Force-Velocity Relationship. 10 At a given velocity of shortening,the muscle exerts greater tension if we stretch it more with a greater preload. At a given afterload, Velocity of the velocity of shortening shortening is greater (mm/s) if we stretch the muscle more with a Short initial length greater preload. (lesser preload) Long initial length 0 (greater preload) 0 5 10 Load(g) The contraction is isometric at zero velocity