Prediction of body density in young and middle-aged women

Performance Evaluation of a New Sport Watch in Sleep Tracking: A Comparison against Overnight Polysomnography in Young Adults

Introduction: This study aimed to validate the ability of a prototype sport watch (Polar Electro Oy, FI) to recognize wake and sleep states in two trials with and without an interval training session (IT) 6 h prior to bedtime. Methods: Thirty-six participants completed this study. Participants performed a maximal aerobic test and three polysomnography (PSG) assessments. The first night served as a device familiarization night and to screen for sleep apnea. The second and third in-home PSG assessments were counterbalanced with/without IT. Accuracy and agreement in detecting sleep stages were calculated between PSG and the prototype. Results: Accuracy for the different sleep stages (REM, N1 and N2, N3, and awake) as a true positive for the nights without exercise was 84 ± 5%, 64 ± 6%, 81 ± 6%, and 91 ± 6%, respectively, and for the nights with exercise was 83 ± 7%, 63 ± 8%, 80 ± 7%, and 92 ± 6%, respectively. The agreement for the sleep night without exercise was 60.1 ± 8.1%, k = 0.39 ± 0.1, and with exercise was 59.2 ± 9.8%, k = 0.36 ± 0.1. No significant differences were observed between nights or between the sexes. Conclusion: The prototype showed better or similar accuracy and agreement to wrist-worn consumer products on the market for the detection of sleep stages with healthy adults. However, further investigations will need to be conducted with other populations.

Criterion-Related Validity of Field-Based Methods and Equations for Body Composition Estimation in Adults: A Systematic Review

PURPOSE OF REVIEW

Overweight and obesity are associated to health prognosis. Therefore, body composition assessment is an important health outcome, especially in adult population. We analyzed the criterion-related validity of existing field-based methods and equations for body composition estimation in adults aged 19-64 years.

RECENT FINDINGS

One hundred studies met inclusion criteria. The field-based methods, waist circumference (WC), body adiposity index (BAI), and body mass index (BMI) are valid to indicate body adiposity. Likewise, several equations, including the classical Durnin/Womersley equation, Jackson/Pollock equation (males), and Jackson, Pollock, and Ward equation (females), are valid to estimate total body fat mass or body fat percentage. Anthropometric field methods can provide a simple, quick, and easy informative indicators of adiposity in adults. Classical equations, such as Durnin/Womersley equation, Jackson/Pollock equation, and Jackson, Pollock, and Ward equation, are still valid to estimate total body fat mass or body fat percentage in adult population. When choosing estimation equations, specific population characteristics, such as age, weight status, or race ethnicity, should be taken into account. (Trial Registration: Registered on PROSPERO (CRD42020194272)).

Quadriceps strength asymmetry as predictor of ankle sprain in male volleyball players

BACKGROUND

Ankle sprain is the most common acute time-loss injury in volleyball and occurs mainly during landing from a jump. Therefore we have evaluated the role of quadriceps strength and countermovement jump height on ankle sprain occurrence, as these intrinsic modifiable risk factors were not yet evaluated. We have also hypothesised that presence of quadriceps strength asymmetry could be a possible risk factor for ankle sprains in male volleyball players.

METHODS

This was a prospective cohort study. Male volleyball players (N = 99) from Slovenian national league participated in the study. Before the start of the season, all participants completed a preseason questionnaire and underwent evaluation of vertical jump performance and bilateral isokinetic strength of the quadriceps (Q) and hamstrings (H). During the subsequent season the players reported acute time loss injuries because of ankle sprain through a weekly questionnaire.

RESULTS

We have registered 19 ankle sprains during the season. Overall ankle sprain incidence was 0.41±0.24 per 1000 h. Previous ankle sprain (odd ratio 0.86; 95% CI 0.25 - 2.89, p = 0.802) and jump height (1.05; 95% C.I. 0.94 - 1.19, p = 0.393) were not significant risk factors, while Q strength asymmetry was a significant predictor of an ankle sprain (odd ratio 0.956; 95% CI 0.919-0.995, p = 0.026). Compared with the uninjured players, the injured players had higher right concentric Q strength, higher Q strength asymmetry, and lower concentric right H-Q strength ratio (all p<0.03).

CONCLUSIONS

Our results suggest that excessive concentric strength of the right Q, which leads to low H-Q strength ratio, and high bilateral Q strength asymmetry in favor of the right side, could be associated with increased risk of ankle sprains in male volleyball.

Preseason shoulder rotational isokinetic strength and shoulder injuries in volleyball players

BACKGROUND: Rotator cuff weakness is considered an important risk factor for shoulder injuries in volleyball. OBJECTIVE: To evaluate association of shoulder preseason strength status with shoulder injury occurrence in subsequent season. METHODS: Volleyball players (N= 181; 99 men) from Slovenian 1st and 2nd national league volunteered to participate in this prospective cohort study. Preseason isokinetic testing of the shoulder was conducted at 60∘/s in the concentric mode of contraction over a RoM of 60∘ with five repetitions of internal (IR) and external (ER) rotation. During the subsequent season the players reported shoulders injuries through a weekly questionnaire. RESULTS: During the season we have registered 14 (7.7%) shoulder injuries (10 in men). All injuries affected the dominant shoulder. There was significant preseason weakness of ER and lower ER/IR strength ratio in players with shoulder injury. Normal strength ratio ER/IR was a significant protective factor (Exp (B) = 0.217, 95% C.I. 0.058–0.811) for shoulder injury occurrence when controlled for sex and previous injury. CONCLUSIONS: The inclusion of systematic strengthening of the external rotators of the shoulder is necessary, especially for male volleyball players, as part of preventive measures for the prevention of shoulder injuries.

Mapping female bodily features of attractiveness

“Beauty is bought by judgment of the eye” (Shakespeare, Love’s Labour’s Lost), but the bodily features governing this critical biological choice are still debated. Eye movement studies have demonstrated that males sample coarse body regions expanding from the face, the breasts and the midriff, while making female attractiveness judgements with natural vision. However, the visual system ubiquitously extracts diagnostic extra-foveal information in natural conditions, thus the visual information actually used by men is still unknown. We thus used a parametric gaze-contingent design while males rated attractiveness of female front- and back-view bodies. Males used extra-foveal information when available. Critically, when bodily features were only visible through restricted apertures, fixations strongly shifted to the hips, to potentially extract hip-width and curvature, then the breast and face. Our hierarchical mapping suggests that the visual system primary uses hip information to compute the waist-to-hip ratio and the body mass index, the crucial factors in determining sexual attractiveness and mate selection.

What is an attractive body? Using an interactive 3D program to create the ideal body for you and your partner

What is the ideal body size and shape that we want for ourselves and our partners? What are the important physical features in this ideal? And do both genders agree on what is an attractive body? To answer these questions we used a 3D interactive software system which allows our participants to produce a photorealistic, virtual male or female body. Forty female and forty male heterosexual Caucasian observers (females mean age 19.10 years, s.d. 1.01; 40 males mean age 19.84, s.d. 1.66) set their own ideal size and shape, and the size and shape of their ideal partner using the DAZ studio image manipulation programme. In this programme the shape and size of a 3D body can be altered along 94 independent dimensions, allowing each participant to create the exact size and shape of the body they want. The volume (and thus the weight assuming a standard density) and the circumference of the bust, waist and hips of these 3D models can then be measured. The ideal female body set by women (BMI = 18.9, WHR = 0.70, WCR = 0.67) was very similar to the ideal partner set by men, particularly in their BMI (BMI = 18.8, WHR = 0.73, WCR = 0.69). This was a lower BMI than the actual BMI of 39 of the 40 women. The ideal male body set by the men (BMI = 25.9, WHR = 0.87, WCR = 0.74) was very similar to the ideal partner set by the women (BMI = 24.5, WHR = 0.86, WCR = 0.77). This was a lower BMI than the actual BMI of roughly half of the men and a higher BMI than the other half. The results suggest a consistent preference for an ideal male and female body size and shape across both genders. The results also suggest that both BMI and torso shape are important components for the creation of the ideal body.

Prognosis in 41 severely malnourished anorexia nervosa patients

BACKGROUND & AIMS

To report the prognosis in 41 anorexia nervosa (AN) patients suffering from very severe malnutrition (mean BMI: 10.1 ± 0.57 kg/m(2)).

PATIENTS AND METHODS

Compared with 443 less malnourished AN patients, the 41 patients were older (27.8 ± 5.4 vs 22.4 ± 2.1 yrs), their AN was longer (9.6 ± 3.4 vs 5.0 ± 1.5 yrs) and more often of the restrictive subtype (P < 0.05).

RESULTS

In 27% of the patients, all nutritional marker levels were in normal range. All patients received a prudent tube-refeeding: energy was increased from 12 to 40 kcal/kg/day, protein from 1.0 to 1.5 g/kg/day within 10 days. During stay, 1 patient died, 2 others suffered from myocardial infarction, 2 others from acute pancreatitis, and 5 from mental confusion. Compared with the other 443 AN patients, the 40 remaining patients had worse 6-yr prognosis: 2 died (7% vs 1.2%), 29% had severe outcome (vs 10%), and only 41% recovered (vs 62%).

CONCLUSION

In AN patients with BMI < 11 kg/m(2), a prudent tube-refeeding could avoid short-term mortality, but long-term prognosis was bad.

Cross-validation of generalised body composition equations with diverse young men and women: the Training Intervention and Genetics of Exercise Response (TIGER) Study

Generalised skinfold equations developed in the 1970s are commonly used to estimate laboratory-measured percentage fat (BF%). The equations were developed on predominately white individuals using Siri's two-component percentage fat equation (BF%-GEN). We cross-validated the Jackson-Pollock (JP) generalised equations with samples of young white, Hispanic and African-American men and women using dual-energy X-ray absorptiometry (DXA) as the BF% referent criterion (BF%-DXA). The cross-sectional sample included 1129 women and men (aged 17-35 years). The correlations between BF%-GEN and BF%-DXA were 0.85 for women and 0.93 for men. Analysis of measurement error showed that BF%-GEN underestimated BF%-DXA of men and women by 1.3 and 3.0 %. General linear models (GLM) confirmed that BF%-GEN systematically underestimated BF%-DXA of Hispanic men and women, and overestimated BF%-DXA of African-American men. GLM were used to estimate BF%-DXA from the JP sum of skinfolds and to account for race/ethnic group bias. The fit statistics (R and standard error of the estimate; see) of the men's calibration model were: white, R 0.92, see 3.0 %; Hispanic, R 0.91, see 3.0 %; African-American, R 0.95, see 2.6 %. The women's statistics were: white and African-American, R 0.86, see 3.8 %; Hispanic, R 0.83, see 3.4 %. These results showed that BF%-GEN and BF%-DXA were highly correlated, but the error analyses documented that the generalised equations lacked accuracy when applied to these racially and ethnically diverse men and women. The inaccuracy was linked to the body composition and race/ethnic differences between these Training Intervention and Genetics of Exercise Response (TIGER) study subjects and the men and women used to develop the generalised equations in the 1970s and using BF%-DXA as the referent criterion.

A new method of body habitus correction for total body potassium measurements

This paper describes an accurate and time-efficient method for the determination of total body potassium via a combination of measurements in the Birmingham whole body counter and the use of the Monte Carlo n-particle (MCNP) simulation code. In developing this method, MCNP has also been used to derive values for some components of the total measurement uncertainty which are difficult to quantify experimentally. A method is proposed for MCNP-assessed body habitus corrections based on a simple generic anthropomorphic model, scaled for individual height and weight. The use of this model increases patient comfort by reducing the need for comprehensive anthropomorphic measurements. The analysis shows that the total uncertainty in potassium weight determination by this whole body counting methodology for water-filled phantoms with a known amount of potassium is 2.7% (SD). The uncertainty in the method of body habitus correction (applicable also to phantom-based methods) is 1.5% (SD). It is concluded that this new strategy provides a sufficiently accurate model for routine clinical use.

Estimation of deep-abdominal-adipose-tissue (DAAT) accumulation from simple anthropometric measurements in Indian men and women

OBJECTIVE

To develop gender-specific predictive equations to measure the amount of deep-abdominal-adipose-tissue (DAAT) accumulation from simple anthropometric measurements.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 120 healthy men and women (40-79 years).

MEASUREMENTS

Body weights, circumferences, skinfolds, computed-Tomography (CT)-derived sagittal-diameters and the DAAT areas.

RESULTS

High significant correlations are seen between the indices of waist-circumferences, sagittal diameters and body weights to DAAT areas in both the sexes. Stepwise multiple regression analysis with all anthropometric measures gave 84% (SEE 38.7 cm(2)) of the variance in men and 72% (SEE 29 cm(2)) in women. Body weights, waist-circumferences and sagittal-diameters had more predictive power in men, and in women, the arm-circumferences replaced the sagittal diameters. Five models with categorical measures of circumferences, skinfolds, and sagittal diameters explained 74.8-82% of the variance in men and 62-70% in women. The simplest equation with least measurement indices, that is, body-weight, waist-circumference and body mass index explained 74% (SEE 27.7 cm(2)) of the variance in men: DAAT (cm(2))= -382.9+(1.09 x weight-(kg))+(6.04 x waist-(cm))+(-2.29 x BMI). For women, body-weight and waist-circumference explained 63% (SEE 31.79 cm(2)) of the variance: DAAT (cm(2))= -278+(-0.86 x weight-(kg))+(5.19 x waist-(cm)).

CONCLUSION

Body weight emerged as the outstanding index to measure the DAAT areas. Following anthropometric measures are the waist circumferences, sagittal diameters and BMI. Although the ability to estimate the amount of DAAT from anthropometry is limited, practical predictive models have been developed.

Relationships of age and weekly running distance to BMI and circumferences in 41,582 physically active women

OBJECTIVE

To assess in women whether age-related increases in adiposity are dependent on exercise, and, contrariwise, whether exercise-related declines in adiposity are dependent on age.

RESEARCH METHODS AND PROCEDURES

Cross-sectional analyses were conducted of 41,582 female runners.

RESULTS

Age affected the relationships between vigorous exercise and adiposity. The decline in BMI per kilometer per week run was linear in 18 to 23 year olds and became increasingly non-linear (convex) with age. Waist, hip, and chest circumferences declined significantly with running distance across all age groups, but the declines were significantly greater in older than younger women, particularly among shorter distance runners. The relationships between body circumferences and running distance became increasingly convex in older women. Conversely, vigorous exercise diminished the apparent increase in adiposity with age. The increase in average BMI with age was greatest in women who ran <8 km/wk, intermediate in women who ran 8 to 15 km/wk or 16 to 31 km/wk, and least in those who averaged over 32 km/wk. Before age 45, waist circumference rose for those who ran 0 to 7 km/wk, showed no significant relationship to age for those who ran 8 to 39 km/wk, and declined in those who ran 40 to 55 and 56 km/wk and more. Age related-increases in hip and chest circumferences before 45 years old were significantly less in women who ran longer weekly distances.

DISCUSSION

These cross-sectional associations are consistent with the hypothesis that exercise may mitigate age-related increases in adiposity and that age affects exercise-induced reductions in adiposity (although causality remains to be determined experimentally).

Comparison of anthropometry to dual energy X-ray absorptiometry: a new prediction equation for women

The purpose of this study was to assess the accuracy of three recommended anthropometric equations for women and then develop an updated prediction equation using dual energy x-ray absorptiometry (DXA). The percentage of body fat (%BF) by anthropometry was significantly correlated (r = .896-.929; p < .01) with DXA, but each equation underestimated %BF (3.2-5.6 %BF; p < .01). The following DXA criterion (DC) equation was created: %BF= -6.40665 + 0.41946(S3SF) - 0.00126(S3SF)2 + 0.12515(hip) + 0.06473 (age); (S3SF = sum of triceps, suprailiac, thigh; hip = circumference in cm; age = years). The predicted residual sum of squares (PRESS) R2 was high (0.86), and the PRESS standard error of estimate (SEE) was low (2.5 %BF) for our sample of 150 women. The DC equation was further crosschecked on a separate sample of women (n = 25) and again showed excellent agreement. The DC equation appears to be a more accurate estimation of %BF in women.

Áreas de secção transversa do braço: implicações técnicas e aplicações para avaliação da composição corporal e da força dinâmica máxima

As áreas do tecido muscular (A MB) e do anel de gordura do braço (A GB), podem ser estimadas por medidas antropométricas. OBJETIVO: Investigar a validade e o erro intertestador da antropometria para inferência A MB e do A GB. Secundariamente, estudou-se a previsão da força dos membros superiores e tronco através da A MB. MÉTODOS: Foram voluntários para este estudo 40 adultos masculinos jovens (25 ± 6 anos; 72,6 ± 9,4kg), divididos aleatoriamente nos grupos de validade interna (VI, n = 30) e validade externa (VE, n = 10). Determinou-se para VI, através de conceitos geométricos, a área total do braço (A TB), A MB, A GB e área percentual de gordura do braço. O somatório de oito dobras cutâneas (S DC8) foi empregado como índice da adiposidade corporal. A força dos membros superiores e do tronco foi medida através da carga máxima alcançada no exercício supino reto livre (1-RM). As medidas antropométricas foram realizadas por dois avaliadores independentes. Os dados foram tratados por meio da análise de regressão, coeficiente de correlação intraclasse (ICC) e teste t de Student pareado (a < 0,05). RESULTADOS: A variância do S DC8 pode ser explicada em 93% (EPE = 14,6mm) a partir da A GB e do peso corporal. A A MB explicou em 66,1% (EPE = 9kg) a 1-RM. Não se observou diferença significativa, para o grupo VE, entre os valores medidos (84,2 ± 16,2kg) e preditos (78,4 ± 14,2kg) de 1-RM. Observou-se pouca variação entre os avaliadores para A MB (ICC = 0,99), A GB (ICC = 0,96) e A TB (ICC = 0,99). CONCLUSÃO: A antropometria pode ser empregada para inferência da A MB e do A GB, com boa concordância entre avaliadores, para estimativa da adiposidade corporal e da força dos membros superiores e tronco.

Age-related pattern of body density and body composition of Japanese men and women 18-59 years of age

Age-related patterns of body size and composition were studied in a cross-sectional sample of Japanese adults 18-59 years of age. Height, weight, the body mass index (BMI), body density (BD), percentage body fat (%Fat), fat mass (FM), fat-free mass (FFM), and the sum of seven skinfold thicknesses (SF) of 288 men and 552 women were considered. Body density was measured by underwater weighing densitometry. Mean values of height, weight, BMI, BD, %Fat, FM, FFM, and SF of males were 169.0 cm, 65.3 kg, 22.8 kg/m(2), 1.0600 g/ml, 17.0%, 11.4 kg, 53.9 kg, and 95.0 mm, respectively, while corresponding values for females were 157.4 cm, 52.9 kg, 21.4 kg/m(2), 1.0420 g/ml, 24.4%, 13.1 kg, 39.7 kg, and 128.2 mm, respectively. Height, BD, and FFM correlated negatively with age in both sexes, while weight, BMI, %Fat, FM, and SF correlated positively with age. The highest BD and the lowest %Fat were observed in males ages 20 to <25 years (G20) and in females 25 to <30 years (G25). The lowest BD and highest %Fat were observed in G50 in both sexes. Correlations among parameters of body size and composition were stable with age in each sex. Height correlated negatively with BMI and %Fat in females, but not in males. In males, FM started to increase between G20 and G25 and continued to increase until G50, while SF and BMI remained stable during this period. In females, FM accumulation started around 30 years of age and continued until G50 and was accompanied by increases in SF and BMI.

Effects of exclusive breastfeeding for four versus six months on maternal nutritional status and infant motor development: results of two randomized trials in Honduras

To examine whether the duration of exclusive breastfeeding affects maternal nutrition or infant motor development, we examined data from two studies in Honduras: the first with 141 infants of low-income primiparous women and the second with 119 term, low birth weight infants. In both studies, infants were exclusively breastfed for 4 mo and then randomly assigned to continue exclusive breastfeeding (EBF) until 6 mo or to receive high-quality, hygienic solid foods (SF) in addition to breast milk between 4 and 6 mo. Maternal weight loss between 4 and 6 mo was significantly greater in the exclusive breastfeeding group (EBF) group than in the group(s) given solid foods (SF) in study 1 (-0.7 +/- 1.5 versus -0.1 +/- 1.7 kg, P < 0.05) but not in study 2. The estimated average additional nutritional burden of continuing to exclusively breastfeed until 6 mo was small, representing only 0.1-6.0% of the recommended dietary allowance for energy, vitamin A, calcium and iron. Women in the EBF group were more likely to be amenorrheic at 6 mo than women in the SF group, which conserves nutrients such as iron. In both studies, few women (10-11%) were thin (body mass index <19 kg/m(2)), so the additional weight loss in the EBF group in study 1 was unlikely to have been detrimental. Infants in the EBF group crawled sooner (both studies) and were more likely to be walking by 12 mo (study 1) than infants in the SF group. Taken together with our previous findings, these results indicate that the advantages of exclusive breastfeeding during this interval appear to outweigh any potential disadvantages in this setting.

Determination of a site-specific reference dose for methylmercury for fish-eating populations

Environmental risk-management decisions in the U.S. involving potential exposures to methylmercury currently use a reference dose (RfD) developed by the U.S. Environmental Protection Agency (USEPA). This RfD is based on retrospective studies of an acute poisoning incident in Iraq in which grain contaminated with a methylmercury fungicide was inadvertently used in the baking of bread. The exposures, which were relatively high but lasted only a few months, were associated with neurological effects in both adults (primarily paresthesia) and infants (late walking, late talking, etc.). It is generally believed that the developing fetus represents a particularly sensitive subpopulation for the neurological effects of methylmercury. The USEPA derived an RfD of 0.1 microg/kg/day based on benchmark dose (BMD) modeling of the combined neurological endpoints reported for children exposed in utero. This RfD included an uncertainty factor of 10 to consider human pharmacokinetic variability and database limitations (lack of data on multigeneration effects or possible long-term sequelae of perinatal exposure). Alcoa signed an Administrative Order of Consent for the conduct of a remedial investigation/feasibility study (RI/FS) at their Point Comfort Operations and the adjacent Lavaca Bay in Texas to address the effects of historical discharges of mercury-containing wastewater. In cooperation with the Texas Natural Resource Conservation Commission and USEPA Region VI, Alcoa conducted a baseline risk assessment to assess potential risk to human health and the environment. As a part of this assessment. Alcoa pursued the development of a site-specific RfD for methylmercury to specifically address the potential human health effects associated with the ingestion of contaminated finfish and shellfish from Lavaca Bay. Application of the published USEPA RfD to this site is problematic; while the study underlying the RfD represented acute exposure to relatively high concentrations of methylmercury, the exposures of concern for the Point Comfort site are from the chronic consumption of relatively low concentrations of methylmercury in fish. Since the publication of the USEPA RfD, several analyses of chronic exposure to methylmercury in fish-eating populations have been reported. The purpose of the analysis reported here was to evaluate the possibility of deriving an RfD for methylmercury, specifically for the case of fish ingestion, on the basis of these new studies. In order to better support the risk-management decisions associated with developing a remediation approach for the site in question, the analysis was designed to provide information on the distribution of acceptable ingestion rates across a population, which could reasonably be expected to be consistent with the results of the epidemiological studies of other fish-eating populations. Based on a review of the available literature on the effects of methylmercury, a study conducted with a population in the Seychelles Islands was selected as the critical study for this analysis. The exposures to methylmercury in this population result from chronic, multigenerational ingestion of contaminated fish. This prospective study was carefully conducted and analyzed, included a large cohort of mother-infant pairs, and was relatively free of confounding factors. The results of this study are essentially negative, and a no-observed-adverse-effect level (NOAEL) derived from the estimated exposures has recently been used by the Agency for Toxic Substances and Disease Registry (ATSDR) as the basis for a chronic oral minimal risk level (MRL) for methylmercury. In spite of the fact that no statistically significant effects were observed in this study, the data as reported are suitable for dose-response analysis using the BMD method. Evaluation of the BMD method used in this analysis, as well as in the current USEPA RfD, has demonstrated that the resulting 95% lower bound on the 10% benchmark dose (BMDL) represents a conservative estimate of the traditional NOAEL, and that it is superior to the use of "average" or "grouped" exposure estimates when dose-response information is available, as is the case for the Seychelles study. A more recent study in the Faroe Islands, which did report statistically significant associations between methylmercury exposure and neurological effects, could not be used for dose-response modeling due to inadequate reporting of the data and confounding from co-exposure to polychlorinated biphenyls (PCBs). BMD modeling over the wide range of neurological endpoints reported in the Seychelles study yielded a lowest BMDL for methylmercury in maternal hair of 21 ppm. This BMDL was then converted to an expected distribution of daily ingestion rates across a population using Monte Carlo analysis with a physiologically based pharmacokinetic (PBPK) model to evaluate the impact of interindividual variability. The resulting distribution of ingestion rates at the BMDL had a geometric mean of 1.60 microg/kg/day with a geometric standard deviation of 1.33; the 1st, 5th, and 10th percentiles of the distribution were 0.86, 1.04, and 1.15 microg/kg/day. In place of the use of an uncertainty factor of 3 for pharmacokinetic variability, as is done in the current RfD, one of these lower percentiles of the daily ingestion rate distribution provides a scientifically based, conservative basis for taking into consideration the impact of pharmacokinetic variability across the population. On the other hand, it was felt that an uncertainty factor of 3 for database limitations should be used in the current analysis. Although there can be high confidence in the benchmark-estimated NOAEL of 21 ppm in the Seychelles study, some results in the New Zealand and Faroe Islands studies could be construed to suggest the possibility of effects at maternal hair concentrations below 10 ppm. In addition, while concerns regarding the possibility of chronic sequelae are not supported by the available data, neither can they be absolutely ruled out. The use of an uncertainty factor of 3 is equivalent to using a NOAEL of 7 ppm in maternal hair, which provides additional protection against the possibility that effects could occur at lower concentrations in some populations. Based on the analysis described above, the distribution of acceptable daily ingestion rates (RfDs) recommended to serve as the basis for site-specific risk-management decisions at Alcoa's Point Comfort Operations ranges from approximately 0.3 to 1.1 microg/kg/day, with a population median (50th percentile) of 0.5 microg/kg/day. By analogy with USEPA guidelines for the use of percentiles in applications of distributions in exposure assessments, the 10th percentile provides a reasonably conservative measure. On this basis, a site-specific RfD of 0.4 microg/kg/day is recommended.

Weight change during lactation does not alter the concentrations of chlorinated organic contaminants in breast milk of women with low exposure

The purpose of this longitudinal study was to evaluate whether a loss of body fat during lactation between 4 and 20 wk postpartum increases the concentration of environmental contaminants in breast milk. We examined this relationship in two different cohorts of exclusively breastfeeding women: (1) California women with low exposure to contaminants (n = 10 whose weight was stable [mean change, 0.0 +/- 0.2 kg] and n = 11 who lost weight [mean loss, -4.1 +/- 0.4 kg]) and (2) Hispanic women (n = 30) who had recently immigrated to North Carolina, primarily from Mexico, and were presumed to have a higher prior exposure to contaminants. Breast milk samples were analyzed for hexachlorobenzene (HCB) and DDT and its related products. There was no significant relationship between change in body composition and change in milk contaminant concentrations in either California or North Carolina women. Concentrations of HCB were similar between the California and North Carolina women, but those of DDT and related products were higher in the North Carolina subjects. Results suggest that moderate weight loss in lactating women with low exposure to environmental contaminants does not increase contaminant concentration in breast milk.

Evaluation of the uncertainty in an oral reference dose for methylmercury due to interindividual variability in pharmacokinetics

An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 microgram/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 microgram/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 microgram/kg/day and an MRL of 0.3 microgram/kg/day.

Randomized trial of the short-term effects of dieting compared with dieting plus aerobic exercise on lactation performance

BACKGROUND

Limiting postpartum weight retention is important for preventing adult obesity, but the effect of weight loss on lactation has not been studied adequately.

OBJECTIVE

We evaluated whether weight loss by dieting, with or without aerobic exercise, adversely affects lactation performance.

DESIGN

At 12+/-4 wk postpartum, exclusively breast-feeding women were randomly assigned for 11 d to a diet group (35% energy deficit; n = 22), a diet plus exercise group (35% net energy deficit; n = 22), or a control group (n = 23). Milk volume, composition, and energy output; maternal weight, body composition, and plasma prolactin concentration; and infant weight were measured before and after the intervention.

RESULTS

Weight loss averaged 1.9, 1.6, and 0.2 kg in the diet, diet + exercise, and control groups, respectively (P < 0.0001) and was composed of 67% fat in the diet group and nearly 100% fat in the diet + exercise group. Change in milk volume, composition, and energy output and infant weight did not differ significantly among groups. However, there was a significant interaction between group and baseline percentage body fat: in the diet group only, milk energy output increased in fatter women and decreased in leaner women. The plasma prolactin concentration was higher in the diet and diet + exercise groups than in the control group.

CONCLUSIONS

Short-term weight loss (approximately 1 kg/wk) through a combination of dieting and aerobic exercise appears safe for breast-feeding mothers and is preferable to weight loss achieved primarily by dieting because the latter reduces maternal lean body mass. Longer-term studies are needed to confirm these findings.

Body composition measurement: a review of hydrodensitometry, anthropometry, and impedance methods

Human body composition is an expression of genetic and nutritional factors. It can change as a consequence of exogenous influences such as training, disease, or diet and is therefore of particular interest to nutrition professionals. Two of the main methods of estimating body composition in this review (hydrodensitometry and anthropometry) have been in use for decades, but the third method (bioelectrical impedance) is more recent. The procedure, theoretical basis, assumptions, standard error of estimates, and comparisons with other techniques are presented for each of the three methods. References to general and specific populations are presented that illustrate regression equations for different ages, ethnic groups, and gender. The advantages and disadvantages of the three methods are reviewed with reference made to the alternative compartment models. Other methods (DEXA, infrared interactance) are briefly reviewed.

Respiratory muscle strength in older adults

Gender-related effects and two measures of muscularity, handgrip strength and fat-free mass (FFM), were examined to determine their relationship to respiratory muscle strength. Subjects were 101 healthy older adults. In 75 subjects, the magnitude of learning effect was examined over four weekly sessions. Maximal inspiratory pressure (PImax) was lower with increasing age in women, and maximal expiratory pressure (PEmax) was lower with increasing age in both genders. The PEmax correlated with handgrip strength and FFM in men only. Performance of PImax plateaued by the third visit in both men and women. Performance of PEmax plateaued by the third measure in women and was unchanged across four measurements for men.

Applied physiology of water-skiing

Water-skiing is a physically demanding sport involving highly coordinated movements, extreme upper body torques, sustained isometric contractions and near maximal stresses on the anaerobic system. Due to the physical demands of the sport, elite skiers have developed physiological characteristics similar to other elite athletes. However, until recently little research has focused on the kinesiology, physiology and physical conditioning of water-skiing.

Prediction equations for body composition of Japanese adults by B-mode ultrasound

A total of 117 Japanese subjects (62 men and 55 women) volunteered for the study. Subcutaneous adipose tissue (AT) and muscle thicknesses were measured by B-mode ultrasonography at nine sites of the body. Body density (BD) was determined the hydrodensitometry. Reproducibility of thickness measurements by ultrasonography was high (r = 0.96-0.99). Correlations between AT thickness and BD ranged from -0.46 (gastrocnemius) to -0.87 (abdomen) for males and -0.46 (gastrocnemius) to -0.84 (abdomen) for females. A higher negative correlation (r = -0.89) was observed for the sum of AT thicknesses (forearm, biceps, triceps, abdomen, subscapula, quadriceps, hamstrings, gastrocnemius, and tibialis anterior) both in males and in females. Slightly lower coefficients were observed between muscle thickness and LBM (r = 0.36 to r = 0.70 for males and r = 0.44 to r = 0.55 for females). Prediction equations for BD and LBM from AT and muscle thickness were obtained by multiple regression analysis. Cross-validation on a separate sample (33 men and 44 women) showed an accurate prediction for BD. The present findings suggest that B-mode ultrasonography can be applied in clinical assessment and field surveys. © 1994 Wiley-Liss, Inc.

The validity generalization of skinfolds as measures of body density

Validity generalization was used to ascertain the generalizability of skinfolds as measures of body density. A literature search was conducted to locate studies employing skinfolds as predictors of body density using hydrostatic weighing as the criterion test. The sites examined included the triceps, subscapula, suprailiac, abdomen, front thigh, midaxillary, and the log sum of the biceps, triceps, suprailiac, and subscapula. Results indicated that no single sites were generalizable across all subjects; however, the log sum of the four sites was generalizable. For adult males, the suprailiac and midaxillary sites were generalizable, while the subscapular site was generalizable for women. No sites were generalizable for boys, while the triceps site was generalizable for girls. Suggestions are provided for additional research.

Body mass index as a measure of body fatness: age- and sex-specific prediction formulas

In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9-40.9 kg/m2), and an age range of 7-83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males = 1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51 x BMI-0.70 x age - 3.6 x sex + 1.4 (R2 0.38, SE of estimate (SEE) 4.4% BF%). In adults the prediction formula was: BF% = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (R2 0.79, SEE = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance.

New approach for estimating excess body fat from changes in abdominal girth

A new method is proposed for determining changes in percent body fat (%BF) based on the difference between an initial value for abdominal girth (AG) and a calculated "target" AG based on a desired %BF. Group data from large-scale anthropometric surveys in the military were used to derive specific reference values for Q, defined as the ratio of AG at a desired %BF to F(√BM_kg /Ht_m ). For an individual, Q*F resulted in an AG that corresponded to a desired %BF (set at approximately 20% for males and 30% for females). The method was applied to professional football players, longshoremen, shot-put and weight-lifting athletes, and obese males and females who reduced body mass and altered their body composition. The results showed that changes in AG with body mass loss were proportional to percentage changes in total body fat loss. These relationships permitted extrapolation to a projected target AG that corresponded to a desired %BF. The proposed method differs from the traditional approach that first determines %BF, and then the individual attempts to achieve a desired change in body mass or body composition. The objective of the new method is straightforward; the individual endeavors to attain a target AG that corresponds to a desired %BF.

Relative body fat and anthropometric prediction of body density of female athletes

Ninety-one percent (n = 182) of the female members of South Australian representative squads in 14 sports volunteered to act as subjects. Twenty-seven percent of them had represented Australia. The underwater weighing method together with the measurement of residual volume (RV) by helium dilution were used to determine body density (BD); the percent body fat (% BF) was then computed according to Siri. A stepwise multiple regression analysis yielded a correlation coefficient (R) of 0.863 between the criterion (BD) and the best weighted sum of predictors (anthropometric variables): BD (g X cm-3) = 1.14075-0.04959 (log10 sigma triceps, subscapular, supraspinale and calf skinfolds in mm) + 0.00044 (age in decimal years)-0.000612 (waist girth in cm) + 0.000284 (height in cm)-0.000505 (gluteal girth in cm) + 0.000331 (breast girth in cm). Only those predictors which resulted in a statistically significant increase in R (p less than or equal to 0.05) were included. The standard error of estimate of 0.00597 g X cm-3 was equivalent to 2.7% BF at the mean. This equation was shown to be largely population specific. There was a range of 7.6-35.8% of BF and the overall mean 18.5% was significantly lower (p less than 0.001) than that of 23.4% obtained on a moderately active reference sample of similar age (n = 135). If group sizes of only one or two are regarded as too small for meaningful comparison, then the lowest mean of 13.5% was achieved by the long-distance runners (n = 14). The highest averages were registered by the heavyweight rowers (24.2%; n = 7) and soccer players (22.0%; n = 11). The overall average for games players (n = 107) was 19.4%.

The relative body fat and anthropometric prediction of body density of South Australian females aged 17-35 years

One hundred and thirty-five females were tested in order to: produce some normative percentage body fat (% BF) data on an Australian sample which represented a cross-section of physical activity patterns, cross-validate existing multiple regression equations which predict body density (BD) from anthropometric measurements, and if necessary develop population specific equations. Measurements were taken of 10 girths, 3 widths and 7 skinfolds. Body density was measured by underwater weighing with the residual volume (RV) being determined by helium dilution. The Siri equation was then used to convert BD to % BF. The % BF scores had an overall mean of 23.4 (range 10.8-49.2). The very active group (n = 45) had a significantly lower (p less than 0.05) relative body fat (X = 20.6% BF) than either the active (n = 45; 23.5% BF) or sedentary groups (n = 45; 26.2% BF). Previously published equations were found to have limited applicability to Australian subjects. A stepwise multiple regression was therefore used to develop the following equation (R = 0.893): BD(g X cm-3) = 1.16957-0.06447 (log10 sigma triceps, subscapular, supraspinale, front thigh, abdominal and calf skinfolds in mm)-0.00081 (gluteal girth in cm) + 0.0017 (forearm girth in cm) + 0.00606 (biepicondylar humerus breadth in cm). Only those predictors which resulted in a statistically significant increase in r (p less than or equal to 0.05) were included. The standard error of estimate of 0.00568 g X cm-3 was equivalent to 2.6% BF at the mean.

Differences in diazepam pharmacokinetics in Chinese and white Caucasians--relation to body lipid stores

We have compared diazepam pharmacokinetics in 16 Chinese and 18 white Caucasian healthy male volunteers, resident in Hong Kong and have correlated them with physical attributes. Serum concentrations of diazepam and desmethyldiazepam were measured in venous blood by an enzyme-linked immunoassay (0-3 h samples) and HPLC (3-72 h samples). Pharmacokinetic parameters were derived assuming a two compartment model, distribution phase less than 6 h, and 100% oral systemic availability. Compared with the Chinese the white Caucasians were older, heavier, taller, and fatter, as judged by skin fold thickness (SFT) and total body weight to 'Ideal' body weight (TBW/IBW) ratio; respective mean differences being 16%, 27%, 4%, 26%, and 15% (p less than 0.05). Mean diazepam apparent volume of distribution (V) and V/IBW were larger in the white Caucasians (52% & 39% respectively, p = 0.002). SFT and TBW/IBW ratio yielded the best correlations with V, V/TBW and V/IBW (0.50-0.75, p less than 0.05). Obesity indices contributed most to the overall regressions (R2 up to 0.52), and for V there was a further small effect (2%, partial F test) due to ethnic group, possibly reflecting stature. Mean peak diazepam concentration (Cmax) was similar in both ethnic groups. Time to Cmax (tmax) was more often prolonged in the Chinese (chi 2 test, p = 0.01). Body fat and stature may thus account for these inter-ethnic differences in the apparent volume of distribution of diazepam, a highly lipid-soluble drug.

The impact of adjustment of a weight-height index (W/H2) for frame size on the prediction of body fatness

The impact of frame-size categories in weight-height tables was studied by comparing the efficiency of the body-mass index (weight/height2 (W/H2] and weight adjusted for body-height and a body-diameter, W/(H2Dp), in predicting body fatness. Body-weight, body-height, six body-diameters and four skinfold thicknesses were measured in ninety-five men and seventy women, aged between 23 and 35 years. Percentage of body fat was calculated from skinfold thicknesses using regression equations according to Durnin & Womersley (1974). The inclusion of a body-diameter increased the explained variation of body fatness from 57% to 62% (knee) and 63% (shoulder) in men and from 63% to 69% (knee) in women. It can be concluded that in the present population the efficiency of the prediction of percentage of body fat was not improved markedly by the inclusion of a body-diameter in the body-mass index, thus giving no support for the inclusion of frame-size categories in weight-height tables.

Prediction of body density from skinfold measurements in lactating women

Regression equations predicting body density from skinfold measurements were derived for a group of lactating women. It was concluded that specific equations for lactation were not necessary, since the resultant equations were not significantly different from those published for non-lactating women. The ability to predict an individual's body density from skinfold thickness measurements was unsatisfactory for either clinical or research applications.

Prediction of body volume by a stepwise linear regression technique

Body volume and 35 anthropometric measurements were obtained from 88 active soldiers using standard techniques. These anthropometric measurements were examined for their possible relationships to body volume using stepwise linear regression analysis. Four measurements (Body weight, anterior thigh skinfold thickness, subscapular skinfold thickness and suprailiac skinfold thickness) accounted for 99.7% of the variation in body volume and the introduction of each of these measurements in the equation was significant. The regression equation for predicting body volume from these 4 anthropometric measurements had a multiple correlation coefficient of 0.9987 (P less than 0.001). Body weight alone was correlated with body volume to the extent of 0.9966. An attempt has therefore been made to develop a multiple linear regression equation without incorporation of body weight in the regression analysis. Nine measurements were selected by stepwise linear regression analysis for predicting body volume. These nine measurements accounted for 97.1% of the variation in body volume. These equations have been validated on another small sample of 22 soldiers. The analysis has also revealed that a direct regression of body density from the anthropometric variables gives more accurate results than when estimated body volumes are utilized for calculating body density.

Taxonomic identification of human fat patterns

The utility of taxonomic approaches in identification of fat patterning was evaluated using hierarchical cluster analysis on a sample of 64 female and 31 male subjects from 18 to 29 years of age. Four clusters, each composed of subjects with similar distributions of 17 skinfold thicknesses corrected for sex, size and total body fat, showed mean pattern profiles that variously contrasted fatness of the trunk and extremities. Average anthropometric differences between clusters corroborated differences in pattern profile. For comparison, principal-components analysis was carried out on these same data. The results suggest that a taxonomic approach offers advantages in initial interpretation and in design flexibility.

Body Composition Methodology in Sports Medicine

In brief Because of its noninvasive approach, anthropometry is one of the oldest and most popular methods of estimating body composition. However, this practical approach is often misused and misinterpreted by both clinicians and researchers. This article reviews the major methods for estimating body composition in various populations, with emphasis on anthropometry. Steps that will help clinicians select an appropriate anthropometric equation and reduce errors include using the same measurement procedures described in the original study and making sure the equation is based on a similar sample of 50 to 150 subjects in terms of age, sex, and activity levels.

Physiological Profile of High School Female Cross-Country Runners

In brief Height, weight, body density, percent body fat, lean body weight, selected skinfolds, girths, and somatotypes were determined for 72 high school female cross-country runners. The mean body fat (15.3%) was lower than the values typically reported for the female nonathlete in this age- group. This low percent body fat was reflected in the relatively low endomorph component of the total group. The average somatotype of these runners (2.8-3.2-4.0) supports the general concept that distance runners of various ages tend to be more linear and leaner than their nonrunning counterparts.