Kansas City Chiefs running back Jamaal Charles tore his ACL in Week 5 of this past season. Four months and eight days later, he's jumping rope and working on his balance.

Take a look:

It's great to see Charles working his way back into shape. He's one of the best running backs of recent vintage, and one of the most efficient on a per-carry basis in NFL history. This is also the second ACL tear of his career, as he also suffered the injury back in 2011.

He came back from that injury to be wildly productive over the following three full seasons -- he rushed for 3,829 yards and 26 touchdowns on 750 carries from 2012 to 2014 (third in the NFL in both rushing yards and touchdowns). He was off to another good start in 2015 with 364 yards and four scores on 76 carries before suffering the ACL tear.

If he's already jumping rope and doing balance and strength exercises, it sure looks like he's on track to be ready by the start of next season. Now 29 years old, Charles likely doesn't have much time left as an elite-level running back, but it's worth noting that he has less tread on his tires than typical 29-year old backs due to his low usage early in his career. That low usage might be negated by the two knee injuries, though, so it'll be interesting to watch how his performance is affected by that balance.

Jamaal Charles, back at work. (USATSI)