Adding to this site’s database of combat sports safety studies, a recent study was published in the Journal of Neurotrauma finding middle aged boxers and Muay Thai fighters showed vestibular damage typically only seen in the elderly population.
In the study, titled Altered Vestibular Balance Function in Combat Sports Athletes, the authors measured muscle responses evoked with electrical vestibular stimulation (“EVS”).
The vestibular organs of the inner ear are sensitive to head movement and assist with things like balance control, eye stabilization and other important functions.
Comparing middle aged boxers and muay thai fighters who were otherwise healthy to a control population, the authors found that the fighters responses were compromised compared to the control group and had responses similar to those seen in the elderly population. They found that the worse responses were linked to the self reported amounts of career head trauma the fighters had.
The authors told CTV News that “The athletes we’re bringing in were very healthy, young adults in (their) 30s to 40s…They presented with patterns of this vestibular response that were matched up almost perfectly with 70 to 80-year-old adults, which was quite alarming that that much change can happen.”
This led the authors to suggest that EVS assessments may be a good tool in helping decide if a fighter has received too much career damage from head trauma helping make more informed decisions on when to retire from the sport.
The full abstract reads as follows:
Combat sports pose a risk for accumulative injuries to the nervous system, yet fighters have remained an understudied population. Here our purpose was to determine whether repetitive blows to the head have an effect on vestibular balance reflexes in combat sports athletes. We compared lower-limb muscle responses evoked with electrical vestibular stimuluation (EVS) between fighters (boxing/muay thai) and non-fighter controls. Each participant received stochastic vestibular stimulation (0-25 Hz, 3 mA) over their mastoid processes while they stood relaxed with their head to the left or right. Surface electromyography was recorded from the medial gastrocnemius and soleus muscles bilaterally. Short and medium latency response (SLR/MLR) peaks were significantly delayed in the fighter group compared to the controls. SLR and MLR peak amplitudes were also significantly lower in the fighters. Fighter-estimated cumulative repetitive head impact (RHI) events demonstrated strong positive correlations with the timing of SLR and MLR peaks. Cumulative RHI events also negatively correlated with peak MLR amplitude and response gain at frequencies above 5 Hz. Our results provide evidence of a progressive vestibular impairment in combat sports athletes, likely resulting from blows to the head accumulated in sparring practice and competitive bouts throughout their careers. Taken together, EVS-based vestibular assessments may provide a valuable clinical diagnostic tool and help better inform ‘return-to-play’ and career length decisions for not only combat sports athletes, but potentially other populations at risk of repetative head impacts.