Cyclic cranked system method and related devices

A cyclic cranked system data gathering system has at least one crank arm (30,50,116,117) operable by a limb of a user, at least one data gathering device (112,113) each mounted to a respective crank arm (30,50,116,117) and having at least one respective sensor (140,141). The or each device is configured to obtain data relating to force applied by the user through the respective crank arm and sensed by the respective sensor, and has a data transmitter capable of sending said data to a remote data logger, remote computer or to a display device. A method of determining power applied to a cyclic cranked system includes using a device (112,113) mounted on a crank arm (30.50,116,117) of the cranked system to sense strain signals resulting from force applied to one or more crank arms by a user, determining power applied by the user from the strain data, and transmitting the strain data, modified or unmodified, to one or more of a display, a data logger, a computer or another similar device mounted on another crank arm of the cranked system.