Proof that women are not unstable at the time of menstruation.
On the subject of proprioception, here is something we found interesting while on a quest for another article. 1st, we had found an article in the NY Times blog, talking about training considerations of women during their monthly cycle.
They state: “There may, however, still be reasons a woman to consider her period when planning training. A study published this year by scientists at the University of Melbourne in Australia, for instance, found that when women’s estrogen levels were at their highest, around the time of ovulation, they landed subtly differently while hopping than at other times of the month. Their feet splayed, the arch collapsing just a little bit more than it did when their estrogen levels were lower. The women also seemed, to a small degree, wobblier. “We contend that the changes in foot biomechanics may be due to the effects of estrogen on soft tissue and/or the brain,” said Adam Leigh Bryant, a senior lecturer at the University of Melbourne and lead author of the study.”
This says, in a nutshell, that women are not unstable around the time of menstruation (dispelling many common myths to the contrary) but rather, they are unstable around the time of their ovulation (proprioceptively speaking, of course). Women on monophasic contraceptives showed less variability (greater stability) and therefore may be more less injury prone.
Of course we pulled the study (abstract below). We found it interesting that it may actually be a neurological/cortical phenomenon, rather that muscle estrogen receptor based. What is the advantage of less proprioceptive awareness with increased estrogen levels? Maybe (in a bit of a stretch), it was for propagation of the species. If the women can’t get away, then they are more likely to be caught (or less likely to be able to run…)
The Gait Guys….Sifting through the literature and sometimes poking a little fun at it.
Ivo and Shawn.
http://www.ncbi.nlm.nih.gov/pubmed/20857138
Estrogen-induced effects on the neuro-mechanics of hopping in humans.
Source
Centre for Health, Exercise and Sports Medicine, School of Physiotherapy, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, VIC, 3010, Australia. albryant@unimelb.edu.au
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.
“There may, however, still be reasons a woman to consider her period when planning training. A study published this year by scientists at the University of Melbourne in Australia, for instance, found that when women’s estrogen levels were at their highest, around the time of ovulation, they landed subtly differently while hopping than at other times of the month. Their feet splayed, the arch collapsing just a little bit more than it did when their estrogen levels were lower. The women also seemed, to a small degree, wobblier. “We contend that the changes in foot biomechanics may be due to the effects of estrogen on soft tissue and/or the brain,” said Adam Leigh Bryant, a senior lecturer at the University of Melbourne and lead author of the study.”
