The findings emerged from a University of Stirling study that assessed boxers before and after a nine-minute sparring session where athletes trade punches without the aim of incapacitating each other.
This study, alongside the team’s 2016 research into the impact of heading footballs, is one of the first to show that routine impact in sport – thought to be innocuous – results in measurable changes in the brain.
Experts believe the findings raise further questions around the safety of other sports, where similar routine impacts occur, and say further research is required.
Dr Thomas Di Virgilio led the latest study alongside colleagues in the university’s brains multi-disciplinary research team.
He said: “There are still questions surrounding the relationship between repetitive routine head impacts – such as heading in football or sparring in boxing – and brain health. The truth is we do not currently know how much impact is safe.
“For many years, a debate has taken place around the safety of boxing. However, these discussions often focus on heavy blows inflicted during competitive fights. In contrast, we looked at subconcussive impacts – those below the concussion threshold – inflicted during training sessions.
“Our findings are important because they show routine practices may have immediate effects on the brain. Furthermore, athletes may be at greater risk of injury if the communications between the brain and muscles are impaired.” The team assessed the motor control and cognitive function of 20 boxers and Muay Thai athletes before and after a nine-minute sparring session, which consists of three rounds of three minutes.
Measurements were taken immediately after the session, and then one hour and 24 hours later. Motor control was measured using transcranial magnetic stimulation, which uses magnetic fields to stimulate the nerve cells in the brains of participants to understand how it communicates with the muscles.
The participants also completed a series of tests providing objective measures of cognitive function. The team found one hour after sparring, the participants showed impaired brain-to-muscle communications and decreased memory performance, relative to controls.