My Boston/Pug (posted earlier) will run like this when he's in full "gallop". It's ****ing funny. In a regular run he can go pretty fast, but get him in open space and holy **** can he fly. I've thrown tennis balls full out at the park and with a 10 yard head start he can catch them on the second bounce.
The big ass grin is classic too. I took my dog out to the farm once, and he had a blast. Running like this in grass that is 4-5 feet deep. Since mine has some Pug in him, he's got a shorter nose, so his tongue hangs out when he gets into a full run.
Long story short .. Nice action Pic. It really is true, a picture says 1000 words.
Can't wait for summer to get into full swing and I get him out like he needs. He's turning into a bit of a fatass this winter.