The Modulatory Effect of Female Sex Hormones on Spinal Neuroplasticity

FEMALES Inclusion Criteria: * Ages 18-39 years * Eumenorrheic (regular monthly cycles of 24-35 days) * Moderately active (less than 7 hours of vigorous physical activity per week) * History of pregnancy is allowed if patient is in post-lactation phase Exclusion Criteria: * History of musculoskeletal or orthopedic injury of the spine, hip, knee, ankle or foot * History of neurological injury of the peripheral or central nervous system * Current smoker * History of disordered eating * History of stress fracture in the lower limb * History of a connective tissue disorder (Marfan's syndrome, Ehlers-Danlos disease) * Pacemaker, metal implants in the head and spine region * Pregnancy * On a hormonal contraceptive regimen (oral, transdermal or vaginal) * History of menstrual dysfunction (primary or secondary amenorrhea, oligomenorrhea, anovulatory cycles, polycystic ovarian disease) * Started or stopped taking oral contraceptives within the previous 6 months * Exercise vigorously more than 7 hours per week or currently participating in competitive level sports. MALES Inclusion Criteria: * Ages 18-39 * Moderately active (less than 7 hours of vigorous physical activity per week) Exclusion Criteria: * History of musculoskeletal or orthopedic injury of the spine, hip, knee, ankle or foot * History of neurological injury of the peripheral or central nervous system * Current smoker * History of disordered eating * History of stress fracture in the lower limb * History of a connective tissue disorder (Marfan's syndrome, Ehlers-Danlos disease) * Pacemaker, metal implants in the head and spine region