Keeley, D. W., Wicke, J., Alford, K., & Oliver, G. D. (2010). Biomechanical analysis of forearm pronation and its relationship to ball movement for the two-seam and four-seam fastball pitches. The Journal of Strength & Conditioning Research, 24(9), 2366- 2371....
In order to throw a four-seam fastball, a pitcher grips the ball with the "horseshoe" oriented horizontally, placing two fingers across the open space between the seams and the edges of his fingers slightly over the seam. The fingers will contact the seams at four points, with both fingers...