The effect of oral contraceptive use on muscle properties across the menstrual cycle

Objective: To investigate the effects of oral contraceptive use on active hamstring muscle stiffness, vertical leg stiffness, and hamstring electromechanical delay (EMD). Hypothesis: Non oral contraceptive pill (Non-OCP) users will have altered muscle properties when hormone levels are greatest resulting in decreased muscle stiffness and increased EMD. Oral contraceptive pill (OCP) users will have no difference in muscle properties. Subjects: 15 physically active females using monophasic oral contraception (OCP; age = 19.87 + 1.13 years, height = 165.40 + 7.96 cm, mass = 61.54 + 13.12 kg) and 15 females not using oral contraception (Non-OCP; age = 20.40 = 1.59 years, height = 169.93 +5.62 cm, mass = 62.75 + 10.61) with a normal menstrual cycle. Design and setting: Controlled laboratory setting. Subjects were tested two times across their menstrual cycle (menses and ovulation). Ovulation was detected using urine based ovulation kits. OCP test sessions were matched to non-OCP sessions using pill counting. Measurements: Active hamstring stiffness, vertical leg stiffness, electromechanical delay. Results: There was no significant effect for group or time, nor a group x time interaction for active hamstring stiffness, vertical leg stiffness, and EMD of the hamstrings. Conclusion: This study does not indicate that taking the oral contraceptive pill would alter muscle properties in manners which are suggested to reduce ACL injury risk