in the review of Jones and coworkers (1994) between BMI and exercise-related injuries, including stress fracture of the lower extremities. Some support exists for a bimodal relationship between BMI and injury risk, with subjects who have either high or low BMIs at greater injury risk.¹ In their study, Jones and coworkers (1992) reported a gender difference in injury risk, with men showing the aforementioned bimodal distribution related to BMI while risk was significantly increased only in women with low BMI. The authors hypothesized that injury-prone women with low body fat may not have adequate FFM to support their weight without ''undue stress." Kowal (1980) has published data on the nature and causes of women's injuries that occurred as part of an endurance training program. Higher weight and percent body fat, possibly secondary to lack of prior fitness, were significantly related to increased incidence of injury during training.

Fatness influences fitness because excessive adiposity may add a functionally inert component of weight that must be carried during various physical activities. According to Friedl (1997), the absence of grossly obese soldiers has limited the ability of the military to demonstrate strong relationships between fatness and physical performance. Nevertheless, when Conway and colleagues (1989) examined the association between circumference-derived fatness measures in Navy men and women and measures of physical fitness, significant negative correlations were observed between fatness and physical fitness measures that tended to be greater in magnitude than the associations observed between body weight/height indices and physical fitness. In another study of Navy personnel, Beckett and Hodgdon (1987) evaluated fatness in active-duty women and found a negative association between underwater weighing-derived fat mass and two measures of fitness and endurance: box carrying capacity and running performance. A study of male and female Canadian Forces troops (for whom BMI was used as an index of body fat until body fat standards were eliminated in 1992²) found a strong association between increasing BMI (> 25) and decreasing fitness and performance (except for grip strength) (Jette et al., 1990). The complex associations among fatness, fitness, and health are demonstrated by the study of Marchitelli and colleagues (1995), in which women who exceeded the fat standard after 8 weeks of basic combat training had lower high density lipoprotein levels, increased cardiovascular risk, and significantly increased 2-mi run times (that is, lower endurance) but were significantly stronger (as measured by performance on machine lift and bench press, for example) than their less fat counterparts. A potential explanation for greater strength accompanying increased levels of fatness is that heavier women may have a larger FFM.