The Physics of the Uneven Bars

One of my neighbors is a gymnast who recently learned--or in gymnast terms "got"--the giant. The giant is a singular rotation around the high bar on the uneven bars apparatus. To do a giant, the gymnast must rotate around the bar in a fully-extended handstand position. This move is crucial and foundational for more advanced skills and dismounts on the uneven bars. The form is crucial and the body must be completely straight in order to gain full points for the skill in competition.

This skill, while incredibly difficult, can be described by simple rotational kinematics. To perform the giant, the gymnast must first do a kip, a motion in which they use to momentum of their lower body to push up into a handstand on top of the bar. At this top position, the gymnast's velocity is zero. After holding their position, the gymnast keeps their abs tight and lets their shoulders relax, resulting in their body swinging around the bar as shown above. The gymnast experiences centripetal acceleration and centripetal force, written as:

a = (v^2/r) and F(c) = m(v^2/r)

The radius in this case is the length of the gymnast's body while in a layout position. Height is crucial to performance on the uneven bars as a smaller radius, or a shorter gymnast, can actually experience a greater centripetal acceleration and produce more force while they swing around the bar. Their muscle mass is also crucial in their strength to weight ratio, containing a greater mass in a smaller body producing a greater force. This force gives them greater power and airtime to perform complicated skills like a tkatchev.

Videos below show both a giant and how this skill is central to great routines.

Giants: https://www.youtube.com/watch?v=shtcoEzjlzA

Routine:

Picture source: http://www.codeofpoints.com/horizontal-bar/