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Title: Effects of estrogen on the mechanical behavior of the human Achilles tendon in vivo
Contributor(s): Bryant, Adam L (author); Clark, Ross A (author); Bartold, Simon (author); Murphy, Aron (author); Bennell, Kim L (author); Hohmann, Erik (author); Marshall-Gradisnik, Sonya (author); Payne, Craig (author); Crossley, Kay M (author)
Publication Date: 2008
DOI: 10.1152/japplphysiol.01281.2007
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Abstract: The purpose of this study was to elucidate the effect of normal fluctuating [nonmonophasic oral contraceptive pill (MOCP) users] and low, consistent (MOCP users) endogenous plasma estrogen levels on the strain behavior of the Achilles tendon in vivo. Twenty women (age 28.0 ± 4.2 yr, height 1.67 ± 0.07 m, mass 61.6 ± 6.8 kg) who had been using the MOCP for at least 12 mo together with 20 matched women who were non-MOCP users (age 31.9 ± 7.3 yr, height 1.63 ± 0.05 m, mass 62.5 ± 5.9 kg) participated in this study. Non-MOCP users were tested at the time of lowest (menstruation) and highest (≈ovulation) estrogen, whereas MOCP users, who exhibited constant and attenuated endogenous estrogen levels, were tested at day 1 and day 14 of their cycle. At each test session, maximal isometric plantarflexion efforts were performed on a calf-raise apparatus while synchronous real-time ultrasonography of the triceps surae aponeurosis was recorded. Achilles tendon strain (%) was calculated by dividing tendon displacement during plantarflexion by resting tendon length. Repeated measures ANOVA revealed a significant (P > 0.05) main effect of subject group with significantly lower Achilles strain (25.5%) in the MOCP users compared with the non-MOCP users. In conclusion, acute fluctuations in plasma estrogen across the menstrual cycle in non-MOCP users did not alter the strain behavior of the Achilles tendon. Conversely, long-term exposure to attenuated estrogen in MOCP users resulted in a decrease in Achilles tendon strain, which is thought to be attributed to the effects of endogenous estrogen on collagen synthesis. These findings have a number of important functional and clinical implications.
Publication Type: Journal Article
Source of Publication: Journal of Applied Physiology, 105(4), p. 1035-1043
Publisher: American Physiological Society
Place of Publication: Bethesda, United States of America
ISSN: 1522-1563
Field of Research (FOR): 110604 Sports Medicine
110602 Exercise Physiology
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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