leg stability and partially explain the increased risk for women. Shultz and colleagues (2001) identified differences in the timing of muscular recruitment within the quadriceps between men and women. When ligament loading occurs, women have been noted to experience increased muscle spasms and attenuated muscular function (Sbriccoli et al., 2005). Cao and colleagues (1998) have described the differences in gait response time between men and women. Collectively, these differences have been found to impact running gait due to significantly greater hip adduction, hip internal rotation, and knee abduction angle in women (Ferber et al., 2003). These differences have also resulted in greater risk for women participating in sports as well as a poorer ability to recover from a tripping (Wojcik et al., 2001).

Similar differences in neuromuscular functioning have been noted in the low back. Lindbeck and Kjellberg (2001) documented differences in the use of knee and trunk kinematics as a function of gender. These differences, when combined with the structural differences noted earlier, interact and result in differences in the magnitude and nature of spine loading (Marras et al., 2002, 2003). They may be further exacerbated by differences in personality, which are often gender related (Marras et al., 2000) as well as by the level and type of mental workload (Davis et al., 2002).

Race and Age Increasing age and white race are noted as risk factors for overall injury (Table 4-10), for injury resulting in hospital stays for disability and for discharges from the service as result of disability (Accessions Medical Standards Analysis and Research Activity, 2002). Sulsky and colleagues (2000) studied age as a risk factor for disabling knee injury and noted that the effect of age was very different for men and women. Non-Caucasians had a lower risk of knee injury (relative risk, RR, of 0.70 for men, 0.40 for women). In contrast, Launder studied hospitalizations for sports-related and training-related injuries and found the highest rates among younger age groups and black men.

The Accessions Medical Standards Analysis and Research Activity conducts routine analysis of the available data on first-term attrition. It reports a higher risk of hospital admission within a year of accession for older age groups (> age 30 versus ages 17-20, RR = 1.46, 95 percent CI: 1.34, 1.60). Similar relationships are observed for discharges for conditions “existing prior to service” and for discharge for disability. Relative to whites, blacks were at slightly higher risk of hospital admission within a year of accession (RR = 1.04; 95 percent CI: 1.01, 1.06) but at lower risk for discharges for conditions existing prior to service (RR = 0.76, 95 percent CI: 0.76, 0.80) and for disability discharge (RR = 0.80, 95 percent CI: 0.72, 0.89).

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