New Zealand rugby health study: motor cortex excitability in retired elite and community level rugby players.

AIMS: Rugby union is a high contact sport in which players frequently experience brain injuries. Acute brain injury is associated with altered corticomotor function. However, it is uncertain if long-term exposure to rugby is associated with any alterations in corticomotor function. The aim of the study was to assess measures of corticomotor excitability and inhibition in retired rugby players in comparison to retired non-contact sport players.

METHODS: The design was a cross-sectional study with three groups of retired athletes: elite rugby (n=23), community level rugby (n=28) and non-contact sport control (n=22). Assessments of corticomotor excitability were made using transcranial magnetic stimulation.

RESULTS: Resting motor threshold was significantly higher and long-interval intracortical inhibition was greater in the elite rugby group compared to the control group. Participants in the two rugby groups had sustained significantly more concussions than the control group.

CONCLUSIONS: We provide some evidence of altered corticomotor excitation and inhibition in retired elite rugby players in comparison to retired non-contact sport players. Given the absence of findings in the community rugby group, who had experienced a similar number of concussions, the association with previous brain injury is unclear.