I shoot a lot of gymnastics meets and I enjoy the challenges... which are abundant. When watching in real-time it's often hard to discern when and if they actually let go of the bar on certain moves. It's even more difficult to capture that split second in a still frame, as it's all about anticipation: if you wait until he/she let's go, they are usually re-attached by the time your brain signals your finger to hit the shutter button. Other technical challenges exist in terms of poor light and the need for very high shutter speeds. But at the end of the day, the technical hurdles can be overcome, the challenge is always timing.