The scene is all too familiar: the play seems perfectly executed until the only player left on the field is not moving. Though this is an extreme scenario of a concussion, it occurs often in the world of sports and is seen most notably in football and rugby.

The official definition of a concussion is trauma-induced alteration in mental status that may or may not involve loss of consciousness. Symptoms can include dizziness, sensitivity to light, vomiting and trouble sleeping.

To contrast the severity of the two concussions, think about the hit that Penn State quarterback Michael Robinson received from Wisconsin's Erasmus James in an September game that knocked him off his feet and out of play for three weeks, and the concussion that quarterback Zack Mills suffered during the Oct. 23 game against Iowa.

Concussions are measured according to three different scales that use loss of consciousness to grade them, even though only about 10 percent of concussions actually result in total loss of consciousness. There are no effective treatments for concussions except for time and rest, and those at best are only suggestions.

While preventive measures exist, such as improving football helmets and pads, and making sure all symptoms are gone before returning to play, there is still an increase of concussion occurrence.

"The probability of concussions growing higher is due to coaching error and student-athletes hiding even the mildest of concussions," said Seymon Slobounov, an associate professor of kinesiology at Penn State.

Even mild trauma should be taken seriously and can cause short- and long-term effects and problems with coordination, he said. After the first concussion, overcoming it can take three to four days to recover fully and an athlete is then at a higher risk for further injury.

"Some of the long-term effects that come from multiple concussions over time lead to loss of executive function," said Doug Aukerman, a team physician for several sports at Penn State, including football and men's basketball. "The loss of short- and long-term memory is still under research."

What could possess an athlete to hide an injury, especially one as serious as a concussion? In a word, fear. Once athletes are diagnosed with an injury, they can go through extreme withdrawal when they cut off from the team while they heal.

"A need for social interaction, a decrease in self-esteem, and the pressure to return to play and a sense of fear adds to stress and a hasty recovery," said Rashanna Moss, a graduate student of Slobonunov's whose thesis "Identifying Athletes at Risk for Re-injury" centers on tying neurological and psychological behavior together to determine athletes at risk for re-injury.

Whether it is six months spent recovering from knee surgery or two weeks with a mild concussion, athletes yearn for social interaction with their team, which often grows to be a type of family. An uncertainty of ability develops and a fear of potentially losing their starting spot adds more stress to those athletes, according to Moss.

"A simple injury such as a sprained ankle that the athlete is trying to hide causes them to use avoidance techniques," Moss said. "If their ankle is bothering them, they could change the way that they run in order to eliminate the pain."

The same thing goes for a concussion. The athlete might change the way that he or she tackles or executes a certain play in order to prevent another concussion from happening, but changing that technique could put an athlete at risk for other injuries.

"It's hard to tell if an athlete is bracing themselves or avoiding an action," Moss said. "But it is usually in response to pain, a decrease in the degrees of freedom, and fear can cause bracing."

Concussions are among the easiest injuries to hide because they are so hard to diagnose.

Players might disguise them because they want to play and coaches also might ignore them because they want their best players on the field.

"Most coaches [whether professional or amateur] are lacking education on what a concussion truly means," Moss said.

Football and rugby players aren't the only ones who can sustain concussions.

Boxers are probably at the highest risk for getting a head injury and severe repercussions of repetitive head trauma can cause an early onset of Parkinson's disease. One of the most famous men speculated to have suffered serious concussions is Muhammad Ali, who now suffers from Parkinson's.

"Extensive tremors in the basal ganglia may lead to Parkinson's," Aukerman said. "Though it is not always the case, it certainly can be in boxers."

Concussion occurrences are slowly on the rise due to a more accurate diagnosis and better understanding of them.

"Improving education and the idea that the symptoms that an athlete can sometimes experience from head trauma are part of the game is making the numbers rise," Moss said.

The equipment that is worn and the advances in athletic performances that have been made over the years can also add to the influx.

Athletes continue to become stronger, faster, and equipment and technology are struggling to keep them healthy.

"Helmets are always trying to make developments and athletes are becoming more and more dependent on the equipment," Moss said.

While rising numbers aren't always good, in this case they are. The elevated numbers are bringing about a newfound awareness and more techniques on how to make the numbers decrease again.

Even though chicks dig scars and glory lasts forever, the consequences of even the mildest of brain injuries needs to be understood so athletes don't wind up being the last man down.