The goal of the compulsory committee on bars in this level is to have a routine with multiple skills that requires no spotting, is safe for a child as young as 6 and novice level gymnasts (so going to the high bar is basically out) and flow/breadth of movement. So yeah, we could have the kids cast and do like five back hip circles in a row, but what is that teaching? And if you do that then some coaches will just be teaching back hip circles anyway.
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With all due respect, most other countries don't offer remotely the same gymnastics program or options as the US. The goal of USA Gymnastics is to provide a platform where every child can participate in gymnastics at he right level for them. That might be Jen Bricker as a tramp/tumbling champion (she has no legs), a child with special needs participating in a class, or the dozens of kids for whom nailing a mill circle will be one of the high points of their career. The position of USA gymnastics is that if a kid is so advanced that a mill circle is beneath her and her coaches want to accelerate the training, there are options to do so (start in level 4, TOPS training, Xcel, etc). for everyone else? The process and physical training involved in learning a mill circle is the same process as anything else in gymnastics. They get stronger using different muscles that they don't use in the back hip circle. They learn to work through frustration. They build synapses in their brains (teaches timing and body awareness). They stay on the bar longer and get better. Those things are "the point."