Bill Belichick is doing for hooded sweatshirts what the 61-year-old has done for football during his 14-year tenure as head coach of the New England Patriots.

Belichick has become so associated with grey hoodies that the Patriots' official store even sells a Belichick model hoodie.

And apparently the sideline isn't the only place where Belichick prefers the sweater. His girlfriend, Linda Holliday, recently posted a photo to Instagram of the two of them working out. And, what do you know, Belichick is wearing a grey hoodie.

Of course, like all of Belichick's hoodies, this one has the sleeves cut:

Belichick is an extremely private, buttoned-up figure, and it's great to get glimpses of him behind the scenes. This photo from the gym and this Twitter Q&A shed some light on Belichick's true personality.

And just in case you were wondering, Belichick does have other outfits in his closet. Here's what he and Holliday wore at the Kentucky Derby in 2012: