Post-Concussion Musculoskeletal Injury Risks

Inclusion Criteria: Concussed Cohort * 18-40 years old. * Self-reported asymptomatic post-concussion following enrollment into the study and monitoring of symptoms by research personnel via daily self-reported symptom questionnaires. * Recruited within 5 days following being diagnosed with a concussion, and at least 72 hours prior to self-reporting as asymptomatic. * Access to a functional email address and the internet for completion of patient reported outcomes (PROs) and musculoskeletal injury measures. Non-Concussed Cohort * 18-40 years old. * Active duty Service members and physically active civilians. * No self-report history of concussion within the previous 5 years. * No lingering post-concussion signs/symptoms. * Same gender as the matched concussed participant. * Within ±5% of the matched concussed participant's height, weight, and body mass index. * Within ±2 years of age of the matched concussed participant. * Participant in the same physical activities (work, recreational sports, average type \[no impact, low-impact, high-impact\] and duration of physical activity) Exclusion Criteria: * Post-Concussion Cohort AND Healthy Non-Concussed Cohort * Unable to read or comprehend the English language. * Admitted to the hospital following concussion. * Sustained a concussion not related to physical activity participation (e.g., blast-related injury, fall from a ladder, motor vehicle accident). * Loss of consciousness longer than 30 minutes. * Alteration in consciousness longer than 24 hours. * Post-traumatic amnesia lasting longer than 1 day. * Glasgow Coma Scale below 13. * Abnormal brain imaging findings. * Sustained a concussion that took longer than 21 days for the individual to report as asymptomatic. * A MSKI within the last 6 months that resulted in altered or missed physical activity for 3 or more consecutive days. * History of MSKI surgery. * Pregnant females (will be eligible for participation in the study once medically cleared to RTD/A by a qualified and licensed healthcare provider following the end of the pregnancy). * Participants will be excluded if they present any known contraindications for electrical stimulation. These contraindications include conditions such as: active deep vein thrombosis/thrombophlebitis, any acute injury with concurrent inflammation, hemorrhagic conditions, impaired circulation, impaired local sensations, presence of infection (osteomyelitis, tuberculosis), malignancy, recently radiated tissue, skin disease/damage and/or at-risk skin. * Present with any implanted pacemaker, electronic device, or plastic/cement material