Wrist follow through

Figure 6: Highlights the correct follow through movement. image courtesy of http://cdn.instructables.com/FD4/083I/G068PYIM/FD4083IG068PYIM.MEDIUM.jpg

Feedback cues

• How did the hand finish after releasing the ball?

Extension and Rotation of the wrist lead to rotational energy being transferred to the ball and thus forcing the ball to ‘spiral’ along it’s trajectory.  This is done purposefully to attempt to reduce the amount of drag the ball has moving through the air thus retaining as much velocity of the ball as possible. Drag occurs when molecules of a fluid (‘fluid’ refers to any moveable medium, including air) collide with an object and take energy away from it. (Blazevich, 2013, p. 137). The unique shape of the American Football in comparison to the spherical balls commonly used throughout different sports helps to allow this rotation. The elliptical shape of the ball leads to the ‘gyroscopic effect’ which increases the rotation of the ball which in turn helps to reduce effect of drag upon the ball. (Rae, 2003, p. 5)The relationship between this shape and the laminar flow is also important; in comparison a spiraling football is able to lower the amount of laminar flow that becomes turbulent. The leading edge of the ball (the side hitting the air first) is pointed, thus ‘the direction of the fluid hitting the object will be changed more slowly’ in comparison to a rounded tennis ball in which the ‘fluid hits the object abruptly.’ (Blazevich, 2013, p. 137)  

The relationship between laminar flow and projectile shape: Round ball in comparison to elliptical.
Images courtesy of : Blazevich, A. (2013). Sports Biomechanics: the Basics: Optimising Human Performance. London: Bloomsbury. Pages 11 and 12