You&#8217;ve heard football coaches say it&#8217;s a game of inches, but there&#8217;s no way they meant this.</p><p>A study found that football players temporarily shrink up to a half an inch during games. The reason: the helmets and pads the players wear coupled with the repeated tackling and blocking, according to research done by Brian Campbell, an assistant professor at the University of Louisiana at Lafayette.</p><p>Campbell, who studied 10 high school players, presented the findings at the annual meeting of the American College of Sports Medicine (ACSM).</p><p>During the course of a day, Campbell said, everyone loses height, although it is only about 2 centimeters. After a night&#8217;s sleep, the height returns.</p><p>&#8220;Where the height (loss) comes from is from water that is found in the intervertebral discs,&#8221; Campbell said in a phone interview. &#8220;These discs that serve as shock absorbers are kind of like water balloons, except in these, water can flow in and out through osmosis. During the course of the day that weight that squishes these water balloons together allows water to exit at a very slow rate.</p><p>&#8220;For the study, we wanted to see if the process was facilitated, if it was sped up, if the magnitude (of playing football) was possibly squishing the spinal cord like an accordion and forcing some of that fluid to be pushed out. We call that creep when water gets pushed out of those discs. We measured their heights and saw that they lost about a half-inch.&#8221;</p><p>Hydration may play a factor, too. Campbell said that as an athlete sweats, the water has to be replenished in the body.</p><p>&#8220;So you have the mechanical forces of the water getting squished out,&#8221; he said, &#8220;and then you have this dynamic of osmosis where water is constantly leaving the body through evaporation, which also may draw some of that water out.&#8221;</p><p>There are some obvious implications to the finding. First, football players are susceptible to back injuries. A significant cause of lower back pain is the pinching of nerves due to the collapsing of vertebral discs in the lumbar spine.</p><p>Campbell said the resulting pain could be prevented if a better way could be found to avoid premature dying of intervertebral disc cells.</p><p>&#8220;The premature dying of disc surface tissue results in the thinning or collapsing of the cells,&#8221; Campbell said. &#8220;The dying of intervertebral disc cells occurs as a result of lack of nourishment. Nourishment of the discs occurs as a result of passive diffusion of nutrient-containing fluids along the upper and lower surfaces of such discs.</p><p>&#8220;The nutritional fluids providing the upper and lower disc surfaces with nutrients and water move by passive diffusion along osmotic and hydrostatic gradients in the passages within the vertebral discs and between the adjacent lumbar vertebrae. Consequently, any continually exerted hydrostatic pressure that prevents such passive diffusion also prevents adequate nourishment and hydration of the disc surfaces.&#8221;</p><p>While back injuries are a potential long-term consequence, there also may be ramifications during a game.</p><p>&#8220;We&#8217;ve seen games, and on the last play of the game, the quarterback throws a touchdown and the defensive back is a quarter-inch from deflecting the pass or the wide receiver is a quarter-inch from making the catch,&#8221; Campbell said. &#8220;So if you lose that half-inch in a game, that might come back to you not making the play or someone making the play.&#8221;</p><p>One question that remains to be answered is how long it takes for the height to return. Campbell plans to do a future study that will answer that, because it could help players during a game.