In Robinson's model, both the downstroke and the upstroke would have been powerful. The upstroke then pushes the wing upward and backward. The exhaust valve opened for the piston upstroke. He often uses percussive techniques and plays intricate down and upstroke patterns with his thumb. This results in an increased threshold for excitation and a decreased upstroke velocity. In the upstroke, one frets the third string first, reversing the rolling action. The traveling valve is opened on the down stroke and closed on the upstroke. This force is developed primarily through the less powerful upstroke of the flapping motion. From the bottom of the down-stroke, the hand is then raised for the upstroke. During the upstroke of the wing, the resilin is stretched. The lumbricals are used during an upstroke in writing.