A power measuring system for an at least partially human powered vehicle or training device with a crank drive, in particular a bicycle, with at least one crank arm of the bicycle being manufactured of fiber-reinforced plastics and the crank arm having a sensor, in particular a strain gage, and with the largest part of the sensor being directly enclosed on all sides by the fiber-reinforced plastics. The force exerted on the respective pedal and from this the torque exerted on the bottom bracket shaft is determined by an electronics unit, which is preferably arranged in a cavity in the bottom bracket shaft, from the signal of sensor. From this, together with the rotational frequency of bottom bracket shaft, which is possibly measured by further sensors or is determined in a calculative way, the power currently generated by the user of the bicycle is determined. The power values can, in particular wirelessly, be sent to a display unit and be displayed thereby in the form of power-related information. The sensors in both crank arms, make it possible to determine the power for the left and the right leg of the cyclist separately.
