A number of studies conducted on female athletes have shown that they are twice likely to suffer from knee injuries like anterior cruciate ligament tears and severe pain than male athletes.

In previous researches, biomechanical differences were found to be the main cause of these problems. A recent study however, suggests another factor; changes in nerves, which control the activity of muscles, over menstrual cycle.

These findings may lead to the development of new remedies for preventing knee troubles in female athletes.

A brief on research

Higher-knee-InjuryResearchers Matthew Tenan, Lisa Griffin and Yi-Ling Peng belonging to the University of Texas-Austin, along with Anthony Hackney, of North Carolina-Chapel Hill University, measured the motor unit activity of the muscles and nerve fibers, which are controlled by them around the female participants’ knees, at different stages of menstruation cycle.

The seven volunteers were aged between 19 and 35 years. These women were asked to chart out their periodic cycles, by taking basal body temperature. Each volunteer was asked to visit her facility, five times at different points of her cycle. At every visit, the researchers inserted a thin wire electrode of hair’s width, into two of the muscles around a knee, of each volunteer. Using these electrodes, the researchers measured the motor unit activity in the muscles, while the women performed knee extensions.

Observations made

It was found that, during late luteal phase, which is one week prior to the onset of next period, the firing rates of these bundles, were much higher. This firing rate difference could have effect on the joint’s stability of a woman, making it potentially susceptible to injuries.

The outcome of the research showed significant variation in the pattern of motor unit firing across the participant’s menstrual cycle.

Tenan and his team of researchers noted that the rate of firing, as compared to earlier rates in the cycle, leaped higher during late luteal phase. It is however not clear whether these findings relate to differences in the rate of knee injuries at different phases in a cycle, which lays the basis for future studies. Tenan states that the motor unit activity changes could increase the vulnerability of women to injuries in general.


Tenan says “Our results suggest that muscle activation patterns are altered by the menstrual cycle. These alterations could lead to changes in rates of injury.”

He further adds that, these findings could possibly prompt a deeper study of neuroendocrine system, besides biomechanics as a probable factor for causing knee injuries among the female athletes.