The Power Meter Handbook: A User’s Guide for Cyclists and Triathletes

started in your sport. They’ve been around since the late 1970s, so athletes have become quite used to them. And they’ve measurably helped toimprove performance for many. But other than the pump-engine relationship I described above, there are still significant limitations to heart rate–based training. Heart rate is affected by “outside” forces, such as diet, race-day excitement, and psychological stress. For example, caffeinated drinks and even a shot of sugar can cause heart rate to rise regardless of how hard you are pushing yourself. Simply being around other riders, especially in a race, will also result in an artificially high heart rate. And even the stuff that goes on between your ears—an argument with the boss, tax time, and other worries—has an effect on heart rate that is unrelated to your riding intensity. Furthermore, in training heart rate is slow to respond when you are doing intervals, so during the first few minutes of each interval you are forced to guess how hard to go. All of this sets you up for poor workout and race pacing. It could very well be the reason you’ve not done as well as you are capable of doing, especially in steady-paced racing such as time trials and triathlons.
    Still, the greatest limitation is that heart rate doesn’t tell you anything about how you are performing. It only tells you, indirectly, how hard the engine is working based on the engine’s demand for fuel and oxygen. To be truly effective, heart rate must be compared with something else. I will show you in Chapter 6 how power and heart rate can be compared and how the benefits of this relationship can be useful for your training.
Speed
    Several years ago, I was invited to go for a long Saturday-morning ride with a couple of Ironman triathletes who were in their final stages of race preparation. They didn’t have power meters. We rolled out of the parking lot, and they immediately increased their speed to about 25 mph and held it there. There was no warm-up or conversation. We were immediately riding all out. After several minutes of this, I rode up next to one of them and asked whatwas going on. Why so fast? He told me that they wanted to average 22 mph and knew that because of hills and the possibility of wind, they had to get the average speed high when they were still fresh. After a couple of hours, the ride slowed to a death march as fatigue set in. They didn’t quite achieve their speed goal that day, which meant they’d have to go out faster at the start on the following weekend. What a strange way of training.
    Speed on a bicycle is largely determined by wind and hills. If you’re riding uphill or into a strong headwind, you’re going slow. Downhill and with a tailwind, you’re riding fast. Whatever my riding companions’ average speed was at the end of the workout would have to be explained based on the environmental conditions, not their fitness. Was it a windy day? How hard was the wind blowing when they rode into or with it? Were they going uphill or downhill? How steep were the hills? How great would the wind speed be on race day? Would there be a tailwind or a headwind on the longest hill of the race? There is absolutely no way of estimating performance requirements and preparing to be ready for them if speed is the measure of intensity.
    With a power meter, hills and wind are of no consequence. In a race, while others are guessing how fast to ride up hills and into the wind, the rider with a power meter is content simply holding the prescribed power. Power is a much easier and much more precise measure of intensity than speed.
Feel
    I recently received a comment from a rider after I posted a blog entry called “Why You Need a Power Meter.” He told me he trained with an elite cyclist who didn’t use a power meter, a heart rate monitor, or even a handlebar computer with a speedometer. And his friend was really fit andfast. So he now believed that riding based strictly on how he feels is the proper way to train. Sport scientists call this method of training “perceived exertion.” They use scales to rate this, such as 0 to 10, with 10 being high. By assigning a number to how hard the effort feels, they create a subjective quantifying system known as “rating of perceived exertion” (RPE).
    Actually, there’s a lot to be said for that way of thinking. If the battery on your power meter or whatever device you use dies on race day, you had better be able to continue on without