Crazy footage has emerged from a downhill longboarding competition with two spectacular crashes, one at 00:06 and the second at 00:30. Slow motion replays included.In the first incident, rider Jed Kenny comes off his board, and competitor Simon Paton adjusted in the corner but struck him with a heavy hit to the chest, sending him rotating and upwards.The second incident shows the importance of head protection, as rider Stephen Hayes is saved by his helmet.Some spectators and participants were critical of the course design which they believe led to the accidents at South Africa's 2014 Urban Descent downhill skateboarding race.Video courtesy of David Beare