If you own a power meter should all of your workouts be based on power? How about if you only have a heart rate monitor? Heart rate only?
I had someone who bought a training plan of mine recently imply that the answer to both is “yes.” He had a power meter and bought a “power” plan so he believed every one of his workouts must therefore be power-based. Some of the workouts on the plan weren’t based on power, but rather on perceived exertion or heart rate. There are a couple of things going on here that I see a lot of from athletes who are highly focused on their available training technology.
First of all, everything you do in training isn’t defined by intensity. The best example of that is skill development. Something many cyclists could improve is their pedaling skills. Turning the cranks on a bike seems pretty straight forward; you just push down on the pedal at the right time. The problem here is that many riders start to push at the wrong time – too late in the downstroke and end it too soon. That results in a short stroke (2 to 4 o’clock) and low power output. You don’t go very fast. It’s like being a runner with a very short stride or a swimmer with a short stroke. You work hard but you just don’t have much speed. (I’m not going to go into detail on pedaling technique, but you can read about it here.)
So what kind of a workout am I suggesting? I like to have riders, regardless of how fast and powerful they are, refine their pedaling skills in the early base period. We’ve all got room for improvement when it comes to skills – some more than others. Power output tells you nothing about skill development. Nor does heart rate. We’re now talking about training the nervous system. Power is not an appropriate measure of skill enhancement. In fact, while working on pedaling skills the intensity, and therefore power, will be quite low even though fitness progress is being made. “Fitness,” in this case, is economy – how much energy is being expended in turning the cranks. The lower the energy expenditure in a given gear combination and cadence, the greater one’s fitness is. So the rider must initially rely on something else besides power to develop skill which will later be reflected in greater power output. In this case that something is perceived exertion. How does it feel when pedaling the bike? Such a workout involves several drills, as you can read about here. Power tells you nothing about how the drill is progressing.
How about heart rate if you have a power meter on your bike? Does one exclude the other? No. Just as with perceived exertion and skill development, there are workouts that are better defined by heart rate. My favorite example of this, and the one the rider who purchased my training plan was concerned about, is the aerobic threshold ride. This is a critical workout year round, but is especially important in the base training season when the focus is largely on aerobic fitness development. Certainly one’s aerobic threshold could be based on power. But I’ve found these low-intensity rides to be better based on aerobic threshold heart rate simply because it’s easier to estimate. I simply have the rider subtract 30 from his or her functional threshold heart rate to get a decent gauge of aerobic threshold. The rider then does the workout at that heart rate +/- 2 bpm. This requires considerable focus. The key to gauge how you’re progressing here is how much power you create during a long ride at that heart rate. By dividing normalized power by average heart rate you get something called “Efficiency Factor” (“EF” on TrainingPeaks) which tells you how your aerobic fitness is coming along. Over several weeks your EF during such a ride should increase. So in this case we’re using both heart rate and power, but heart rate defines the workout intensity. Power is a variable derivative of that heart rate.
It’s also a good idea to do some workouts without paying attention to either power or heart rate. I’ve had riders put a piece of tape over their handlebar or wrist device so it can’t be read during the workout. Then they do whatever the workout calls for. Only now they are determining intensity based on perceived exertion. Afterwards we check to see how their perceived exertion compares with their power or heart rate. This is the ultimate measure of workout intensity – how it felt. It’s the way all athletes determined how intense the workout was before there were gadgets like power meters and heart rate monitors. If you never train with perceived exertion what will you do when your device’s battery dies during a race? It’s a critical skill all should master.
The bottom line here is that there are certain times when workout intensity should be based on perceived exertion, heart rate, or perceived exertion regardless of what device you happen to own.