Relation between Isometric Neck Strength and White Matter Organization in Collegiate Athletes

Abstract

Soccer athletes frequently experience repetitive head impacts (RHI) during games and practices, which may affect neural integrity over time and lead to altered brain structure. Neck strength is hypothesized to limit the transfer of force to the brain and decrease the effect of RHI on brain structure. The goal of our work was to examine whether greater neck strength is associated with more intact white matter organization (WMO) in collegiate athletes exposed to RHI. Collegiate soccer (n = 17) and limited/non-contact sport (n = 39) athletes were assessed prior to their athletic seasons. Participants completed neck strength assessments using handheld dynamometry in six test positions and diffusion tensor imaging. Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were calculated for 20 white matter (WM) regions. A multi-variate approach was used to examine the relationship between neck strength and diffusion measures in soccer and limited/non-contact athletes. Neck strength was positively associated with FA and negatively associated with RD across several WM regions in soccer players only. Neck strength was not significantly associated with MD or AD in either group. Greater neck strength was related to more intact WMO in athletes with high exposure to RHI, particularly in regions prone to damage from brain trauma such as the basal ganglia, superior longitudinal fasciculus, and frontoparietal WM. Future studies should examine neck strength as a factor to moderate neural outcomes in athletes with exposure to RHI.

Diffusion Imaging of Sport-related Repetitive Head Impacts—A Systematic Review

“…Of the 17 studies included, 11 had a longitudinal study design (Bahrami et al, 2016;Bazarian et al, 2014;Brett et al, 2021;Champagne et al, 2019;Holcomb et al, 2021;Koerte et al, 2012b;Kuzminski et al, 2018;Mayinger et al, 2018;Saghafi et al, 2018;Slobounov et al, 2017;Strauss et al, 2021), and six had a cross sectional study design (Churchill et al, 2017;de Souza et al, 2020;Kawata et al, 2020;Koerte et al, 2012a;Lefebvre et al, 2021;Lipton et al, 2013). Most studies related their testing time points to the start and end of a competitive sport season.…”

“…Mean age of participants in the 17 studies ranged between 11.0 and 30.9 years (Holcomb et al, 2021;Lipton et al, 2013). Two studies included individuals younger than 13 years (Bahrami et al, 2016;Holcomb et al, 2021), three studies included individuals between 13 and 17 years (Kawata et al, 2020;Kuzminski et al, 2018;Saghafi et al, 2018), 10 included individuals between 17 and 24 years (Bazarian et al, 2014;Brett et al, 2021;Champagne et al, 2019;Churchill et al, 2017;de Souza et al, 2020;Koerte et al, 2012a, b;Lefebvre et al, 2021;Mayinger et al, 2018;Slobounov et al, 2017), and two studies included individuals Table 3 Summary of risk of bias assessment using QUADAS-2 based rating of methodological study quality…”

“…Of note, because American football is most commonly played by male athletes, these studies investigated male individuals only (Bahrami et al, 2016;Bazarian et al, 2014;Brett et al, 2021;Champagne et al, 2019;Churchill et al, 2017;Holcomb et al, 2021;Kawata et al, 2020;Kuzminski et al, 2018;Mayinger et al, 2018;Saghafi et al, 2018;Slobounov et al, 2017). Only five studies included mixed samples with females and males (Churchill et al, 2017;de Souza et al, 2020;Lefebvre et al, 2021;Lipton et al, 2013;Strauss et al, 2021). The remaining 12 studies included males only (Bahrami et al, 2016;Bazarian et al, 2014;Champagne et al, 2019;Holcomb et al, 2021;Kawata et al, 2020;Koerte et al, 2012a, b;Kuzminski et al, 2018;Mayinger et al, 2018;Slobounov et al, 2017) or did not specify sex or gender (Brett et al, 2021;Saghafi et al, 2018).…”

“…Regarding potential sex or gender differences, one study specifically investigated sex or gender differences (de Souza et al, 2020), two studies controlled their statistical analyses for sex or gender (Lipton et al, 2013;Strauss et al, 2021), and three studies discussed sex or gender in their limitation section (Bahrami et al, 2016;Kawata et al, 2020;Koerte et al, 2012a). Nine out of 17 studies included control groups (Bazarian et al, 2014;Brett et al, 2021;Churchill et al, 2017;de Souza et al, 2020;Holcomb et al, 2021;Koerte et al, 2012a;Lefebvre et al, 2021;Mayinger et al, 2018;Strauss et al, 2021), of which five studies included non-contact sport controls (Brett et al, 2021;Churchill et al, 2017;de Souza et al, 2020;Holcomb et al, 2021;Koerte et al, 2012a), two studies included non-athlete controls (Bazarian et al, 2014;Mayinger et al, 2018), and two studies included both (Lefebvre et al, 2021;Strauss et al, 2021). The most common non-contact sport was swimming, with four studies that included swimmers in their control group (Holcomb et al, 2021;Koerte et al, 2012a;Lefebvre et al, 2021;Strauss et al, 2021).…”

“…The way in which history of concussion was assessed and reported varied across studies. More specifically, five of 17 studies did not include individuals with a history of concussion (Bahrami et al, 2016;de Souza et al, 2020;Koerte et al, 2012a;Lefebvre et al, 2021;Saghafi et al, 2018). Six studies included individuals with a history of concussion prior to study participation, but considered this in the statistical analyses only (Brett et al, 2021;Churchill et al, 2017;Holcomb et al, 2021;Kawata et al, 2020;Lipton et al, 2013;Strauss et al, 2021).…”