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Thigh Muscle Activity and the Female Knee

Female athletes have many more injuries to the anterior cruciate ligament (ACL) of the knee than male athletes. Studies have shown that women college soccer and basketball players have two to four times as many ACL injuries as men. And among professional basketball players, women have 10 times more ACL injuries than men. ACL injuries are especially serious. They often require surgery and intense rehabilitation. And they force many injured athletes to give up their sports.

No one is exactly sure why women suffer so many ACL injuries. It is known that the thigh muscles help stabilize the knee joint during start-and-stop sports like basketball and soccer. These researchers tested the muscle activity of male and female college athletes during exercise. They wanted to see if the thigh muscles worked differently when doing intense extension and flexion exercises.

The results showed that the men's quadriceps muscles (in the front of the thigh) produced much more force than the women's. But the women's quadriceps muscles showed greater activity during knee bending actions, which the authors think could be a factor in putting added strain on the ACL. Women also seemed to have less "fast-twitch" muscle in the hamstrings. Less fast-twitch muscle could make this muscle slower to react in cutting and quick-stop situations, putting more demand on the ACL.

Taken together, all these differences suggest that female athletes need to pay special attention to their hamstring muscles in their strength training. The hope is that stronger and quicker hamstring muscles would decrease women athletes' risk of ACL injury.

References: Klane K. White, et al. EMG Power Spectra of Intercollegiate Athletes and Anterior Cruciate Ligament Injury Risk in Females. In Medicine & Science in Sports & Exercise. March 2003. Vol. 35. No. 3. Pp. 371-376.

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