I was training at Cressey Performance today did some sled pushes. Here is one:
I need to gain a LOT of strength still but my weird back does some magical things for me in pushing. Basically I have a hyper mobile lumbar spine that hinges at a weird point and it allows my spine to rotate while also going from flexion to extension quickly and with force. While this is probably not good for upright running, its a huge advantage for running bent over like I do for skeleton pushes-- Think greyhound spine:
Exciting stuff, eh?