Pilot Evaluation of a Supervised Neck Strengthening Program in High School Athletes: A Potential Intervention to Reduce the Risk of Sport-related Concussion
A pilot study to investigate the effect of a supervised eight-week neck strengthening intervention in high school athletes to help prevent concussion.
Sport-related concussion (SRC) is a common and significant injury that affects athletes of both genders, in all sports, across all levels of play. Athletes with weaker necks may be at greater risk for concussion because their necks are less able to absorb impact forces and couple their heads to their bodies during sport collisions. We have previously demonstrated that greater neck strength is associated with smaller changes in head linear and angular velocity following the application of a standardized external load in youth and adult athletes, suggesting that neck strengthening interventions may reduce an athlete’s risk for sustaining sport-related concussion. However, optimal neck strengthening protocols are unknown and neck strengthening interventions have never been studied in youth athletes. The purpose of this pilot study was therefore to determine the effect of an 8-week supervised manual resistance training program on overall neck girth, the cross-sectional area (CSA) of the sternocleidomastoid (SCM) muscle, and the neck’s force generating capacity in each primary plane of motion in youth athletes. Seventeen youth athletes were allocated into intervention (n = 13) and control (n = 4) groups using weighted block randomization. All participants completed 16 whole-body resistance training sessions over an 8-week period with a Certified Strength and Conditioning Specialist. In addition, the intervention group also performed barbell shrugs and manual resistance exercises targeting the neck. Before and after the exercise program, each participant completed a laboratory-based assessment of neck girth, sonographic SCM CSA, and force generating capacity in flexion, extension, lateral flexion, and axial rotation, with surface electromyography (EMG) of the SCM, upper trapezius, splenius capitis, and semispinalis capitis muscles during maximum voluntary contraction in each plane of motion and during voluntary bracing. Descriptive statistics were calculated to compare pre-post changes between the two groups. Mean neck girth increased by 0.54 cm and 0.25 cm in the intervention and control groups. However, SCM CSA showed minimal change (mean 0.0 cm in both groups). Across all planes of motion, force generating capacity increased in 35 of 48 (72.9%) and 11 of 16 (68.8%) measurements taken in the intervention and control groups, respectively, with mean increases of 13.7 N in the intervention group vs. 5.3 N in the control group. The intervention group experienced the largest strength increase in extension (mean 28.2 N) and the smallest strength increase in axial rotation (mean 4.7 N). Across the 4 cervical muscles, surface EMG activation (% of maximum), increased in 26 of 52 (50%) measurements in the intervention group and 5 of 16 (31.3%) of measurements in the control group during voluntary bracing. In flexion and extension, antagonist cervical muscle activation (% of maximum) decreased in 23 of 39 (59.0%) and 2 of 12 (16.7%) measurements taken in the intervention and control groups, respectively. In this pilot study, an 8-week manual resistance training program was effective in increasing neck strength in male and female youth athletes. Our results suggest that the mechanism of this change may be more attributable to greater efficiency of muscle recruitment than to muscle