Maj. Vancil McNulty
U.S. Army Center for Health Promotion and Preventive Medicine
The reasons why women get injured at twice the rate of men are not entirely understood.
Gender differences in anatomy, hormones and biomechanics act singularly or together to increase the risk of injury.
Civilian studies have shown that collegiate female basketball and soccer players are two to three times more likely to injure the anterior cruciate ligament of the knee when compared to men.
Biomechanical studies also have demonstrated reduced ability of the lower spine to handle compressive loading in females. This finding may, in part, predispose females to lower back injury while running, marching with a load or jumping from military vehicles.
Getting back into exercise after pregnancy is also a challenge for a woman. A study showed female Soldiers have a harder time returning to pre-pregnancy fitness and passing physical training tests within the currently allotted time of six months.
Military studies from varying countries consistently show that females suffer a much higher rate of stress fractures to the leg, thigh and hip. This finding suggests a biomechanical or physiological difference between male and female bone resistance to stress and fatigue.
Low bone density has been shown to be a risk factor for stress fractures. Young females who do not participate in load impact exercise (running, jumping, gymnastics, etc.) as they physically mature have lower bone density in the lower extremities.
While one might conclude that women are injured more often primarily because of structural and physiologic differences, the actual reason may have much more to do with physical fitness level.
Low fitness levels, particularly aerobic fitness, as well as prior inactivity, are risk factors for injury. Women typically enter military training at lower levels of physical fitness than men, and about twice the numbers of women than men fail the initial basic training fitness test.
A study of Fort Jackson basic trainees showed that those who failed the initial Army Physical Fitness Test were twice as likely to be discharged for physical reasons. However, when low-fit recruits were involved in a preconditioning program prior to basic training, attrition reduced, and they tended to have lower injury risk when compared with recruits of similar low fitness who did not precondition.
Other risk factors also contribute to injury risk in a military training environment. Data strongly links smoking to a significant increase for an exercise-related musculoskeletal injury.
Age greater than 25 has also been shown to increase likelihood of injury. Women who are at the high and low extremes of BMI (body mass index, a calculation of the ratio of your body weight to your height) have been shown to have a greater risk of injury.
Having a previous injury, especially ankle sprains, has an increased risk of re-injury.
Several “take home” points will help in preventing injuries in women:
•Young girls should be encouraged to perform weight-bearing exercise in the formative growth years to maximize peak bone mass to prevent stress fracture in later life.
•The less fit are much more likely to incur an injury during military training. Inability to pass the aerobic portion of a physical fitness test is a good indicator to determine if a service member is fit.
•A gradual run progression up to 30 minutes, no more than three times a week, is safe guidance. Frequency and duration may vary by fitness level and fitness goals. Fitness programs should also include core stability (multi-joint) strength exercises versus just running.
Based on BMI surveillance, overweight women should lose weight and underweight women should gain weight, as these groups tend to have a higher injury risk in military training environments. To calculate your BMI go to www.nhlbisupport.com/bmi.
•Women six to nine months post-partum should focus on low-intensity exercise, such as walking, and return to jogging after about four to eight weeks. Runs should be brief (five to 10 minutes) and progressively increase over six to 12 months. Fitness tests should probably be taken eight to 12 months postpartum.
•Smoking will increase the risk of an exercise-related injury. Smoking should be discouraged due both to short- and long-term health benefits.
(Editor’s Note: Maj. Vancil McNulty is the staff physical therapy officer at the U.S. Army Center for Health Promotion and Preventive Medicine.)