Sport-related concussion is a common and serious injury that can affect athletes of all ages in any sport. The purpose of this project is to study the effect of a 12-week manual resistance neck strengthening exercise program on participants' neck size and strength and how their heads and necks move during simulated sport-associated tasks. This study will help determine if greater neck strength may lower an athlete's risk of sport-related concussion. Each healthy male and female soccer athlete between the ages of 13-19 enrolled in the study will participate for approximately four months. Study participation includes routine visits with various assessments (i.e. certain body measurements, magnetic resonance imaging, ultrasound) in addition to the strengthening exercise program.

This study was updated to remove the low-volume group and the amendment was approved 3/29/2023 at the Institutional Review Board. This change to remove the low-volume exercise group was due to reduced enrollment numbers following the Corona Virus Disease (COVID) Pandemic.

Inclusion Criteria:

• Provision of signed and dated informed consent form, or assent form with parental consent for minors
• Stated willingness to comply with all study procedures and availability for the duration of the study
• Participated in a soccer team, club, or other soccer program/organization within the preceding 2 years
• Be willing to adhere to the assigned exercise regimen

Exclusion Criteria:

• Prior history of trauma-induced neck injury of sufficient severity to require treatment by a medical provider within 30 days of injury or to limit sport participation for > 1 day (note: having received routine chiropractic treatment in the absence of a recent traumatic injury to the neck will not be considered to meet this criterion)
• Any prior history of whiplash injury, stinger/burner, or cervical radiculopathy diagnosed by a medical provider
• Any prior history of bone, disk, neural, or ligamentous abnormality identified on cervical spine medical imaging performed for any reason that is felt by the PI (or designee) to present a risk to study participation
• Any prior history of surgery involving the cervical spine (note: having undergone non-spine surgery to the soft tissue structures in the neck will not necessarily exclude participation, but will be considered on a case-by-case basis by the PI, or his designee, with consultation from the performing surgeon when deemed appropriate)
• Self-report of moderate or severe neck pain (rated as 5 or greater on a 10-point pain scale) lasting > 1 day in the previous 6 months that required any evaluation or treatment by a medical provider or that limited sport participation for > 1 day (note: having received routine chiropractic treatment in the absence of moderate-severe neck pain will not be considered to meet this criterion)
• Self-report of low back pain (any severity) associated with morning stiffness occurring 30 days or more in the previous 3 months.
• Prior episode(s) of unexplained upper extremity numbness, tingling, or weakness suspicious to the PI, or designee, for a stinger/burner or cervical radiculopathy in the last 3 years
• Prior history of concussion in the previous 6 months diagnosed by a medical provider or suspected by the subject, or the parent/guardian of a minor (if no medical evaluation was sought), or any diagnosed/suspected concussion without full recovery and clearance to resume unrestricted sport participation.
• Personal history of migraine headaches within the previous 3 years diagnosed by a medical provider, with one or more headache episodes, or requiring treatment.
• Personal history of anxiety disorder diagnosed by a medical provider that has either been difficult to control, affected daily function, or required treatment with medication or counseling within the previous 3 years.
• Parental/guardian known history of anxiety disorder diagnosed by a medical provider that has either been difficult to control, affected daily function, or required treatment with medication or counseling within the previous 3 years.
• Prior personal of any of the following or known family history of the following medical conditions known to be associated with atlanto-axial instability diagnosed by a medical provider: parental history of Down Syndrome, Ehlers-Danlos Syndrome, or Marfan syndrome; parental, or sibling history of rheumatoid arthritis/other systemic inflammatory disease with joint involvement or mucopolysaccharidosis
• Known exposure to or infection with head lice in the previous 30 days
• Known or suspected pregnancy (for females)
• Serious allergic reaction to nickel/metal jewelry
• Any contraindication to MRI scanning
• Presence of significant abnormality on a standardized screening neurological and musculoskeletal physical examination
• Prior participation in a resistance exercise training program including exercises specifically intended to target the neck muscles within 3 months of enrollment, or intention to begin participating in such an exercise program outside of the study protocol during the upcoming 12-week study period
• Unable to speak and understand English

Up to four months

Neither subjects nor the study team members responsible for performing the laboratory- or radiology-based assessment will be informed of group allocation status, although subjects will be aware of whether or not they are performing neck strengthening exercises during their exercise sessions. Subjects will be instructed not to reveal their group status during subsequent assessment sessions.