Sex Differences in Neck Strength Force and Activation Patterns in Collegiate Contact Sport.

The purpose of this study was to assess changes in cervical musculature throughout contact-heavy collegiate ice hockey practices during a regular season of NCAA Division III ice hockey teams. In this cross-sectional study, 36 (male n = 13; female n = 23) ice hockey players participated. Data were collected over 3 testing sessions (baseline; pre-practice; post-practice). Neck circumference, neck length, head-neck segment length, isometric strength and electromyography (EMG) activity for flexion and extension were assessed. Assessments were completed approximately 1h before a contact-heavy practice and 15 min after practice. For sternocleidomastoid (SCM) muscles, males had significantly greater peak force and greater time to peak force versus females. For both left and right SCMs, both sexes had significantly greater peak EMG activity pre-practice versus baseline, and right (dominant side) SCM time to peak EMG activity was decreased post-practice compared to pre-practice. There were no significant differences for EMG activity of the upper trapezius musculature, over time or between sexes. Sex differences observed in SCM force and activation patterns of the dominant side SCM may contribute to head stabilization during head impacts. Our study is the first investigation to report changes in cervical muscle strength in men's and women's ice hockey players in the practical setting.

Sex Differences in Anthropometrics and Heading Kinematics Among Division I Soccer Athletes.

BACKGROUND: Soccer players head the ball repetitively throughout their careers; this is also a potential mechanism for a concussion. Although not all soccer headers result in a concussion, these subconcussive impacts may impart acceleration, deceleration, and rotational forces on the brain, leaving structural and functional deficits. Stronger neck musculature may reduce head-neck segment kinematics. HYPOTHESIS: The relationship between anthropometrics and soccer heading kinematics will not differ between sexes. The relationship between anthropometrics and soccer heading kinematics will not differ between ball speeds. STUDY DESIGN: Pilot, cross-sectional design. LEVEL OF EVIDENCE: Level 3. METHODS: Division I soccer athletes (5 male, 8 female) were assessed for head-neck anthropometric and neck strength measurements in 6 directions (ie, flexion, extension, right and left lateral flexions and rotations). Participants headed the ball 10 times (25 or 40 mph) while wearing an accelerometer secured to their head. Kinematic measurements (ie, linear acceleration and rotational velocity) were recorded at 2 ball speeds. RESULTS: Sex differences were observed in neck girth ( t = 5.09, P < 0.001), flexor and left lateral flexor strength ( t = 3.006, P = 0.012 and t = 4.182, P = 0.002, respectively), and rotational velocity at both speeds ( t = -2.628, P = 0.024 and t = -2.227, P = 0.048). Neck girth had negative correlations with both linear acceleration ( r = -0.599, P = 0.031) and rotational velocity at both speeds ( r = -0.551, P = 0.012 and r = -0.652, P = 0.016). Also, stronger muscle groups had lower linear accelerations at both speeds ( P < 0.05). CONCLUSION: There was a significant relationship between anthropometrics and soccer heading kinematics for sex and ball speeds. CLINICAL RELEVANCE: Neck girth and neck strength are factors that may limit head impact kinematics.

Genetic variation in SLC17A7 promoter associated with response to sport-related concussions.

OBJECTIVE: To determine the association of the single nucleotide polymorphism (SNP) rs74174284 within SLC17A7 promoter with concussion severity or duration. DESIGN: A between-subjects design was utilized. METHODS: Saliva samples and concussion severity and duration data were collected from 40 athletes diagnosed with a sport-related concussion by a physician, utilizing a standardized concussion assessment protocol. DNA was extracted, estimated and genotyped. RESULTS: An association was found between the dominant genetic model (CC vs GG + GC; p = 0.0179) and recovery, where those carrying the minor allele were 6.33-times more likely to experience prolonged recovery rates. Within the ImPACT assessment, those carrying the CC genotype (33.38 ± 10.15, p = 0.01) had worse motor speed scores upon initial assessment compared to both heterozygous (CG) and homozygous (GG) genotypes (41.59 ± 7.39). CONCLUSIONS: This study was the first to demonstrate an association between genetic polymorphism at rs7417284 SNP in the promoter region of the SLC17A7 gene and concussion severity and duration. Based upon these findings, rs74174284 is a potential predictive genetic marker for identifying athletes who are more susceptible for altered recovery times and worse motor speed ImPACT scores after sport-related concussion.

Effect of soccer heading ball speed on S100B, sideline concussion assessments and head impact kinematics.

OBJECTIVE: To examine the effect of soccer heading ball speed on S-100B serum concentration, concussion sideline assessments and linear head impact acceleration. METHODS: Sixteen division I soccer players participated in this pre-test post-test design study. Athletes performed five standing headers over a 10 minute period at 30 (n = 5), 40 (n = 5) or 50 (n = 6) miles per hour (mph) (randomized). S-100B serum concentration (ng mL-1) and sideline concussion assessments were measured prior to and post-heading. Peak resultant linear head acceleration (gravitational units; g) was measured during soccer heading. RESULTS: No statistically significant interaction effects were identified between ball velocity groups over time on S100B (effect sizes ranged from 0.03-0.23) or concussion assessments tests. There was a non-significant increase (p = 0.06) in head impact acceleration from the 30 (30.6; SD = 6.2 g) to 50 mph (50.7; SD = 7.7 g) ball speed. CONCLUSIONS: In this controlled setting, an acute bout of soccer heading across various ball velocities did not affect S100B or concussion assessment test scores. These findings are preliminary, as the small sample size in each group may have played a role in the lack of significant findings.

Neuronal structural protein polymorphism and concussion in college athletes.

OBJECTIVE: To examine the association between a neuronal structural protein polymorphism and the frequency and severity of concussions in college athletes. METHODS: Forty-eight athletes with previous self-reported history of a concussion were matched with 48 controls that did not report a history of concussion. Each group was genotyped for neurofilament heavy (NEFH) polymorphism rs#165602 in this retrospective case-control study. RESULTS: There was no significant association (χ(2 )= 0.487, p = 0.485) between carrying the NEFH rare allele and a history of one or more concussions due to small effect sizes. A Fisher's exact test revealed no significant association (p = 1.00, ϕ = -0.03) between the presence of NEFH rare allele and a history of multiple concussions. The independent t-tests revealed no significant differences in duration of signs and symptoms (t = 1.41, p = 0.17, d = 0.48) or return to play (t = 0.23, p = 0.82, d = 0.08) between NEFH rare allele carrier and non-carriers. CONCLUSIONS: Among college athletes, carrying the rare allele assessed may not influence an athlete's susceptibility to sustaining a concussion or return to play duration following a concussion.

Apolipoprotein E genotype and concussion in college athletes.

OBJECTIVE: To evaluate the association between apolipoprotein E (APOE) polymorphisms (E2, C/T Arg158Cys; E4, T/C Cys112Arg; and promoter, g-219t) and the history of concussion in college athletes. We hypothesized that carrying 1 or more APOE rare (or minor) allele assessed in this study would be associated with having a history of 1 or more concussions. DESIGN: Multicenter cross-sectional study. SETTING: University athletic facilities. PARTICIPANTS: One hundred ninety-six male football (n = 163) and female soccer (n = 33) college athletes volunteered. INTERVENTIONS: Written concussion history questionnaire and saliva samples for genotyping. MAIN OUTCOME MEASURES: Self-reported history of a documented concussion and rare APOE genotype (E2, E4, promoter). RESULTS: There was a significant association (Wald χ² = 3.82; P = 0.05; odds ratio = 9.8) between carrying all APOE rare alleles and the history of a previous concussion. There was also a significant association (Wald χ² = 3.96, P = 0.04, odds ratio = 8.4) between carrying the APOE promoter minor allele and experiencing 2 or more concussions. CONCLUSIONS: Carriers of all 3 APOE rare (or minor) alleles assessed in this study were nearly 10 times more likely to report a previous concussion and may be at a greater risk of concussion versus noncarriers. Promoter minor allele carriers were 8.4 times more likely to report multiple concussions and may be at a greater risk of multiple concussions versus noncarriers. Research involving larger samples of individuals with multiple concussions and carriers of multiple APOE rare alleles is warranted.