Longitudinal changes in network-based functional connectivity over a rugby season in adolescent males

Objectives This study examined the impact of a single season of rugby union – and subsequent exposure to head acceleration events (HAEs) – on functional connectivity in adolescent males compared to non-collision sport athletes.

Resting-state functional MRI scans were acquired from 72 rugby players and 20 non-collision sport athletes. The rugby cohort were scanned longitudinally throughout the season. Voxel-wise maps of functional connectivity (FC) for 15 resting-state brain networks were generated for 178 datasets. Cross-sectional comparisons were performed between the rugby cohort at different stages of the season and the non-collision sport group. Longitudinal analyses were performed within the rugby cohort. An exposure analysis estimated HAE exposure based on the number of matches played.

No significant cross-sectional differences in FC were found between rugby and non-collision sport athletes or between rugby players with high versus low exposure to HAEs. Longitudinally, rugby players showed increased inter-network FC over the season, with strengthening of connectivity in the temporal, motor, secondary visual, and anterior intraparietal sulcus networks, and mid-season decreases in the cerebellar-visual network. No association was found between longitudinal FC changes and changes in self-reported symptoms.

These findings suggest that participation in a season of rugby is associated with neuroplastic changes. These changes may reflect compensatory adaptations to preserve neurological function during periods of HAE exposure. Alternatively, they may also represent developmental changes or responses to physical activity and/or motor learning. This highlights the complexity of interpreting changes in FC in adolescent athletes participating in collision sports and the need for further research. Competing Interest Statement The authors have declared no competing interest. Funding Statement The authors would like to acknowledge funding support provided by: the Ministry of Business, Innovation & Employment (MBIE) Catalyst Strategic Fund NZ-Singapore Data Science Research Programme (UOAX2001); the Hugh Green Foundation; the Neurological Foundation of New Zealand First Fellowship (2243 FFE); the New Zealand Health Research Council Explorer Grant (22-625-A); the Te Titoki Mataora Research Acceleration Programme Fund; and an anonymous donor. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This work was conducted under ethical approval from the New Zealand Health and Disability Ethics Committee (Ethics Ref: 20/NTB/14/AM09) in accordance with the Declaration of Helsinki. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability Data availability is limited due to data sovereignty considerations. Requests for access will be considered on a case by case basis.