Fitness, Conditioning May Reduce Leg Injuries - Menstrual Irregularities A Risk

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Fitness, Conditioning May Reduce Leg Injuries - Menstrual

Irregularities A Risk Factor In Stress Fractures

http://www.medicalnewstoday.com/medicalnews.php?newsid=52038

Physically active women with lower aerobic fitness and poorer overall

fitness may be at greater risk for stress fractures and other lower-

extremity overuse injuries. A new study released by the American

College of Sports Medicine (ACSM) also found that many women who

suffered lower extremity stress fractures had previously experienced

a lower extremity non-stress fracture overuse injury. The research

was published in the September issue of Medicine & Science in Sports

& Exercise®, the official journal of ACSM.

Researchers led by J. Rauh, Ph.D., P.T., M.P.H., also noted

that menstrual irregularities (six or more consecutive missed menses

during the past 12 months) quadrupled the likelihood of a lower-

extremity stress fracture during training. " This underscores the

importance of bone health for active women, " said Rauh. He recommends

early screening efforts to identify women with a history of menstrual

irregularity, followed by proper medical management.

The study involved 824 female recruits at the Parris Island Marine

Corps Recruit Depot in South Carolina. The women, whose average age

was 18, completed a questionnaire that included demographic

information as well as injury history, physical activity and fitness

practices, and menstrual history. Measurements of height and weight

allowed researchers to calculate the body mass index (BMI) for each

participant. Researchers assessed each recruit's aerobic fitness

through a 1.5-mile timed run conducted before the start of training.

During the 13 weeks of Marine Corps basic training, 399 of 824 women

(48.4 percent) incurred 868 lower-extremity overuse injuries.

Investigators calculated risk of injury per training day exposure

(TDE), defined as any day in which the recruit was not held out of

training activity because of an injury and was at risk of sustaining

a lower-extremity stress fracture or non-stress fracture overuse

injury. The 868 injuries over 68,686 TDE yielded a rate of 12.6 per

1,000 TDE. The rate for initial overuse injuries (399 over 46,061

TDE) was 8.7 per 1,000 TDE and the rate for subsequent overuse

injuries (469 over 22,625 TDE) was 20.7 per 1,000 TDE. The most

common injuries involved the shin, calf, knee, or hip.

" The overall rate of lower extremity subsequent overuse injury was

more than double that for initial lower extremity overuse injury, "

said Rauh. " Further, once injured with a stress fracture, the female

recruit was three-and-one-half times more likely to suffer a

subsequent stress fracture. " Although the study did not specifically

examine possible causes for the greater likelihood of reinjury, Rauh

said injured recruits:

- May alter their gait to compensate for an injury

- May fatigue more rapidly, predisposing them to subsequent injury

- May have a diminished ability to adapt to new or repeated stressors

After controlling for other potential risk factors, women in the

slowest quartile in the timed run (taking more than 14.4 minutes to

run 1.5 miles) were 3.3 times more likely to suffer a lower-extremity

stress fracture than those in the fastest quartile (12.5 minutes or

less). Women who had participated in weight-training activities on a

consistent basis for seven or more months were less likely to incur a

stress fracture. " Given the high injury rate among recruits who were

less fit, " said Rauh, " there may be benefit in having recruits

participate in aerobic and strength-training programs on a consistent

basis at least seven months prior to basic training. "

Rauh said overall injury rates in this study were comparable to those

noted in previous research. However, the opportunity to measure

injuries against training day exposure allowed calculation of risk

per TDE. " To our knowledge, " he noted, " this is the first study to

assess lower-extremity stress fracture and non-stress fracture

overuse injury rates using this method of exposure in female

recruits. "