Body composition assessment in athletes with spinal cord injury: comparison of field methods with dual-energy X-ray absorptiometry.

STUDY DESIGN: Cross-sectional. OBJECTIVES: To compare relative body fatness (%Fat) estimates from field methods (skinfold thickness measurement (SKF) and bioelectrical impedance analysis (BIA)) with measures by dual-energy X-ray absorptiometry (DXA). SETTING: University of Illinois, Urbana-Champaign, IL, USA. METHODS: Field methods used both three- and seven-site SKF prediction equations and BIA generalized, spinal cord injury (SCI)-specific and athlete-specific equations. DXA was used as the reference method. College-aged varsity athletes with SCI (women=8, men=8; time since injury 16.2+/-5.7 years; injury level range T5-L5) were recruited. RESULTS: Mean BMI was 20.8+/-2.6 and 22.5+/-2.1 kg m(-2), and mean DXA %Fat was 31.9+/-3.8 and 20.6+/-8.4%, for women and men, respectively. All field methods under-predicted the %Fat when compared with DXA (ranges in mean differences: SKF women 2.9-8.2%, SKF men 6.9-12.4%; BIA women 0.5-3.9%, BIA men 0.3-7.0%). None of the field methods accurately predicted the %Fat compared with DXA (total error (TE): SKF women 7.4-12.1%, SKF men 8.4-15.2%; BIA women 5.1-9.3%, BIA men 6.7-10.7%). Of the SKF and BIA prediction equations, Evans et al.'s three-site SKF (r=0.95, P<0.001, standard error of the estimate (SEE)=2.8 %Fat) prediction equation provided the best fit for this population. CONCLUSION: Further studies with larger samples are necessary to develop appropriate prediction equations for field methods in the athletic SCI population.

Location of body fat and body size impacts DXA soft tissue measures: a simulation study.

OBJECTIVE: The aim of this study was to determine the ability of dual X-ray absorptiometry (DXA) to detect exogenous fat in men and women simulating typical sex-specific weight changes. SUBJECTS: A diverse sample including 29 elderly (52-83 years) and 61 young (18-40 years) individuals (45 women, 45 men) of varying body mass index (BMI; M+/-s.d.: 26.1+/-4.9 kg/m2, range=16.4-39 kg/m2). METHODS: Whole body (WB) DXA scans (Hologic QDR 4500A) were completed with Scan 1 performed as a normal baseline scan, Scan 2 with 1 kg packet of lard placed on each thigh and Scan 3 with two 1 kg lard packets placed on the abdomen (men) or chest and abdomen (women). RESULTS: Measurement error of fat mass (FM) was more pronounced in the trunk as lard packets were detected with 59% accuracy (error=0.82+/-0.42 kg, P<0.001), whereas 94% of thigh lard (error=0.11+/-0.45 kg, P<0.001) was determined to be FM, while the remainder in both conditions was determined to be mineral free lean mass. Initial FM (r=0.37, P<0.001) for thigh loading and trunk bone mineral content (r=0.30, P<0.01) for trunk-loaded conditions had the most impact on measurement error of WB FM. CONCLUSIONS: Regional differences impact measurement error of simulated changes in FM with greater measurement error in the trunk compared to the thigh region and initial FM and higher levels of bone mineral content in the trunk region impacting error.

The association between regional body composition and metabolic outcomes in athletes with spinal cord injury.

STUDY DESIGN: Cross-sectional study comparing athletes with spinal cord injury (SCI) and age and body mass index matched able-bodied controls (AB). OBJECTIVE: To examine the impact of exercise training on the relation between whole body, regional and intermuscular adipose tissue (IMAT) and glucose tolerance, insulin action and lipid profile. SETTING: University Research Laboratory, USA. METHODS: Fourteen college-aged athletes with SCI (seven men; duration of injury 16.5+/-5.7 years, level of injury T5-L5) and 17 sedentary AB (eight men) were assessed for body composition via dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging. Insulin sensitivity index (ISI) was determined via 2-h oral glucose challenge; standard lipid profile was determined from fasting blood samples. RESULTS: Although ISI was 30% higher in SCI, there were no significant differences between groups in glucose and insulin responses or in lipid measures. Adjusting for absolute and relative thigh IMAT area, fasting insulin (13.8+/-5.3 microIU, 16.3+/-5.6 microIU; P<0.05; SCI vs AB respectively) and ISI (4.0+/-1.4, 3.1+/-1.3; P<0.05) were significantly better among SCI athletes compared to AB. Measures of adiposity did not correlate with glucose response or most lipid measures. Within SCI and AB, respectively, ISI correlated strongly (all P<0.05) with absolute (r = -0.70, -0.54) and relative IMAT (r = -0.54, -0.50), than with trunk (r = -0.62, -0.64) and whole body fat mass (r = -0.61, -0.64). CONCLUSION: Habitual physical activity can maintain insulin sensitivity in SCI compared to sedentary AB controls. Total body fat mass, central adiposity and thigh IMAT appear to impact risk for metabolic disease in SCI individuals with IMAT playing a larger role in SCI than AB.