Thursday, July 31, 2008

Cutting Edge Research: No Adverse Effects of Heading

Given the growing popularity of soccer in the US and other countries, there is the need to continually look at safety issues surrounding the sport. Over the past years, some have raised the issue that heading the ball can lead to neurological problems. Most agree that striking the ball (or other objects) with enough force to cause concussion can lead to brain injury. However, the adverse effects of routine heading are debatable. Two recently published studies examined the effects of purposeful heading, headers performed as part of a regular match, on neuropsychological function in female players. The results showed that purposeful heading was not associated with any of the measures of cognitive function, postural balance or neuropsychological test performance.

Both studies were authored by Dr. Thomas Kaminski at the University to Delaware. The first article appears in the July 2007 issue of the Journal of Clinical and Experimental Neuropsychology and the second appears in the June 2008 issue of the journal, Perceptual and Motor Skills. Dr. Kaminski and colleagues reasoned that if heading the ball caused neurological damage then the number of headers performed during a competitive season would correlate with changes in cognitive learning, postural balance and/or neuropsychological test performance.

The female participants in the two studies ranged from high school freshmen to college aged players and included a wide range of skill levels. A group of college-aged non-soccer players served as the control group.

Before and after the competitive season, the players were administered two batteries of tests. In one study, cognitive function and postural balance tests were administered. In the second study, various tests of neuropsychological function were given. These included tests of reaction time, math processing and memory. Over the course of the season, the number of times each player headed the ball during sanctioned matches were tallied. The competitive seasons ranged in length from 12 to 14 weeks.

The researchers found that on average, high school level players performed less than one header per game whereas the college players executed 2.7 per game. Most importantly, changes in test performance across the course of the season were not different between the high school players, the college players and the control group. In fact, the college players tended to out perform their high school and non-playing counterparts in many of the tests. Further, there were no correlations between the average number of headers performed during matches and changes in neurological test performance. That is, players who executed more headers during matches did not show any adverse effects compared to players who headed less and non-playing control subjects.

These results lead the authors to conclude that purposeful heading, headers performed during matches, is not linked to any neuropsychological changes in female players.

The two studies do have some limitations. A major limitation is that the investigators recorded only headers performed during games. Training sessions were not examined as the focus of the study was on purposeful heading. It is likely that players perform far more headers during training than during individual matches. Also, only a single season was examined. The authors point out that longer term studies would reveal any long-term deficits develop in association with headers. For now though, there wee no effects seem over the course of a season.

Despite these limitations, both studies add to a large body of research indicating that heading the ball does not cause any adverse neurological or psychological problems. The risk of long-term injury from performing headers appears to be very minimal.

References:

Kaminski TW, Cousino ES, Glutting JJ (2008) Examining the relationship between purposeful heading in soccer and computerized neuropsychological test performance. Research Quarterly for Exercise and Sport, 79:235-244.

Kaminski TW, Wilkstrom AM, Gutierrez, Glutting JJ (2007) Purposeful heading during a season does not influence cognitive function or balance in female soccer players. Journal of Clinical and Experiemental Neuropsychology, 29:742-752.