Abstract: A crank has a crank arm (3) and a freewheel element (1, 2) for fastening the crank arm (3) on a crankshaft. When the crank arm (3) is rotated in a first direction, a torque is transmitted to the crankshaft. When the crank arm (3) is rotated in a second, opposite direction, the crank arm (3) rotates in freewheeling mode. The crank furthermore has at least one fixing means (6, 6?) for cancelling freewheeling, allowing the torque of the crank arm (3) to be transmitted to the crankshaft in both directions of rotation. This crank allows simple switching between one-way coupling and two-way coupling and significantly increases the available training and therapy options.