Repetitive head acceleration events experienced during athletic training and competition can potentially affect an athlete’s cognitive abilities. There are limited empirically supported treatments to counter the possible cognitive decline from repetitive head acceleration events in contact sports like American football. Transcranial photobiomodulation (tPBM), also known as low-level light or laser therapy, is an emerging possible preventative measure against repetitive head injuries. Our study aimed to evaluate the effectiveness of tPBM on cognitive and motor abilities throughout a football season among Division I NCAA athletes. We hypothesized that while both the tPBM and sham groups would start with similar cognitive scores, by season's end, the tPBM group would maintain better cognitive function, whereas the sham group would show a decline.

40 healthy, non-injured, NCAA Division I male American football student-athletes were recruited for participation, with 35 completing the 18-week intervention over the course of the football season (18 players randomized to tPBM [M_age: 21.6 +/- 1.5 years] and 17 players randomized to sham control [M_Age: 21.9 +/- 2.0 years]). Athletes from both groups utilized the Vielight NeuroGamma system and wore either the tPBM device (810 nM light pulsing at 40-Hz) or a visually identical SHAM headset for 20 minutes, three times weekly. We assessed cognitive functions using the C3 Logix System (which includes Trails A & B, Digit Symbol, and simple and decision reaction time tests) and the Conners Continuous Performance Task, Third Edition (CPT-3). Grip strength was assessed using a hand dynamometer. Assessments took place both prior to the football season and after the final game.

There were no significant differences between groups for treatment adherence (PBM [M_treatment 38.8 +/- 7.6] & SHAM [M_treatment: 34.9 +/- 12.2]). We used latent difference score analysis to test for group differences in change scores between assessments. There were no significant between-group effects for cognitive or grip strength measures (all p > .05). Due to the pilot/proof of concept nature of the study and small sample size, we also compared the pattern of results between groups. For more intricate visual search and switching tasks (Trails B, CPT-3 correct response speed, and CPT-3 response speed accuracy), outcomes favored tPBM over sham. In contrast, simple response time (simple RT), basic psychomotor speed (Trails A), and inhibition tasks on the CPT-3 yielded results that favored sham over tPBM.

Overall, the current study presents variable findings for cognitive and motor function. Although there were no statistically significant differences between the groups, there was a noticeable improvement in grip strength and visual search and switching measures of processing speed in tPBM participants compared to sham; however, simple response time and measures of inhibition favored the sham group. The current study's findings show some promise but highlight the variability in outcomes and the need for better-powered studies. Notably, results are in a healthy, non-injured group of athletes, so future research in those with pathology is also needed.