I was playing 18 today, riding shotgun with my partner in a two man team best ball tournament. As he approached his ball for me to pick up on my side of the cart, I leaned down to scoop the ball up, full speed, and as I bent down he for some reason veered left, and out I went, head first, rolled up like a window blind, and somehow momentum carried me foreward back up on my knees, grass clippings in my hair and all down my back. What causes this?