We should probably go through a few disclaimers. The other day, through the miracle of , I watched about 90 minutes of nothing but Jamaal Charles with the football in 2013.I did this for a few reasons. The grander purpose^ was to explore a thought after a few weeks ago — a thought .^ That’s cool of you guys to let me pretend I had a grander purpose.The basic idea is nothing new. NFL running backs have a heartlessly short shelf life. Emmitt Smith is the exception. is the rule. The Chiefs know this personally. In that blog post, I pointed out that the last running back before Charles to get big money in Kansas City was Larry Johnson.When Johnson signed his big deal, he was three months shy of his 28th birthday with 892 carries, 97 receptions and no major surgeries.Charles is now about four months from his 28th birthday, with 1,043 carries, 222 receptions and an ACL surgery.Johnson, of course, broke down shortly after signing that contract. There’s a reason Charles couldn’t sign for more than $18 million in new money.Anyway, I don’t know of any way to measure this scientifically, but it seems intuitive that even with about 300 more NFL touches at the same age, Charles may have less wear and tear than Johnson had. You know how when you buy a used car, the person selling always tells you the mileage is “all highway miles?” Well, just watching the styles and usages of Charles and Johnson, I think we can say Charles has more highway miles than Johnson.The mind’s image of Johnson is busting through the line between the tackles, shouldering a linebacker, stiff-arming a safety, and running in for a touchdown. The mind’s image of Charles is more vroom than violence, gliding around an edge and outrunning everyone into the end zone.Charles had 329 touches last year, the most of his career, but he also seems to do a good job avoiding hits. But it’s one thing to think that, another to see it, so I thought it might be instructive to go through Charles’ 2013 season with a more careful eye.So I watched all of his touches and tried to put them in one of three categories.Hard contact: basically, the ones where you make a noise or grimace. These are the ones the NFL used to promote until the lawyers pointed out the hypocrisy. This includes helmets coming off, defenders getting clear shots in, and the times one guy hits you and another comes in and pops you on the way down.Routine contact: the vast majority of contact. These are the ones that would probably leave you or I in bed for at least a day, but the ones you hardly notice watching games. Just regular ol’ tackles.No or light contact: pretty self-explanatory. This includes running out of bounds, and knowing your feet are wrapped up and going down before the second hit.Now, the disclaimers:* Obviously, this is very subjective. What you think is a routine hit, I might think is a hard hit, and vice versa.* This doesn’t include contact taken while blocking, and Charles takes blocking very seriously.* NFL Rewind is fantastic, but not flawless. There were a few Knile Davis carries that made it in the Charles video, and a few pass plays that didn’t go to Charles. I assume I missed some of his action, too.* I have no point of comparison here, because I’m not planning on watching every catch and carry for any more running backs.So with all of that out of the way, if you’re still interested, here’s what I found:Thirty-six of Charles’ carries and six of his catches ended in hard contact. This included, most notably, the double-hit that gave him the concussion in the playoff game but also a helmet-to-helmet hit against the Eagles that knocked Charles’ helmet off; a juke against the Titans that didn’t work; being slammed to the ground by Brian Cushing; and a horse collar that wasn’t called against Washington.His roughest game, at least by my measure, was at Denver: seven hard hits, mostly being slammed at the line of scrimmage by a defense daring the Chiefs to do something besides give the ball to Charles.Twenty-seven of his carries and 13 of his catches ended in no or very light contact. Almost without exception, these were touchdowns (including a lot in Oakland) or running out of bounds.If we can pretend that this little exercise has merit, that means that out of 329 touches last year, we’re really looking at 42 that might worry you about an injury or adding to the wear and tear that all NFL running backs must deal with. That’s 12.8 percent.Just something to keep in mind when you hear about running backs being beat up. Not all hits are equal.To reach Sam Mellinger, call 816-234-4365, send email to or follow on Twitter . For previous columns, go to KansasCity.com.