There are many reasons that it is beneficial to use a power meter. The following are what I believe to the most important reasons to train and race with power.
Take the Variables out of Your Training and Racing
Power is a direct measure of the energy a cyclist is able to put into the pedals. When you use a power meter it allows you to eliminate variables in training and racing. If an athlete states that he was able to hold 18 MPH for one hour it tells us something but does not describe the whole story. Did he ride up a hill at 18 MPH? Was he on a flat road riding into a headwind? Did he coast downhill without pedaling at all? Because a power meter is able to look at your direct energy output, it is possible to more accurately compare rides that you have done (or others have done) on different terrain or in different conditions.
Train and Race at the Correct Intensity
When you train or race with a power meter you know precisely the intensity that you are working at within a few pedal strokes. Training by heart rate will give you a relative idea of your effort level but it is best to think about heart rate as the input (how hard you are working) and power as output (what you are actually producing). Training by heart rate has value, however there are downsides. Outside variables effect your heart rate such as fatigue, stress, caffeine, etc. Heart rate lags behind actual effort; it can take anywhere from a couple of minutes to tens of minutes for your heart rate to ‘catch up’ to your actual intensity. At a given intensity (output) an athlete will also experience cardiac drift, meaning their heart rate will gradually increase over a period of time. A simple cycling workout such as 5 minute hill repeats (recovering on the downhills) is very effective using a power meter because you can accurately gauge your power output within a few pedal strokes. Because your heart rate will take several minutes to ‘catch up’ to your intensity and you may experience cardiac drift between subsequent intervals, it is easy to see how important it is to be able to accurately measure your output (power on a bike).
Accurately Pace your Workouts and Races
Because a power meter enables you to remove many variables, an athlete is able to accurately pace themselves during a cycling workout or race. This is common practice in running (thanks to the introduction of GPS devices) and it’s interesting to note that in endurance running, nearly all of the record-breaking times in the last 40 years have been run with even or slightly negative splits. What this shows us is that output (not input) is what’s most critical to performance. A power meter is key to accurately pacing yourself (by measuring output) on a bike. Staying within a power range determined before you begin will take out the guess work. This becomes most valuable in a long distance race such as a Full or Half Ironman event. When most people are fighting the wind, or estimating how hard to go on a climb, the athlete with a power meter is able to just keep rolling along at the prescribed power, allowing them to produce the fastest possible race given the conditions.
Measure Fitness Changes and Analyze Performance
One of the most exciting things about training with power is that you are able to track changes in fitness. Not only can you do this from week to week and month to month but also from one year to the next. An athlete in reasonable shape will have a fairly consistent heart rate while their power output should increase as they become more fit. If you were able to output 200 watts for 20 minutes at a heart rate of 150 four weeks ago and now you can output 220 at the same heart rate for the same amount of time, you have proof that your fitness has improved. A power meter allows you to observe a quantitative measurement of a particular workout or race. Most power meters on the market today also allow you to easily download your power data for analysis. This is a great way to get an objective view of a workout or race performance and it may bring to light things that were not observed while engaged in the training session or race. For example you may be able to determine that your average power begins to drop after two hours on a training ride or that you are able to run much better in a race if you do not exceed a particular average power.
Working With a Coach
A power meter gives a coach an inside look into your cycling training. The information from a power meter is a clear and concise way for them to interpret a workout or race. When a coach is able to objectively look at power data as opposed to getting a subjective view from the athlete they are able to coach much more effectively.
Written by Kyle Visin
Santa Barbara Triathlon Club Co-President
USAT Level 1 Coach
Certified CycleOps Power Coach
Co-Founder of KillerTri
A duplicate post is also available at www.killertri.com