EXCI252Ch8AssessingBodyCompostionF2023Part2 (1).pptx

Chapter 8 Assessing Body Composition Part 2 EXCI 252 1 Field Methods For Assessing Body Composition  Bioelectrical Impedance Analysis Method  Ultrasound Method  Skinfold Method  Anthropometric Methods EXCI 252 2 Bioelectrical Impedance Analysis Method  Also called impedance ple...

Chapter 8 Assessing Body Composition Part 2 EXCI 252 1 Field Methods For Assessing Body Composition  Bioelectrical Impedance Analysis Method  Ultrasound Method  Skinfold Method  Anthropometric Methods EXCI 252 2 Bioelectrical Impedance Analysis Method  Also called impedance plethysmography.  Developed in the 1960s.  Has emerged as 1 of the most popular methods for estimating relative body fat.  A small, harmless 50-kHz current (800 microamps maximum) is generated & passed through the person being measured.  The measurement of electrical impedance is detected as the resistance to electrical current. EXCI 252 3 Bioelectrical Impedance Analysis Method  Electrical Impedance  is greatest in fat tissue and least in fat-free tissue  Conductive Pathway  is greatest in tissues with greater amounts of water  Conduction  is inversely related to resistance  Impedance (Z)  opposition to flow of current  is a function of reactance & resistance  Resistance (R)  is a measure of pure opposition of current flow through the body  Reactance (Xc)  is the opposition to current flow caused by the capacitance produced by the cell membrane  BIA indirectly estimates or predicts  Fat-free mass (FFM) & total body water (TBW) EXCI 252 4 Bioelectrical Impedance Analysis Method  Whole-body impedance measures used in BIA prediction equations to estimate TBW and FFM:  Z, R, and Xc  BIA Prediction Equations  Population-Specific Equations  Homogeneous populations  Age, Ethnicity, Body fatness, Physical activity level  Generalized Equations  Heterogeneous populations varying in age, gender, & body fatness EXCI 252 5 Traditional BIA Method  Measures whole-body resistance using a tetrapolar wrist-to-ankle electrode configuration Estimates TBW and FFM.  Electrode placement and client positioning EXCI 252 6 Bioelectrical Impedance Analyzers  These  2 analyzers estimate %BF & FFM: Typically, it is not possible to obtain R & Xc data from these analyzers. Tanita BI Analyzer Omron BI Analyzer Lower-body BIA device Upper-body BIA device EXCI 252 7 BIA Pretesting Client Guidelines  No eating or drinking within 4 hr of the test  No moderate or vigorous exercise within 12 hr of the test  Void completely within 30 min of the test  Abstain from alcohol consumption within 48 hr of the test  Do not ingest diuretics, including caffeine, before the test unless they are prescribed by a physician  Postpone the test for female clients who are in the stage of their menstrual cycle when they retain water EXCI 252 8 Advantages of the BIA Method  Rapid method  Relatively inexpensive method  Noninvasive method  Does not intrude as much upon a client’s privacy  Generally, more comfortable  Does not require a high degree of technician skill  Used in field settings  Can be used to estimate the BC of obese individuals EXCI 252 9 Sources of BIA Measurement Error  The accuracy & precision of the BIA method are affected by:  Instrumentation  Client factors  Technician skill  Environmental factors  Client’s body position  Prediction equations used to estimate FFM EXCI 252 10 Sources of BIA Measurement Error  Instrumentation  The brand of single-frequency analyzer that is used for the BIA measurement  Differences may exist within a given model of analyzer  Client Factors  Hydration Level  The major source of measurement error  Eating, drinking, dehydrating, & exercising  Menstrual Cycle  Large body weight gain due primarily to an increase in total body water (TBW) EXCI 252 11 Sources of BIA Measurement Error Condition Eating (R measured 2-4 hrs after a meal) Dehydration Aerobic Exercise Moderate Intensity Low Intensity Resistance FFM %BF Decreases (13 to 17  ) Overestimates Underestimates Increases (~ 40  ) Underestimates Overestimates Decreases (50-70  ) Decreases (1-9  ) Overestimates Underestimates EXCI 252 12 Sources of BIA Measurement Error  Technician Skill  Not a major source of measurement error unless the standardized procedures for electrode placement & client positioning are not followed by the technician.  Environmental Factors  Ambient (room) temperature affects skin temperature.  R varies inversely with skin temperature.  Low ambient temperature leads to a lower skin temperature.  R increases, therefore, FFM is underestimated and % BF is overestimated. EXCI 252 13 Sources of BIA Measurement Error  Client’s Body Position during Whole-Body Resistance Measurement  Z values are altered by changes in body position  Z increases over time when in the supine position  Expert Recommendation: Lie supine at least 10 min before BIA measurement  Client’s arms must be abducted 30 to 45 degrees from the trunk  Client’s thighs must not be touching each other  Use of the Appropriate Prediction Equations to Estimate FFM  Generalized or population-specific equations EXCI 252 14 Ultrasound Method  Portable, noninvasive alternative to the SKF method.  Hand-held wand or probe sends and receives sound signals.  Allows the assessment of adipose tissue thicknesses deep within the body.  Two Types of Signal Images  A-Mode  Line drawing of peaks with different amplitudes.  B-Mode  A series of dots forming horizontal bands of varying brightness. EXCI 252 15 Ultrasound Method  A-Mode Ultrasound (Amplitude Mode)  Uses the same sites as the SKF method.  Conversion of site-specific subcutaneous fat thicknesses into %BF.  Use proprietary conversions & prediction equations that mimic the traditional SKF prediction equations.  A standardized A-mode ultrasound technique has not been developed yet. EXCI 252 16 Ultrasound Method  B-Mode Ultrasound (Brightness Modulation)  Uses a linear array of transducers to create a 2-dimensional image.  The transducer interprets the reflected signals & presents them as dots on a graphical display.  Lines or bands of dots depict tissue depths and interfaces.  Interpretation of the results of an ultrasound scan is more difficult than performing the scan.  Muller et al. (2016) standardized a B-mode ultrasound technique that uses 8 sites & specific positioning of the client during the identification of measurement sites. EXCI 252 17 Sources of Ultrasound Measurement Error  The accuracy & precision of ultrasound measurements & the ultrasound method are directly related to:  Technician Skill  Mode of Ultrasound  Signal Frequency  Sound Speed EXCI 252 18 Sources of Ultrasound Measurement Error  Technician Skill  During A-mode ultrasound measurements, a technician should apply just enough pressure with the probe so that the image begins to appear on the computer monitor.  The operator should apply the least force possible through the transducer to prevent tissue compression.  The application of too much pressure results in lower subcutaneous adipose tissue (SAT) thickness.  Mode of Ultrasound  A-Mode Ultrasound: No standardized ultrasound technique.  B-Mode Ultrasound: Has a standardized ultrasound technique. EXCI 252 19 Sources of Ultrasound Measurement Error  Signal Frequency  An inverse relationship exists between the transducer’s signal frequency & depth of penetration.  A-Mode Ultrasound: higher frequencies increase image resolution.  B-Mode Ultrasound: image resolution is greatest at the highest frequency (18 MHz).  Sound Speed  Wrong speed = error of about a 6% BF.  Thick layers of SAT: use a slow sound speed. EXCI 252 20 Skinfold Method  A Skinfold (SKF)  indirectly measures the thickness of subcutaneous adipose tissue.  Standardized Procedures for SKF Measurements  Skinfold Sites from the Anthropometric Standardization Reference Manual (ASRM)  Skinfold Sites for Jackson & Pollock (1978) and Jackson & Colleagues (1980) Generalized Equations  Recommendations for Skinfold Technicians EXCI 252 21 Skinfold Method Assumptions  A SKF is a good measure of subcutaneous (SC) fat.  The distribution of subcutaneous and internal fat is similar for all individuals within each gender.  The sum of several SKFs can be used to estimate total body fat because there is a relationship between SC fat & total body fat.  A relationship exists between the sum of SKFs & Db.  Age is an independent predictor of Db for both men & women. EXCI 252 22 Skinfold Method Assumptions  Population-Specific SKF Equations       Based on a linear relationship between SKF fat and Db Linear model Developed using homogeneous samples Underestimate %BF in fatter clients Overestimate %BF in leaner clients Generalized SKF Equations  Based on a non-linear relationship between SKF fat and Db  Quadratic (curvilinear) model  Developed using heterogeneous samples  Select the appropriate equation in Table 8.2 to convert Db (Table 8.3) to %BF EXCI 252 23 Skinfold Method Assumptions  Most SKF equations have been validated against HW at measured RV.   Most SKF equations use the sum of 2 or 3 SKF sites.   Assumptions of the 2-component model of body composition apply. Sites from both the upper and lower body are used. Good technicians accurately estimate the %BF of clients within ±3.5% BF of HW. EXCI 252 24 Sources of SKF Measurement Error  The accuracy & precision of SKF measurements & the SKF method are affected by:  Technician Skill  Type of SKF Caliper  Calibration of Caliper  Client Factors EXCI 252 25 Sources of SKF Measurement Error  Technician’s Skill  A lack of intertechnician reliability  Intertechnician error is a major source of measurement error.  The major causes of low intertester reliability are the improper location & measurement of the SKF sites.  Intertechnician Error • Abdomen = 8.8% • Thigh = 7.1% • Triceps = 3.0% • Subscapular = 3.0-5.0% • Suprailiac = 4.0% EXCI 252 26 Sources of SKF Measurement Error  Technician’s Skill  A lack of intratechnician reliability  Another source of error for the SKF method.  Need to practice your SKF technique on 50 to 100 clients to develop a high degree of skill & proficiency.  ASRM and ACSM (2018) • Take a minimum of 2 measurements at each site in a rotational order. EXCI 252 27 Sources of SKF Measurement Error  Technician’s Skill  A lack of intratechnician reliability  Take additional measurements if skinfold values vary from each other > 10%. • ASRM recommends ± 10% for duplicate measurements at each site.  ACSM (2018) recommends that 2 measurements at a given site need to be within 2 mm of each other. EXCI 252 28 Sources of SKF Measurement Error  Type of SKF Caliper High-quality metal calipers are accurate & precise throughout the range of measurement. Select a SKF caliper according to cost, durability, accuracy, precision, & type of caliper used to develop a specific SKF equation. EXCI 252 29 Sources of SKF Measurement Error  To minimize measurement error due to the type of caliper used to assess SKF thickness, follow these suggestions:  Use the same caliper when monitoring changes in SKF thicknesses.  Use the same type of caliper used to develop the specific SKF prediction equation, otherwise use a caliper that provides similar SKF measurements.  Periodically check the accuracy of your caliper & calibrate it if necessary. EXCI 252 30 Sources of SKF Measurement Error  Client Factors  Compressibility of adipose tissue  Hydration level  Immediately after exercise, especially in hot environments  Water retention during the menstrual cycle EXCI 252 31 Other Anthropometric Methods  Anthropometry  refers to the measurement of the size & proportion of the human body.  Anthropometric Methods  can be used to estimate body composition.  assess total & regional body composition.  Anthropometric Prediction Equations  estimate total body density (Db), relative body fat (%BF), & fat-free mass (FFM) from combinations of body weight, height, skeletal diameters, & circumferences. EXCI 252 32 Other Anthropometric Methods  Measures of Body Size  Body weight & stature (height)  Measures of Body Proportion  Ratios of weight to height  i.e., BMI  Assessment of the Sizes & Proportions of Body Segments  Circumferences, SKF thicknesses, skeletal diameters, & segment lengths EXCI 252 33 Circumference (C)  is a measure of the girth of a body segment.  e.g., arm, thigh, waist, or hip.  is affected by:  fat mass,  muscle mass, &  skeletal size. EXCI 252 34 Skeletal Diameter (D)  is a measure of bony width or breadth.  e.g., knee, ankle, or wrist.  Skeletal size is directly related to lean body mass (LBM).  LBM can be estimated from skeletal diameters.  is used to classify frame size in order to improve the validity of height-weight tables for evaluating body weight.  is an important estimator of the bone & muscle components of fat-free mass (FFM). EXCI 252 35 Anthropometric Indices Used to Assess Regional Fat Distribution & to Identify & Classify Disease Risk  Body Mass Index (BMI)  Waist Circumference (WC)  Waist-to-Hip Circumference Ratio (WHR)  Waist-to-Height Ratio (WHTR)  Sagittal Abdominal Diameter (SAD) EXCI 252 36 Body Mass Index  is the ratio of body weight to height squared.  = Wt / Ht2  Assumes that a disproportionately heavy person is so because of an excessive amount of fat mass.  Uses of BMI  To classify individuals as obese, overweight, & underweight.  To identify individuals at risk for obesity-related diseases.  To monitor changes in body fatness of clinical populations. EXCI 252 37 Body Mass Index Classification Classification Underweight BMI (kg·m-2 ) Obesity Class < 18.5 Normal 18.5 - 24.9 Overweight 25.0 - 29.9 Obesity 30.0 - 34.9 I 35.0 - 39.9 II ≥ 40.0 III From Panel E. Executive summary of the clinical guidelines on the identification, evaluation, & treatment of overweight & obesity in adults. Arch. Intern. Med. 1998; 158: 1855-1867. EXCI 252 38 Limitations of BMI  Overestimates body fat in persons who are very muscular.  Can underestimate body fat in persons who have lost muscle mass.  Gives a high BMI for very short persons (< 5 feet).  Not a good measure of visceral fat.  However, BMI is a better measure of nonabdominal & abdominal subcutaneous fat.  Does not provide information about body fat distribution.  Does not provide an assessment of body composition.  Factors such as age, ethnicity, body build, & frame size affect the relationship between BMI & %BF.  For a given BMI value, the % BF:  Older individuals > Younger individuals  Young adult females > Young adult males EXCI 252 39 Waist Circumference  is a useful measure of regional (abdominal) adiposity.  is a predictor of obesity-related cardiometabolic disease.  can be used to estimate health-related differences in cardiorespiratory fitness.  when coupled with BMI, predicts musculoskeletal injury risk & health risk better than BMI alone.  National Cholesterol Education Program (2001) WC Recommendations  Men: > 102 cm (40 in)  Women: > 88 cm (34.6 in)  evaluate obesity as a risk factor for cardiovascular & metabolic diseases EXCI 252 40 Waist Circumference  The waist circumference (WC) measurement depends on the method used:  CSEP-PATH (2021)  measure at the superior border of the iliac crest.  World Health Organization (WHO)  measure midway between the lowest ribs & the iliac crest.  Anthropometric Standardization Reference (ASRM)  measure at the narrowest part of the torso. EXCI 252 Manual 41 Waist-to-Hip Circumference Ratio  is an indirect measure of lower- and upper-body fat distribution.  has been used as an anthropometric measure of central adiposity & visceral fat.  = waist circumference / hip circumference.  values indicating a high risk for adverse health consequences:  Men: WHR > 0.94  Women: WHR > 0.82 EXCI 252 42 Waist-to-Hip Circumference Ratio  The WHR depends on the method used to measure waist circumference and hip circumference. CIRCUMFERENCE WHO ASRM Waist Midway between the lowest ribs & the iliac crest Narrowest part of the torso Hip Widest point over the greater trochanters Maximum extension of the buttocks EXCI 252 43 Limitations of WHR  Women’s WHR is affected by menopausal status.  Postmenopausal women demonstrate more of a male pattern of fat distribution.  Not valid for evaluating fat distribution in prepubertal children.  Accuracy in assessing visceral fat decreases with increasing fatness.  May not accurately detect changes in visceral fat accumulation.  Hip Circumference  is influenced only by subcutaneous fat deposition.  Waist Circumference  is affected by both visceral fat & subcutaneous fat depositions. EXCI 252 44 Waist-to-Height Ratio  = waist circumference / standing height.  has been suggested to be a better indicator of adiposity & health risks than WC alone.  As a rule, WC should be less than half the height.  Recommended Optimal WHTR + Adult BMI  Men: WHTR = 0.50 & BMI = 24.0 kg⋅m-2  Women: WHTR = 0.46 & BMI = 26.0 kg⋅m-2  Increased Risk of Premature Mortality  WHTR = 0.50 to 0.60 = “Consider Action” category  WHTR > 0.60 = “Take Action” category  risk increases dramatically. EXCI 252 45 Waist-to-Height Ratio  has been found to be consistently superior to both BMI & WC in terms of serving as an indicator of disease outcome or risk factors for:  cardiovascular diseases, hypertension, dyslipidemia, diabetes mellitus, & metabolic syndrome.  Ashwell Body Shape Chart  can be used to identify a client’s health risk based on body shape for:  men & women,  people of different ethnic groups, &  children ≥ 5 yrs of age. EXCI 252 46 Sagittal Abdominal Diameter  is a measure of the anteroposterior thickness of the abdomen at the umbilical level.  is a simple indicator of the amount of dysfunctional visceral adipose tissue in the body.  is more strongly related to risk factors for cardiovascular & metabolic diseases than WC, WHR, & BMI. EXCI 252 47 Sources of Anthropometric Measurement Error  The accuracy & reliability of anthropometric measures are potentially affected by:  Equipment  Technician Skill  Client Factors EXCI 252 48 Sources of Anthropometric Measurement Error  Equipment  Type of skeletal anthropometer or caliper (sliding or spreading) used to measure bony widths & body breadths  Precision characteristics & range of measurement  Improper maintenance of equipment  Lack of periodic calibration  Not using an anthropometric tape measure to measure circumferences  Gulick handle – a spring-loaded handle found in some anthropometric tapes that allows the application of a constant tension to the end of the tape. EXCI 252 49 Sources of Anthropometric Measurement Error  Technician Skill for Circumferences & Skeletal Diameters  Not a major source of error for C and SD compared to the SKF method  Must practice identification of measurement sites & measurement technique  Intertechnician variability is small for circumference measurements EXCI 252 50 Sources of Anthropometric Measurement Error  Client Factors  Although it is more difficult to obtain circumference measurements for obese individuals, circumferences are preferable to SKFs for measuring obese clients.  Accurate measurement of bony diameters in heavily muscled or obese individuals may be difficult. EXCI 252 51