Effects of plyometric training on cervical muscle strength, activation, and head impacts in female high school soccer players

Recent research has highlighted alarming rates of concussion incidence among female soccer athletes. Studies have demonstrated neck strength as a possible predisposition to concussive forces, but no research has incorporated a dynamic training program emphasizing neuromuscular control related to the cervical musculature. The objective of this study was to investigate the effects of a sport-specific plyometric and functional training program on cervical muscle strength, size, and activation, and subsequent head impacts. An experimental, between-groups design was utilized using high school athletic training and sports facilities. Eight high school female soccer players (age = 16.24 +/- 1.07 years; height = 165.89 +/- 10.95 cm; mass = 55.17 +/- 7.09 kg) participated in the research. An 8 week plyometric and functional training program consisting of 3 sport-specific drills was implemented for the intervention group. The control group did not perform any additional cervical muscle strength training. Isometric cervical neck strength (lbf) was measured using a MicroFET 2 handheld dynamometer, neck girth (cm) was recorded using a standard metric tape measure, muscle activation (% maximum voluntary contraction of the sternocleidomastoid and upper trapezius muscles) was measured using a 16 channel wireless TeleMyo DTS EMG system, and head impact acceleration values (G) were recorded pre- and post-intervention by a DTS 3D 24G Accelerometer. Significant differences were identified between groups related to the mean peak head accelerations between the 3 axes of measurement. Additionally, differences in mean upper trapezius activation (p < 0.001), right sternocleidomastoid (p = 0.002), and left sternocleidomastoid (p < 0.001) muscles were identified over time. No significant group effects were discovered related to neck strength, neck girth, mean acceleration upon impact, or cervical muscle activation or duration throughout heading activities (p ? 0.05). The plyometric intervention did not result in significant strength gains compared to the control group, but subjects did reveal a trend in strength gains over time. Functional plyometric training resulted in increased peak head accelerations within the intervention group. The results suggest that plyometric training resulted in greater neuromuscular control and heading force in soccer specific activities, but further research needs to be conducted as it relates to brain injury susceptibility.