I enjoy several sports that have been good practice for falling in "friendlier", softer conditions: snowboarding, skiing, hockey and mountain-biking. Keeping the arms inboards and wrists off the deck is key for each. I have fallen countless times without wrist, arm, shoulder or head injuries, and presumably built some muscle memory along the way.

I agree with an earlier poster that having less time to react to a collision can be a good thing - 3 weeks ago I was blindsided by an oncoming van driver who basically tried to take a left turn into a driveway though my body and bicycle. My hands were on the bars when I went down. I suffered some bloody knuckle-bruising and my left leg was badly bruised by the car impact. I realize that I was lucky overal - bike commuting again after 5 days and mountain-biking after 3 weeks.