American Football Position-Specific Neurometabolic Changes in High School Athletes: A Magnetic Resonance Spectroscopic Study.

Reports estimate between 1.6-3.8 million sports-related concussions occur annually, with 30% occurring in youth male American football athletes. Many studies report neurophysiological changes in these athletes, but the exact reasons for these changes remain elusive. Investigation of injury mechanics highlights a need to address how player position might impact these changes. Here, 55 high school American football athletes (20 linemen; 35 non-linemen) underwent magnetic resonance spectroscopy four times over the course of a football season-once prior to the season (Pre), twice during (In1, In2), and once following (Post) to quantify metabolites (N-acetyl aspartate, choline, creatine, myo-inositol, and glutamate/glutamine) in the dorsolateral prefrontal cortex (DLPFC) and primary motor cortex (M1). Head acceleration events (HAEs) were monitored at each practice and game. Spectroscopic and HAE data were analyzed by imaging session and player position. Linear regression analyses were conducted between metabolite levels and HAEs, and metabolite levels in football athletes were compared with age-and gender-matched non-contact athletes. Across-season (i.e., between Pre and In1, In2, Post), different DLPFC and M1 metabolites decreased (p < 0.05) according to player position (i.e., linemen vs. non-linemen). The majority of regression results involved DLPFC metabolites in linemen, where metabolite levels were higher from Pre to Post, with increasing HAE load. Comparisons with control athletes revealed higher metabolite levels in football athletes both before and after the season. This study highlights the importance of player position when conducting analyses on American football athletes and demonstrates elevated DLPFC and M1 brain metabolites in football athletes compared with control athletes at both Pre and Post, suggesting potential HAE-related neurocompensatory mechanisms.

Head acceleration event metrics in youth contact sports more dependent on sport than level of play.

The goal of the study was to evaluate how repetitive head traumas sustained by athletes in contact sports depend on sport and level of play. A total of 16 middle school football players, 107 high school football players, and 65 high school female soccer players participated. Players were separated into levels of play: middle school (MS), freshman (FR), junior varsity (JV), junior varsity-varsity (JV-V), and varsity (V). xPatch sensors were used to measure peak translational and angular accelerations (PTA and PAA, respectively) for each head acceleration event (HAE) during practice and game sessions. Data were analyzed using a custom MATLAB program to compare metrics that have been correlated with functional neurological changes: session metrics (median HAEs per contact session), season metrics (total HAEs, cumulative PTA/PAA), and regressions (cumulative PTA/PAA versus total HAEs, total HAEs versus median HAEs per contact session). Football players had greater session (p<.001) and season (p<.001) metrics than soccer players, but soccer players had a significantly greater player average PAA per HAE than football players (p<.001). Middle school football players had similar session and season metrics to high school level athletes. In conclusion, sport has a greater influence on HAE characteristics than level of play.

Accumulation of high magnitude acceleration events predicts cerebrovascular reactivity changes in female high school soccer athletes.

Mitigating the effects of repetitive exposure to head trauma has become a major concern for the general population, given the growing body of evidence that even asymptomatic exposure to head accelerations is linked with increased risk for negative life outcomes and that risk increases as exposure is prolonged over many years. Among women's sports, soccer currently exhibits the highest growth in participation and reports the largest number of mild traumatic brain injuries annually, making female soccer athletes a relevant population in assessing the effects of repetitive exposure to head trauma. Cerebrovascular biomarkers may be useful in assessing the effects of repetitive head trauma, as these are thought to contribute directly to neurocognitive symptoms associated with mild traumatic brain injury. Here we use fMRI paired with a hypercapnic breath hold task along with monitoring of head acceleration events, to assess the relationship between cerebrovascular brain changes and exposure to repetitive head trauma over a season of play in female high school soccer athletes. We identified longitudinal changes in cerebrovascular reactivity that were significantly associated with prolonged accumulation to high magnitude (> 75th percentile) head acceleration events. Findings argue for active monitoring of athletes during periods of exposure to head acceleration events, illustrate the importance of collecting baseline (i.e., pre-exposure) measurements, and suggest modeling as a means of guiding policy to mitigate the effects of repetitive head trauma.