PURPOSE: To examine the acute effects of soccer heading on brain chemistry and function using advanced neuroimaging techniques.

METHODS: Fourteen male soccer players (age: 26 ± 5 years [Mean ± SD]) completed two trials at Neuroscience Research Australia. On one occasion, they performed a ‘Heading’ task (Head) involving 20 headers in 20 mins (launched at 35 km·h-1 over 12 m) and on the other, an equivalent ‘Kicking’ task (Control). The trials were separated by ≥7 days and the order randomized. Neuroimaging scans were obtained 45mins post-task. Magnetic resonance spectroscopy was used to measure brain chemistry (glutamate/glutamine [Glx], N-acetylaspartate, creatine, choline, and inositol; i.u.) in the dorsolateral prefrontal (dlPFC) and motor cortices (M1). Brain function was assessed using: 1) arterial spin labelling measuring cerebral blood flow (CBF; mL/min/100 g), 2) electroencephalography (acquired 2 hrs post-task) measuring alpha (α), beta, delta, and infra-slow frequency power (μV2), and 3) cognitive function using the spatial working memory (SWM) task for errors and strategy, and paired associates learning task for errors at pre-, 0 hrs post-, 2 hrs post-, and 24 hrs post-task. Results presented as Mean ± SD.

RESULTS:Brain Chemistry: The Glx signal was higher on the Head trial in the M1 (Head: 2.03 ± 0.21; Control: 1.90 ± 0.20, p = 0.03), but not the dlPFC (Head: 2.34 ± 0.28; Control: 2.33 ± 0.33, p = 0.87). There were no differences in any other metabolite between trials for either brain region (all p’s > 0.05). Brain Function: There were no changes in global CBF (Head: 18.8 ± 3.8; Control: 18.9 ± 2.9, p = 0.83), or individual voxels when using cluster analyses (all p’s > 0.05). There were no changes in global α frequency power (Head: -5.63 ± 0.74; Control: -5.39 ± 0.97, p = 0.15), nor in other frequencies (all p’s > 0.05). No Intervention x Time interaction was observed on SWM errors (Head: pre: 1.46 ± 4.12, 0 hrs post: 1.57 ± 4.78, 2 hrs post: 0.50 ± 1.40, 24 hrs post: 0.86 ± 2.21; Control: pre: 1.21 ± 2.99, 0 hrs post: 0.93 ± 1.69, 2 hrs post: 0.29 ± 0.61, 24 hrs post: 0.08 ± 0.28, p = 0.65), or any other cognitive function outcome.

CONCLUSION: Our results suggest that this soccer heading task led to an acute brain chemical but not functional change, from the techniques utilized in this study. Funder: Lambert Initiative for Cannabinoid Therapeutics