Estrogen-induced effects on the neuro-mechanics of hopping in humans

Abstract

Estrogen receptors in skeletal muscle suggest a tissue-based mechanism for influencing neuromuscular control. This has important physiological implications for both eumenorrheic women with fluctuating estrogen levels and those with constant and attenuated estrogen levels, i.e., women using the monophasic oral contraceptive pill (MOCP). This study examined the effects of endogenous plasma estrogen levels on leg stiffness (K (LEG)) and foot center of pressure (COP) during hopping. Nineteen females (Age = 28.0 ± 4.2 years, Ht = 1.67 ± 0.07 m, Mass = 61.6 ± 6.8 kg) who had been using the MOCP for at least 12 months together with 19 matched, female, non-MOCP users (Age = 31.9 ± 7.3 years, Ht = 1.63 ± 0.05 m, Mass = 62.5 ± 5.9 kg) participated. Non-MOCP users were tested at the time of lowest (menstruation) and highest (≈ ovulation) estrogen whilst MOCP users were tested at Day 1 and Day 14 of their cycle. At each test session, K (LEG) (N m(-1) kg(-1)) and foot COP path length (mm) and path velocity (mm s(-1)) were determined from ground reaction force data as participants hopped at 2.2 Hz on a force plate. Statistical analysis revealed no significant (p < 0.05) differences for K (LEG). In contrast, significantly higher COP path length (30%) and COP path velocity (25%) were identified at ≈ ovulation compared to menstruation in the non-MOCP users. Whilst there was no evidence of an estrogen-induced effect on K (LEG); significantly elevated estrogen at ≈ ovulation presumably increased extensibility of connective tissue and/or diminished neuromuscular control. Consistent lower limb dynamics of MOCP users demands less reliance on acutely modified neuromuscular control strategies during dynamic tasks and may explain the lower rate of lower limb musculoskeletal injuries in this population compared to non-MOCP users.

Is the Use of Oral Contraceptives Associated With Operatively Treated Anterior Cruciate Ligament Injury?

“…One of the potentially important unmeasured life-style confounders in this study is if our subjects were athletes or not. Although few studies show no association between being an OC user and being an athlete or between the use of OC and the extent of physical activity, [8][9][10]18 there is no clear evidence to determine if use of OC differs between athletes and the general population. Hence, we cannot rule out ''being an athlete'' as a potential unmeasured confounder in our study.…”

Influência das fases do ciclo menstrual no desempenho funcional de mulheres jovens e saudáveis

“…In this sense, the literature reports that the female physiology seems to be affected by cyclical hormonal changes arising from the menstrual cycle; in which estrogen and progesterone, in addition to the regulation of reproductive function, show actions on the central nervous system (CNS). Studies show that these sex hormones may influence on neurotransmitters such as GABA, serotonin, and glutamate, acting on membrane receptors [1][2][3] , being able to influence different brain regions with alteration of sensory perception and motor responses [4][5][6][7][8][9] .…”

Influence of Menstrual Cycle and Oral Contraceptive Phase on Spinal Excitability

“…Interest in a hormonal role is based on our evolving understanding of the pleitropic, or multiple and varying, effects of ovarian steroids, as well as the presence of estrogen and progesterone receptors throughout the neuromusculoskeletal system [3‐5]. Whether or not gross neuromuscular control changes across the menstrual cycle remains controversial [6‐10]. Two recent studies have demonstrated changes in more basic units of neuromuscular control across the menstrual cycle, particularly the activation patterns of the vastus medialis muscle [11], as well as in the muscle stretch reflex response at the rectus femoris [12].…”