objective power numbers to confirm that we were not performing to the best of our abilities. For example, if in training you can hold 300 watts at 150 heart rate, but then on race day your heart rate is at 180 at that same wattage, something is off.

Another area that we find limitations with heart rate monitors, is that there is usually a lag in the data coming through. That means that shorter efforts will be more difficult to execute based on heart rate alone. Power data is nearly instantaneous, but heart rate may take a couple of minutes to catch up with your effort.

Finally, when training off of heart rate alone, it can be very difficult to determine improvements. Even small improvements in heart rate can be difficult to really hone in on without an objective measure like power attached to it. Maximum heart rate will not change very much so completing all out efforts, while effective, won’t likely demonstrate improvement because you’ll be left with a similar max heart rate each time.

Power Meter Training Benefits

Power meters really are the gold standard for cycling training at this point and time. They are objective measurements, meaning that they aren’t influenced by outside factors such as weather or fatigue or hydration level.

We can easily determine training zones based on power tests or even power tests relative to heart rate. Then we know what power levels we should be training at. Power allows us to train our muscular system as well as our cardiovascular system. For example, we might see that due to subjective variability in our heart rate, one day we might reach max heart rate at 300 watts and another day we might reach our max heart rate at 250 watts. If just training with heart rate, we would count those workouts as the same because we pushed our heart to the same point, but with the power meter, we know that the workout was not equivalent because we did not have the same load on our bodies, specifically, muscularly.

As also stated above, the power meter will show changes in force almost immediately meaning that a power meter will allow you to complete shorter intervals while still gaining numeric data.

Finally, the power meter is excellent for demonstrating improvements. With a power meter, at any point, you can complete a test to see your best power numbers for anything from 5 seconds to over 5 hours. An increase in power numbers correlates with increased fitness so you can see your improvement almost daily. From a personal standpoint, this is one of the reasons that I love the powermeter the most. It allows athletes to constantly monitor improvements and I believe that that correlates to increased motivation.

Power Meter Training Limitations

The biggest limitation of a power meter is really the price point and the intimidation of the technology, but as power meters are becoming more common, they are becoming less expensive and easier and easier to install.

The Best of Both Worlds:

In the most perfect world, we would train with both heart rate monitors and power meters in order to see our effort level (heart rate) at an objective power marker. Additionally, this allows us to see improvements across all training zones. For example, if you used to do 30 minutes at 300 watts with a heart rate of 180 and now you do 30 minutes at 300 watts with a heart rate of 150, that is an improvement! We always want to go faster with less effort!

Enjoy the Ride:

At the end of the day, the most important thing is to just enjoy the ride. Use the technology that makes you enjoy riding your bike the most. Whether it is measuring your effort with a heart rate monitor, your ability with a power meter, or measuring nothing at all and just feeling the wind at your back and the sun on your face, the most important thing is that you just go ride.

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