Does Neck Strength Predict Repetitive Head Impacts In Youth Football Athletes?

PURPOSE: Neck strength and pubertal development may contribute to the number and magnitude of repetitive head impacts (RHIs) in youth football athletes. Greater neck strength is associated with decreased head movement (i.e., peak linear acceleration [PLA] and rotational velocity [PRV]) during laboratory testing, but not throughout a season in teenage hockey players. The pubertal development scale (PDS) accurately assesses physical maturation and may provide a more global representation of strength not captured by isolated neck strength. Determining the relationship between RHIs, PDS, and neck strength will provide insight into physical factors associated with RHI exposure during youth football. The purpose of this study was to determine whether neck strength and pubertal development predicted RHI number and magnitude across a youth football season in 6th grade youth football athletes. METHODS: Athletes were provided a custom-fit instrumented mouthguard (iMG); athletes with braces received a “boil and bite” iMG. iMGs contained a tri-axial accelerometer and gyroscope collecting data at 3.2 kHz. Games were recorded to video verify RHIs. RHI counts were defined as the number of true positive RHIs divided by the number of games (i.e., athlete exposures [AE]). Parents completed the PDS prior to the season and isometric neck strength was collected using a hand-held dynamometer for flexion, extension, bilateral lateral flexion, and bilateral rotation; the average of 3 trials was used for data analysis. Stepwise linear regressions were performed to determine if neck strength or total PDS score predicted RHIs/AE, median PLA, or median PRV. RESULTS: 23 athletes (Age:11-12 y.o., all male) participated in 1 to 7 games with exposure data (median = 4.5 games). There were no statistically significant predictors of head impacts per exposure, median PLA or median PRV for any strength models or PDS models (p>.05 for all models, Adjusted R2 range .001 to .083). Only the PDS had a p value < .2 at p = .196. CONCLUSIONS: Isometric neck strength and PDS are not associated with RHI number or magnitude during youth tackle football, suggesting isometric neck strengthening may not be a potential modifiable risk factor. Other physical attributes contributing to the number and magnitude of RHIs should be explored in youth football athletes. R01HD110401