Directional Neck Muscle Strength in Response to Optimal Positioning of Mandible Occlusion Can Reduce Concussion Risk

Research Objectives: Risk management of concussive blows to the head continues to be investigated as significantly related to reduced sports-related injuries. Recent evidence suggests cervical muscle activation is enhanced if the lower jaw is optimized in its physiologic resting position. (Streifer 2019;Garret 2023).

Objective: Investigate directional neck strength and endurance with and without customized, optimal mandibular interocclusal appliance positioning.

Design: Cohort group design with repeated measures of two conditions

Setting: University outpatient physical therapy clinic.

Participants: 42 healthy participants (20 females/22 males) ages >18 to 52 yrs. were sampled by convenience. Inclusion criteria: normal cervical spine AROM, no recent head or neck trauma or surgery. Exclusion criteria: active cervical pain and any cervical spine postural abnormalities.

Interventions: Participants were tested by a physical therapy orthopedic specialist, using a standardized neutral head-neck position in sitting, the feet on the floor, neck muscle strength was tested in six directions including: flexion, extension, bilateral rotation and side-flexion. Flexion-Extension muscle endurance was timed in supine/prone. Bilateral grip strength was measured using the Jamar hand dynamometer. Participants were tested in each condition without and then with an interocclusal appliance in place. Statistical Analysis: SPSS was used for descriptive statistics, paired T-Tests and 2-way repeated measures ANOVA to explore differences at p = 0.05 with a Greenhouse-Geisser correction factor.

Main Outcome Measures: Variables of interest included: Muscle force (kg-force): neck muscle flexion, extension, right/left rotation, right left side-flexion. Muscle endurance (seconds): neck muscle flexion (supine w/ chin tuck), extension (prone w/forehead two finger clearance from surface), bilateral grip strength (kg)
Additional Variables of interest: Demographics (age, gender, weight, height, pain score, fatigue, prior sleep hours), Neck Disability Index & Disability Arm Shoulder Hand assessments,

Results: There were significant differences in endurance in both directions: Neck Flex Endurance Test-Supine, t= -3.645, p= 0.009, Neck Ext Endurance Test-Prone, t= -4.602, p = 0.002. Also, significant differences were found in strength based on Condition (F (1,39)-6.849, p < 0.001) and Trial (F (1,39) = 27.508, p < 0.001).

Conclusions: Results suggest immediate directional neck strength and endurance gains with an interocclusal appliance for optimized positioning compared to no appliance use. Suggested gains in cervical spine strength and endurance may assist concussion risk management for contact sports at all levels. Preliminary results also suggest the need for further research about how proper jaw alignment might optimize neck muscle strength over a broad spectrum of subjects regardless of gender, age or athletic ability.

Author(s) Disclosures: All authors have no conflict to declare