Abstract: A device for absorbing energy from a bicyclist's foot on the downward pedal stroke and releasing it shortly afterward into the drive chain to propel the bicycle is disclosed. The energy is stored in a coil spring which is connected between the sprocket wheel and an adjacent crank. The sprocket wheel is fitted to a bearing on the crankshaft and is free to rotate independently of the crank except as it is restrained by the connecting spring. If the crank and the sprocket wheel rotate relative to one another away, from the equilibrium position of the spring, the spring is compressed or stretched and the resulting force causes a restoring torque. When the magnitude and angle of the force stretch the spring on the pedal stroke, the invention allows the rider's foot to move quickly through the power stroke, where great force is exerted. Less time is spent by the rider in exerting force on the pedal; this saves muscle energy, since a muscle, unlike a spring, uses energy in exerting a static force.