There could be a direct correlation between neck strength and susceptibility to concussions in rugby, according to a Dunedin study that measured impacts in the 2016 national provincial competition.

Rugby players with weaker necks or uneven strength in that area appeared more vulnerable to severe impacts that may cause concussion, the study found.

Preliminary findings from the South Island Brain Injury Research Group (SIBIRG) research, led by the University of Otago's Dr Hamish Osborne and research fellow Dr Danielle Salmon, of the School of Physical Education and Exercise Sciences, have been released.

The study examined head-acceleration forces and its relations to neck strength in order to inform concussion prevention research.

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The research was undertaken during five home games by the Otago national championship squad, with players wearing bluetooth sensors about the size of a $2 coin behind their right ears to record the acceleration forces sustained during impacts.

Dr Salmon said the number of impacts to the head sustained by Otago players last year may have been related to a large difference in strength between the left and right sides of the neck.

"Those players who had larger differences sustained more impacts and impacts of greater severity," he said.

The impact data also revealed props sustained the most frequent and strongest head acceleration forces as a result of impacts during the games. Wingers had the fewest hits but those they did receive were often powerful.

The latest analysis, which is on-going, involves matching head-impact data with videos of the games.

"Over these five games we observed an average head-acceleration linear force of 29g (g is the force of gravity on the Earth's surface), with a minimum of 10g and a maximum of 184 g," Dr Salmon said. "That is slightly higher than previously reported impact forces on club players, with an average of 22.2 g, a minimum of 10g and maximum of 165g.

"While these impacts seem large, similar forces, of up to 200g can be obtained by just tapping the sensor on the table.

"However, one of the key things is to understand the length of time the impact was for, with respect to the acceleration forces experienced, as this will influence the effects on the brain."

Based on the data collected, the Otago players, on average, sustained 48 impacts per game, well down on the 95 reported for club players, Dr Salmon added.

"When we break down the game to specific events, we observed that the average head-acceleration force for a carry was 45g. For a tackle it was 42g and for a ruck 31g."

Not every impact could be correlated with a specific event.

"That would help explain why the number of impacts we observed is substantially higher than the number of contact events for a player during the game.

"Video shows many of these impacts are sustained when players make contact with others while running or kicking the ball, which would be interpreted as relatively harmless."

The aim of the study, the first of its kind at a professional (or semi-pro) level in New Zealand, was to improve knowledge of concussion in sport.

"What we are hoping to do next is to look at the large impacts that were sustained in the games and using the video footage we would like to describe what is happening in these events," Dr Salmon said.

"Were these sustained during the tackle? Is the acceleration profile of the head a result of the head making contact with another player's knee, shoulder or hip? These are questions we don't fully have the answer for but hope to soon."