Man, bad timing for me and this adventure event. Last Friday, I got a herniated disc which makes walking and general movement super painful. It's not healing quickly either. <_<
Though, on the other hand, it actually would've been perfect timing because next weekend I have a 71k ultra marathon, so grabbing that 50k distance would've been easy.
Having a spinal injury SUCKS! Fix your posture folks. Don't cross your legs when you sit. Don't lean to one side when you sit. And, in general, try to sit up straight. Otherwise, all that uneven movement and pressure will grind away and your spine's weak point and eventually knock something loose.