Relaxing muscles always seems to be a best practice when you're about to take any sort of high-speed injury. I've been on disability since June when I fell at work and blew out my knee. If I hadn't thought I could catch myself, I probably would have been sore from the fall, but I wouldn't have exposed my leg to the impact that I ended up causing by trying to catch my fall.

To go with a more vehicular concept... if I'm not mistaken drunks have a pretty good survival rate in automobile accidents, and a lot of this has to do with the tendency for drunks not to tense up before and during a crash, unlike their sober counterparts who typically tense up and sustain more serious injuries.