Studies across various sports and physical activities have consistently shown that females incur more injuries compared to their male counterparts, but the underlying reasons for this disparity remain poorly understood. While differences in hormone levels between males and females have been speculated to play a role, very little rigorous research has been conducted to directly examine potential connections between sex hormones and injury risk. Specifically, females have been shown to be at greater risk for hand and wrist injuries. The higher injury incidence begins at puberty and persists across the lifespan, suggesting a link to hormonal factors. However, significant gaps remain in understanding the relationships between the menstrual cycle, exogenous hormones from birth control, and risk factors for sports-related injury in females. The purpose of this study is to examine changes in muscle strength and neuromuscular activation among females using monophasic oral contraceptives, females not using oral contraceptives, and males during one week of wrist/hand immobilization.

Inclusion Criteria:

• Right handed males and females
• Ages 18-35 years
• For females, consistent use of monophasic oral contraceptives for the previous 6 months OR having completely refrained from contraceptives for the previous 6 months.

Exclusion Criteria:

• Gender identity inconsistent with biological sex (due to the influence that drugs used for gender reassignment may have)
• Females that are amenorrheic (lack of menstruation for ≥3 consecutive cycles) or oligomenorrheic (menstrual cycle length ≤36 days)
• Menstrual cycle irregularities among females not using oral contraceptives (regularity defined as every 21 to 35 days and/or at least 5 periods in the last six months)
• Any contraceptive use other than monophasic oral contraceptives within the last 6 months
• Monophasic oral contraceptives that has been inconsistent over the previous 6 months
• Score of greater than 2/5 on question 9, or a score of greater than 1/5 on question 10 or 11 on the quick Disabilities of the Arm, Shoulder and Hand outcome measure indicating pain/discomfort of the upper extremities (shoulder, elbow, wrist, hand)
• Dominant hand is the left hand
• Body Mass Index less than 18.5 kg/m2 or greater than 29.9 kg/m2
• Current depression or anxiety
• History of musculoskeletal injury, pain, or surgery of the elbow, wrist, or hand
• Unwillingness to avoid upper-body exercise during Phase 1
• Unwillingness to avoid exercise and alcohol 24 hours prior to each testing visit.
• Neuromuscular disease (e.g., Multiple Sclerosis, amyotrophic lateral sclerosis, Parkinson's)
• Metabolic disease (e.g., diabetes, thyroid disorder, metabolic syndrome)
• Personal or family history of blood clots
• Trouble using or controlling muscles
• History of cancer
• History of stroke
• History of heart attack
• History of arthritis
• Allergy to rubbing alcohol
• Lack of transportation to and from the laboratory
• Current or planned pregnancy (within the next three months)
• Implant of any kind
• The use of medications that may increase the risk of blood clots (i.e., corticosteroids such as prednisone, testosterone and anabolic steroids, selective estrogen receptor modulators like tamoxifen, aromatase inhibitors including anastrozole, thalidomide and lenalidomide, erythropoiesis-stimulating agents such as epoetin alfa, antipsychotics like chlorpromazine, antidepressants including paroxetine, various cancer chemotherapies, immune modulating drugs, antivirals such as ritonavir, and tamoxifen).
• The use of creatine monohydrate and beta alanine supplementation within the previous 6 months.
• The use of any medication or supplement that could influence hormone levels within the previous 6 months.

Biological males and females. Gender identity must be consistent with biological sex.

We plan to make de-identified individual participant data (IPD) from this study available to other researchers once the primary analysis is completed and the study results have been published. The data will be shared in a manner that protects participant confidentiality and adheres to applicable laws and regulations.

IPD will be made available beginning 1 year after the study completion date.

Researchers must submit a methodologically sound proposal outlining their planned analysis of the data. Proposals will be reviewed and approved by an independent panel appointed by the Principal Investigator. Requests should be sent to matt.stock@ucf.edu