Why a Power Meter?
Most every athlete who follows a program or has a coach has periodization in their schedule; short workouts, long workouts, faster workouts, slower workouts, strength workouts, et cetera are all part of the plan. To accomplish this, an athlete needs some measure of defining their exertion level. The more common methods are perceived exertion, speed/pace and heart rate. These methods are all reasonable indicators of exertion but are somewhat inexact. Perceived exertion can be influenced by fatigue and emotions, speed/pace can be influenced by weather and terrain. Heart rate is fairly accurate, but can be influenced by fatigue and stress. Heart rate monitors accurately portray your current heart rate but unfortunately, there is a lag of 30 seconds or so for your heart rate to react to a change in exertion level.
This is where a power meter on a bike comes in. The feedback is immediate. When you start pushing harder, the power numbers go up accordingly without the lag associated with heart rate training. Let’s say you set out to keep your heart rate in a certain zone on a rolling course. You hit your first hill and halfway up your heart rate jumps well above your desired range, so you slow down. You slow down, but because of the lag in heart rate, you’ve actually been working too hard for at least 20-40 seconds. Multiply this by many hills and you will find you are getting fatigued much more quickly than if you kept the effort even.
With a power meter, you are able to conduct some tests to determine power zones to train in. You will have a much better idea of how hard you are pushing so that you can even out the pace during your ride. Also, you will have a better understanding of how hard to push during strength, interval and speed workouts. Most new owners of power meters have a very eye-opening experience with how well-paced they actually ride and just how hard they are working.
For the time-trialist or triathlete, even pacing is the name of the game. For road racers, in addition to even pacing, the athlete now has a gauge of just how much power is required to stay with the pack and can train those outputs accordingly.
Which Power Meter?
There are several systems out there, the most common being SRM and PowerTap. SRM is a meter contained in a crankset and PowerTap is contained in a hub. If you only have one bike to train and race on, an SRM may work well. Personally, I prefer the PowerTap since you can have a wheel built with the hub and move it from bike to bike. Also, you can find a bike shop with a rental program to “try before you buy.” I don’t know of any shops doing that with SRM. Here in the Vancouver area, Speed Theory has a PowerTap rental program and they stock PowerTaps for purchase.
In the next installment on training with power, I’ll try to have pricing information and some more detail on power-based training.