Originally Posted by jimmuller

Well, there is a good reason not to shift the front, and I'm sure you know this but noobies might not have thought if it yet. Front shifts move the section of chain under tension from pedaling. Rear shifts move the section of chain whose only tension is from the RD cage

That's not to say some stress isn't still involved in a rear shift. The chain moves from one sprocket to another underneath the FW, but eventually those links which straddle two sprockets move around to the top and come under pedaling tension. That puts some lateral stress on the sprockets. Teeth can break off. We've had that happen a few times on our tandem.

If you're in a race and absolutely need to keep hammering while you click your lever, well, whatever clicks your lever.