In recent years, sports-related mild traumatic brain injury (also called concussion) has received significant attention from media outlets, athletes, and researchers. Evidence indicates that repeated concussions sustained during sports activities can cause long-term neurological, cognitive, and physical impairments among athletes. However, very few studies have focused on the effects of subconcussive head impacts, or hits to the head that do not meet diagnostic criteria for concussion. Researchers suspect that these subconcussive events can still damage the athlete’s brain, particularly when the athlete experiences multiple head impacts over time.
A research team in Japan studied the effects of subconcussive head impacts among amateur boxers. During routine boxing practice (or sparring), a boxer may receive light blows to the head. Although blows sustained during light sparring are not thought to cause head injuries, the researchers wanted to know if boxers actually sustain brain damage from these relatively soft impacts. They used a series of magnetic imaging techniques and nerve stimulation procedures to measure physical and cognitive performance among 20 amateur boxers after sparring for nine minutes. To determine the time trajectory of potential brain damage, the researchers took measurements at 1 hour and 24 hours after the sparring match. They found that:
- The boxers showed decreased motor control an hour after sparring. Their motor function slowly returned to baseline levels over the next 24 hours.
- Boxers made 52 percent more errors on a cognitive task following sparring, compared to 28 percent more errors among a control group who exercised without head impact.
- Participants had decreased memory function after sparring.
These findings indicate that even relatively gentle, non-concussive head impacts can impair cognitive and motor function. Clinicians and athletes alike should remain alert to the possibility of head trauma, even when head impacts do not cause observable concussion symptoms.
Di Virgilio TG, Ietswaart M, Wilson L, et al. Understanding the consequences of repetitive head impacts in sport: Brain changes and dampened motor control are seen after boxing practice. Frontiers in Human Neuroscience. (September 2019).