A device for measuring a force applied to a bicyclical pedal by a rider is attachable to a standard bicyclical article. The device comprises (a) attaching means adapted for quickly embracing and detaching from said crank； (b) a spring-loaded leaf attached to the crank； (c) at least one strain gage adapted to measure a strain of the spring-loaded leaf； and (d) a control unit. The spring- loaded leaf is glued to the crank.
