Simplify how you measure intensity by using a power meter during cycling training

To quote my good friend Alan Lim, "You would never build a house without a tape measure or cook a turkey without a thermometer." The same is true for training: unless you have quantifiable information on how you are performing on a daily basis, you never know if you are undercooking or overcooking yourself with your efforts.

The common measures of intensity-rate of perceived exertion (RPE), speed and heart rate-measure the results of your effort. There is another option that measures the effort itself and is rapidly gaining popularity in the triathlon and cycling world: the power meter.

In mechanical terms, power is work done or energy transferred over a given time. For our purposes, it is how hard you are pushing on the pedals, and we measure that in watts. Power is the purest measurement of how hard you're actually working; even the gold standard of heart rate is not as direct, reliable or useful as power.

The rapid growth in the number of cyclists training, and even racing, with power meters in recent years can be attributed to a greater access to power-measuring equipment, be they on-the-bike power meters like PowerTap and SRM, or stationary trainers such as CompuTrainer. This growth has also taken place because many people are beginning to understand the substantial advantages of training with power: the more you understand about power training, the better you are able to associate your RPE with your training and racing loads.

Why train with power

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RPE (how you feel)
If you complete a "hard" interval workout, all you can say at the end is that you worked "hard". Maybe it was hard because you were actually doing a lot of work, but maybe it was hard because you were sick, stressed, tired, overtrained, undertrained or didn't eat enough. RPE gives you a great picture of how you are affected by the load, but doesn't allow you to quantify the load itself. Adding a power meter allows you to better understand RPE by giving it an objective value.

Speed
Introducing speed allows you to quantify how fast or how far you went, but by itself actually it means very little. This is because speed is highly dependent on environmental factors such as wind, hills and rolling resistance. While riding at 15 mph up a very steep hill may be hard, riding 20+ mph on a smooth, flat road with a nice tailwind may be relatively easy. No matter what the conditions, you must push on the pedals. Power measures how hard and fast you are pushing.

Heart rate
Although it can be a great reference point, the major disadvantage of heart rate is that it only gives you the "how" of training, not the "what." Like speed, heart rate is also very susceptible to external factors including sleep, stress, overtraining and undertraining, hydration and heat. Furthermore, heart rate response has a lag time, whereas power gives you instant feedback.

For example, if you complete a 30-minute effort at a heart rate of 165 bpm, you can assume it was harder than a 30-minute effort at 155 bpm. But what if the second interval felt harder in terms of RPE? In reality, you have no idea if you did more work-if you were tired, if you cracked on the first interval, if your HR drifted, if you started the interval at a higher HR therefore there was less lag, etc. However, no matter what the HR, if you did the first interval at 200 watts and the second at 205 watts and they both felt hard, that is all you need.

Power
The major advantage that power has over all other measures of intensity is that a watt is a watt, just like a 5-pound plate at one gym is the same as a 5-pound plate at any other gym. This consistency means that when you see a power value, you can directly compare it to other power values-it is quantifiable. All the other measures are simply responses to how much power you're putting out.

Continued...
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