February 2017

Subconcussive subtleties: Lacrosse study links balance, impacts

In the moment: Sports medicine

By Katie Bell

Measures of cumulative subconcussive head impacts during a men’s lacrosse season are associated with decreases in balance scores from pre- to postseason, according to findings from Sacred Heart University in Fairfield, CT, that could have implications for lower extremity injury risk.

The findings suggest that, even in the absence of a concussion, repetitive subconcussive impacts can negatively affect an athlete’s balance, which in turn can increase the risk of lower extremity injury, said Theresa L. Miyashita, PhD, ATC, assistant professor in the Athletic Training Education Program at Sacred Heart University and first author of the study.

“Balance deficits are linked to a predisposition for lower extremity injuries,” Miyashita said.

For example, a 2006 study of high school basketball players found that poorer preseason performance on the Star Excursion Balance Test was associated with a higher risk of lower extremity injury during the season.

The Sacred Heart study, which was epublished by Sports Health in January, included 34 collegiate men’s lacrosse players (average age 19 years) who wore instrumented helmets that collected head impact exposure data. The researchers evaluated linear acceleration along with two injury tolerance scores, head injury criteria and Gadd Severity Index.

The participants also completed a Balance Error Scoring System (BESS) test once during the preseason and once during the postseason.

The number of errors on the BESS test increased from pre­season to postseason for double-
leg stance on foam, tandem stance on foam, total number of errors on a firm surface, and total number of errors on foam. The total errors on the foam were significantly correlated with linear acceleration, head injury criteria, and Gadd Severity Index scores.

Miyashita said the research­ers believe the association found between the subconcussive mea­sures and BESS scores on the foam surface suggests the cumulative subconcussive impacts contributed to the decrease in BESS performance from pre- to postseason.

Correlations between subconcussive impacts and change in BESS score were significant for the foam-based BESS trials, but not the trials done on a firm surface; this suggests assessments that highly stress the vestibular system may be needed to detect microtrauma to that system caused by repetitive subconcussive impacts, Miyashita said.

The findings also suggest the BESS test, which is often included in concussion management protocols, could also be used to help screen for high levels of subconcussive impacts.

Douglas Martini, PhD, postdoctoral researcher at the Sensorimotor Neuroimaging Laboratory at Oregon Health & Science University in Portland, noted that, compared with sideline concussion evaluation tests, “the BESS is easier and cheaper to implement, which is important for schools with limited discretionary funds.”

A growing body of research suggests athletes who suffer concussions are more likely than other athletes to sustain a lower extremity injury (see “Concussion repercussions: Studies explore lower extremity effects,” June 2016, page 13), but it remains to be seen whether similar injury risks are associated with subconcussive impacts.

“I’m hesitant to say that cumulative subconcussive impacts would increase the likelihood of sustaining a musculoskeletal injury,” Martini said. “However, I don’t think it’s unrealistic to expect the combination of subconcussive impacts and a concussion history (particularly three or more previous concussions) to have a meaningful impact on the odds of sustaining a musculo­skeletal injury.”

Also yet to be determined is whether head impacts are a cause or an effect of balance
impairment, Martini noted.

“The ‘chicken or the egg’ dilemma has yet to be answered for concussions,” he said. “That is, do some athletes have poorer balance which leads to a concussion, resulting in a worsening baseline of balance? Or does the poor balance result from sustaining a concussion, or more likely multiple concussions? For these types of questions to be properly addressed, a longitudinal study would need to be completed, starting with kids, prior to collision sport participation.”

Sources:

Miyashita TL, Diakogeorgiou E, Marrie K. Correlation of head impacts to change in balance error scoring system scores in Division I Men’s lacrosse players. Sports Health 2017 Jan 1. [Epub ahead of print]

Plisky PJ, Rauh MJ, Kaminski TW, Underwood FB. Star Excursion Balance Test as a predictor of lower extremity injury in high school basketball players. J Orthop Sports Phys Ther 2006;36(12):911-919.

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