Some of us spend hours a week at the gym trying to strengthen our muscles, but how much do we really know about those pieces of soft tissue that keep us moving? For example, ever wonder how many muscles it takes to coordinate one step? Around 200. A video uploaded by BuzzFeed gives us 10 facts about muscles that will probably surprise even the most devoted gym rat.

Any fitness expert can tell you how important squats are, but you may not know it’s because when you’re doing squats you’re training the largest muscle in the human body: the gluteus maximus. The smallest muscle, on the other hand, is located just behind the ear. Probably why there aren’t a lot of ear exercises.

Your butt may be the biggest muscle in your body, but your jaw muscle contains more force than most of your muscles.

Ever get to that point in a race where you feel like your heart is going to give up before your legs? That’s because your heart muscles are working twice as hard as your leg muscles. Oh, and next time someone asks why you look so sad tell them it's because we use more muscles when we smile compared to when we frown.

To leave you with some last minute words of muscle-building encouragement, don’t become discouraged next time you step on the scale. Remember, your muscles make up anywhere between 35 and 40 percent of your body weight.