The freestyler below has his right arm in an effective position to begin the push phase (first image). His hand force increased to about 20 lbs at the end of the pull phase. (The vertical gray lines are synchronized with the video image.) As he pushed his hand back, his elbow rotated upward in synch with the torso rotation. (Note how his elbow is at the surface in the second image.) Since the elbow rapidly moved upward, the hand also moved upward and he was unable to increase force on the push phase. (Scroll over the image to see the arrows to change the image.)
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