26 Analyses of Human Body Physique and Body Composition
Dr. Meenal Dhall
Contents of this unit
Introduction
1) Factors Affecting Body Composition And Physique
1.1)Environment
1.2)Genetics
2) Models For Analysing Body Composition And Physique
2.1)Two Component Model
3)Analysis of Human Body Physique
3.1)Kretschmer’s System
3.2)William Sheldon
3.3) Conrad
3.4) Richard Parnell
3.5) Lundmann
3.6) Heath and Carter
4) Analysis of Body Composition
4.1) Lab Based Methods
4.1.1) Densitometric Methods
4.1.2) Potassium 40
4.1.3) Isotope Dilution
4.1.4) Absorptiometry
4.1.5) Neutron Activation
4.1.6) Computed Tomography
4.1.7) Magnetic Resonance Imaging
4.2) Field Based Methods
4.2.1) Anthropometry
4.2.2) Bioelectrical
Methods Summary
Learning Outcomes:-
- To understand the basic concepts of human body composition and physique.
- To understand how physique is dependent upon body composition.
- To know about the factors affecting human body physique and composition.
- To know the methods used to analyse body physique and composition.
INTRODUCTION
The basic body form of an individual which is visible only by looking at his or body shape and contours is known as his or somatotype or body physique. The concept of somatotype was introduced by William Sheldon in 1930’s. Since then it is awidely used concept by nutritionists, exercise physiologists and even medical practitioners. We all are combination of three basic body types or physiques i.e. ectomorph(linear), mesomorph(muscular) and endomorph(relative fatness). These morphological characterisation is basically inherited and is based upon skeletal frame and body composition. Body composition can be attributed to relative concentrations of basic elements present in the boy i.e. water, lipid, protein, and minerals. Body composition and physique are not constant entities and are altered both by genetics and environment.
1) FACTORS AFFECTING BODY COMPOSITION AND PHYSIQUE :-
1.1)ENVIRONMENT: It comprises of all the factors related to diet, physical activity level, exercise and environmental stress. For example. diet high in fat, carbohydrates alongwith low physical activity level leads towards a state of high fat content and contributing to increase in the endomorphy element.
1.2)GENETICS: Contribution of genetics in influencing body composition and physique can be explained with the help of following concepts:
1.2.1)Heritability:- Heritability accounts for variations caused due to recessive and dominant alleles and parental effect.
1.2.2)Body fat as polygenic trait:- So far 125 genes have been identified Buckhard (2007) associated with body fat out which 22 have been tested and proved by many scholars.
1.2.3)Imprinted genes:- Imprinted genes are those genes which are differentially expressed according to parental origin. For example there are two insulin genes IGF2 and IGFr which regulate foetal growth. These genes when are paternally inherited promote foetal growth and increase the chances of childhood obesity. While when it ismaternally inherited it leads to hindered foetal growth and decreased chances of childhood obesity.
1.2.4)Epigenetics :- This field of genetics deals with the gene and environment interaction leading to genotypic and phenotypic variability in bodycomposition and physique.
2) MODELS FOR ANALYSING BODY COMPOSITION AND PHYSIQUE
Naturally occurring basic elements like carbon, hydrogen and oxygen combine to form molecules, molecules combine to form cell organalles, cells which combine to form tissue compartments, tissues further combine giving rise to organs and organ system which leads to formation of body ofa full fledged organism. These levels of biological hierarchy represnt various models for analysyis of body type and its compostion. Two broadly classified models are two component model and multicomponent model.
2.1)TWO COMPONENT MODEL: it was given by Behnke et al in 1942. An inverse relation was established between body density and adiposity. On the basis of this equation for percentage body fat was given as (4.57/D – 4.142)*100 which was modified by Siri in 1956 as (4.95/D – 4.50)*100. Siri’s equation is considered to be more accurate as it also takes into account various errors calculaed as[ (Relative percentage ofwater)2 + (Protein:Mineral)2 + (Composition of adipose tissue)2]1/2 . Value of each error being 2.7%, 2.1% and 1.9% respectively.
3)ANALYSIS OF HUMAN BODY PHYSIQUE
Analysis of human body physique is majorly based upon somatotyping and somatometry. These are regarded as central techniques for determining ones body physique. Somatotyping refers to analysis of body physique based upon exteranally visible morphological characters while somatometry refers to analysis made with the help of body measurements. Attempts for analysing human body physique have a long and honourable history with Hippocrates being the first to analyse human physique as linear(habitus phythiscus) and lateral(habitus appoplecticus).
3.1)Kretschmer’s System (1921):
Kretschmer described four main types of physiques:
3.1.1) PYKNIC: The individuals with short and thick set with large body cavities,short extremities, round chest, smallhands and feet and body being well padded with fat belong to this category.
3.1.2) ATHLETIC: It includes individuals with well developed musculature,bony structure and well proportioned body.
3.1.3) LEPTOSOME: Individuals belonging tothis category areharacterised by linear trunk,limbs and face with small bones and little musculature.
3.1.4) DYSPLASTIC: It includes individuals having admixture of characteristics of other three types.
3.2) William Sheldon (1940):
William Sheldon and his colleagues photographed 4000 collegemen in three poses namely dorsal, ventral and lateral. Height and weight measurements were also taken. With the help of photographs and measurements eighteen indices were derived which were used to classify individuals based upon the proportion of three basic components of body structure which are endomorphy, mesomorphy and ectomorphy.These components correspond to the three germinal layers i.e endoderm, mesoderm and ectoderm. The three components can be explained as follows:
3.2.1) ENDOMORPHY: The endomorphic individuals have preponderance of digestive viscera and are characterised by round and soft physique with less prominent body contours.
3.2.2) MESOMORPHY: The mesomorphic individuals have preponderance of bones, muscles and connective tissue. They have muscular, sturdy and heavy physique.
3.2.3) ECTOMORPHY: The ectomorphic individuals are characterised by linearity and fragility of body built. They have little muscle and fat.
The eighteen indices prepared by sheldon and his colleagues were used to classify each individual on a seven point scale. Least expression of a particular component was shown by the point ‘1’, moderate by ‘4’and complete expression by ‘7’. Hence the three components were assigned ponts as follows:
3.2.4) ENDOMORPHIC- 7-1-1
3.2.5) MESOMORPHIC-1-7-1
3.2.6) ECTOMORPHIC-1-1-7
Balanced physique was assumed to be having points as 3-4-3.
3.2.7) ADAVANTAGES:
- The methods used for assigning any physique were based upon somatometric measurements which can be taken as being reliabe and easy for others to apply for obtaining similar comparable data.
- The nature of the variation in physical traits was continuous.
3.2.8) DISADVANTAGES:
- Analysis of physique using Sheldon’s approach requires detailed training and practice.
- The method of photoscopy appeared to be more of subjective type.
- Scales used were arbitary and so less reliable.
- Many scholars argued that a person’s somatotype isn’t fixed and hence can change over a period of time.
3.3) Conrad (1941):
Conrad tried to rectify the shortcomings of Sheldon’s classifications by taking into account other quantitative measures. He defined two indices namely metric and plastic. Metric index was calculated using body stature and transverse and sagittal chest girths while plastic index was calculated using shoulder width and forearm and hand girth. The values of these two indices were then plotted in a coordinate system. Centre of the coordinate designated an ideal body physique being metromorphic-metroplastic type. Other types were designated using various axes on the coordinate representing other types of physiques such as leptomorphic, pyknomorphic etc.
3.3.1) ADVANTAGE: The advantage of the method lies in its being practical, objective and distinct.
3.4) Richard Parnell (1958):
He took into account following anthropometric measurements to derive the classification of human physique:
He used these ten measurements to derive the estimates of three body components fatness, linearity and muscularity. Just as in case of a Sheldonian somatotype these components were also rated on a seven point scale.
3.4.11) ADVANTAGE: The method was too objective and it paved the way for other upcoming researchers to work on the concept.
3.5) Lundmann (1964) :
Lundmann described the body forms on the basis of racial and ethnic grounds. He used photographs, anthropometric indices and other relevant physiological data.
3.6) Heath and Carter (1967):
This method is the most widely used one as it applied both Sheldon’s photoscopic method as well as
Parnell’s anthropometric method. The analysis involves following steps :
3.6.1) Anthropometry: The ten anthropometric measurements applied by Parnell are taken and used to calculate various indices and ratios.
3.6.2) Rating form and equations: The measurements are then filled into rating form or into equations.
3.6.3) Somatocharts: Individual and mean somatotypes are plotted on an an improved somatotype chart which was proposed by Parnell.
3.6.4) Somatotype categorisation: The subjects are then classified in the following seven categories :
3.6.4.1) Central:- No component differs by more than one unit from the other two.
3.6.4.2) Endomorph-mesomorph:- Endomorphy and mesomorphy are almost equal and ectomorphy is smaller.
3.6.4.3) Mesomorph:- Mesomorphy is dominant , endomorphy and ectomorphy are pretty much smaller.
3.6.4.4) Mesomorph-ectomorph:-Mesomorphy and ectomorphy are equal and endomorphy is smaller.
3.6.4.5) Ectomorph: – Ectomorphy is dominant, endomorphy and mesomorphy are smaller.
3.6.4.6) Ectomorph-endomorph:- Ectomorphy and endomorphy are equal and mesomorphy is lower.
4) ANALYSIS OF BODY COMPOSITION
Assessment of body composition can be done both in the laboratory as well as on the field. Thus methods used for analysing human body composition can be broadly categorised as lab based and field based methods.
4.1) LAB BASED METHODS
4.1.1) DENSITOMETRIC METHODS:
Density of human body can be calculated as body mass divided by its volume. In densitometry methods this density is used to find out fat free mass, fat mass and percentage body fat by putting it into various conversion formulae. The density of body can be found out using any of the methods described below:
4.1.1.1) Hydrodensitometry – Using Archimedes principle body volume is determined by weighing body once in air and then under water. The difference between the two masses is equivalent to the volume of the body. The density is then calculated by dividing mass by volume. Corrections are made for the amount of air present in the lungs and gut.
LIMITATION: This method can only be used in adults, adolescents and children above eight years of age.
4.1.1.2) Air displacement plethysmography – In this method instead of water, volume of air displaced is taken into account to find out the body volume. The instrument is known as Bod Pod and for children its Pea Pod. The instrument consists of two chambers separated by a pulsating diaphragm which is used to vary the air pressure. Volume of air displaced by the body when seated in the chamber is used to calculate the density. Breathing apparatus is used to measure the volume of air present in the lungs.
LIMITATION: Same as hydrodensitometry.
4.1.2) POTASSIUM 40:
Potassium is a vital mineral found in the intracellular fluids which can be used to estimate body cell mass. Body cell mass is the metabolically active fat free intracellular space. Along with intracellular fluids it also contains some intracellular solids. Hence, by measuring the Potassium content in the intracellular fluid body cell mass can be calculated.
LIMITATION: The level of Potassium in the body fluid can sometimes give inaccurate estimate of fat free mass.
4.1.3) ISOTOPE DILUTION METHOD:
The stable isotopes like deuterium oxide (2H2O) and oxygen (18O2) administered orally in small doses. This increases the level of naturally occurring isotopes in the body. Body fluid sample is then analysed using mass spectrometry. It gives the estimate of fat mass and fat free mass is calculated using total body weight measurement.
4.1.4) ABSORPTIOMETRY METHODS:
There are two well know absorptiometry methods the earlier used DPA(Dual Photon Absorptiometry) and the recent one DXA(Dual X-ray Absorptiometry). In DPA a radionuclide source and a digital detector was used. In DXA low energy X-ray source is used which gives more accurate results. The method uses two compartment body composition model. It gives an estimate of bone mass, lean body mass and fat mass.
LIMITATION: Can’t be used for subjects having metal implants and those who are unable to lie in supine position
4.1.5) NEUTRON ACTIVATION:
The method makes estimation at atomic level. A shielded chamber is there in which subject is bombarded with fast moving neutrons. These neutrons interact with the elements of interest in the body like carbon, nitrogen, hydrogen etc. and form their respective unstable isotopes. These unstable isotopes emit gamma rays detection of which gives the estimate of body component made out of molecules of that element.
LIMITATION: The technique isn’t acceptable for infants and children.
4.1.6) COMPUTED TOMOGRAPHY:
3D images of tissues and various parts of the organs are created from different angles in slices and spiral form. Equipment makes use of an X-ray source and a detector. The estimates of visceral adipose tissue, organ volumes, bone mineral densityetc. can be made at highly accurate level.
4.1.7) MAGNETIC RESONANCE IMAGING:
The subject is positioned in a strong magnetic field and is exposed to radiofrequency pulses. These pulses are capable of exciting the hydrogen atoms in the tissues. Thus the estimates of visceral adipose fat, organ volume, skeletal muscle size, bone mineral density etc can be made accurately as every part of the body contains hydrogen atom in some or other form.
4.2) FIELD BASED METHODS
4.2.1) BIOELECTRICAL METHODS:
4.2.1.1) TOBEC (Total Body Electrical Conductivity): Low energy electromagnetic coil is there in a gantry table. The body is made to transverse the coil which creates disturbances in the measured conductance because of water and electrolytes present in the body. This disturbed conductance is then converted into electrical signals which are further converted into body composition estimates.
4.2.1.2) BIA (Bioelectrical Impedance Analyser): The basic principle is similar as that of TOBEC. Instead of a gantry table electrodes are there which are used to pass low frequency electrical signals through palm and feet. The variation in the conductance due to body fluids and electrolytes gives the estimates of fat free mass which can be further used to estimate other body components.
4.2.2) ANTHROPOMETRY:
During population based studies anthropometric measurements have been proven to be highly successful. Basic measurements like weight, stature, waist circumference, hip circumference can be used to calculate indices like BMI, Ponderal, WHR etc. Measurements like mid upper arm circumference, triceps and biceps skinfold thickness can be used to calculate total area, fat area, muscle area and muscle thickness of upper arm. Anthropometric measurements can also be used to calculate whole body fat and fat free mass and percentage body fat.
- 5) CHANGES TAKING PLACE IN BODY COMPOSITION AND PHYSIQUE DURING VARIOUS STAGES OF LIFE
5.1) Infancy: There are rapid changes in the body composition and physique during birth and following time. During first few days 5-10% of infant body weight is lost which is primarily water. Amount of extracellular water decreases while intracellular water content increases. Weight gets doubled by 4-5 months of age major portion of which is represented by the brain. An infant contains great amount of brown adipose tissue. As a result it can be said that infants have more reserved stores of fat in them shifting their body physique towards more of endomorphic type.
5.2) Childhood: There is a little shift to body composition changes as infancy approaches childhood period. Girls have higher percentage of body fat that boys. There is a small increase in body weight. BMI peaks during late childhood.
5.3) Adolescence: Adolescence is a stage when drastic and rapid changes take place in the body. Sexual dimorphism appears to be more pronounced. Females get additional fat deposits as breast tissue and in hips and thighs. Boys have an increase in lean muscle mass. It’s an age of linearity. However, endomorphic content and obesity can result due to hypoactive lifestyle and bad food habits. Secular trends can result in varied levels of body physique in different individuals though the age being of that of a balanced physique.
5.4) Adulthood and senescence: Visible fluctuations in bone and fat mass are there. Females gain weight during pregnancy giving rise to increase in endomorphic element resulting in increase in fat reserves. Males however tend to have nearly stagnant body composition during adulthood. Progressing towards senescence both males and females suffer from unhealthy changes in body composition and physique. There occurs an increase in visceral fat, subcutaneous fat and fat in the blood vessels. Women have drastic loss of bone minerals while premenopausal and menopausal period. Body physique changes from being more idealized one towards more of imbalanced type.
SUMMARY:
The basic body form of an individual which is visible only by looking at his or body shape and contours is known as his or somatotype or body physique.. We all are combination of three basic body types or physiques i.e. ectomorph(linear), mesomorph(muscular) and endomorph(relative fatness). These morphological characterisation is basically inherited and is based upon skeletal frame and body composition. Body composition can be attributed to relative concentrations of basic elements present in the boy i.e. water, lipid, protein, and minerals. Body composition and physique are not constant entities and are altered both by genetics and environment.The levels of biological hierarchy represnt various models for analysyis of body type and its compostion. Analysis of body composition can be performed both in the lab and on the field. Lab based methods include densitometry, neutron activation, isotope dilution, absorptiometry, CT scan and MRI. Field based methods include anthropometry and bioelectrical impedence. Analysis of human body physique is majorly based upon somatotyping and somatometry.Variuos researchers like Sheldon, Parnell and Heathe-Carter have given different techniques based upon these concepts of somatometry and somatotyping. Body composition and physique keep changing during various stages of life. Basic concept into play is the relative proportion of fat and fat free mass leading to idealised and non idealised body physique conditions.
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