Over the past 25 years, women’s participation in sports has increased six-fold. Unfortunately, these increases have been outpaced by even more dramatic increases in certain sports-related injuries among women. Female runners are twice as likely to experience patellofemoral pain syndrome (anterior knee pain), iliotibial band friction syndrome, and tibial stress fractures as compared to male runners (Taunton et al, 2002). Researchers have hypothesized that differences in anatomical structure, muscular strength and flexibility, and running biomechanics may predispose female runners to these injuries.
It is believed that differences in anatomical structure may lead to different running biomechanics, which in turn place women at greater risk for injury compared to male runners. Several researchers have measured a wider pelvis, a more adducted hip position (thigh collapsed inwards), greater hip internal rotation range of motion, and a more knock-kneed (genu valgum) alignment in women compared to men (Horton & Hall, 1989; Simoneau et al, 1998). Consequently, women runners also demonstrate significantly greater peak hip adduction, hip internal rotation, and greater knee genu valgus angle while running compared to male runners (Ferber et al., 2003; Malinzak et al., 2001). In addition, these researchers have also reported that the hip muscles controlling the amount of hip adduction and internal rotation in female runners are under greater eccentric loading while running compared to men.
Over time, repetitive stress to these hip muscles can increase the incidence of musculoskeletal injury in female runners. For example, the iliotibial band (a thick band of tissue that extends from the lateral thigh down over the knee) functions to control the amount of hip adduction and minimize the rotational forces experienced at the hip and knee. Since female runners demonstrate a greater hip adduction and internal rotation angle while running, excessive forces at the hip and knee can result over time and iliotibial band friction syndrome may develop (Ferber et al., 2003).
The structural combination of greater pelvic width, increased hip adduction and internal rotation, and knee genu valgum may explain, in part, the well-documented larger Qangle measured in women compared to men (Livingston, 1998). The Q-angle, or quadriceps angle, is the angle of pull the quadriceps (thigh) muscles have on the patella (knee cap). Tiberio (1987) suggested that a greater Q-angle, combined with greater hip internal rotation angle while running, may result in malalignment of the patella. For example, an increased Q-angle can pull the patella to the outside of the knee. The patella will experience greater contact forces and this may play a role in the increased incidence of patellofemoral pain syndrome that women runners experience (Mizuno et al, 2001; Messier et al, 1991). In addition, Cowan et al. (1996) suggested that a Q-angle greater than 15° increases frontal plane motion and ground reaction forces experienced in the lower leg and thus increases the incidence of tibial stress fractures which are also more common in female runners.
Now that key anatomical and biomechanical factors have been identified as to why female runners are at greater risk for running-related injuries, the question remains of how to prevent injuries. Core stability training has been shown to be highly effective in preventing lower extremity injuries (Clark et al., 2000). The lumbar, pelvis and hip region together are considered to be the core of the body. When the core is functioning efficiently, advantageous length:tension relationships are maintained, allowing the runner to produce strong movements in the extremities.
Core stability training may be particularly important for the female runner because weakness in the core could alter running biomechanics and exacerbate factors that are believed to contribute to injury. For example, weakness of the hip abductor and external rotator muscles could result in a greater hip adduction and hip internal rotation angles while running. Thus, these muscles would be under greater amounts of loading while running and increase the likelihood of injury. In addition, weakness of these hip muscles has been hypothesized to cause tightness in the iliotibial band which significantly contributes to the development of iliotibial band friction syndrome (Clark et al., 2000).
Various programs are available and are specifically designed for improving core stability. Most notably are Pilates, Yoga, Swiss ball and medicine ball exercises. Regardless of the specific exercise program initiated for core stabilization training, the training program should be systematic, progressive, and functional to produce the best outcome. However, consultation with a trained health professional can help to identify whether improvements in core stability, increases in muscular flexibility or alterations in running biomechanics are the proper course of action. After all, a proactive approach to identify which factors need improvement is the best way to avoid injury.
References available on request.