I have a road bike that I use to commute ~6 miles to work every day. Some of the portions of the ride are at a steep incline, and I've noticed that when I get up to stand on some of these hills, my gear slips.
I'm not sure if "gear slips" is the right term, but basically after I stand up my gear switches without me triggering it. It's very annoying and sometimes painful when I completely lose control of pedaling for half a second, not to mention the different gear setting.
What could be the cause of this?