Ankle pumps just means lifting your foot up and down. I used to tell patients that were going to be flying on a plane, along with getting up every once in a while and walking, to do a whole bunch of ankle pumps. This is to help prevent a blood clot from forming by using the muscles which in turn makes the veins work better and manually pumps the blood. When you are sedentary for a long time the blood can pool and form a clot. And when on a plane something about the altitude makes it easier for blood clots to form. Now, I had a blood clot which I had absolutely no indication was there and it went to my brain and caused a massive stroke at the age of 30. Shit happens.