Effects of covert subject actions on percent body fat by air-displacement plethsymography.

Air-displacement plethysmography (ADP) is used for estimation of body composition, however, some individuals, such as athletes in weight classification sports, may use covert methods during ADP testing to alter their apparent percent body fat. The purpose of this study was to examine the effect of covert subject actions on percent body fat measured by ADP. Subjects underwent body composition analysis in the Bod Pod following the standard procedure using the manufacturer's guidelines. The subjects then underwent 8 more measurements while performing the following intentional manipulations: 4 breathing patterns altering lung volume, foot movement to disrupt air, hand cupping to trap air, and heat and cold exposure before entering the chamber. Increasing and decreasing lung volume during thoracic volume measurement and during body density measurement altered the percent body fat assessment (p < 0.001). High lung volume during thoracic gas measures overestimated fat by 3.7 ± 2.1 percentage points. Lowered lung volume during body volume measures overestimated body fat by an additional 2.2 ± 2.1 percentage points. The heat and cold exposure, tapping, and cupping treatments provided similar estimates of percent body fat when compared with the standard condition. These results demonstrate the subjects were able to covertly change their estimated ADP body composition value by altering breathing when compared with the standard condition. We recommend that sports conditioning coaches, athletic trainers, and technicians administering ADP should be aware of the potential effects of these covert actions. The individual responsible for administering ADP should remain vigilant during testing to detect deliberate altered breathing patterns by athletes in an effort to gain a competitive advantage by manipulating their body composition assessment.

Submaximal treadmill test predicts VO2max in overweight children.

OBJECTIVE: To demonstrate the ability of a submaximal test to predict VO(2max) in overweight children. STUDY DESIGN: A total of 130 children, 11 to 14 years old, with body mass index >85 percentile for age and sex performed a submaximal walking test. VO(2max) was measured by using open circuit spirometry during a graded exercise test to volitional fatigue. An equation to predict VO(2max) was modeled by using the variables of sex, weight (kg), height (cm), heart rate (HR) after 4 minutes during the submaximal test (4minHR), HR difference (4minHR - resting HR), and submaximal treadmill speed (miles per hour [mph]) in 75% of the subjects. Validation was performed by using the remaining 25% of subjects. RESULTS: A total of 113 subjects achieved a maximal effort and was used in the statistical analysis. Development and validation groups were similar in all aspects. On validation, the mean square error was 241.06 with the predicted VO(2max) within 10% of the observed value in 67% of subjects. CONCLUSION: VO(2max) was accurately predicted in this cohort of overweight children by using a submaximal, treadmill-based testing protocol.

School-based exercise improves fitness, body composition, insulin sensitivity, and markers of inflammation in non-obese children.

BACKGROUND: Poor cardiovascular fitness (CVF) is a risk factor for obesity, as well as insulin resistance (IR), inflammation, and cardiovascular disease. We have previously shown that a school-based fitness curriculum can improve CVF, as well as IR and body composition in obese children. Whether such a program improves CVF, IR, and other health indicators in non-obese children is unresolved. AIM: To determine whether a school-based fitness program improves body composition, CVF, markers of inflammation (e.g. CRP, TNF-alpha, adiponectin), and insulin sensitivity in nonobese children. STUDY DESIGN: 35 non-obese middle school children with body mass index below the 95th percentile for age were enrolled in a 'fitness-oriented' gym class. Children underwent fasting evaluation of insulin, glucose, adiponectin, CRP, TNF-alpha, body composition by dual X-ray absorptiometry (DXA), and maximal VO2 treadmill testing at baseline (prior to the school year) and again at end of the school year. MAIN OUTCOME MEASURES: Testing for CVF (maximal VO2 treadmill testing), DXA, and fasting evaluation of insulin, glucose, adiponectin, CRP and TNF-alpha. RESULTS: Children demonstrated a decrease in BMI z-score (-0.14 +/- 0.33, p = 0.02), HOMA-IR (-0.15 +/- 0.35, p = 0.016), and TNF-alpha (-2.55 +/- 1.79 pg/ml, p < 0.001), and an increase in VO2(max) (+1.58 +/- 2.34 ml/kg/min, p < 0.001), adiponectin (+7,553 +/- 11,100 ng/ml, p < 0.001), and muscle mass (+2,282 +/- 1,882.73 g, p < 0.001) after nine months of study. CONCLUSIONS: The school-based fitness oriented curriculum resulted in improved body composition and insulin sensitivity, increased CVF, and decreased inflammation in non-obese children. Combined with prior studies, these data demonstrate that school-based fitness curricula can benefit both obese and non-obese children. Partnerships with schools to promote fitness should be part of a public health approach to improving children's health.

Measuring aerobic cycling power as an assessment of childhood fitness.

The emergence of obesity, insulin resistance, and type 2 diabetes in children requires a rational, effective public health response. Physical activity remains an important component of prevention and treatment for obesity, type 2 diabetes, and insulin resistance. Studies in adults show cardiovascular fitness to be more important than obesity in predicting insulin resistance. We recently demonstrated that a school-based fitness intervention in children who are overweight could improve cardiovascular fitness, body composition, and insulin sensitivity, but it remains unclear whether accurate assessment of fitness could be performed at the school or outside of an exercise laboratory. To determine whether new methodology using measurement of cycling power could estimate cardiovascular aerobic fitness (as defined by VO2max) in middle school children who were overweight. Thirty-five middle school children (mean age 12 +/- 0.4 years) who were overweight underwent testing on a power sensor-equipped Cycle Ops indoor cycle (Saris Cycling Group, Fitchburg, WI) as well as body composition by dual x-ray absorptiometry and VO2max by treadmill determination. Insulin sensitivity was also estimated by fasting glucose and insulin. Maximal heart rate (MHR) was determined during VO2max testing, and power produced at 80%MHR was recorded. Spearman's rank correlation was performed to evaluate associations. Mean power determined on the indoor cycle at 80% of MHR was 129 +/- 77 watts, and average power at 80% MHR divided by total body weight was 1.5 +/- 0.5. A significant correlation between watts and total body weight was seen for VO2max (P = 0.03), and significant negative correlation was seen between watts/total body weight and fasting insulin (P < 0.05). Among middle school children who were overweight, there was a significant relationship between the power component of fitness and cardiovascular aerobic fitness (measured by VO2max). This more accessible and less intimidating field-based measure of power may prove useful in predicting changes in cardiovascular fitness. Thus, accurate assessment of childhood aerobic fitness may be achievable by measurement of power, possibly within the school environment, at substantially less cost and effort than laboratory-based measurements.

Fitness is a stronger predictor of fasting insulin levels than fatness in overweight male middle-school children.

OBJECTIVE: We studied the relationship between % body fat (%BF), cardiovascular fitness (CVF), and insulin resistance (IR) in overweight middle-school children. STUDY DESIGN: Middle school children (n = 106, body mass index [BMI] > 95th percentile for age) underwent evaluation of body composition, maximal volume of oxygen utilization (VO2) uptake/kg lean body mass (VO2max/kgLBM), and fasting glucose and insulin (FI) concentrations and derived homeostasis model assessment index (HOMA(IR)). RESULTS: Both %BF (r = .33, P < .001) and VO2max/kgLBM (r = -0.42, P < .0001) were significantly correlated with FI. Bivariate regression analysis revealed %BF (P = .008 vs FI, P = .035 vs HOMA(IR)) and VO2max/kgLBM (P < .001 vs FI, P = .009 vs HOMA(IR)) to be independent predictors of insulin sensitivity. In males, VO2max/kgLBM was a better predictor of FI and HOMA(IR) than %BF. CONCLUSIONS: In obese middle-school children, both %BF and VO2max/kgLBM are independent predictors of FI levels. The relationship between CVF and FI levels was significant in both sexes but was particularly profound and stronger than %BF in males. Efforts to reduce risk of type 2 diabetes mellitus in an increasingly obese child population should include exercise intervention sustained enough to improve CVF.

School-based fitness changes are lost during the summer vacation.

OBJECTIVE: To determine the changes in percentage of body fat, cardiovascular fitness, and insulin levels during the 3-month summer break in overweight children enrolled in a school-based fitness program. STUDY DESIGN: Overweight middle-school children were randomized to a lifestyle-focused physical education class (treatment) or standard physical education class (control) for 1 school year (9 months; previously reported). This analysis reports changes during the 3-month summer break in children who participated in the fitness intervention group and who remained at this school the following year and repeated a fitness class. At the beginning and end of the school year, children underwent evaluation of (1) fasting levels of insulin and glucose, (2) body composition by means of dual x-ray absorptiometry, and (3) maximum oxygen consumption as determined by treadmill use. SETTING: Rural middle school and an academic children's hospital. PARTICIPANTS: Overweight middle-school children. INTERVENTION: School-based fitness curriculum, followed by summer break, and an additional year of school-based fitness intervention. MAIN OUTCOME MEASURES: Cardiovascular fitness test results (maximum oxygen consumption), body composition, and fasting insulin levels. RESULTS: Improvements seen during the 9-month school-year intervention in cardiovascular fitness, fasting insulin levels, and body composition were lost during the 3-month summer break. During this summer break, mean +/- SD fitness level decreased (maximum oxygen consumption, -3.2 +/- 1.9 mL/kg per minute; P = .007), fasting insulin level increased (+44 +/- 69 pmol/L [+6.1 +/- 9.7 mIU/mL]; P = .056), and percentage of body fat increased (+1.3% +/- 1.3%; P = .02) to levels that were similar to those seen before the school intervention. CONCLUSION: In obese middle-school children, school-based fitness interventions are an important vehicle for health promotion, but without sustained intervention, these benefits may be lost during the extended summer break.

DXA provides a valid minimum weight in wrestlers.

PURPOSE: To cross-validate the DXA prediction of minimum weight (MW) in high school wrestlers, using a criterion-referenced analysis. The goal was to independently evaluate whether DXA provided a MW within acceptable limits for the sport of wrestling. Secondarily, the DXA prediction error was compared against the currently approved skinfold (SF) method. METHODS: Criterion MW was calculated by hydrostatic weighing (HW) with measured residual lung volume. Whole-body scans were performed with a Norland XR-36 bone densitometer. All skinfolds were taken by the same experienced measurer. The subject's body density was computed by Lohman and was converted to percent body fat, using the equation of Brozek et al. The measured fat-free mass was used to calculate each wrestler's MW at 7% body fat. Subjects were 94 Wisconsin high school wrestlers (mean (SD): age = 15.1 yr (1.2), height = 170.3 cm (7.1), weight = 63.2 kg (9.6). RESULTS: There was no significant difference in mean MW from DXA (60.6 kg (9.0)) and the HW criterion (59.8 kg (9.0)). The correlation was strong (r = 0.98), and the regression for the relationship between HW and DXA (y = 0.976 x DXA + 0.698 kg) did not significantly deviate from the line of identity. A low standard error of estimate (SEE) of 1.7 kg and a pure error (PE) of 1.9 kg were found, with residuals ranging from -3.94 to 2.88 kg. This PE was similar to the SF method (2.1 kg) in the sample. Bland-Altman analysis showed no systematic bias in the prediction of MW across weight classes. CONCLUSION: We conclude that DXA provided a valid prediction of MW in this sample of high school wrestlers.

Innovative Assessments Help Elucidate Sustained Improvements in Fitness and Metabolic Health in Obese Children.

OBJECTIVE: Treatment of childhood obesity is a medical challenge and limited data are available describing successful long term interventions. This study presents a multi-disciplinary intervention that resulted in sustained physiological improvement over a one-year period. METHODS: The criterion outcome variables include cardiovascular fitness (CVF) measured by a population-specific treadmill test to predict maximal oxygen uptake (predicted VO2 max) and the body composition (BC) variables of fat mass, non-bone lean mass and percent body fat from whole body dual energy x-ray absorptiometry (DXA) scans. Subjects were overweight and obese children (N=79) evaluated at baseline, 6 and 12 months at a University Hospital-based pediatric fitness clinic. RESULTS: Statistically significant improvements in non-bone lean body mass (+4.24 kg ± 5.0, p<0.0001) and predicted VO2 max (+0.14L/min ± 0.10, p<0.0001) were seen at 6 months. These significant improvements were sustained over 12 months: body fat percentage (-2.28 ± 3.49, p<0.0001), lean mass (+6.0 kg ± 4.0, p<0.0001) and predicted VO2 max (+0.22 L/min ± 0.19, p<0.0001). These results were observed despite increases in weight and body mass index (BMI) at 6-months (weight: +6.6 kg ± 6.93, p<0.0001; BMI: +0.37 ± 1.21, p=0.47) and 12-months (weight: +6.3 kg ± 5.8, p<0.0001; BMI: +0.91 ± 2.06, p=0.0002). CONCLUSION: These results reflect the sustained effect of a multidisciplinary approach, and the value of using valid and reliable assessment methods to measure sustained physiological changes in a sample of 79 overweight and obese children.

Improvement of fitness, body composition, and insulin sensitivity in overweight children in a school-based exercise program: a randomized, controlled study.

BACKGROUND: Obesity and poor physical fitness constitute a health problem affecting an increasing number of children. Causes include a pervasive "toxic" environment that facilitates increased caloric intake and reduced physical activity. An effective strategy for prevention and treatment of childhood obesity likely includes a collaborative effort in the school setting. OBJECTIVE: To determine whether a school-based fitness program can improve body composition, cardiovascular fitness level, and insulin sensitivity in overweight children. DESIGN: Fifty overweight middle school children with a body mass index (BMI) above the 95th percentile for age were randomized to lifestyle-focused, fitness-oriented gym classes (treatment group) or standard gym classes (control group) for 9 months. Children underwent evaluation of fasting insulin and glucose levels, body composition by means of dual energy absorptiometry, and maximum oxygen consumption (V0(2)max) treadmill testing at baseline (before the school year) and at end of the school year. SETTINGS: Rural middle school and an academic children's hospital. MAIN OUTCOME MEASURES: Baseline test results for cardiovascular fitness, body composition, and fasting insulin and glucose levels. RESULTS: At baseline, there were no differences between groups before intervention (values for age, 12 +/- 0.5 years [all results, mean +/- SD]; BMI [calculated as weight in kilograms divided by the square of height in meters], 31.0 +/- 3.7; percentage of body fat, 36.5% +/- 4.6%; lean body mass, 41.4 +/- 8.6 kg; and V0(2)max, 31.5 +/- 5.1 mL/kg per minute). Compared with the control group, the treatment group demonstrated a significantly greater loss of body fat (loss, -4.1% +/- 3.4% vs -1.9% +/- 2.3%; P = .04), greater increase in cardiovascular fitness (V0(2)max, 2.7 +/- 2.6 vs 0.4 +/- 3.3 mL/kg per minute; P<.001), and greater improvement in fasting insulin level (insulin level, -5.1 +/- 5.2 vs 3.0 +/- 14.3 microIU/mL [-35.4 +/- 36.1 vs 20.8 +/- 99.3 pmol/L]; P = .02). CONCLUSIONS: Children enrolled in fitness-oriented gym classes showed greater loss of body fat, increase in cardiovascular fitness, and improvement in fasting insulin levels than control subjects. The modification to the school physical education curriculum demonstrates that small but consistent changes in the amount of physical activity has beneficial effects on body composition, fitness, and insulin levels in children. Partnering with school districts should be a part of a public health approach to improving the health of overweight children.

Is leg-to-leg BIA valid for predicting minimum weight in wrestlers?

BACKGROUND: The National Collegiate Athletic Association (NCAA) and several state associations require prediction of minimum weight (MW) for collegiate and high school wrestlers. The rule requires assessment of body composition before the competitive season to minimize unhealthy weight-loss practices. Leg-to-leg bioelectrical impedance analysis (BIA) has been suggested for use with wrestlers. PURPOSE: To evaluate leg-to-leg BIA against a four-component (4C) criterion to determine whether leg-to-leg BIA predicted MW within acceptable limits for the sport of wrestling. METHODS: Criterion MW was calculated by the 4C equation of Lohman (19) using independent measurement of body density (BD) by hydrostatic weighing, bone mineral content (BMC) by dual x-ray absorptiometry (DXA), and total body water (TBW) by deuterium dilution. Subjects were 57 wrestlers (mean +/- SD; age = 19.7 +/- 1.3 yr, height = 176.6 +/- 7.3 cm, weight = 77.7 +/- 12.4 kg). Hydration was confirmed by the NCAA guidelines. Accuracy, precision, and systematic bias were examined. RESULTS: Comparable mean values (72.2 +/- 9.7 vs 72.2 +/- 10.3 kg), a high correlation (r = 0.94), and a regression line similar to the line of identity were found between BIA and 4C. However, large individual differences and systematic bias were seen across the range of MW. BIA predicted MW within 3.5 kg 68% of the time and within 7.0 kg 95% of the time. MW residuals ranged from -10.4 kg to +6.9 kg. When using 2.0 kg as an acceptable cutoff for error, only 40% of the BIA values were within 2.0 kg of the criterion. CONCLUSION: Large individual variation was seen, and, by definition, the precision was poor when estimating MW for individuals. In practical terms, the prediction error may span multiple weight classes, thus making leg-to-leg BIA unacceptable for prediction of MW in this sample under the conditions of the study.

Multicomponent cross-validation of minimum weight predictions for college wrestlers.

UNLABELLED: In 1998, the National Collegiate Athletic Association (NCAA) adopted a rule requiring that skinfolds (SF) or hydrostatic weighing (HW) be used to estimate minimum weight (MW) in college wrestlers. PURPOSE: To cross-validate the NCAA methods for estimation of MW using a multicomponent criterion (4C). METHODS: Criterion MW was calculated from body density (BD), bone mineral content (BMC), and total body water (TBW) using the 4C equation of Lohman (1992). BMC was measured by dual energy x-ray absorptiometry (DXA), TBW by deuterium dilution, and BD by HW. Subjects were Division I athletes from the University of Wisconsin (mean +/- SD; N = 33, age = 19.5 +/- 1.3 yr, height = 177.3 +/- 7.8 cm, weight = 74.2 +/- 9.3kg). RESULTS: There was no significant difference between mean MW from HW (69.6 +/- 8.5 kg) and SF (70.1 +/- 8.3 kg) ( P = 0.113), and between mean MW from HW (69.6 +/- 8.5 kg) and 4C (69.5 +/- 8.6 kg) ( P = 0.46). A clinically small, yet significant difference was seen when comparing mean MW from SF to 4C ( P = 0.013). The regression for the relationship between 4C and HW (y = 0.994 x HW + 0.294 kg, R2 = 0.985) and 4C and SF (y = 1.019 x SF - 1.885 kg, R2 = 0.979) did not significantly deviate from the line of identity. Pure error (PE) values of 1.04 kg and 1.35 kg were found for HW and SF, respectively. The difference between the methods was plotted as a function of the 4C criterion. The regression line for HW and 4C (y = -0.009x + 0.743, r = -0.07, P = 0.69) and SF and 4C (y = -0.038x + 3.259, r = -0.27, P = 0.13) suggest that no systematic differences in the prediction were associated with the size of the criterion. CONCLUSION: These data support the NCAA methods of HW and SF to predict MW when cross-validated using a 4C criterion in this sample.

Minimum weight prediction methods cross-validated by the four-component model.

UNLABELLED: The National Collegiate Athletic Association (NCAA) requires prediction of minimum weight (MW) for collegiate wrestlers. The rule was implemented to minimize unhealthy weight loss practices and requires assessment of body composition before the competitive season. PURPOSE: This study cross-validated the body composition methods of dual energy x-ray absorptiometry (DXA), leg-to-leg bioelectrical impedance analysis (BIA), hydrostatic weighing (HW), and skinfolds (SF) for predicting MW using a four-component criterion (4C). METHODS: Criterion MW was calculated by the 4C model using independent measurement of body density (BD), bone mineral content (BMC), and total body water (TBW). Subjects were 53 Division I athletes from the University of Wisconsin (mean +/- SD; age = 19.7 +/- 1.3 yr, height = 176.2 +/- 7.4 cm, weight = 75.6 +/- 8.9 kg). Accuracy, precision, and systematic bias were examined in the predictions. RESULTS: There were no significant differences in mean MW from HW (70.5 +/- 7.3 kg, P = 0.57), SF (70.5 +/- 7.2 kg, P = 0.29) BIA (70.6 +/- 7.6 kg, P = 0.39), DXA (70.3 +/- 7.5, P = 0.97), and the 4C criterion (70.3 +/- 7.4 kg). The regression for the relationships between 4C and HW (y = 0.994 x HW + 0.077 kg), 4C and SF (y = 1.003 x SF-0.437 kg), 4C and DXA (y = 0.942 x DXA + 4.034 kg), and 4C and BIA (y = 0.896 x BIA + 6.987 kg) did not significantly deviate from the line of identity. Pure error (PE) values ranged from 1.34 kg for HW to 3.08 kg for BIA. CONCLUSION: Comparable means, high correlations, regression lines that did not significantly deviate from the line of identity, and no systematic bias were found. However, the methods differed widely in precision. The best precision, based on SEE and PE values, were seen in the HW and SF methods. In conclusion, this rigorous four-component cross-validation study supports the NCAA methods as the most accurate and precise MW prediction methods in this sample.

Hydration testing in collegiate wrestlers undergoing hypertonic dehydration.

UNLABELLED: Because dehydration (DEH) violates assumptions used in the assessment of body composition, hydration testing has become an integral part of minimal weight (MW) assessment. PURPOSE: To determine the accuracy of hydration tests for the detection and quantification of hypertonic DEH. METHODS: Twenty-five male collegiate wrestlers (mean +/- SD, age: 20.0 +/- 1.4 yr, height: 175.0 +/- 7.1 cm, body mass: 81.7 +/- 15.3 kg) had their hydration assessed under well-controlled conditions of euhydration (EUH) and DEH. The DEH phase occurred on the same day as EUH, after subjects acutely dehydrated 2-6% of body weight through fluid/food restriction and exercise in a hot environment. RESULTS: All hydration tests except plasma potassium significantly increased from EUH to DEH, and meaningful cutoff values could be established for most tests. Cutoff values for urine tests were 586 mOsm.L(-1) for osmolality and 71 mEq.L(-1) for potassium. Plasma cutoff values were 293 mOsm.L(-1) for osmolality, 140 mEq.L(-1) for sodium, 103 mEq.L(-1) for chloride, and 3.5 pg.mL(-1) for arginine vasopressin. For ratio tests, a urine:plasma osmolality of 2.06 and an extracellular:intracellular water of 0.533 measured by the bioelectrical impedance spectroscopy were cutoff values. For urine specific gravity, a cutoff value of 1.020 g.mL(-1) had a sensitivity and specificity of 96% each for the automated harmonic oscillation technique and 87% and 91% (respectively) for the dipstick technique. Protein (by dipstick) was detected in 5% of subjects in EUH, and 100% of subjects in DEH. Correlations between hydration tests and dehydration were only low to moderate. CONCLUSION: This study supports a specific gravity cutoff of 1.020 g.mL(-1) for the identification of hypertonic DEH. Future research should test the cutoff values established in this study and explore the relationship between DEH and urine protein.

An after-school exercise program improves fitness, and body composition in elementary school children.

Reduced cardiovascular fitness (CVF) is a risk factor for obesity and cardiovascular disease. It has previously shown that a school-based fitness curriculum can improve CVF, and other health indicators in middle school aged children. Whether an afterschool program improves CVF and other health markers in elementary-school children is unresolved. The objective of this study was therefore to determine whether an on-site afterschool-based fitness program improves body composition, cardiovascular fitness level, in elementary school children. 80 elementary school children were evaluated in a "fitness-oriented" afterschool program managed by the local YMCA. Children underwent evaluation of cardiovascular fitness by maximal VO2 treadmill testing and body composition by dual x-ray absorptiometry (DXA), at baseline (prior to the school-year) and again at end of the school year. Findings revealed that, at baseline, children had a mean age of 8.8 years, BMI of 18.7± 3, with a maximal VO2 of 40.03 ± 7.6 ml/kg/min, and percent body fat of 28.7 ± 7%. After a 9-month intervention, children maximal VO2 increased to 44.8 ± 7.5 ml/kg/min (p=0.04) and percent body fat decreased to 25.8 ± 6.2% (p=0.033). The study concluded that on-site afterschool programming focusing on fitness improved body composition and cardiovascular fitness, in elementary school children. Combined with prior studies, these data demonstrate that afterschool-based fitness curricula can benefit both obese and non-obese children. It was therefore recommended that, partnerships with schools to promote fitness even outside of school time should be a part of a school approach to improving children's health.

Bioelectrical impedance vs. four-compartment model to assess body fat change in overweight adults.

OBJECTIVE: The Tanita TBF-305 body fat analyzer is marketed for home and clinical use and is based on the principles of leg-to-leg bioelectrical impedance analysis (BIA). Few studies have investigated the ability of leg-to-leg BIA to detect change in percentage fat mass (%FM) over time. Our objective was to determine the ability of leg-to-leg BIA vs. the four-compartment (4C) model to detect small changes in %FM in overweight adults. RESEARCH METHODS AND PROCEDURES: Thirty-eight overweight adults (BMI, 25.0 to 29.9 kg/m2; age, 18 to 44 years; 31 women) participated in a 6-month, randomized, double-blind, placebo-controlled study of a nutritional supplement. Body composition was measured at 0 and 6 months using the Tanita TBF-305 body fat analyzer [using equations derived by the manufacturer (%FM(T-Man)) and by Jebb et al. (%FM(T-Jebb))] and the 4C model (%FM(4C)). RESULTS: Subjects in the experimental group lost 0.9%FM(4C) (p = 0.03), a loss that did not reach significance using leg-to-leg BIA (0.6%FM(T-Man), p = 0.151; 0.6%FM(T-Jebb), p = 0.144). We observed large standard deviations (SDs) in the mean difference in %FM between the 4C model and the Tanita(Manufacturer) (2.5%) and Tanita(Jebb) (2.2%). Ten subjects fell outside +/-1 SD of the mean differences at 0 and 6 months; those individuals were younger and shorter than those within +/-1 SD. DISCUSSION: Leg-to-leg BIA performed reasonably well in predicting decreases in %FM in this group of overweight adults but resulted in wide SDs vs. %FM(4C) in individuals. Cross-sectional determinations of %FM of overweight individuals using leg-to-leg BIA should be interpreted with caution.

Measuring aerobic cycling power as an assessment of childhood fitness.

The emergence of obesity, insulin resistance (IR), and type-2 diabetes (T2DM) in children requires a rational, effective public health response. Physical activity remains an important component of prevention and treatment for obesity, T2DM, and IR. Studies in adults show cardiovascular fitness (CVF) to be more important than obesity in predicting IR. We recently demonstrated that a school-based fitness intervention in children who were overweight can improve cardiovascular fitness, body composition, and insulin sensitivity, but it remains unclear whether accurate assessment of fitness could be performed at the school or outside of an exercise laboratory. The purpose of the study was to determine if a new methodology using measurement of cycling power could estimate cardiovascular aerobic fitness (as defined by maximum oxygen consumption; VO(2)max) in middle school children who were overweight. Thirty-five middle school children who were overweight (mean age 12 +/- 0.4 years) underwent testing on a power sensor- equipped Cycle Ops Indoor Cycle (IC), as well as body composition by dual x-ray absorptiometry (DXA), and VO(2)max by treadmill determination. Insulin sensitivity was also estimated by fasting glucose and insulin. Maximal heart rate (MHR) was determined during VO(2)max testing, and power produced at 80% of MHR was recorded. Spearman's rank correlation was performed to evaluate associations. Mean power determined on the IC at 80% of MHR was 129 +/- 77 watts, and average power at 80% MHR divided by total body weight (TBW) was 1.5 +/- 0.5. A significant correlation between watts/TBW was seen for VO(2)max (ml/kg/min) (p = 0.03), and significant negative correlation was seen between watts/TBW and fasting insulin (p < 0.05). In middle-school children who were overweight, there was a significant relationship between the power component of fitness and cardiovascular aerobic fitness (measured by VO(2)max). This more accessible and less intimidating field-based measure of power may prove useful in predicting changes in cardiovascular fitness. Thus, accurate assessment of childhood aerobic fitness may be achievable by measurement of power, possibly within the school environment at substantially less cost and effort than laboratory-based measurements.

Cross-validation of the NCAA method to predict body fat for minimum weight in collegiate wrestlers.

OBJECTIVE: In 1998, the National Collegiate Athletic Association (NCAA) adopted a new rule that required minimum weight testing for collegiate wrestlers. The objective of the study was to cross-validate the method used by the NCAA to estimate minimum weight in collegiate wrestlers. DESIGN: The NCAA skinfold equation was cross-validated against a criterion value from hydrostatic weighing (HW). SETTING The subjects were tested at the Universities of Wisconsin and Iowa. SUBJECTS: A sample of 93 college wrestlers from the Universities of Wisconsin and Iowa (mean +/- SD; age = 20.20 +/- 1.67 years, height = 171.98 +/- 6.63 cm, weight = 74.44 +/- 11.48 kg) were studied. OUTCOME MEASURES: Cross-validation included analysis of the standard error of estimate (SEE), total error (TE), and residual plots. RESULTS: The mean body fat from the NCAA prediction (10.61 +/- 3.58%) was not significantly different than HW (9.70 +/- 3.95%). The SEE was low (2.32%), and the TE was low (2.49%). The difference in methods was related to the size of the HW value. The residual plot (y = -0.26x + 3.45, R(2) = 0.198) suggests that fat is overestimated in the leaner wrestlers and underestimated in fatter wrestlers. CONCLUSION: The authors found the NCAA method to be a valid predictor of body fat in this sample of 93 collegiate wrestlers under the conditions of the study. Although some bias was seen across the range of fatness, these data support the NCAA method to estimate body fat in college wrestlers for establishment of minimum weight.

Grappling With Weight Cutting.

In response to a new state rule, the Wisconsin Minimum Weight Project was formed to curtail "weight cutting" among high school wrestlers. The project uses skinfold testing to determine a minimum competitive weight and nutrition education to help the wrestler diet safely. It serves as a model for other states and other sports.