How can the tables be used
The power, cadence and resistance table provided below can be used in a number of ways:
- Use the table to establish the correct power output (in Watts), by resistance setting and cadence (in 5 rpm bands) required for any particular training session. For ease of reference the Watts have been rounded to the nearest 5 W.
- Conversely at the table air resistance setting required you can increase/reduce the cadence to match the power output.
The Wattbike load cell measurement system is on the chain and tracks pedals. The load cell measures directly the force the rider is applying through the cranks onto the chain (the data is collected at a resolution of 100 samples a second – a pedal revolution can be measured to 5 decimal places). The accuracy of the Wattbike relates to the measurement system.
The measurement system is not influenced by the air resistance (this just creates variable resistance for the rider to work against), nor by environmental conditions (heat/cold, humidity, altitude), nor by the chain being 'tight’/'slack’. THE LOAD CELL WILL MEASURE AT ALL TIMES THE FORCE BEING APPLIED INCLUSIVE OF ANY VARIABLE 'CONDITIONS’. There will be variances between Wattbikes to reflect calibration (+/- 2%) and manufacturing tolerances but each Wattbike is precisely calibrated at the factory.
What does this mean?
There is a common belief that every bike produces the same 'result’ on the same air brake setting i.e.
- 80 rpm at level 1 = 115 W OR
- 90 rpm at level 3 = 200 W
This is incorrect - the tables are mathematically constructed (and rounded to nearest 5 rpm and 5 W) and assume perfection i.e. constant application of force and constant cadence under set environmental conditions and are for guidance only.
Around the individual Wattbike calibration/tolerances, 80 rpm for 115 W may be at air resistance setting 1.5 and 90 rpm for 200 W at level 3.5 (or higher/lower).
Any differences may be also due to the air resistance conditions. For example significant differences will be seen at altitude (due to the density of air – 'drag’ is reduced). We have 6 Wattbikes in Colorado Springs (altitude 1839 m) which are 15% (at level 10) - 25% (at level 1) below the standard table figures. To apply the same force at the same rpm as on a sea level Wattbike the air resistance would need to be increased.
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