The Effect of an Acute After-School Exercise Bout on Percentage of Body Fat Using Leg-to-Leg Bioelectrical Impedance Analysis in Children

In the past 30 years, the prevalence of obesity among children and adolescents has tripled in the United States (Hedley et al., 2004; Ogden, Flegal, Carroll, & Johnson, 2002). Obesity has been associated with significant health problems in the pediatric age group and is an important risk factor for adult morbidity and mortality (Eriksson et al., 1999; Gunnell, Frankel, Nanchahal, Peters, & Smith, 1998; Must, Jacques, Dallas, Bajema & Dietz, 1992). Effective strategies for prevention and treatment include interventions that target changes in body composition; however, the effectiveness of these programs requires valid tools to track change. Bioelectrical impedance analysis (BIA) is a fast, easy to administer, and relatively inexpensive method of evaluating body composition. Due to the ease of operation, interest in using BIA to estimate percentage of body fat (%BF) has grown, especially in settings where body composition assessments are often performed without the benefit of properly-trained personnel (e.g., school districts). Extremely popular are the relatively new legto-leg bioelectrical impedance analysis (LBIA) devices that measure body composition as the individual stands on a bathroom-like scale. The LBIA method introduces a low level electrical current into the body and measures the lower-body impedance, or resistance, to the current flow (Nunez et al., 1997). From impedance, fat-free mass and %BF can be estimated using equations developed for adults and children (Heyward & Wagner, 2004). A few studies have examined the validity of LBIA to assess body composition in children, and their findings are inconsistent (Goldfield et al., 2006; Lazzer, Boirie, Meyer, & Vermorel, 2003; Tyrrell et al., 2001). Tyrrell et al. (2001) found a high correlation (r = .94) between LBIA and dual-energy X-ray absorptiometry (DXA) in estimating %BF in primarily normal weight children, ages 5–10 years. Two other studies showed significant correlations but large intraperson variation when comparing LBIA to DXA in overweight or obese adolescents (Lazzar et al., 2003) and preadolescents (Goldfield et al., 2006). Although preliminary, these data indicate the validity of LBIA may vary as a function of adiposity. To increase the accuracy of LBIA measurement it is recommended that individuals perform no exercise within 12 hr of assessment to control for fluctuations in hydration status (Heyward & Wagner, 2004). Such a restriction would significantly reduce the usability of these analyzers in schools and clinical sites where controlling a child’s preassessment behavior would be unrealistic. Several studies have examined the effect of acute aerobic exercise on LBIA-measured %BF estimates in children. Minimal but significant reductions in %BF have been reported following maximal cycle ergometry (Goss et al., 2003) and submaximal intermittent treadmill exercise (Andreacci, Dixon, Ledezma, & Goss, 2006). In addition, Andreacci, Dixon, Lagomarsine, et al. (2006) reported The Effect of an Acute After-School Exercise Bout on Percentage of Body Fat Using Leg-to-Leg Bioelectrical Impedance Analysis in Children