Momentum and Mayhem: A Running Back’s Time on the Gridiron Freeway

It goes without saying that injuries are a serious problem in the NFL. But it seems that problems with injury are much worse, or at least more prevalent, in recent years. Perhaps we are only hearing about injuries more because of various law suits against the league and, as a result, attempts to make the game less vicious. Regardless, injuries are always a high possibility when you have two high-powered athletes running full-speed at each other in full body armor. But what is the extent of these collisions? Is there any way to truly comprehend of what players are experiencing play in and play out, game in and game out? Hall of Famer Emmitt Smith once stated,

“Some of it may seem hokey to some people, but…playing in a football game is like being in 30-40 car accidents. You can find yourself in awkward positions. That stuff takes its toll.”

I’ll admit, Smith’s statement sounds like an extreme use hyperbole. Thirty to 40 car accidents a game? That’s simply not believable, especially coming from the man who pioneered this intelligent statement:

“Don’t worry about the game you just won or the team that we just blew out…uhhh…blown…blown out…Let’s think about what we need to do going forward, and they had…blown out.”

By extension of his interview skills, Smith does not seem like the most credible source when it comes to science. However, the concept Smith poses is an interesting one. How many equivalents of a car accident do players experience in a game? How many in a play? What can we learn about the game of football from these calculations? Let’s look and see what the data actually says.

First, we need to consider the force and acceleration in a car accident. If a car crashes into a tree at a speed of 30 mph with a 160 lb person at the wheel and no seatbelt, the driver will experience a force of 24,068 lbs, which is a deceleration of 4836 ft/s2. That kind of acceleration is equal to 150 “g’s”! A more normal assumption is that the driver will be wearing some sort of stretching seatbelt, which will reduce the force to 3,211.39 lbs. That is equivalent to 20 g’s of acceleration, which seems like a more reasonable estimate. A collision involving someone the size of a football player, like Emmitt Smith, who was 216 lbs, does not change the force too much, however. Regardless, a Smith colliding into a tree at 45 mph in a car would generate 45 g’s. For comparison, a barrel roll in an F-16 fighter jet generates only 9.0 g’s, 5 times less than this car accident. To make a long story short, a car accident causes a ton of force.

With this sort of force generated by just one car accident, it seems improbable at this point that a game could generate the force of 30 of them. If an Emmitt Smith-size player were running in a game, it is reasonable that he would be running at around 15 mph, which equates to about 22 ft/second. In terms of 40-yard dash time, that is 5.45 seconds; yes, it is a slow 40 time, but it is unreasonable to think a player would sprint his maximum speed the entire game. At this kind of speed, a football player will, shockingly, receive an acceleration of a whopping 90 g’s, twice as much as was generated by a car crash at 45 mph. In order to experience a force equivalent to a football collision, Emmitt Smith would need to drive his car, with stretchable seat belts, into a tree at 63.5 mph, just under the speed limit of a normal Interstate Highway.

So, how many car accidents does a running back experience in one game? Between the 2011 and 2013 seasons, the top 45 running backs in rushing yards averaged 14.51 carries and 2.01 receptions per game. If the running back were only hit on plays where he had the ball, and if he went down after the first hit every time, he would experience around 33 car accidents. However, running backs are normally hit more than just once on carries and get hit if they drop a pass. It is therefore conceivable that a running back could easily experience a combined force of 35 or more car accidents, which is unfathomable considering that a player could experience this combined force 16 times a season, excluding playoffs, for years. Thus, surprisingly, Emmitt Smith was actually correct about the number of car accidents NFL players experience.

What are the implications of these calculations? First, it is quite easy to absorb a lot of force in football, which could easily result in injury. As players continue to become faster and more athletic, it could become exponentially more dangerous to play at the professional level. The increase in the number of “physical specimens” entering the league on both sides of the ball could be contributing to a massive influx of injuries in the NFL.

Second, if the NFL and the NFLPA want to reduce the number of retired players suffering from long-term brain damage, it would be smart for them to try to alter the way players play. As pads and helmets have become harder and seemingly more protective, players may have gradually become more violent on hits, for they are less fearful of injury. This lessened fear has possibly caused a more violent mentality, a mentality that needs to change for the safety of the league’s players.

Finally, for years, Commissioner Roger Goodell has been adamant about extending the season from 16 to 18 games. Given that players experience these 35 or more car collisions per game, adding another 70 car accidents’ worth of damage to the players seems absolutely ludicrous. Goodell needs to stop this pursuit in order to save the lives of the players he claims to care so much about.

I would like to thank Dr. John M. Beggs of the Indiana University Physics Department for his assistance in these calculations.

Follow Zak on Twitter @zakberliner1 and listen to him on “The War Room” Fridays from 6-7pm