Has anyone heard this before? That compared to men, women have weaker hamstrings and stronger quads, and this sets them up for ACL tears? Men's hams and quads tend to be more balanced, but females quads fill out more beginning at around age 15 and are stronger for their bodyweight than men's quads.
A friend who is a female college athlete was recently diagnosed with an ACL injury, which luckily is not a tear. She just has to recover and take it easy for a few weeks and is seeing a PT.
The PT commented that it might be her overdeveloped quads which caused the injury. She explained that this is common: women tend to have stronger quads and weaker hamstrings than men. Female soccer players in particular tend to develop very large, strong quads in order to compensate for the wider angle of their hips, and their hamstrings are in turn are too weak to balance out the quads. ACL tears may occur due to the high degree torque exerted by the quads when jumping or cutting. She proposed that female athletes need to work more on the hamstrings to balance out the strength of their quads.
According to the PT, the quads are supposed to be no more than 30% stronger than the hamstrings for optimal bio mechanics. She also said that it used to be thought that women had weak hamstrings, but recent findings provide evidence that it is actually the quads that are too strong, and that this is due to the way the female's quads respond to the higher degree of mechanical stress generated by the greater "Q-angle" between the hips and kness. She said that it has been known for decades that the average woman has roughly 75% the quad strength and only 55% of the hamstring strength of the average man. But what previous studies failed to account for is that average men are significantly taller and heavier than the average woman. Once normalized or adjusted for bodyweight and amount of lean mass, she said that woman have on average 90% of the hamstring strength and, get this, 120% the quadricep strength that men have. In other words, their hamstrings are nearly as strong as those of men of a similar bodyweight, while their quads are actually 20% stronger than men's quads. Thus, these female athletes have overdeveloped quads for their bodyweight, and that is what produces the torque that ruptures the ACL. Combined with the fact that the ACL is attached at a steeper angle, this is a potential recipe for injury. Intuitively, she said this might also be the scientific basis for the old wives tale that women's legs are overall stronger. They're actually not, of course, but women's quadriceps specifically do tend to be stronger, and it wasn't until some new type of ballistic strength measurement that they found out. She says the fact that females have longer thighs and shorter lower legs than men in proportion to height may also play a role in being susceptible to ACL tears.
These are some snips from articles that the PT gave my friend that explain how and why females become prone to overdeveloped quads and thus ACL injuries:
"Initial findings from the MSU study come down on the side of estrogen fluctuations playing little role in the increased incidence of ACL injuries. However, the study had other interesting outcomes, including that the quadriceps muscle group on the front of the thigh acted with greater strength as the lower leg flexed backward than previous research suggested would be the case. The quadriceps worked to balance the efforts of the hamstrings as the knee was flexed."
"While boys continue to grow mostly vertically through the end of development, girls' bodies undergo some major changes starting around the beginning of high school. In lay terms the process is generally referred to as "filling out," but the source of more womanly curves isn't just about gaining padding in a few key spots. Structurally, the female pelvis begins to widen during adolescence, changing the alignment of bones from the hip down. This is the reason, said Lewellen, that many high school-aged girls appear knock-kneed. The imbalance in the pelvis forces the knees in, strengthening the muscles of the outer thigh while leaving the inner thigh underdeveloped."
"Women have a disproportionally large percentage of quadriceps muscle mass versus the hamstring."
"Strength differences: Women develop a greater fat-to-lean-muscle-mass ratio than men. They also typically have stronger quadriceps muscles than men, creating an imbalance."
"Women’s quadriceps muscles (front of the thigh) are significantly stronger than their hamstrings (back of the thigh). This imbalance puts strain on the ligaments."
"Also studies have shown that women’s quadriceps are much stronger than their hamstrings when compared to men. This could mean that even when the hamstrings are activating correctly, they are simply not strong enough to counter-act the strength of the quads."
"Another contributing factor to women’s knee injuries is an imbalance between their quadriceps and hamstrings muscles. Generally, the quadriceps are too strong and the hamstrings too weak. This imbalance causes weak knees."
"According to Dr. Ahmad adolescent girls tend to develop quadriceps strength without a corresponding increase in hamstring strength. When very strong quads overpower the hamstrings, an imbalance occurs, leading to stress on the ACL."
"Women soccer players probably have the highest incidence of [ACL tears] of anybody because they have such strong quadriceps, and women - when they land or cut - seem more quadricep dependent rather than hamstring dependent. Shaffer said what that does is pull the shin bone forward out from underneath the thigh bone, creating a larger risk to tear."
"Women tend to have wider hips, causing their thigh muscles to meet their knees at a slightly wider angle than men's do. Women's quadriceps tend to be stronger on the outside than the inside, which can pull the kneecap outward."
"The next time you around a female (or if you are a female) take a side view of the knee joint. Most likely, a woman standing in a straight leg position will be slightly to moderately hyper-extending her knee. The reason? Her quads are disproportionately stronger than her hamstrings. While this can happen with guys too, females are most at risk for having weaker hamstrings with strong quads. It not only looks kinda weird, this unmatched strength ratio can cause a number of problems."
"When I read this I was reminded of research that Cosgrove and others have cited about knee injuries and female athletes. The upshot is that everyone's quadriceps start out stronger than their hamstrings; over time, however, a male athlete will become less quad-dominant (disproportionately stronger in the quadriceps than the glutes and hamstrings), whereas, unless they are given specific exercises to address the imbalance, women tend to become even more quad-dominant with training. This accounts, at least in part, for the large number of ACL tears among female athletes."
A friend who is a female college athlete was recently diagnosed with an ACL injury, which luckily is not a tear. She just has to recover and take it easy for a few weeks and is seeing a PT.
The PT commented that it might be her overdeveloped quads which caused the injury. She explained that this is common: women tend to have stronger quads and weaker hamstrings than men. Female soccer players in particular tend to develop very large, strong quads in order to compensate for the wider angle of their hips, and their hamstrings are in turn are too weak to balance out the quads. ACL tears may occur due to the high degree torque exerted by the quads when jumping or cutting. She proposed that female athletes need to work more on the hamstrings to balance out the strength of their quads.
According to the PT, the quads are supposed to be no more than 30% stronger than the hamstrings for optimal bio mechanics. She also said that it used to be thought that women had weak hamstrings, but recent findings provide evidence that it is actually the quads that are too strong, and that this is due to the way the female's quads respond to the higher degree of mechanical stress generated by the greater "Q-angle" between the hips and kness. She said that it has been known for decades that the average woman has roughly 75% the quad strength and only 55% of the hamstring strength of the average man. But what previous studies failed to account for is that average men are significantly taller and heavier than the average woman. Once normalized or adjusted for bodyweight and amount of lean mass, she said that woman have on average 90% of the hamstring strength and, get this, 120% the quadricep strength that men have. In other words, their hamstrings are nearly as strong as those of men of a similar bodyweight, while their quads are actually 20% stronger than men's quads. Thus, these female athletes have overdeveloped quads for their bodyweight, and that is what produces the torque that ruptures the ACL. Combined with the fact that the ACL is attached at a steeper angle, this is a potential recipe for injury. Intuitively, she said this might also be the scientific basis for the old wives tale that women's legs are overall stronger. They're actually not, of course, but women's quadriceps specifically do tend to be stronger, and it wasn't until some new type of ballistic strength measurement that they found out. She says the fact that females have longer thighs and shorter lower legs than men in proportion to height may also play a role in being susceptible to ACL tears.
These are some snips from articles that the PT gave my friend that explain how and why females become prone to overdeveloped quads and thus ACL injuries:
"Initial findings from the MSU study come down on the side of estrogen fluctuations playing little role in the increased incidence of ACL injuries. However, the study had other interesting outcomes, including that the quadriceps muscle group on the front of the thigh acted with greater strength as the lower leg flexed backward than previous research suggested would be the case. The quadriceps worked to balance the efforts of the hamstrings as the knee was flexed."
"While boys continue to grow mostly vertically through the end of development, girls' bodies undergo some major changes starting around the beginning of high school. In lay terms the process is generally referred to as "filling out," but the source of more womanly curves isn't just about gaining padding in a few key spots. Structurally, the female pelvis begins to widen during adolescence, changing the alignment of bones from the hip down. This is the reason, said Lewellen, that many high school-aged girls appear knock-kneed. The imbalance in the pelvis forces the knees in, strengthening the muscles of the outer thigh while leaving the inner thigh underdeveloped."
"Women have a disproportionally large percentage of quadriceps muscle mass versus the hamstring."
"Strength differences: Women develop a greater fat-to-lean-muscle-mass ratio than men. They also typically have stronger quadriceps muscles than men, creating an imbalance."
"Women’s quadriceps muscles (front of the thigh) are significantly stronger than their hamstrings (back of the thigh). This imbalance puts strain on the ligaments."
"Also studies have shown that women’s quadriceps are much stronger than their hamstrings when compared to men. This could mean that even when the hamstrings are activating correctly, they are simply not strong enough to counter-act the strength of the quads."
"Another contributing factor to women’s knee injuries is an imbalance between their quadriceps and hamstrings muscles. Generally, the quadriceps are too strong and the hamstrings too weak. This imbalance causes weak knees."
"According to Dr. Ahmad adolescent girls tend to develop quadriceps strength without a corresponding increase in hamstring strength. When very strong quads overpower the hamstrings, an imbalance occurs, leading to stress on the ACL."
"Women soccer players probably have the highest incidence of [ACL tears] of anybody because they have such strong quadriceps, and women - when they land or cut - seem more quadricep dependent rather than hamstring dependent. Shaffer said what that does is pull the shin bone forward out from underneath the thigh bone, creating a larger risk to tear."
"Women tend to have wider hips, causing their thigh muscles to meet their knees at a slightly wider angle than men's do. Women's quadriceps tend to be stronger on the outside than the inside, which can pull the kneecap outward."
"The next time you around a female (or if you are a female) take a side view of the knee joint. Most likely, a woman standing in a straight leg position will be slightly to moderately hyper-extending her knee. The reason? Her quads are disproportionately stronger than her hamstrings. While this can happen with guys too, females are most at risk for having weaker hamstrings with strong quads. It not only looks kinda weird, this unmatched strength ratio can cause a number of problems."
"When I read this I was reminded of research that Cosgrove and others have cited about knee injuries and female athletes. The upshot is that everyone's quadriceps start out stronger than their hamstrings; over time, however, a male athlete will become less quad-dominant (disproportionately stronger in the quadriceps than the glutes and hamstrings), whereas, unless they are given specific exercises to address the imbalance, women tend to become even more quad-dominant with training. This accounts, at least in part, for the large number of ACL tears among female athletes."
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