Residual volume on land and when immersed in water: effect on percent body fat

There is a large residual volume (RV) error when assessing percent body fat by means of hydrostatic weighing. It has generally been measured before hydrostatic weighing. However, an individual's maximal exhalations on land and in the water may not be identical. The aims of this study were to compare residual volumes and vital capacities on land and when immersed to the neck in water, and to examine the influence of the measurement error on percent body fat. The participants were 20 healthy Japanese males and 20 healthy Japanese females. To assess the influence of the RV error on percent body fat in both conditions and to evaluate the cross-validity of the prediction equation, another 20 males and 20 females were measured using hydrostatic weighing. Residual volume was measured on land and in the water using a nitrogen wash-out technique based on an open-circuit approach. In water, residual volume was measured with the participant sitting on a chair while the whole body, except the head, was submerged . The trial-to-trial reliabilities of residual volume in both conditions were very good (intraclass correlation coefficient > 0.98). Although residual volume measured under the two conditions did not agree completely, they showed a high correlation (males: 0.880; females: 0.853; P < 0.05). The limits of agreement for residual volumes in both conditions using Bland-Altman plots were -0.430 to 0.508 litres. This range was larger than the trial-to-trial error of residual volume on land (-0.260 to 0.304 litres). Moreover, the relationship between percent body fat computed using residual volume measured in both conditions was very good for both sexes (males: r = 0.902; females: r = 0.869, P < 0.0001), and the errors were approximately -6 to 4% (limits of agreement for percent body fat: -3.4 to 2.2% for males; -6.3 to 4.4% for females). We conclude that if these errors are of no importance, residual volume measured on land can be used when assessing body composition.     

Validity and reliability of body composition assessed by the sulphur hexafluoride dilution method

The aims of this study were to assess the validity and reliability of body volume and percent body fat determined by sulphur hexafluoride dilution, using underwater weighing as the criterion method, and to determine the influence of the magnitude of body volume. Thirty-one healthy Japanese individuals aged 18-27 years (16 males: height 1.70 +/- 0.06 m, mass 64.8 +/- 7.7 kg; 15 females: height 1.60 +/- 0.05 m, mass 55.2 +/- 6.2 kg; mean +/- s) participated in the study. Sulphur hexafluoride dilution measures the concentration of sulphur hexafluoride gas in the chamber (BSF-200, Shimazu Corp.). Underwater weighing was performed five times using a weight scale (AD-6204, A&D) after residual volume had been determined (System9, Minato Medical Corp.). There were no significant differences in the mean between two trials for body volume, body density or percent body fat determined by sulphur hexafluoride dilution. The intra-class correlation coefficient of these variables ranged from 0.985 to 0.999. The results suggest that sulphur hexafluoride dilution is a reliable method for assessing body composition. There was no significant difference in body volume or percent body fat between sulphur hexafluoride dilution (males: 61.3 +/- 7.6 litres, 18.4 +/- 6.7%; females: 52.8 +/- 6.9 litres, 21.0 +/- 8.9%) and underwater weighing (males: 60.6 +/- 7.0 litres, 15.6 +/- 3.5%; females: 53.0 +/- 6.5 litres, 23.7 +/- 6.1%) and there was a high correlation between the two (r = 0.997, P < 0.05). A Bland-Altman plot of the difference between percent body fat estimated by underwater weighing and sulphur hexafluoride dilution versus average percent body fat by the two methods showed no systematic difference (mean difference = -0.12 +/- 6.6 kg). The upper and lower limits of agreement were 13.2% and -13.4%, respectively. Determination by sulphur hexafluoride dilution resulted in both over- and underestimations in body volume and the difference between the two body volumes (determined by underwater weighing and by sulphur hexafluoride dilution) was inversely proportional to the mean body volume by the two methods. This suggests that improvements need to be made to the device or to the technique to maintain a constant volume of sulphur hexafluoride in the chamber.     

Editorial

The aims of this study were to assess the validity and reliability of body volume and percent body fat determined by sulphur hexafluoride dilution, using underwater weighing as the criterion method, and to determine the influence of the magnitude of body volume. Thirty-one healthy Japanese individuals aged 18-27 years (16 males: height 1.70 - 0.06 m, mass 64.8 - 7.7 kg; 15 females: height 1.60 - 0.05 m, mass 55.2 - 6.2 kg; mean - s) participated in the study. Sulphur hexafluoride dilution measures the concentration of sulphur hexafluoride gas in the chamber (BSF-200, Shimazu Corp.). Underwater weighing was performed five times using a weight scale (AD-6204, A&;D) after residual volume had been determined (System9, Minato Medical Corp.). There were no significant differences in the mean between two trials for body volume, body density or percent body fat determined by sulphur hexafluoride dilution. The intra-class correlation coefficient of these variables ranged from 0.985 to 0.999. The results suggest that sulphur hexafluoride dilution is a reliable method for assessing body composition. There was no significant difference in body volume or percent body fat between sulphur hexafluoride dilution (males: 61.3 - 7.6 litres, 18.4 - 6.7%; females: 52.8 - 6.9 litres, 21.0 - 8.9%) and underwater weighing (males: 60.6 - 7.0 litres, 15.6 - 3.5%; females: 53.0 - 6.5 litres, 23.7 - 6.1%) and there was a high correlation between the two ( r = 0.997, P ? 0.05). A Bland-Altman plot of the difference between percent body fat estimated by underwater weighing and sulphur hexafluoride dilution versus average percent body fat by the two methods showed no systematic difference (mean difference =- 0.12 - 6.6 kg). The upper and lower limits of agreement were 13.2% and-13.4%, respectively. Determination by sulphur hexafluoride dilution resulted in both over- and underestimations in body volume and the difference between the two body volumes (determined by underwater weighing and by sulphur hexafluoride dilution) was inversely proportional to the mean body volume by the two methods. This suggests that improvements need to be made to the device or to the technique to maintain a constant volume of sulphur hexafluoride in the chamber.     

A comparison of men's and women's strength to body mass ratio and varus/valgus knee angle during jump landings

The purpose of this investigation was to compare valgus/varus knee angles during various jumps and lower body strength between males and females relative to body mass. Seventeen recreationally active females (age: 21.94 ± 2.59 years; height: 1.67 ± 0.05 m; mass: 64.42 ± 8.39 kg; percent body fat: 26.89 ± 6.26%; squat one-repetition maximum: 66.18 ± 19.47 kg; squat to body mass ratio: 1.03 ± 0.28) and 13 recreationally active males (age: 21.69 ± 1.65 years; height: 1.77 ± 0.07 m; mass: 72.39 ± 9.23 kg; percent body fat: 13.15 ± 5.18%; squat one-repetition maximum: 115.77 ± 30.40 kg; squat to body mass ratio: 1.59 ± 0.31) performed a one-repetition maximum in the squat and three of each of the following jumps: countermovement jump, 30 cm drop jump, 45 cm drop jump, and 60 cm drop jump. Knee angles were analysed using videography and body composition was analysed by dual-energy X-ray absorptiometry to allow for squat to body mass ratio and squat to fat free mass ratio to be calculated. Significant differences (P ≤ 0.05) were found between male and female one-repetition maximum, male and female squat to body mass ratio, and male and female squat to fat free mass ratio. Significant differences were found between male and female varus/valgus knee positions during maximum flexion of the right and left leg in the countermovement jump, drop jump from 30 cm, drop jump from 45 cm, and drop jump from 60 cm. Correlations between varus/valgus knee angles and squat to body mass ratio for all jumps displayed moderate, non-significant relationships (countermovement jump: r = 0.445; drop jump from 30 cm: r = 0.448; drop jump from 45 cm: r = 0.449; drop jump from 60 cm: r = 0.439). In conclusion, males and females have significantly different lower body strength and varus/valgus knee position when landing from jumps.     

Is bioelectrical impedance spectroscopy accurate in estimating changes in fat-free mass in judo athletes?

Abstract Bioelectrical impedance spectroscopy (BIS) provides an affordable and practical assessment of fat-free mass (FFM). However, little information is available on the assessment of changes in fat-free mass in top-level athletes using BIS. The aim of this study was to examine the accuracy of BIS in tracking changes in fat-free mass of elite male judo athletes from a period of weight stability to just before competition, using the four-compartment model (4C model) as reference method. In total, 27 elite male judo athletes (age 22.2?±?2.8 years) were evaluated. Measures of body volume assessed by air displacement plethysmography, bone mineral content by dual-energy X-ray absorptiometry, and total-body water assessed with deuterium dilution were used in a 4C model. Fat-free mass was also assessed by BIS (FFM(BIS)). Changes in FFM(BIS) were not significantly different from measured by the reference method (P?=?0.000). Furthermore, the r (2) was 0.62 and the standard error of the estimate was 1.03 kg. The limits of agreement ranged from -3.36 to 2.59 kg with no bias observed. These findings demonstrate the viability of BIS as a valid tool for tracking fat-free mass in elite male judo athletes. However, based on the wide limits of agreement observed, BIS is less valid at an individual level for tracking fat-free mass in these athletes.     

Classification of obesity varies between body mass index and direct measures of body fat in boys and girls of Asian and European ancestry

Body mass index is a common proxy for proportion of body fat. However, body mass index may not classify youth similarly across ages and ethnicities. We used sex- and ethnic-specific receiver operating characteristic curves to determine how obesity classifications compared between body mass index and dual energy x-ray absorptiometry-based body fat percent. Male and female participants 9- to 18-years-old (n = 944; 487 female) were measured 1 to 13 times (1999–2012; 4,411 observations). Body mass index identified < 50% of those classified as obese from body fat percent. Specificity was 99.7%, and sensitivity was 35.8%. Using area under the curve and standard error values, body mass index performed significantly better for: Male versus female at 10 years, Asian versus European female except at 13-, 15-, and 16-years-old, Asian female versus male except at 10- and 15-years-old, and for European male versus female, 9- to 11-years-old (p < .05). Our findings provide evidence that users of body mass index should use caution when comparing body mass index across age, sex, and ethnicity.     

Reliability and agreement between DXA-derived body volumes and their usage in 4-compartment body composition models produced from DXA and BIA values

Two research groups recently produced equations for estimation of body volume from dual-energy x-ray absorptiometry (DXA) scans. These body volume estimates can be used for body composition evaluation in modified 4-compartment models. In the present analysis, the reliability of body volume calculations, as well as their usage in 4-compartment models, was explored while employing precise scheduling of assessments and dietary standardization. Forty-eight recreationally active males and females completed two pairs of identical assessments, which included a DXA scan and single-frequency bioelectrical impedance analysis. Each assessment within a pair was separated by 24 hours, during which participants were provided a standardized diet. Body volume and 4-compartment equations were applied to the data, and metrics of reliability and agreement were calculated for body volume and 4-compartment components. While both body volume equations demonstrated excellent reliability individually, substantial disagreement between equations was present when utilized in 4-compartment equations. The magnitude of this disagreement was 4.3 kg for lean mass and fat mass and 6.9% for body fat percentage. At present, the large discrepancies in body composition components when using existing body volume equations preclude their interchangeability and demonstrate the need for continued exploration of the utility of body volume estimates.     

Determination of body composition based on hydrostatic weighing without head submersion for Japanese young adults

Abstract

The purpose of this study was to examine the accuracy and reliability of whole-body volume, body density, and percent body fat calculated from body volume without the head (V _NH), as assessed by hydrostatic weighing without head submersion and predicted head volume (pV _H) based on head parameters, as compared with standard hydrostatic weighing. Participants comprised 29 males and 27 females aged 17–26 years. Head volume was predicted from anthropometric head parameters using a prediction equation. Underwater weights with/without head submersion were measured five times. The reliability of underwater weighing without head submersion was very good (intraclass correlation coefficient: males=0.998, females=0.998) as was that for traditional head submersion. The relationship between the sum of V _NH and pV _H and the whole-body volume measured by hydrostatic weighing was very high (males=0.998, females=0.999), and their values were very similar with an error range of 300–400 ml. Although percent body fat assessed from the sum of V _NH and pV _H showed a slight scatter of 2–3% from the identity line of percent body fat assessed by hydrostatic weighing, the relationships for both sexes were very strong (males=0.918, females=0.957). The errors (2 standard deviations) as determined by Bland-Altman plots between the two methods were ?3.2 to 2.6% in males and ?2.3 to 2.8% in females. There was no significant bias in percent body fat estimated by the two methods (hydrostatic weighing with/without head submersion), and the sum of V _NH and pV _H could validly estimate body composition, regardless of physical size. It is suggested that hydrostatic weighing without head submersion is a valid and convenient alternative technique.     

Effect of immersion on lung capacities and volumes: implications for the densitometric estimation of relative body fat

Immersion of 18 male subjects in water caused a 20.4% (787 ml) increase (P less than 0.05) in the mean inspiratory capacity (IC) whereas there were no changes (P greater than 0.05) in tidal volume (VT) and the frequency of respiration. All the means for the other pulmonary variables decreased (P less than 0.05) by varying amounts: total lung capacity (TLC) = 8.4% (599 ml), vital capacity (VC) = 5.5% (308 ml), functional residual capacity (FRC) = 42.6% (1386 ml), expiratory reserve volume (ERV) = 61.9% (1095 ml) and residual volume (RV) = 19.7% (292 ml). Variation of only the RV in the body density (BD) formula from which the percentage body fat (%BF) is estimated resulted in a significantly (P less than 0.05) lower mean of 15.2% BF for the RV in air (means = 1482 ml) compared with that of 17.1% BF for the RV in water (means = 1190 ml). All but one of the subjects exhibited a smaller RV in water than in air; the six largest differences were equivalent to 2.4-5.1% BF. These results indicate that the net effect of the hydrostatic pressure (decreases RV), pulmonary vascular engorgement (decreases RV) and diminished compliance (increases RV) is to reduce the ventilated RV. It is therefore advisable to measure the RV when the subject is immersed in order to minimize error in the determination of BD and hence the estimation of % BF.     

Is bioelectrical impedance spectroscopy accurate in estimating changes in fat-free mass in judo athletes?

Abstract

Bioelectrical impedance spectroscopy (BIS) provides an affordable and practical assessment of fat-free mass (FFM). However, little information is available on the assessment of changes in fat-free mass in top-level athletes using BIS. The aim of this study was to examine the accuracy of BIS in tracking changes in fat-free mass of elite male judo athletes from a period of weight stability to just before competition, using the four-compartment model (4C model) as reference method. In total, 27 elite male judo athletes (age 22.2 ± 2.8 years) were evaluated. Measures of body volume assessed by air displacement plethysmography, bone mineral content by dual-energy X-ray absorptiometry, and total-body water assessed with deuterium dilution were used in a 4C model. Fat-free mass was also assessed by BIS (FFM_BIS). Changes in FFM_BIS were not significantly different from measured by the reference method (P = 0.000). Furthermore, the r ² was 0.62 and the standard error of the estimate was 1.03 kg. The limits of agreement ranged from ?3.36 to 2.59 kg with no bias observed. These findings demonstrate the viability of BIS as a valid tool for tracking fat-free mass in elite male judo athletes. However, based on the wide limits of agreement observed, BIS is less valid at an individual level for tracking fat-free mass in these athletes.     

Assessing Body Composition of Children and Adolescents Using Dual-Energy X-Ray Absorptiometry,Skinfolds, and Electrical Impedance

To determine the validity and reliability of percent body fat estimates in 177 boys and 154 girls between 12–17 years of age, percent body fat was assessed once using dual-energy X-ray absorptiometry and twice using the sum of two skinfolds and three bioelectrical impedance analysis devices. The assessments were repeated on 79 participants on a second day. The agreement between the percent body fat estimates from the four prediction methods and dual-energy X-ray absorptiometry was evaluated using Bland–Altman analyses and a mixed linear model. All methods were reliable within and between days. The sum of two skinfolds (±6.8% body fat), OMRON (OMRON Healthcare Inc., Vernon Hills, Illinois, USA) bioelectrical impedance analysis (0 ± 7.3% body fat), and TANITA 521 (TANITA Corporation, Tokyo, Japan) bioelectrical impedance analysis (±7.6% body fat) had wide prediction intervals and are acceptable for use in large population-based studies. The TANITA 300A bioelectrical impedance analysis is not recommended for use in children and adolescents due to its wide prediction interval (±8.1% body fat) and large bias. A criterion method should be used when the accurate assessment of body composition of an individual is critical.     

Analysis of the body composition of Paralympic athletes: Comparison of two methods

Body composition is a physiological variable associated with physical activity and, in some cases, is related to athletic performance. Our objectives were to describe the body composition of participants in three distinct Paralympic sports and to compare the values of body density and estimated body fat obtained from the Paralympic athletes on the National Team by air-displacement plethysmography (ADP) and by the anthropometric method (skinfolds (SFs)). The sample consisted of 70 volunteers of both genders. The body composition of the volunteers was evaluated using the ADP in a Bod Pod^® and seven SFs. There were no significant differences between the values obtained by ADP and SF for body fat percentage (p?=?.58) and body density (p?=?.49). Analysis by Bland–Altman plots showed mean differences of 0.56?±?4.94 (?9.12–10.23) and ?0.0017?±?0.0113 (?0.024–0.020) for body fat percentage and body density, respectively. In conclusion, body composition analyses of Paralympic athletes by the ADP and SF methods show similar results, and ADP should be used as the first option when available. When the use of ADP is not possible, estimating body density and fat percentage by SF is a viable alternative for Paralympic athletes when future comparisons will use the same analysis method.     

The accuracy and precision of DXA for assessing body composition in team sport athletes

Abstract

This study determined the precision of pencil and fan beam dual-energy X-ray absorptiometry (DXA) devices for assessing body composition in professional Australian Football players. Thirty-six professional Australian Football players, in two groups (fan DXA, N = 22; pencil DXA, N = 25), underwent two consecutive DXA scans. A whole body phantom with known values for fat mass, bone mineral content and fat-free soft tissue mass was also used to validate each DXA device. Additionally, the criterion phantom was scanned 20 times by each DXA to assess reliability. Test–retest reliability of DXA anthropometric measures were derived from repeated fan and pencil DXA scans. Fat-free soft tissue mass and bone mineral content from both DXA units showed strong correlations with, and trivial differences to, the criterion phantom values. Fat mass from both DXA showed moderate correlations with criterion measures (pencil: r = 0.64; fan: r = 0.67) and moderate differences with the criterion value. The limits of agreement were similar for both fan beam DXA and pencil beam DXA (fan: fat-free soft tissue mass = ?1650 ± 179 g, fat mass = ?357 ± 316 g, bone mineral content = 289 ± 122 g; pencil: fat-free soft tissue mass = ?1701 ± 257 g, fat mass = ?359 ± 326 g, bone mineral content = 177 ± 117 g). DXA also showed excellent precision for bone mineral content (coefficient of variation (%CV) fan = 0.6%; pencil = 1.5%) and fat-free soft tissue mass (%CV fan = 0.3%; pencil = 0.5%) and acceptable reliability for fat measures (%CV fan: fat mass = 2.5%, percent body fat = 2.5%; pencil: fat mass = 5.9%, percent body fat = 5.7%). Both DXA provide precise measures of fat-free soft tissue mass and bone mineral content in lean Australian Football players. DXA-derived fat-free soft tissue mass and bone mineral content are suitable for assessing body composition in lean team sport athletes.     

Body fat measurement in elite sport climbers: Comparison of skinfold thickness equations with dual energy X-ray absorptiometry

Abstract

The aim of this study was to compare equations for estimating percentage body fat from skinfold thickness in elite sport climbers by assessing their agreement with percentage body fat measured using dual-energy X-ray absorptiometry (DXA). Skinfold thickness was measured in a convenience sample of 19 elite sport climbers [9 women and 10 men; mean age 31.2 years (s = 5.0) and 28.6 years (s = 3.6), respectively]. Percentage body fat was estimated using 17 different equations, and it was also measured by DXA. A significant inter-methods difference was observed for all equations, except for Durnin's equation in men (inter-methods difference: ?0.57% and ?0.29%; 1.96 s: 5.56 and 5.23 for Siri's and Brozek's equation, respectively) and women (inter-methods difference: ?0.67% and ?1.29% for Siri's and Brozek's equation, respectively), and for Wilmore's equation using Siri's body fat equation in women (inter-methods difference: ?1.86%). In women, the limits of agreement were lower when using Durnin's equation compared with Wilmore's equation (1.96 s: 3.86% and 5.13%, respectively). In conclusion, of the 17 studied equations, Durnin's equation was the most accurate in estimating percentage body fat in both male and female elite climbers. Therefore, Durnin's equation could be used to assess percentage body fat in elite sport climbers if more accurate methods are not available. The generalizability of the results is limited by the fact that the sample was not selected at random.     

Effects of age, walking speed, and body composition on pedometer accuracy in children

The objective of this study was to investigate the effects of age group, walking speed, and body composition on the accuracy of pedometer-determined step counts in children. Eighty-five participants (43 boys, 42 girls), ages 5-7 and 9-11 years, walked on a treadmill for two-minute bouts at speeds of 42, 66, and 90 m x min(-1) while wearing a spring-levered (Yamax SW-200) and a piezoelectric (New Lifestyles NL-2000) pedometer. The number of steps taken during each bout was also recorded using a hand counter Body mass index (BMI) was calculated from height and mass, and percentage of body fat (%BF) was determined using hand-to-foot bioelectrical impedance analysis. The tilt angle of the pedometer was assessed using a magnetic protractor. Both pedometers performed well at 66 and 90 m x min(-1), but undercounted steps by approximately 20% at 42 m x min(-1). Although age group, BMI, waist circumference, and %BF did not affect pedometer accuracy, children with large pedometer tilt angles (> or =10 degrees) showed significantly greater percent bias than those with small tilt angles (< 10 degrees). We suggest that the style of waistband on the child's clothing is a more important determinant of tilt angle and thus pedometer accuracy than body composition. Our results also indicate that the NL-2000 pedometer provides similar accuracy and better precision than the SW-200 pedometer, especially in children with large tilt angles. We conclude that fastening pedometers to a firm elastic belt may improve stability and reduce undercounting in young people.     

Determination of muscle activity during running at reduced body weight

The aim of this study was to investigate how lower extremity muscles are influenced by body weight support during running at different speeds. Nine participants (age 24 ± 2 years, height 1.75 ± 0.12 m, mass 73.5 ± 15.7 kg) ran at 100%, 115%, and 125% of preferred speed at 100%, 90%, 80%, 70%, and 60% of body weight on a treadmill that provided body weight support. Preferred speed was self-selected by each participant and represented a speed that he or she could sustain if going for a 30 min run. Electromyography (EMG) data were recorded (1000 Hz, 1 min) from the bicep femoris, rectus femoris, tibialis anterior, and gastrocnemius for each condition together with knee angle (electrogoniometer). Average and root mean square EMG were calculated across 30 s. Muscle patterns were determined by smoothing (low-pass filter, 4 Hz) and extracting patterns for 49 cycles defined by consecutive maximum knee flexion angles. Repeated-measures analyses of variance were used to compare average and root mean square across body weight and speeds. Correlations were computed between the 100% speed/100% body weight condition and all other conditions per muscle. There was no interaction between body weight and speed (P > 0.05). Average and root mean square decreased as body weight decreased for all muscles (P < 0.05) and increased across speeds for all muscles (P < 0.05). Correlations for all muscles between conditions were high (range: 0.921-0.999). Although a percent reduction in body weight did not lead to the same reduction in muscle activity, it was clear that reducing body weight leads to a reduction in muscle activity with no changes in muscle activity patterns.     

Childhood single skinfold thickness is a better predictor for adult relative fat mass in females than the body mass index: Data from a 30-year longitudinal growth study

Abstract

Information on the prediction of adult relative fat mass (percent body fat,%BF) using measures from pre-pubertal ages and early childhood is scarce. In the present longitudinal study, we assess the development of different anthropometric indicators of percent body fat during childhood, adolescence, and adulthood in 37½-year-old females stratified for low and high percent body fat. Consequently, we study the predictability of percent body fat based on simple anthropometric measurements during childhood and adolescence.

Anthropometric data from the Belgian longitudinal experimental growth study “LEGS” were used. Beginning in 1969, five yearly cohorts of about 100 individuals each (mean age 6 years) were recruited in public kindergartens. Of the original 515 participants (260 males, 255 females) that were measured annually from age 6 to 18 years, 59 males and 60 females agreed to participate in a follow-up study in 2004. During the follow-up measurements, the participants were invited for a body-composition assessment by bioelectrical impedance analysis (BIA). We stratified the participants into low (%BF-BIA < 35%) and high (%BF-BIA≥35%) relative fat mass samples. Pearson correlations were calculated and used as tracking coefficients. Multiple stepwise linear regression was applied with anthropometric variables at each age separately as predictors for adult percent body fat, expressed as%BF-BIA, %BF-Segal, and %BF-D&W (Durnin & Womersley, 1974).

The results indicate that a single skinfold thickness during adolescence is a better predictor for adult percent body fat than adolescent body mass index. Additionally, our results suggest that this holds during childhood as early as from age 8 onwards. The use of single skinfold measurements as predictors for adult adiposity and obesity is supported by other arguments, including: (1) body mass index as a proxy for overweight does not discriminate between fat mass and fat-free mass, and (2) an excess of adipose tissue is more strongly associated with morbidity than the body mass index.     

Effect of body composition on oxygen uptake during treadmill exercise: body builders versus weight-matched men.

Oxygen uptake (VO2) during treadmill exercise is directly related to the speed and grade, as well as the participant's body weight. To determine whether body composition also affects VO2 (ml.kg-1.min-1) during exercise, we studied 14 male body builders (M weight = 99 kg, SD = 7; M height = 180 cm, SD = 8; M body fat = 8%, SD = 3; M fat free mass = 91 kg, SD = 7) and 14 weight-matched men (M weight = 99 kg, SD = 9; M height = 179 cm, SD = 5; M body fat = 24%, SD = 5; M fat free mass = 73 kg, SD = 9). Percentage of body fat, t(13) = 8.185, p < .0001, and fat free mass, t(13) = 5.723, p < .0001, were significantly different between groups. VO2 was measured by respiratory gas analysis at rest and during three different submaximal workrates while walking on the treadmill without using the handrails for support. VO2 was significantly greater for the lean, highly muscular men at rest: 5.6 +/- 1 vs. 4.0 +/- 1 ml.kg-1.min-1, F(1, 26) = 21.185, p < .001; Stage 1: 1.7 mph/10%, 18.5 +/- 2 vs. 16.1 +/- 2 ml.kg-1.min-1, F(1, 26) = 6.002, p < .05; Stage 2: 2.5 mph/12%, 26.6 +/- 3 vs. 23.1 +/- 2 ml.kg-1.min-1, F(1, 26) = 7.991, p < .01; and Stage 3:3.4 mph/14%, 39.3 +/- 5 vs. 33.5 +/- 5 ml.kg-1.min-1, F(1, 26) = 7.682, p < .01, body builders versus weight-matched men, respectively. However, net VO2 (i.e., exercise VO2 - rest VO2) was not significantly different between the two groups at any of the matched exercise stages. The findings from this study indicate that VO2 during weight-bearing exercise performed at the same submaximal workrate is higher for male body builders compared to that measured in weight-matched men and that which is predicted by standard equations. These observed differences in exercise VO2 appear to be due to the higher resting VO2 in highly muscular participants.     

Comparison of Body Composition Estimates among Norland Elite®, Lunar iDXA®, and the BodPod® in Overweight to Obese Adults

ABSTRACT

Accurate body composition assessment, which includes fat mass (adipose tissue mass, FM), fat-free mass (FFM), and percent fat mass (%FM) is needed to evaluate health and treatment efficacy. The current study compared body composition estimates obtained from the Norland Elite® DXA, BodPod®, and iDXA® before and after a12-week exercise intervention in adults (n=30, BMI 25–35 kg/m²) . Bland-Altman methods determined mean bias and limits of agreement for FM, %FM, and FFM between methods. Compared to the iDXA® and BodPod®, Elite® overestimated BF% and FM (P < .01). FFM was similar between iDXA® and Elite® but lower in Elite® than BodPod® (P < .01). There were no differences between methods in changes in FM or FFM after the exercise intervention. Prior to this study, it was unknown how the Norland Elite®, a DXA model marketed to bariatric surgery patients, compared to other common body composition assessment methodologies..