How do they measure rider power output?

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Legendary Member
First came across this in the Michael Hutchinson book and have now seen it in relation to the Tour. Is it done by a speed/pedal RPM comparison?


New Member
Deal, Kent
There are 3 main methods
SRM Cranks which have a strain meter (don't know the correct term) in the bottom bracket.

Power tap.
Similar to SRM but located in the rear hub

Which is the least accurate which works on the movement of the chain and the cadence I think.
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