The first time I saw him do it I thought "he is about to get on his hands and knees", but then he never bent his knees. He just held this push-up position for about 10 seconds, laid back down on the floor and then immediately did a second push-up. Now, when he is on his tummy he will pretty much always do one or two of these. I guess he decided it was time to do something about that extra chin and oversized cheeks! Granted, they are the girl-style push-ups. Give him time, he is only 8 months!
Here is a good close-up of a before picture of the cheeks and chin. I'll post an after picture once he has a more regimented workout plan going: )