Soccer players who head the ball may be more likely to experience short-term balance problems, suggesting that repetitive head impacts could have the potential to cause subtle neurological deficits not previously known, according to a preliminary study by University of Delaware researchers. More research is needed to understand the long-term effects of these repetitive head impacts and potentially develop interventions to address them.
“Soccer headers are repetitive sub-concussive head impacts that may be associated with problems with thinking and memory skills and structural changes in the white matter of the brain,” said study author Dr John Jeka, a professor and chair of the department of kinesiology and applied physiology in the College of Health Sciences. “But the effect of headers on balance control has not been studied.”
The abstract will be presented 21 July at the American Academy of Neurology’s Sports Concussion Conference in Indianapolis.
The team of researchers led by Jeka studied 20 recreational and club soccer from the UD community, Wilmington and Newark. Participants answered questions about the number of times they headed the ball and how often they played and practiced. The average player was 22 years old and reported heading the ball 451 times in the past year.
Players were asked to walk on a foam pad with their eyes closed. They were tested under two conditions – one with electrodes placed behind their ears to make them feel like they were falling sideways and another without the stimulation. The electrodes make use of tool called galvanic vestibular stimulation that stimulates the nerves in the inner ear and brain that affect balance.
The study found that players exposed to more repetitive head impacts were more affected by the vestibular stimulation while walking, suggesting subtle balance problems. For every 500 headers that a player reported, their food placement and hip adduction responses slightly increased, said Dr Jaclyn B Caccese, one of the authors of the study. “At this point, it appears that frequent soccer heading may result in subtle balance impairments. The question is, how do we get these really subtle effects and how do they manifest to later life complications?”
Because the balance problems are so subtle, there may be no outward indication of the impact from the repetitive head impact, said Dr Fernando V Santos, another study author. “We are looking to understand the relationship between head impacts and concussion,” said Santos, a doctoral student in the biomechanics and movement science interdisciplinary programme. “These athletes, they’ve experienced head impact and they don’t show any signs.”
Santos and Caccese said more research is needed to learn about the effects of repetitive head impact. A next step is to gain a better understanding of how people use sensory information to maintain balance following concussion and even mild head impact that does not result in acute symptoms of concussion.
“The hope is if you can identify concussion and treat it, but also if there are effects from repetitive head impacts, identify individuals who are going to be susceptible to those. Not everyone has effects from repetitive soccer headings,” Caccese said. “We need to identify individuals who do have it, identify why they have it and how to treat it – and if balance deficits persist, then you can design targeted interventions to rehabilitate those balance deficits.”
Objective: The purpose of this study was to investigate the association of soccer heading with subclinical balance deficits during walking.
Background: Exposure to repetitive subconcussive head impacts (RSHI), specifically soccer heading, is associated with white matter microstructural changes and cognitive performance impairments. However, the effect of soccer heading exposure on vestibular processing and balance control during walking has not been studied. Design/Methods: Twenty adult amateur soccer players (10 males and 10 females, 22.3±4.5years, 170.5±9.8cm, 70.0±10.5kg) walked along a foam walkway with the eyes closed under two conditions: with Galvanic vestibular stimulation (GVS – a tool that can be used to probe the vestibular system) (~40 trials) and without GVS (~40 trials). Outcome measures included mediolateral center-of-mass (COM)–center-of-pressure (COP) separation, foot placement, mediolateral ankle modulation, hip adduction, and ankle push off. For each balance mechanism, a GVS response was calculated (GVS – mean (without GVS)). In addition, participants completed a questionnaire, reporting soccer heading exposure over the past year.
Results: A linear regression model was used to determine if vestibular processing and balance during walking were related to RSHI exposure. Both foot placement (R2=0.324, p=0.009) and hip adduction (R2=0.183, p=0.05) were predicted by RSHI; whereby, greater exposure to RSHI was associated with greater foot placement and hip adduction responses. However, COM-COP separation (R²» 0.001, p=0.927), ankle modulation (R2=0.037, p=0.417), and push off (R²» 0.001, p=0.968) were not related to RSHI exposure.
Conclusions: Individuals who were exposed to greater RSHI were more perturbed by vestibular stimulation during walking, suggesting that there may be vestibular dysfunction and balance impairments with frequent heading; specifically, individuals with greater exposure to RSHI responded with larger foot placement and hip adduction responses to GVS.
Fernando V Santos; Jaclyn B Caccese; Mariana Gongora; Ian Sotnek; Elizabeth Kaye; Felipe Yamaguchi; John Jeka