Guinea Pig's Body Pumping (with Adrenaline?)

[koella]

My guinea pig's body sometimes does this motion that's a big hard to describe. I call it 'pumping' simply cause it's not quite a shake or remble. Her whole body seems to jerk repeatedly as if on the verge of popcorning (sometimes she does this when I put vegetables in her cage) though it usually doesn't result in a full popcorn. I'm guessing it's an adrenaline rush. Do any of your piggies do this?

 

[Wiebke]

I haven't particularly noticed; my guinea pigs usually mill around like mad, but they live in groups.