Relation of bone mineral density and content to mineral content and density of the fat-free mass

Accuracy and precision of multiple body composition methods and associations with muscle strength in athletes of varying hydration: The Da Kine Study

BACKGROUND

Athletes vary in hydration status due to ongoing training regimes, diet demands, and extreme exertion. With water being one of the largest body composition compartments, its variation can cause misinterpretation of body composition assessments meant to monitor strength and training progress. In this study, we asked what accessible body composition approach could best quantify body composition in athletes with a variety of hydration levels.

METHODS

The Da Kine Study recruited collegiate and intramural athletes to undergo a variety of body composition assessments including air-displacement plethysmography (ADP), deuterium-oxide dilution (D2O), dual-energy X-ray absorptiometry (DXA), underwater-weighing (UWW), 3D-optical (3DO) imaging, and bioelectrical impedance (BIA). Each of these methods generated 2- or 3-compartment body composition estimates of fat mass (FM) and fat-free mass (FFM) and was compared to equivalent measures of the criterion 6-compartment model (6CM) that accounts for variance in hydration. Body composition by each method was used to predict abdominal and thigh strength, assessed by isokinetic/isometric dynamometry.

RESULTS

In total, 70 (35 female) athletes with a mean age of 21.8 ± 4.2 years were recruited. Percent hydration (Body Water6CM/FFM6CM) had substantial variation in both males (63-73 %) and females (58-78 %). ADP and DXA FM and FF M had moderate to substantial agreement with the 6C model (Lin's Concordance Coefficient [CCC] = 0.90-0.95) whereas the other measures had lesser agreement (CCC <0.90) with one exception of 3DO FFM in females (CCC = 0.91). All measures of FFM produced excellent precision with %CV < 1.0 %. However, FM measures in general had worse precision (% CV < 2.0 %). Increasing quartiles (significant p < 0.001 trend) of 6CM FFM resulted in increasing strength measures in males and females. Moreover, the stronger the agreement between the alternative methods to the 6CM, the more robust their correlation with strength, irrespective of hydration status.

CONCLUSION

The criterion 6CM showed the best association to strength regardless of the hydration status of the athletes for both males and females. Simpler methods showed high precision for both FM and FFM and those with the strongest agreement to the 6CM had the highest strength associations.

SUMMARY BOX

This study compared various body composition analysis methods in 70 athletes with varying states of hydration to the criterion 6-compartment model and assessed their relationship to muscle strength. The results showed that accurate and precise estimates of body composition can be determined in athletes, and a more accurate body composition measurement produces better strength estimates. The best laboratory-based techniques were air displacement plethysmography and dual-energy x-ray absorptiometry, while the commercial methods had moderate-poor agreement. Prioritizing accurate body composition assessment ensures better strength estimates in athletes.

Bone Density and Bone Geometry in University Athletes From Sports With Different Levels of Impact: Simultaneous Association With Multiple Factors

ABSTRACT

Moraes, MS, Fernandes, RA, Moreno, YMF, Pelegrini, A, and Silva, DAS. Bone density and bone geometry in university athletes from sports with different levels of impact: simultaneous association with multiple factors. J Strength Cond Res XX(X): 000-000, 2022-The aim of this study was to use the bone loading unit (BLU) classification to compare bone density and bone geometry of sports with different levels of impact, simultaneously controlling the multiple factors that interfere with bone metabolism in athletes. Overall, 167 university athletes (92 men) participated in the study. Bone mineral density (BMD), strength index, cross-sectional area (CSA) at the moment of inertia, section modulus (Z), CSA, neck-shaft angle (NSA), and hip axis length (HAL) were measured. Sports were categorized by level of impact, high BLU (higher impact) and moderate/low BLU (lower impact). Covariates were fat mass, lean tissue mass, training volume, time of practice, dietary supplementation, use of oral contraceptives and menstrual status. Multiple linear regression with 5% significance level (p < 0.05) was used. In men, HAL was higher in sports with high BLU compared with those with moderate/low BLU (β: -0.21; R2: 0.30; p = 0.03). In women, NSA was higher in sports with moderate/low BLU compared with those with high BLU (β: 0.31; R2: 0.11; p = 0.02). There was no difference between BLU groups for BMD. These results persisted when the simultaneous interference of covariates was controlled. Thus, this study recommends BLU to classify sports and reinforces the importance of monitoring HAL and NSA in athletes in addition to the control of multiple factors that interfere with bone metabolism, because they influence physical performance and bone health during and after athletic life.

Examining Race-Related Error in Two-Compartment Models of Body Composition Assessment: A Systematic Review and Meta-Analysis

BACKGROUND

The Brozek and Siri formulas estimate relative adiposity (%Fat) from total body density (D_b) using a 2-compartment (2C) model. Racial/ethnic differences in D_b have been reported, along with subsequent errors in estimated %Fat.

OBJECTIVE

The primary aim of this systematic review and meta-analysis was to examine potential race/ethnic differences in the accuracy of the Brozek and Siri 2C formulas using aggregate-level data.

METHODS

Peer-reviewed studies available in English that provided 2C and 4C estimates of %Fat were located using searches of the PubMed (n = 150), Scopus (n = 170), and Web of Science (n = 138) online electronic databases. Random-effects models were used to determine potential differences between racial groups using a mean ES and 95% confidence intervals.

RESULTS

The cumulative results from 78 effects indicate that the relative accuracy of the Brozek equation did not vary between racial groups (between group p = 0.053). In contrast, the Siri equation slightly underestimated %Fat for Asian adults (ES_WMD = -1.40%, 95%CI -2.33% to -0.46%; p = 0.004) and Black adults (ES_WMD = -1.10%, 95%CI -2.11% to -0.08%; p = 0.034), with no significant differences observed in Hispanic adults (ES_WMD = 0.64%, 95%CI -1.02% to 2.31%; p = 0.448) and White adults (ES_WMD = 0.08%, 95%CI -0.42% to 0.57%; p = 0.766) (between group p = 0.019).

CONCLUSION

Small, but statistically significant, error was found between racial groups when estimating %Fat using the 2C Siri equation when compared to 4C models. However, the observed error due to race/ethnicity appears to be of little clinical or practical significance when using either equation.

Differences in distal lower extremity tissue masses and mass ratios exist in athletes of sports involving repetitive impacts

This study aimed to examine the effects of sex and sport on the tissue composition of the distal lower extremity of varsity athletes, in sports that involve repetitive-impact loading patterns. Fat mass, lean mass, bone mineral content and wobbling mass were predicted for the leg and leg + foot segments of varsity basketball, cross-country, soccer and volleyball athletes. The absolute masses were normalised to body mass, and also expressed relative to each other as ratios. Females and males differed on most normalised tissue masses and ratios by 11-101%. Characteristic differences were found in the normalised tissue masses across sports, with the lowest and highest values displayed by cross-country and volleyball (female)/basketball (male) athletes, respectively. Conversely, cross-country athletes had the highest wobbling mass:bone mineral content and lean mass:bone mineral content ratios for females by 10% and 16%, respectively. The differences between sports may be explained in part by different impact loading patterns characteristic of each sport. Tissue mass ratio differences between sports may suggest that the ratios of soft to rigid tissues are optimised by the body in response to typical loading patterns, and may therefore be useful in investigations of distal lower extremity injury mechanisms in athletes.

Influence of mineralization and microporosity on tissue elasticity: experimental and numerical investigation on mineralized turkey leg tendons

A combined experimental and numerical study correlating indentation stiffness with mineralization and microporosity was performed on mineralized turkey leg tendon. Two distinct tissue morphologies were distinguished by quantitative backscattered electron imaging and called "circumferential" and "interstitial" zones. These two zones showed different tissue organization, microporosity, and mineralization. Stiffness, measured by microindentation, was also different in the two zones. The mean field method of modeling of mineralized collagen fibers was employed to explain the differences.

National Athletic Trainers' Association position statement: safe weight loss and maintenance practices in sport and exercise

OBJECTIVE

To present athletic trainers with recommendations for safe weight loss and weight maintenance practices for athletes and active clients and to provide athletes, clients, coaches, and parents with safe guidelines that will allow athletes and clients to achieve and maintain weight and body composition goals.

BACKGROUND

Unsafe weight management practices can compromise athletic performance and negatively affect health. Athletes and clients often attempt to lose weight by not eating, limiting caloric or specific nutrients from the diet, engaging in pathogenic weight control behaviors, and restricting fluids. These people often respond to pressures of the sport or activity, coaches, peers, or parents by adopting negative body images and unsafe practices to maintain an ideal body composition for the activity. We provide athletic trainers with recommendations for safe weight loss and weight maintenance in sport and exercise. Although safe weight gain is also a concern for athletic trainers and their athletes and clients, that topic is outside the scope of this position statement.

RECOMMENDATIONS

Athletic trainers are often the source of nutrition information for athletes and clients; therefore, they must have knowledge of proper nutrition, weight management practices, and methods to change body composition. Body composition assessments should be done in the most scientifically appropriate manner possible. Reasonable and individualized weight and body composition goals should be identified by appropriately trained health care personnel (eg, athletic trainers, registered dietitians, physicians). In keeping with the American Dietetics Association (ADA) preferred nomenclature, this document uses the terms registered dietitian or dietician when referring to a food and nutrition expert who has met the academic and professional requirements specified by the ADA's Commission on Accreditation for Dietetics Education. In some cases, a registered nutritionist may have equivalent credentials and be the commonly used term. All weight management and exercise protocols used to achieve these goals should be safe and based on the most current evidence. Athletes, clients, parents, and coaches should be educated on how to determine safe weight and body composition so that athletes and clients more safely achieve competitive weights that will meet sport and activity requirements while also allowing them to meet their energy and nutritional needs for optimal health and performance.

Predicting fat percent by skinfolds in racial groups: Durnin and Womersley revisited

PURPOSE

Despite their widespread use in research and fitness settings, Durnin and Womersley's (DW) 1974 prediction equations using skinfold thickness to estimate body fat percent by hydrodensitometry have not been systematically evaluated in racial or ethnic groups using body fat percent measured by dual-energy x-ray absorptiometry (%BF(DXA)) as the standard.

METHODS

This cross-sectional, population-based study examined whether the DW skinfold equations predict %BF(DXA) in a large, multiracial sample. Four skinfold measures (biceps, triceps, subscapular, and suprailiac), other clinical anthropometrics, and %BF(DXA) were obtained from 1675 healthy adults, age 18-110 yr, who were classified into four racial or ethnic categories: Caucasian, African American, Hispanic, or Asian. Predicted body fat percent using DW equations was compared with %BF(DXA) and evaluated within race/ethnicity- and sex-specific groups.

RESULTS

Mean body fat percent predicted by DW equations was significantly different from %BF(DXA) in four of eight race/ethnicity- and sex-specific groups, particularly in Asian women and African American men (3.3 and 2.4 percentage point overestimates, respectively, P < 0.0001). New linear regression equations were developed estimating %BF(DXA) specific to each race/ethnicity and sex group, using the original DW skinfold sites. Body weight, height, and waist circumference independently predicted fat percent and were also included in the new equations.

CONCLUSIONS

The 1974 DW equations did not predict %BF(DXA) uniformly in all races or ethnicities. Using %BF(DXA) as the criterion measure, the original DW skinfold equations have been updated specific to sex and race/ethnicity while maintaining the DW options for a minimalistic model using fewer predictors.

The impact of different types of physical activity on total and regional bone mineral density in young Brazilian athletes

Bone turnover is affected by exercise throughout the lifespan, especially during childhood and adolescence. The objective of this study was to investigate the impact of different sports on total and regional bone mineral density in male Brazilian adolescent athletes. Forty-six adolescents aged 10-18 years participated in the study: 12 swimmers, 10 tennis players, 10 soccer players, and 14 sedentary individuals. The athletes had engaged in physical activities for more than 10 h per week in the previous 6 months. Bone mineral density of the lumbar spine (L1-L4), left proximal femur region, and whole body was evaluated by dual-energy X-ray absorptiometry. Results showed higher mean values in the proximal femur region of tennis and soccer players (1.02 ± 0.18; 0.96 ± 0.16, respectively) than swimmers and controls (0.91 ± 0.14 and 0.87 ± 0.06, respectively) (P < 0.05). In relation to the impact of sporting activities based on bone age determination, we observed significant differences in bone mineral density at all evaluated sites at the end of puberty (16-18 years) compared with 10-12 years, with increases of 78% in the lumbar spine, 47% in the proximal femur, and 38% in the whole body.

Skinfold prediction equation for athletes developed using a four-component model

INTRODUCTION

Skinfold (SKF) equations exist to predict percent body fat (%BF) in athletes; however, none have been derived from multicomponent model reference measures.

PURPOSE

To develop and cross-validate a %BF prediction equation based on SKF in athletes using a four-component model as the reference measure.

METHODS

Subjects were 132 collegiate athletes (20.7 +/- 2.0 yr; 78 males: 28 black, 50 white; 54 females: 10 black, 44 white). Four-component model estimates of %BF (%BF4C) included measures of total body water from deuterium dilution, bone mineral by dual- energy x-ray absorptiometry (DXA), and body density by densitometry using underwater weighing. SKF measures included subscapular, triceps, chest, midaxillary, suprailiac, abdominal, and thigh sites (7SKF). A prediction equation was developed on 102 athletes using 7SKF, race, and gender as predictor variables. Cross-validation was performed on a representative holdout sample of 30 athletes.

RESULTS

The equation cross-validated well (slope and intercept both not different (P > 0.05) from the line of identity (LOI); r(YY') = 0.85, total error (TE) = 3.76%BF) and was better than the existing athlete SKF equations (intercept and slope both different from LOI (P < 0.01); r(YY') = 0.76, TE = 4.51%BF). Notably, a prediction equation developed using 3SKF sites (abdomen, thigh, and triceps) produced a similar accuracy (intercept and slope both not different from LOI (P > 0.05); r(YY') = 0.85, TE = 3.66%BF).

CONCLUSIONS

The new 7SKF equation improved on SKF equations developed using densitometry. The final equation based on the whole sample was %BF' = 10.566 + 0.12077*(7SKF) - 8.057*(gender) - 2.545*(race). Moreover, a 3SKF equation was comparable in accuracy to the 7SKF equation: BF' = 8.997 + 0.24658*(3SKF) - 6.343*(gender) - 1.998*(race).

Efeitos da atividade física na densidade mineral óssea e na remodelação do tecido ósseo

Este artigo revisa os efeitos de diferentes modalidades esportivas e do treinamento de força na remodelação óssea e discutir as possíveis relações da densidade mineral óssea (DMO) com a força muscular e a composição corporal. Numerosos estudos indicam que a atividade física de alto impacto, ou que exija alta produção de força, pode ter um efeito benéfico na DMO, devido à deformação desse tecido, ocorrida durante a atividade. Alguns autores têm avaliado os efeitos do treinamento físico em alguns marcadores bioquímicos da remodelação óssea, já que a variação das concentrações desses marcadores pode indicar um estado de formação ou reabsorção óssea. Entretanto, a inconsistência dos resultados encontrados sugere que a análise dos efeitos da atividade física na remodelação óssea, através desses marcadores, deve ser mais investigada. Existem muitas discrepâncias a respeito da relação entre a DMO com a força muscular e a composição corporal, principalmente na determinação de qual desses fatores está mais associado com a DMO. A determinação de qual o tipo de atividade física seja ideal para aumentar o pico de massa óssea na adolescência, ou mesmo mantê-la após a idade adulta, é muito importante para a prevenção e o possível tratamento da osteoporose.

QDR 4500A DXA overestimates fat-free mass compared with criterion methods

This study evaluated the accuracy with which the dual-energy X-ray absorptiometer (Hologic QDR 4500A) measured fat-free mass (FFM), fat mass (FM), and hydration of FFM. In a study of 58 men and women (ages 70-79 yr), the QDR 4500A was found to provide a systematically higher estimate of FFM and lower estimate of FM than a four-component model of body composition. A correction factor from this study was developed and applied to two other samples (n = 13 and 37). We found mean corrected levels of FFM and FM to be equivalent to that obtained by the four-component model or total body water. In addition, the hydration of the corrected FFM was closer to the established hydration level in adult samples and that obtained from the four-component model. These findings suggest that the current calibration of the fan-beam system of the Hologic QDR 4500A provides an overestimate of FFM and underestimate of FM compared with reference methods.