Complex sentence: Hanging from the rope are a series of vertical recoiling cables attached to a T-shaped bar, about a meter in both dimensions, that is placed behind the skier's or snowboarder's buttocks.
Split into simpler sentences: Hanging from the rope are a series of vertical recoiling cables, each attached to a T-shaped bar measuring about a meter in both dimensions. The horizontal bar is placed behind the skier's or snowboarder's buttocks.