An innovative study by James Cook University researchers has found a link between rugby league injuries to young players in the tropics and the colour of their jersey.
Dr Kenji Doma is a lecturer at JCU’s College of Healthcare Sciences. He said it’s known that dark-coloured clothing increases heat absorption and was a risk factor for heat illness.
“But no study had investigated the relationship between the environment, the colour of the jersey, and the incidence of injury in rugby league, particularly for junior players,” he said.
The scientists looked at injuries in 64 junior rugby league players playing in Cairns over one season. 24 of the players wore striped jerseys, while the remaining 40 players wore either black jerseys or orange jerseys.
The researchers also measured environmental factors such as the hardness of the ground and the air temperature. Dr Doma said injuries had doubled in senior professional rugby league players when the playing season changed from winter to summer.
“We didn’t see any correlations between ground conditions and injury rates. So, it seems that seasonal variations observed in the incidence of injuries may not be influenced by ground conditions, but rather by the heat experienced during the game,” said Dr Doma.
He said the colour of the jerseys worn by players seemed to be a factor, with those in black jerseys being injured more.
“The team in black may have experienced greater thermal stress than their opponents. It has also been found that when athletes’ core temperature is high, they will modify their pacing strategies and reduce playing intensity, which puts them more at risk of injury,” said Dr Doma.
He said a lot more experiments would have to be done before the results were considered conclusive, with a need for standardised playing times and age groups and a greater sample size.
“But we can probably say now that a greater emphasis should be placed on environmental temperature and humidity than ground conditions, and players with a darker coloured jersey may be at a higher risk of injury than those wearing a lighter coloured jersey,” said Dr Doma.
Dr Doma said the research may have implications for other similar codes, featuring some famously dark uniforms.
“You could see it as bad news for the All Blacks,” he said.