A stationary exercise machine in accordance with some examples herein may include a frame, a crankshaft rotatably supported by the frame, an upper moment-producing mechanism and a lower moment-producing mechanism both operatively engaged to the crankshaft to cause the crankshaft to rotate. The lower moment-producing mechanism and the upper moment-producing mechanism may be resiliently coupled to one another, such as via a resilient coupling between a crank arm of the lower moment-producing mechanism and a link or virtual crank arm or the upper moment-producing mechanism. The exercise machine may further include a measurement apparatus which may be configured to measure differential forces between the upper and lower mechanisms.