For the purpose of this column, we’ll define a swing skill as any skill in which the gymnast uses momentum gained from gravity to rotate around the bar (I should note that this isn’t a formal definition used throughout gymnastics literature, this is just the definition I’m using for this column). In some cases, this can be a complete rotation (as in a back hip circle or a giant); in others, the gymnast performs only a partial rotation (as in a tap swing or a kip). With the exception of a few strength skills (such as the pullover), all bar skills are swing skills (though dismounts and release moves are slightly more complicated in that they combine swing with airborne rotation – however, with this column we’ll be focusing on pure swing skills, which maintain contact with the bar).
A swing can be broken down into two distinct phases; the descent and the ascent. Any time a gymnast is descending in a swing, he is building up momentum. Any time he is ascending, he is spending that momentum.
As with airborne rotation, the distribution of mass relative to the axis of rotation is crucial. Unlike in airborne rotation, however, the lateral axis of rotation does not go through the body’s center of mass – rather, it runs through the bar.
The swing’s radius can be defined as the distance from the bar to the gymnast’s center of mass. A position with a long radius can be thought of as a high-power position, whereas a position with a short radius can be thought of as a low-power position. A long radius will cause the body to gain more momentum in the descent phase, but will also cause it to spend more momentum in the ascent phase. A short radius will cause the body to gain less momentum in the decent phase, but will also cause the body to spend less momentum in the ascent phase.
Therefore, in order to gain more momentum, the gymnast must seek to maximize his radius in the descent phase and minimize it in the ascent phase. This is the most crucial concept around which all bar skills are built.
If gymnastics were done on a rigid bar, this would be all there is to it. However, there is a nuance that we have not yet addressed – the elasticity of the bar. By bending the bar, a gymnast can effectively store some of his power in the bar, which he can then use later (bearing in mind that “later” in this context means “a fraction of a second later”).
While the effect of the bar’s flexibility is negligible on the most basic beginner-level skills (ie pullovers, back hip circles), it is absolutely crucial in intermediate and advanced skills (ie kips, freehip circles, giants, and especially release moves). Usually, this means the gymnast should bend the bar downward as he passes under it in order to cause the bar to snap up and boost his momentum in the ascent phase. In some instances, however, the gymnast may also bend the bar forward or backward to gain a boost in horizontal momentum; this is usually done leading into a release move or dismount; the most dramatic examples of this are visible in men’s high bar, particularly leading into Tkatchevs and dismounts. The method used to accomplish this bend varies depending on the skill.