You cannot watch a bicycle race on the television without having the commentators debating about power or wattage. Also more and more training plans are based on power. Maybe even your training partner just bought a power meter recently. As a cyclist you can’t get around the fact that cycling has a lot to do with power nowadays. But why would you need power or a power meter? This article will tell you more about the advantages of training with a power meter.
A little history
A power meter is simply the best tool to monitor your training load. Back in the days, athletes and cyclists started monitoring their training load by using speed (km/h) and or time. But as you probably have experienced yourself: factors like wind or temperature and not to mention altitude have a drastic effect upon your speed. So speed isn’t the best tool for analyzing a training or monitoring your training load.
In the seventies and eighties heart rate monitors where the new kids on the block. A great development, because the environment and circumstances have a less drastic impact. The idea of measuring your heart rate was that you could actually measure how hard the body had to work. But as the knowledge of training expanded, heart rate also turned out to be quite variable. It also seemed to be influenced by external factors like temperature, altitude, stress, fatigue or day-to-day variability. Drinking a cup of coffee can increase your heart rate, but does not make your effort any harder. So the idea that heart was a valid and reliable tool to quantify the stress on the body was already questioned from the day it became commonplace.
So we (or they, since I was still in my diapers) started looking for another tool to quantify the effort. In the early nineties the power meter made its appearance. Lance Armstrong was actually one of the first professional cyclists using a power meter to monitor his training load.
So what is power?
In physics, the equation of power is: Power = force x distance. Which means that power is the force on your pedals times the distance your pedals covered, reflected in your cadence. Power is a direct measurement of your output, without being influenced by external factors. In contrast to heart rate, power is also capable of measuring your progress. As you get better, your power output over a certain time interval will improve. This is not possible by using only speed or heart rate, because while you improve your power output, the heart rate and even speed could remain the same.
So with power you are able to see what you’re actually doing. But in order to know how hard a certain power output is for you as an individual or to use a training plan, we use power zones. There are multiple ways to set power zones. At Robic, we use eight power zones based on your FTP. You can determine your FTP by doing an exercise test at a testing facility. This will tell you more about your strengths and weaknesses and will probably provide your aerobic and anaerobic thresholds. A slightly less accurate way is to perform a 20 minute FTP test as set in the Tacx Software. This is like a time trial of 20 minutes full gas after a warming-up. By taking 95% of the average power output over 20 minutes, you get a pretty fair estimation of your FTP.
Most power zones are based upon setting FTP as 100%. This results in the following classification:
- Recovery (0-60%)
- Extensive (60-75%)
- Intensive (75-85%)
- Tempo (85-95%)
- Threshold (95-105%)
- VO2-max (105-120%)
- Anaerobic (120-200%)
- Sprint (200%-max)
Power often is divided by your body weight, which results in relative power in Wattage per kilogram. This is a great way to include weight in the equation which is a big factor in riding uphill. By looking at relative power, it gives the opportunity to compare a lighter cyclist with a heavier one especially when the road goes up. Whereas if you want to be the fastest sprinter it is absolute power what counts.
Nowadays power meters are getting cheaper by the day, which doesn’t mean they get more accurate. The most reliable power meters are power meters located in your bottom bracket or in an advanced indoor trainer like the Tacx NEO 2T Smart, FLUX 2 Smart Smart and FLUX S Smart. Most power meters promise to be +/- 2 percent accurate, but a NEO 2T Smart even promises a +/- 1 percent accuracy.
Power meters are also located on cranks or in pedals and are available for measurements on both sides to give a left right balance. There are also power meters for just the left side, which is a great solution to save some money but not the most reliable option out there. A more advanced indoor trainer like the NEO 2T Smart doesn’t only measure power, but also shows your pedal pattern and left right balance, which is a great tool to improve your pedal technique.