All things equal, the more power you can produce, the further you can ride in a given time. Power is the most consistent and quantifiable measure, as it measures the direct output of your muscles. This differs from common measurements like heart rate - an aerobic response that is an indicator of effort and conditioning - or speed / cadence - a result influenced by many factors.
What is power (watts)?
Power = force x velocity. It shows your ability to move yourself and your bike over a given distance and time. It is independent of external factors like wind resistance and incline.
Know this concept. Threshold is the maximum power output you can effectively maintain while removing lactic acid produced. This is the difference between quantifiably knowing how hard you can push yourself, and having a ‘feel’ for it.
A power meter is your energy display unit. Once you’ve trained and tested with power, you understand you much you have to give. The power meter shows how much you are using allowing you to correctly pace yourself for your training or race distance.
Speed and cadence are important, but are impacted by many factors - making it difficult to use them as a baseline for performance. Heart rate takes time to respond to your effort, and can be affected by hydration, energy levels, temperature and more. Power is the only direct and real time measure of your effort.
Harness your power.
- Eliminate guesswork from training and race day.
- Accurate and objective baseline to measure your training improvements
- Help to define your weaknesses.
- Train more specifically for the demands of your chosen event.
- Aerodynamic position testing.
Buying a power meter
Accurate measurement is the biggest consideration. Placement of the gauge on the bike, the quality of the gauge itself and the quality of installation can all affect this. You should also consider how challenging it is to install or move between bikes, as well as any potential accuracy issue related to the install.
Different ways to read power
Power meters use strain gauges to calculate power - they can be placed on different parts of the bike with different pros and cons.
The rear wheel hub
- Has fewer forces acting on the gauges, leading to greater accuracy.
- Measures power that is remaining after what is lost in the drivetrain. Reading will be less than pedal or crank based, and may be affected by the drivetrain condition.
The bottom bracket/spindle
- Accurate and low maintenance.
- Difficult to install.
- Added complexity due to variable bottom bracket sizes across bikes.
Chainrings and crank spiders
- Can be difficult to swap between bikes
- Estimate of left/power rather than direct measure
- Reasonably easy to move between bikes
- Can be single or double sided measurement
- Very easy to fit and swap between bikes
- Can be slightly less accurate (+/- 1%)
- Greater risk of damage given their location on the bike
Single sided power meters
- Measure power from one side and then double the reading to estimate your total output from two legs. More affordable, but may be less accurate.
- Combined power meters
Combine the power from both right and left legs, but do not measure it independently.
- Accurate, but will not differentiate which leg the power comes from.
Left/right side independent measurement
- Accurate, with an extra level of information can be useful if working on pedalling technique.