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Journal of Women's Health Physical Therapy:
Research Study

Examination of Effects of Oral Contraceptive Use on Electromyography and Mechanomyography Findings During Muscle Fatigue of the Rectus Femoris

Drake, Shawn M. PhD1; Evetovich, Tammy K. PhD2; Eschbach, Chris L. PhD3; Webster, Michael J. PhD4

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Background:: Female athletes are reported to be at an increased risk for anterior cruciate ligament (ACL) injuries compared to male athletes. Fatigue may play a role in the occurrence of ACL injuries due to changes in dynamic stability of the knee.

Purpose:: To determine changes in muscle function across the menstrual cycle for women not using oral contraceptive (NOC) and women using oral contraceptives (OC) during concentric (CON) and eccentric (ECC) isotonic muscle fatigue actions.

Study Design:: Prospective quasi‐experimental cohort design.

Methods:: Fourteen healthy, physically active women (Mean ± SEM, 23 ± 1 yrs, 1.7 ± 1 m, 60 ± 2 kg) were recruited and tested 3 times throughout one complete menstrual cycle. The NOC group (N = 6) was not taking any form of hormonal treatment and all had normal menstrual cycles lasting between 26 and 32 days. The second group (N = 8) had been taking OC for at least 6 months. Each participant performed one maximal isotonic strength (1‐RM) test of the leg extensors. For each of the 3 testing sessions, each participant performed a fatigue protocol at 50% of 1‐RM. Bipolar surface EMG electrodes were placed mid‐thigh over the rectus femoris with a piezoelectric MMG recording device placed between the two electrodes.

Results:: No significant 2‐way interactions for number of repetitions performed on each day, CON EMG, ECC EMG, CON MMG, or ECC MMG during fatigue.

Conclusions:: Based on the results from our sample population, no evidence was found to support the hypotheses of differences in muscle function between NOC and OC females.

© 2005 Lippincott Williams & Wilkins, Inc.

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