This is _NOT_ Matt Smith. It’s actually fitness model/bodybuilder Cory Mason.
The gifs come from this All American Guys video (starts at the 1:27 mark; note that this is a preview only of the full video). If you get the wrong video, choose the one of Cory from the “All Previews” drop-down menu below the video.
You can also see an excerpt here.
Sorry to disappoint some of you (including myself). :(