ACSM CH4: Health-Related Physical Fitness Testing & Interpretation - Body Composition

A Comprehensive Health Fitness Evaluation:

*Prescreening/risk classification Resting HR, BP, height, weight, body mass index, and ECG (if appropriate) Body composition Cardiorespiratory fitness Muscular strength Muscular endurance Flexibility -Informed consent & exercise preparticipation screening -Preexercise evaluation -Resting measurements -Circumference measurements & body comp analysis -CRF, muscular fitness, & flexibility measurements *Risk vs potential benefits of health-related physical fitness testing

Conversion of Body Density to Body Comp:

-% BF can be estimated once body density has been determined -The most commonly used prediction equation to estimate % BF from body density was derived from the 2-component model of body comp *[(4.95/Db) - 4.50] X 100 -Db = body density -Age, gender, race, & certain disease states may affect the density of FFM, w/ much of this variance related to the BMD component of FFM

Measurement of Resting HR & BP:

-A comprehensive physical fitness assessment includes the measurement of resting HR & BP -HR Measurements *Pulse palpitation *Auscultation *HR monitor BP measurements *See Box 3.5

Standardized Description of Circumference Sites & Procedures:

-Abdomen: W/ the subject standing upright & relaxed, a horizontal measure taken at the height of the iliac crest, usually at the level of the umbilicus. -Arm: W/ the subject standing erect & arms hanging freely at the sides w/ hands facing the thigh, a horizontal measure midway b/n the acromion & olecranon processes. -Buttocks/Hips: W/ the subject standing erect & feet together, a horizontal measure is taken at the max circumference of buttocks. This measure is used for the hip measure in a waist/hip measure. -Calf: W/ the subject standing erect (feet apart ~20 cm), a horizontal measure taken at the level of the max circumference b/n the knee & the ankle, perpendicular to the long axis. -Forearm: W/ the subject standing, arms hanging downward but slightly away from the trunk & palms facing anteriorly, a measure is taken perpendicular to the long axis at the max circumference. -Hips/Thigh: W/ the subject standing, legs slightly apart (~10 cm), a horizontal measure is taken at the max circumference of the hip/proximal thigh, just below the gluteal fold. -Mid-Thigh: W/ the subject standing & 1 foot on a bench so the knee is flexed at 90 degrees, a measure is taken midway b/n the inguinal crease & the proximal border of the patella, perpendicular to the long axis. -Waist: W/ the subject standing, arms at the sides, feet together, & abdomen relaxed, a horizontal measure is taken at the narrowest part of the torso (above the umbilicus & below the xiphoid process). *The National Obesity Task Force (NOTF) suggests obtaining a horizontal measure directly above the iliac crest as a method to enhance standardization. Unfortunately, current formula are not predicated on the NOTF suggested site.

Skinfold Sites:

-Abdominal: Vertical fold; 2 cm to the right side of the umbilicus -Triceps: Vertical fold; on the posterior midline of the upper arm, halfway b/n the acromion & olecranon processes, w/ the arm held freely to the side of the body -Biceps: Vertical fold; on the anterior aspect of the arm over the belly of the biceps muscle, 1 cm above the level used to mark the triceps site -Chest/Pectoral: Diagonal fold; 1-half the distance b/n the anterior axillary line & the nipple (men), or 1-third of the distance b/n the anterior axillary line & the nipple (women) -Medial calf: Vertical fold; at the max circumference of the calf on the midline of its medial border -Midaxillary: Vertical fold; on the midaxillary line at the level of the xiphoid process of the sternum. An alternate method is a horizontal fold taken at the level of the xiphoid/sternal border in the midaxillary line -Subscapular: Diagonal fold (at a 45-degree angle); 1-2 cm below the inferior angle of the scapula -Suprailiac: Diagonal fold; in line w/ the natural angle of the iliac crest taken in the anterior axillary line immediately superior to the iliac crest -Thigh: Vertical fold; on the anterior midline of the thigh, midway b/n the proximal border of the patella & the inguinal crease (hip)

Standardized Description of Circumference Sites & Procedures (cont.): PROCEDURES

-All measurements should be made w/ a flexible yet inelastic tape measure. -The tape should be placed on the skin surface w/out compressing the subcutaneous adipose tissue. -If a Gulick spring-loaded handle is used, the handle should be extended to the same marking w/ each trial. -Take duplicate measures at each site & retest if duplicate measurements are not w/in 5 mm. -Rotate through measurement sites or allow time for skin to regain normal texture.

Body Comp (cont.) (1):

-Anthropometric methods: *Height, weight, & BMI *Circumferences *Skinfold measurements -Densitometry: *Hydrodensitometry (underwater) weighing *Plethysmography -Other techniques *Dual-energy X-ray absorptiometry (DEXA) *Total body electrical conductivity (TOBEC) *Bioelectrical impedance analysis (BIA)

Body Comp (cont.):

-Basic body comp can be expressed as the relative % of body mass that is fat & fat-free tissue using a 2-compartment model. Body comp can be estimated w/ methods that vary in terms of complexity, cost, & accuracy -Before collecting data for body comp assessment, the technician must be trained, experienced in the techniques, & already have demonstrated reliability in his or her measurements

Skinfold Measurements:

-Body comp determined from skinfold thickness measurements correlates well (r = 0.70-0.90) w/ body comp determined by hydrodensitometry. -The principle behind skinfold measurements is that the amount of subcutaneous fat is proportional to the total amount of body fat. -It is assumed that close to 1-third of the total fat is located subcutaneously.

Height, Weight, & BMI

-Body weight should be measured using a calibrated balance beam or electronic scale w/ the client wearing minimal clothing & having empty pockets. -Shoes should be removed prior to the use of a stadiometer for the measurement of height. -The BMI is used to assess weight relative to height & is calculated by dividing body weight in kilograms by height in meters squared (kg · m−2)

Basic Principles & Guidelines-Test Organization (cont.):

-Calibrate all equipment (e.g., cycle ergometer, treadmill, sphygmomanometer) at least monthly, or more frequently based on use. -Certain equipment such as ventilatory expired gas analysis systems should be calibrated prior to each test according to manufacturers' specifications. -Skinfold calipers should be regularly checked for accuracy & sent to the manufacturer for calibration when needed. -Document all equipment calibration.

Purposes of Health-Related Physical Fitness Testing:

-Collecting baseline data & educating participants about their present health/fitness status relative to health-related standards & age- & sex-matched norms -Providing data that are helpful in development of individualized exercise prescriptions (Ex Rx) to address all health/fitness components -Collecting follow-up data that allow evaluation of progress following an Ex Rx & long-term monitoring as participants age -Motivating participants by establishing reasonable & attainable health/fitness goals

Other Techniques:

-Dual-energy X-ray absorptiometry (DEXA) -Total body electrical conductivity (TOBEC) *Subject lies in a cylinder that generates a very weak electromagnetic field. The strength of the field depends on the electrolytes found in the subject's body water. -Bioelectrical impedance analysis (BIA)

Densitometry (cont.):

-Hydrodensitometry (underwater) weighing -Based on Archimedes' principle: When a body is immersed in water, it is buoyed by a counterforce = to the weight of the water displaced. -This loss of weight in water allows for calculation of body volume -Bone & muscle tissue are denser than water, whereas fat tissue is < dense. Therefore, when 2 individuals have the same total body mass, the person w/ more fat-free mass (FFM) (i.e., body mass 2 fat mass [FM]) weighs more in water & has a higher body density & lower % of BF compared to the person w/ < FFM.

Body Comp.

-It is well established that excess body fat, particularly when located centrally around the abdomen, is associated w/ many chronic conditions including hypertension, metabolic syndrome, T2DM, stroke, CVD, & dyslipidemia *Approximately 2-thirds (68.5%) of American adults are classified as either overweight or obese, & more than a third (34.9%) are classified as obese *Nearly 1-third (31.8%) of American children & adolescents are overweight or obese -Health-related changes in body comp that accompany aging such as sarcopenia

Plethysmography:

-Measured by air rather than water displacement -Uses a dual-chamber plethysmograph that measures body volume by changes in pressure in a closed chamber -This technology is now well established & generally reduces the anxiety associated w/ the technique of hydrodensitometry

Basic Principles & Guidelines-Test Environment:

-Test anxiety, emotional problems, food in the stomach, bladder distention, room temp, & ventilation should be controlled as much as possible. -To minimize subject anxiety, the test procedures should be explained adequately, & the test environment should be quiet & private. -The room should be equipped w/ a comfortable seat &/or exam table to be used for resting BP & HR. -The demeanor of personnel should be relaxed & confident to put the subject at ease -The exercise professional should be familiar w/ the emergency response plan

Circumferences (cont.): WHR

-The WHR is the circumference of the waist (above the iliac crest) divided by the circumference of the hips (buttocks/hips measure) & has traditionally been used as a simple method for assessing body fat distribution & identifying individuals w/ higher & more detrimental amounts of abdominal fat. -Health risk increases as WHR increases, & the standards for risk vary w/ age & sex. -Health risk is very high for young men when WHR is >0.95 & for young women when WHR is >0.86. -For individuals aged 60-69 yr, the WHR cutoff values are >1.03 for men & >0.90 for women for the same high-risk classification as young adults.

Densitometry:

-The estimate of total BF % can be derived from a measurement of whole-body density using the ratio of body mass to body volume -Densitometry has been used as a reference or criterion standard for assessing body comp for many years although DEXA has recently gained popularity -The limiting factor in the measurement of body density is the accuracy of the body volume measurement bc body mass is measured simply as body weight

Skinfold Measurements (cont.):

-The exact proportion of subcutaneous to total fat varies w/ sex, age, & race. -Therefore, regression equations used to convert sum of skinfolds to % BF should consider these variables for > accuracy. -The accuracy of predicting % BF from skinfolds is approximately 3.5%, assuming appropriate techniques & equations have been used

Circumferences:

-The pattern of body fat distribution is recognized as an important indicator of health & prognosis. -Android obesity that is characterized by more fat on the trunk (abdominal fat) increases the risk of hypertension, metabolic syndrome, T2DM, dyslipidemia, CVD, & premature death compared w/ individuals who demonstrate gynoid or obesity (fat distributed in the hip & thigh). -Individuals w/ increased visceral fat (i.e., fat w/in & surrounding thoracic & abdominal cavities) confer a higher risk for development of the metsyn -A cloth tape measure w/ a spring-loaded handle (Gulick tape measure) reduces skin compression & improves consistency of measurement. -Duplicate measurements are recommended at each site & should be obtained in a rotational instead of a consecutive order (take measurements of all sites being assessed & then repeat the sequence). -The average of the 2 measures is used provided they do not differ by more than 5mm.

Circumferences (cont.): WAIST

-The waist circumference can be used alone as an indicator of health risk bc abdominal obesity is the primary issue -Although BMI & waist circumference are correlated, waist circumference is a better measure of visceral adiposity which can be varied w/in a given BMI -Previous research demonstrated that the waist circumference thresholds shown in Table 4.1 effectively identify individuals at increased health risk across the different BMI categories. -This data is based on a waist circumference taken at the level of the iliac crest

Skinfold Measurements (cont.): (1)

-Various regression equations have been developed to predict body density or % BF from skinfold measurements. Box 4.3 lists generalized equations that allow calculation of body density for a wide range of individuals -A useful alternative to using skinfolds to predict BF is to just track change in measurements at individual skinfold sites or use the sum of skinfolds

Basic Principles & Guidelines-Test Organization (cont.) (2):

-When multiple tests are to be administered, the organization of the testing session can be very important, depending on what physical fitness components are to be evaluated. -An optimal testing order for multiple health-related components of fitness (i.e., CRF, muscular fitness, & flexibility) has not been established, but sufficient time should be allowed for HR & BP to return to baseline b/n tests conducted serially. -Bc certain meds, such as β-blockers which lower HR, will affect some physical fitness test results, use of these meds should be noted.

Skinfold Procedures:

1) take measurements on the right side of the body 2) place the calipers 1 cm away from the thumb and finger, perpendicular to the skinfold and halfway between the crest and the base of the fold 3) maintain the pinch while reading the calipers 4) wait 1-2 seconds (and not longer) before reading the calipers 5) take duplicate measurements at each side 6) retest if the measurements do not fall within 1-2 mm 7) rotate through the measurement sites, or allow time for the skin to regain its normal texture and thickness 8) record the measurements on data sheets

Skinfold Measurements (cont.): ERRORS

Factors that may contribute to measurement error w/in skinfold assessment include: -Poor anatomical landmark identification -Poor measurement technique -An inexperienced evaluator -An extremely obese or extremely lean subject -An improperly calibrated caliper

Basic Principles & Guidelines-Test Organization (cont.) (1):

Resting measurements should be obtained 1st: -HR -BP -Height -Weight -Body comp

Basic Principles & Guidelines-Test Organization:

The following should be accomplished before the client/patient arrives at the test site: -Ensure consent & screening forms, data recording sheets, & any related testing documents are available in the client's file & available for the test's administration. -Ensure a room temp b/n 68-72F (20-22C) & humidity of < than 60% w/ adequate airflow

Body Composition:

The ratio of body fat to lean body tissue, including muscle, bone, water, and connective tissue such as ligaments, cartilage, and tendons

Body Comp Norms:

There are no universally accepted norms for body comp, however, -A range of 10%-22% & 20%-32% for men & women, respectively, has long been viewed as satisfactory for health -More recent data support this range although age & race, in addition to sex, impact what may be construed as a healthy % BF