A study by Jette and coworkers (1990b) examined the relationship between BMI and measures of fitness and strength among Canadian Forces personnel (17,098 men and 2,087 women) stratified into five BMI zones (<20, 20–25, 25–27, 27–30, and > 30). In this population, 50 percent of the men and 25 percent of the women had BMI greater than 25, while 26 percent of the men and 12 percent of the women had BMI greater than 27. The study showed that over the entire range of BMI, predicted VO₂max decreased as BMI increased for both men and women. Scores on the push-up test were lower for the two highest women's BMI groups (> 27) than for the lower BMI groups, and for the sit-up test, the scores were lower for the three highest BMI groups of women (> 25). In contrast, grip strength tended to increase with BMI. Thus, except for grip strength, fitness test performance decreased with increasing BMI. In this study, BMI was significantly associated with weight-height ratio and waist-hip ratio, all predictors of fatness. Thus, according to this study, increased fatness appears to be associated with poorer performance on fitness tests.

The use of current military PFTs as indicators of ability to perform a job, as acknowledged by Vogel and Friedl (1992), Hodgdon (1992), Robertson and Trent (1985) and others presents a problem; it is that the majority of the military's physically demanding MOSs involve occasional to frequent lifting and carrying, also known as manual material handling. Thus the capacity to lift and carry is a significant aspect of military task performance. Although little association has been found between body fat and lifting capacity, numerous military studies have demonstrated a strong association between FFM and lifting capacity (strength) (Beckett and Hodgdon, 1987; Harman and Frykman, 1992; Vogel and Friedl, 1992). A study of recruits in BCT found that women who failed the body fat standard performed better on measures of strength than those who passed. When these same women were stratified into those who exceeded and those who passed the weight-for-height standard (Sharp et al., 1994), the difference was even more pronounced; women who failed the weight-for-height standard performed significantly better on several measures of lifting and carrying than did those who were within the standard. In the study by Westphal and coworkers (1995), increased waist-hip ratio also was found to predict significantly increased strength in a torque performance test but was not a significant factor in other strength measures. The implication of these studies is that, clearly for women, increased weight for height and waist-hip ratio are associated with higher FFM, which is associated with greater strength.

Although strength is recognized as a vital component of military performance and fitness, controversy still exists regarding how to measure this aspect of fitness in a valid way, particularly in a field situation (Vogel and Friedl, 1992). This controversy also exists for civilian tests of task performance. Sit-ups and push-ups are used to measure strength on the Army PFT. Although Army PFT scores for push-ups and sit-ups correlated well with strength and load carriage performance in the study of Westphal et al. (1995), none of the Army PFT tasks correlated well with the power or muscle strength tasks. Westphal and coworkers (1995) and other military researchers (for example, Harman and Frykman, 1992; Sharp et al., 1994) have recommended the use of