They studied 10 high school football players -- lineman, defensive tackles, and others whose positions involved repetitive blocking and tackling. The average height of players before the game was 69.5 inches. Afterward, it was 69.2 inches.
Brian J. Campbell, PhD, an assistant professor of biomechanics at the University of Louisiana in Lafayette, headed the study. The findings were presented at the annual meeting of the American College of Sports Medicine (ACSM).
Defensive Maneuvers Compress Spinal Cord
Campbell says that it's well known that people shrink over the course of a day. "If you think of your body as an accordion, gravity squeezes you together as the day goes on," he says.
Football, he says, accelerates the process in two ways.
First, there's intermittent high-impact compression on the spinal column during defensive maneuvers. Then, there are low-impact continuous compressive forces from the weight of the football gear, he tells WebMD.
Campbell says that the loss in height has the potential to affect performance. "In a game such as football, being just a little shorter could mean the difference between a game-winning catch or a blocked field goal," he says.
It could also increase the chance of injury, Campbell says. Rubber-like discs pad the bones of the spine and absorb shock as you move -- acting as a shock absorber.
"But if you take that disc and squish down on it, you'll lose some of that absorption. As a result, there's a lot more load being distributed on your back, and a greater chance of injury," Campbell says.
Gary I. Adler, MD, chairman of ACSM's communication and public information committee and an associate professor of medicine at New York University, says the study is "interesting. But whether there are any long-term consequences from the transient diminution of height remains to be seen."