Repetitive strain injury risk, seated vs standing on pedals At the same cadence and torque, and hence at the same power output, which generally presents the lower repetitive strain injury risk: pedalling seated, or out of the saddle?

How does the distribution of forces on the body and the risk of injury change as force on the pedals goes up, both for seated and for out of the seat cycling?

For an aging recreational cyclist, with no great need to sprint, is it always the better choice to downshift and remain in the saddle, rather than to get up and stand on the pedals?

(Edited: made clear I'm interested in repetitive strain injuries specifically, rather than injury in general. Apologies to those who answered with respect to general injury risk - these answers are interesting, but not what I was looking for)
This depends entirely on the conditions one is riding in.  Crashing on ice, one is probably better seated as the fall has a lower drop and sliding is easy enough.  In a rock garden, you may be better standing so that you can clear obstacles and not have your bike as an extra factor involved with the crash.  On a busy sidewalk, being seated and stopping more quickly might avoid entangling pedestrians/additional cyclists, etc.  On a roadside, it might be preferable to stand and roll away from the road to avoid the dangers of laying in a heap on a roadside with your bike.  

Additionally personal skill comes into play, people who don't know how to roll with a fall are perhaps more likely to be injured from a higher fall (standing).  However, there are skills that help with a sitting fall as well.  Taking a sitting fall on your side (rolling up from hip to shoulder without slamming knees or elbows) is preferable to going over the bars while sitting or putting an arm out and breaking it.

I think conditions and personal skill with falls will make a larger difference than what position you start in.