mrdiko

I would imagine doing some trampoline time would help. The key is to train intervals similar to that of your tunnel times. And then you must ask, why are you doing the tunnel training.

The interesting thing about lumbar spine pathologies is that around 80% of people without pain have one. Here is a study: http://www.contentnejmorg.zuom.info/cgi/content/abstract/331/2/69

Do your next skydive blindfolded and see if you get bored.