The distribution in manual labor includes major catastrophic injury. I'm 28, work in landscaping: the second day of this season I fell through a metal grate and was lucky to not snap my leg. I passed out at work last year due to dehydration/exhaustion after nicking my leg with a pair of electric hedge trimmers; it could have been much worse.

There's quite a few engineers I know that are fat and unshapely, and that likely takes a toll on their health, but I doubt any of them encounter daily situations where they're at decent chance of being maimed.