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INTRODUCTION

The physical structure of the growing child has been systematically studied for over 150 years

(Meredith, 1936; Krogman, 1955; Tanner, 1981). The basic concepts are built on a strong

historical foundation in the medical, anthropological and human biological sciences (Morley et

al., 1968; Cameron, 1991; Malina et al., 2004). These aspects of human biology have been

studied at the level of the individual as well as in samples of children within communities and

national populations (Tanner, 1953; Johnson, 1970, 1971; Marshall, 1981; Malina and Roche,

1983). These studies have contributed to our understanding of human biological variation. It is

clear that there is a wide range of variation among individuals in the population (Eveleth andTanner, 1990; Cameron, 1992). A significant portion of this biological variation in adults in any

population has its origin in the prenatal period (Tanner, 1989) and the growing years by

processes which have been shown to be quite plastic (Tanner and Thomson,1970; Roche, 1999).

The influence of environmental factors such as infant and childhood diseases thought to interact

with a childs genetic potential for growth and maturation has been elaborated (Cameron, 1991,

1992). The role of the socioeconomic background and lifestyle variables which may influence

patterns of nutritional intake (Ulijaszek, 2006), the patterns of physical activity and other

environmental stresses which affect the development of the physique during growth is currently

engaging research (Field et al., 2005; Wardle et al., 2006). The study of growth and maturation

has provided useful information relevant to several more specific issues including the physical

status, progress, prediction, tracking, comparison and interpretation of growth and maturity

(Malina et al., 2004).

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Adolescent growth period

From birth to early adulthood, growth in stature has been shown to follow a four-phase pattern:

1) rapid gain in infancy and early childhood, 2) steady gain during middle childhood, 3) rapid

gain during the adolescent spurt, and 4) slow increase until growth ceases with the attainment of

adult stature (Kuczmarski et al., 2000). Body mass, however, usually continues to increase into

adult life.

The adolescent period is a phase of rapid physical growth characterized by increase in body

dimensions in all directions (Tanner, 1962). This measurable increase in size occurs as a result of

changes in the composition as well as the relative proportions of the constituent parts of the bodysuch as bone, muscle, adipose tissue and the internal or visceral organs (Cameron, 1984). These

changes are induced primarily by the brain which sends the appropriate signals in the form of

hormones at specific periods during the normal aging process (Bloom, 1964). The period

represents an important transition stage in the development of adult morphologic character of all

individuals. Inherited physical and behavioral traits that both determine and influence

performance attain to their full potential during this period. It also represents a critical stage in

the establishment and manifestation of adult health risk factors (Malina et al., 2004).

Adolescence is difficult to define in terms of chronological age because of the variation in the

time of its onset and termination. The World Health Organization (WHO) defines the age of

adolescence as between 10 and 18 years (WHO, 1995)but certain authorities (Rolland-Cachera

et al., 1991; Suwa et al., 1992; Roche and Guo, 2001; Malina et al., 2004), recommend that the

age ranges 8 to 19 years in girls and 10 to 22 years in boys are more appropriate as limits for

normal variation in the onset and termination of adolescence. During this period, most bodily

systems become adult both structurally and functionally, i.e. they reach maturity. Structurally,

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adolescence commences with acceleration in the rate of growth in stature, which marks the onset

of the adolescent growth spurt. The rate of growth in height reaches a peak, then begins a slower

or decelerative phase, and finally terminates with the attainment of adult stature. Functionally,

adolescence is usually viewed in terms of sexual maturity, which actually begins with changes in

the neuroendocrine system before overt physical changes and terminates with the attainment of

mature reproductive function. Somatic growth and maturation during adolescence has also been

investigated in the context of the body build or physique (Carter, 2006).

Role of urban population dynamics the development of the Adolescent Physique

Post-colonial urban populations represent an interesting ecological milieu for the critical

evaluation of the scope and extent of the evolutionary plasticity and resilience ofHomo sapiens

(Leonard and Crawford, 2002). The manner in which pre-colonial adolescent populations in

West Africa have responded to the sociocultural dimension of the interventionist policies of the

colonial and post-colonial state and the biological impact of such responses have only recently

begun to receive the attention of biological anthropologists (Garnieret al., 2003; Benefice et al.,

2003). An examination of the anthropological features- social, cultural and biological- of this

sub-region may reveal patterns which could illustrate the role of cross-cultural interaction in

defining some metaphorical trends of biological adaptation observable in contemporary West

Africa. Nigeria is a country located on the west coast of Africa. With a southern Atlantic

coastline extending around the Gulf of Guinea (4.20N 6.00E), its centre in the Sahel savannah

and its northernmost part reaching as far as the Sahara desert (Illela, in Sokoto State lies due

13.49N 5.20E: source: Collins-Longman Atlas, 1981) and with a human population officially

determined at 140.8 million (National Population Commission of Nigeria, 2006), it consists of a

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heterogeneous mixture of numerous and diverse ethnic groups whose fairly well defined socio-

cultural habits and life-styles have been established for many centuries. European colonization,

urbanization and modernization since the late 19th century, however, have combined to cause

huge socio-cultural schisms in the polity, with relocation of a substantial portion of the rural

population from its traditional and mainly agrarian lifestyle into quasi-industrial townships and

cities with the attendant evolution of ghettos and urban slums. This massive overhauling of age-

old social structures, values, privileges and lifestyles has created new and often entirely different

kinds of loci for physical and social interactions through such places as the office, school and

residential environment. Changes in job and business opportunities across the various socialstrata appear to have resulted in a socio-economic paradigm shift that could be defined in terms

of new or westernized lifestyles. Two major and direct consequences of this development have

been the change in the dietary patterns of many families as well as an increase in the frequency

of inter-ethnic marriages. Transformations arising from the additional variability in the genotypic

and phenotypic disposition of children born and nurtured in such communities would thus be

manifested as changes in their growth patterns and their body builds. It would, therefore, be

expected to represent an additional source of genetic variability, a phenomenon apparently not

limited to Nigeria but most probably occurring in several other countries in the West African

sub-region that have also experienced similar patterns of western colonization. The city of Lagos

is a community where the interventionist policy of colonial and post-colonial government has

had a major sociocultural impact. Originally founded and predominantly inhabited by Yoruba-

speaking natives, the cumulative effects of five hundred years of socioeconomic interaction with

the Portuguese and other European and Mediterranean maritime traders, two hundred years as a

major trans-Atlantic slave trade seaport, a century of British colonization and the final

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destination of more than one hundred years of intense rural-urban migration of people from

native Yoruba groups as well as non-native Nigerian ethnic groups, has transformed the city into

an intensely multi-ethnic hotbed. It has been suggested that approximately one-third of the

current population consists of Ibo-speaking Nigerians, aside of other substantially well-

represented non- indigenous ethnic groups. This wide spectrum of variability, in terms of the

sociocultural lifestyles, economic and living standards and dietary habits, would expectedly be

manifested in widely variable physiques of the people especially, among the children and

adolescent youth. (www.lagosstate.gov.ng/about/about3.htm).

While the foregoing description is partly anecdotal and may be viewed as having little scientificbasis, such reports of socio-cultural interaction and behavior are rare in scientific literature on

Nigerian children, and therefore, should not be ignored as a possible explanation for the

variations in somatotype distribution in the area being investigated. The transformations

described may have implications for the genetic structure, the social organization, and in turn the

biological well-being of the population.

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LITERATURE REVIEW

European and American growth studies

A review of the history of the study of growth suggests that the earliest published work on the

subject was based on data generated from North America and Europe. A detailed account has

been published in Origins of the Study of Human Growth, (Boyd, 1980), and A History of the

Study of Human Growth, (Tanner, 1981). The work of Boyd (1980) was based on the unfinished

manuscripts of Richard Scammon, which were first reported in 1923 in the 11th edition of

Morris Anatomy and subsequently republished in his 1930 Sigma XIlecture (Scammon, 1930).

Boyd (1980) considered early discussions of the life cycle, including description of prenatal and

postnatal stages, from antiquity to A.D.1700 and then more specific studies of growth in Europe

and North America from 1700 to 1940. Tanner (1981) briefly considered the ancient world, the

Middle Ages, and the Renaissance and then presented a comprehensive discussion of growth

studies from the 18th century through the major North American and European longitudinal

studies. Earlier reports also provide an excellent background to the relatively long history of the

study of growth in Europe and the United States (U.S.). Meredith (1936) reviewed American

research on growth of children before 1900, and Krogman (1941) provided a comprehensive

compilation of European and North American growth studies before 1940, focusing primarily on

data from the 1920s and 1930s. Krogman (1950, 1955) also presented a syllabus of concepts and

techniques for the study of growth which was followed by a summary of related literature

published between 1950 and 1955. Meredith (1969, 1971, and 1987) also reported summaries of

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data from different areas of the world dealing with specific body dimensions in specific age

groups between birth and adulthood.

Roche and Malina (1983) provide detailed tabular summaries for a variety of indicators of

growth and maturity in North American since 1940 in a two-volume compendium, Manual of

Physical Status and Performance in childhood. Eveleth and Tanners (1990) Worldwide

Variation in Human Growth is a compendium of data on growth and maturation from many

regions of the world and also includes a discussion of factors that influence these processes.

Malina et al. (2004) presented an in-depth description and analysis of growth studies from the

U.S., Europe, Australia, Latin America and Asia in Growth, Maturation and Physical Activity

(2nd ed.).

African growth Studies.

Marshall (1981) has reviewed the available literature that examined stature and body mass in

Africa before 1980. In a comprehensive and voluminous document published by the Food and

Agricultural Organization (FAO) in 2002, all anthropometric growth studies on children were

summarized by geographical region and country. The studies were grouped into cross-sectional

and mixed/longitudinal categories. The document indicates that the earliest reported growth

study from Africa was done by Kark (1957) who, in a mixed longitudinal study from June 1950

to December 1952, investigated sexual maturation and variation in the height and weight growth

among 819 year-old girls of the Bantu origin in Lamontville, a municipal or urban township of

low socio-economic status in Durban, South Africa. Also, the earliest reported growth study

from West Africa was a mixed-longitudinal study by McGregoret al. (1961) on children from a

rural community in the Gambia. The earliest reported cross-sectional somatotype study from

Africa was that of Parizkova and Merhautova (1971) who described somatic development in

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relation to various functional characteristics in Tunisian primary school boys and girls aged 11

and 12 years from middle to high socioeconomic status families in urban Tunis from the native

African Mediterranean stock in 1968. The FAO list includes a compendium of national surveys

organized by various departments of the United Nations as well as other international bodies

endowed with the resources to conduct such programmes (Marshall, 1981). The document shows

that the earlier growth studies tended to be mixed-longitudinal.

Nigerian growth studies

Growth studies from Nigeria before 1980 have been summarized by Marshall (1981) in the FAO(2002) document. The emphases of these studies have been on the physical status as assessed by

growth in stature (height) and body mass (weight). The studies were all cross-sectional with the

exception of the mixed-longitudinal study reported by Morley et al. (1968) that was carried out

between 1957 and 1963 and involving preschool children in Imesi-Ile, a rural community in

Osun State of Southwest Nigeria. Tanner and O'Keefe (1962) reported the heights, weights and

age at menarche in 12 to 19 year-old Nigerian Ibo schoolgirls in Onitsha and Owerri Eastern

region of Nigeria from a high socio-economic background. Hauck and Tabrah (1963) reported

the heights and weights of 416 male and 314 female, living in Awo Omamma, a rural community

in Eastern Nigeria. Edozien (1965) provided anthropometric data for Nigerian boys and girls

aged 111 years sampled from upper-middle class socio-economic status in Ibadan, Western

Nigeria. Johnson (1970, 1972) reported the height and weight and the physique of urban

Nigerians in the adolescent period in a sample taken as representative of Lagos, Nigeria. Oomen

(1979) described the body build and nutritional status of male adults of the Fulani, Hausa and

Maguzawa ethnic groups of Northern Nigeria from a middle class socio-economic status

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inhabiting the same rural locality. Apart from reports of skinfold thickness of urban Lagos

children (Johnson, 1971), limited information is available regarding changes in body

composition associated with growth during the adolescent period in the pre-1980 era in Nigeria.

In the post 1980 period, the emphasis appears to have shifted with the report of the prevalence of

obesity among Nigerian school children living in the Abeokuta metropolis in southwest Nigeria

by Akesode and Ajibode (1983). Owa and Adejuyigbe (1997) reported a comparison of

measurements of fat mass, fat mass percentage, body mass index and mid-upper arm

circumference taken by anthropometric and bioelectric impedance techniques in a healthy

population of Nigerian school children aged 5-15 years in Ile- Ife in Southwest Nigeria. By theturn of the millennium, Ansa et al. (2001) had examined the profile of body mass index and

obesity in Nigerian children and adolescents aged 6-18 years resident in Calabar. Jeroh (2003)

has reviewed growth and nutritional status studies in Nigeria while Eboh and Boye (2005)

reported on the body composition of normal and malnourished children aged 3-11 years in the

Niger Delta.

The assessment of somatic growth and maturation during adolescence, often considered within

the context of the physical status, is presently being investigated in the context of the somatotype

(Parizkova and Merhautova, 1971; Carter, 2006). However, with the exception of the efforts of

Toriola and Igbokwe (1985) in determining the relationship between perceived physique and

somatotype characteristics of 10-18 year old boys and girls resident in Iseyin in rural southwest

Nigeria and Salokun (1991) on the body composition and somatotype of rural high school

children, literature regarding the physique and somatotypes of Nigerian children and youth is

sparse.

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Classification of physique

Physique, or body build, refers to an individuals body form, the configuration of the entire body

rather than its specific features. The development of physique has central importance in the study

of growth, maturation, and performance (Malina et al., 2004). Physique is probably the one

single aspect of the human constitution that is most amenable to systematic study because it can

be readily observed (Sheldon et al., 1940; Sheldon et al., 1954; Parnell, 1958; Heath and Carter,

1967; Carter and Heath, 1990). The concept of classification of the human physique has a long

history dating back to the so-called Hippocratic era. Through the ages, the concept has evolved

through several systems of subjective constitutional typology. It was not until the 1940s whenWilliam H. Sheldon and his colleagues introduced their landmark system which they termed

somatotyping. The concept represented a major and the last of the systems of constitutional

classification in human biology during the 20th century.

A somatotype is a classification of physique based on the concept of shape and disregarding size.

The technique of somatotyping is used to appraise body shape and composition. The somatotype

is defined as the quantification of the present shape and composition of the human body (Ross

and Marfell-Jones, 1991).

A review of the literature indicates that from as early as the 5th century B.C., the concept of

classifying the human physique has enjoyed a high status in the practice of medicine. During that

period, along with other humoral doctrines, the custodians of the Hippocratic tradition offered a

twofold description of people (Sheldon et al., 1969; Damon, 1970; Hunt, 1981). In this

constitutional typology, it was conceived that people with long thin bodies dominated by the

vertical or linear dimension (habitus phthisicus) were susceptible to tuberculosis, while those

with short, thick bodies, strong in horizontal or lateral dimension (habitus apoplepticus) were

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susceptible to stroke (Foucault, 1973). In the 4th century B.C., Aristotle proposed that a specific

body shape always designated a specific character or personality, and, later in the 1st century

A.D., Celsus wrote about why some people are fat and some thin. Indeed, in a 9th century Arabic

version by Hunan ibn Ishaq (the physician-translator), the humoral temperaments were thought

to be expressed in body builds. On the assumption that heat made for growth in stature, and that

moisture for weight (stockiness), the choleric individual was tall and lean, the sanguine tall and

plump, the phlegmatic short and fat, and the melancholic short and lean (Evans, 1945). Since

these early efforts at classifying the human form, numerous attempts at classifying physique have

been made, some rather simplistic while others more elaborate (Comas, 1957).In the 19th century, Rostan in 1828 described three types of human physique: type digestive,

type muscular and type cerebrale. Rostan, however, did not invent this

terminology. The Frenchman, Halle, had used it earlier in 1797. Later on in 1869,

Samuel Wells described the human body as a motive temperament, a vital or

nutritional system together with a mental or nervous system. He postulated that

this motive temperament is marked by the superior development of the osseous

and the muscular system, forming the locomotor apparatus of the body. The vital

temperament- the principal seat of which is in the trunk- gives tone to the

organization of different body parts while the mental system exerts the controlling

power (Carter and Heath, 1990). Thus, all the many efforts at describing and

classifying physiques, eventually described body form in terms of two or three

major types: lateral (round), muscular and linear.

The development of anthropometry, however, introduced a new dimension to the study of human

morphology and physique (Sheldon et al., 1940; Carter and Heath, 1990). Late in the 19th

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century, Di Giovanni conducted one of the earliest anthropometric studies in the School of

Clinical Anthropology (Petersen, 1967; Tittle and Wutscherk, 1972). Along with his pupil,

Viola, they differentiated between three different types of human physique. Their classification

referred to subjects with large, heavy bodies and relatively short limbs as macro-splanchnic,

those with a small trunk and relatively long limbs as micro-splanchnic and those with

intermediate variations as normo-splanchnic. In 1880, Huter classified human beings as

cerebral those with a predominant ectodermic structure, muscular, those with a predominant

mesodermic structure and digestive, those with a predominant endodermic structure (Carter

and Heath, 1990). In Korperbau und charakter, Ernst Kretschmer (1931) described fourphysical body types viz: Athletic, Pyknic, Asthenic and Dysplastic physiques. Later he

substituted the word leptosomic for asthenic and made a distinction between the linearity

and the slender fragility of the leptosomic and gracility of the athletic type.

The earlier systems of constitutional classification described in this preceding account represent

views of the human body according to the philosophical tradition popularly referred to as

essentialism, an argument that a major task of scholarship is to discover the hidden nature, form

or essence of things (Mayr, 1968). Essentialism is a key concept of traditional Chinese, Indian

and western medicine, as well as in vitalistic biology to this day (Lessa, 1968). Clearly, their

general emphasis was on typology, which did not accommodate variation in body build within

and among individuals (Tanner, 1953; Comas, 1957; Damon, 1970).

The work of William Sheldon (1898-1977) and his associates, somatotyping represents the last

major system of constitutional classification, especially in the early 20th century and was the first

to attain worldwide recognition (Meredith, 1940). Their efforts marked the beginning of the

modern era in the development of the concept of the human physique or body build. Although

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the initial publication has three authors, Sheldon was the primary contributor and the method is

usually attributed to him.

The Sheldonian somatotype

Sheldons essays were major contributions to the study of relationships between physique,

psychology and delinquency (Carter and Heath, 1990). In 1940 he published, along with S.S.

Stevens and W.B. Tucker, "The Varieties of Human Physique". They coined and described the

term "somatotype" and the names of its three components, "endomorphy", "mesomorphy" and

"ectomorphy". Sheldon claimed that the components were derived from the embryonic tissue

layers, that is, endoderm, mesoderm and ectoderm. He stated also that an individualssomatotype was permanent. His method, based on the assessment or rating of photographs

carefully taken from the front (anterior view), the rear (posterior view) and the side (lateral view)

positions called photoscopic ratings, aided by some indices derived from the photographs, was

based on 4,000 undergraduate men from the Ivy League American universities. Another book,

The Varieties of Temperament followed in 1942, in collaboration with S.S. Stevens, and in

1949 by "The Varieties of Delinquent Youth" in collaboration with E.M. Hartl and E.

McDermott. In 1954 he published, along with C.W. Dupertuis and E. McDermott, the "Atlas of

Men". The latter book in particular served as a reference work for somatotyping men and

reflected Sheldon's determination to continue with the constitutional approach of permanence of

the somatotype. A proposed companion book,Atlas of Women, was never published.

Sheldon recognized that every individual consists of a mixture of three basic components. These

components vary in different degrees in an individual. The three components were originally

designated as pyknosomic, somatosomic and leptosomic, but later substituted with the

terms endomorphic, mesomorphic and ectomorphic (Carter and Heath, 1990). The approach was

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based on the premise that continuous variation occurs in the distribution of physiques, and this

variation is related to differential contribution of the three specific components that characterize

the configuration of the body- endomorphy, mesomorphy and ectomorphy. Endomorphy, the

first component, is characterized by the predominance of the digestive organs, the softness and

roundness of contour throughout the body. Mesomorphy, the second component is characterized

by the predominance of muscle, bone and connective tissue, so muscles are prominent with sharp

definition. Ectomorphy, the third component, is characterized by the linearity and fragility of

build, with limited muscular development and predominance of surface area over body mass

(Carter and Heath, 1990). Each component of the physique was assessed individually. Ratingswere based on a 7-point scale, with 1 representing the smallest expression and 7 representing the

fullest expression (Malina et al., 2004). A component rating was always recorded together with

the other two components in order to ensure that the somatotype meaning was not lost. For

example, a reading of 7-1-1 represented extreme endomorphy, 1-7-1 extreme mesomorphy while

a 1-1-7 implied extreme ectomorphy. The first number always referred to endomorphy, the

second to mesomorphy and the third ectomorphy.

Sheldon's concept of the three components of physique rated on scales from 1-7 was a unique

break from the traditional categorical placement of all physiques into only 2, 3 or 4 categories.

The three-number rating provided for a wide variety of possible somatotypes. Sheldon had, in

fact, identified 19 different categories of the somatotype (Tanner, 1953, 1988; Barton and Hunt,

1962).The assumptions in this method were many. An individuals somatotype does not change

with age, nutritional status or state of physical training, implying a "permanent

morphogenotype". Each component of the somatotype was the contribution of one of each of the

three embryonic germ layers endoderm, mesoderm and ectoderm- to individual growth and

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development. The concept was developed on adult males and, therefore, the change in body

build during growth was not a factor. When this method was applied to children, it met with

limited success (Heath, 1963; Sheldon et al., 1969). As long as Sheldon maintained that the

somatotype was "permanent morphogenotype", there were persistent criticisms of the method.

Human biologists and others saw greater utility in the somatotype as a morphophenotype - one

that could change (Hunt, 1949, 1952; Hunt and Baston, 1959). The erroneous assumption that the

morphogenetic pathway for the derivation of post-natal body tissues from the three embryonic or

germ layers coincided with the somatotype components of Sheldon and his colleagues, and the

wide criticism that followed seriously undermined the validity of the concept and severelyimpeded further research in the subject for nearly a decade (Bakeret al., 1958; Hunt, 1981). The

need for a review and possible modification of the concept became imperative.

Modifications of Sheldons method

Sheldons Trunk Index method

In response to criticisms of his somatotype method, Sheldon developed a "new" method called

the Trunk Index method (Sheldon, 1961, 1965; Sheldon et al., 1969). This

consisted of planimetry of trunk areas marked on somatotype photographs, along

with tables of maximal and minimal weight and stature, and a table of the

somatotype height- weight ratio and trunk indices. This method, however, did not

answer the main criticisms of the original method and has not been widely used

(Walker, 1962; Walker and Tanner, 1980).

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Parnells phenotype method

Richard W. Parnell (1911-1985), who began his studies into physique and behavior at a pilot

Student Health Service at Oxford University in 1948, measured aspects of physique and related it

to behavior, achievement and temperament (Carter and Heath, 1971). He developed a method

that utilized anthropometry to estimate the somatotypes. In modifying Sheldons method, Parnell

(1954) incorporated several anthropometric dimensions to derive a phenotype, which is defined

as a physique at a given point in time. Stature, body mass, three skinfolds, two limb

circumferences and two bone widths were used to calculate the three components, namely fat

(F), muscularity (M) and linearity (L), resembling Sheldons endomorphy, mesomorphy andectomorphy component, respectively (Malina et al., 2004) and this led to his M.4 deviation chart

method. He made age-adjusted scales for ratings of Fat (F), Muscularity (M) and Linearity (L).

His book, "Behavior and Physique (Parnell, 1958) reported on extensive investigations into

many different aspects of behavior, health, occupation and sport. Much later he developed

further studies in the heritability of physiques, parental disharmonies, and family mental stress

and breakdown. These studies resulted in his book, Family, Physique and Fortune (Parnell,

1984). Parnell's insight and articulate writings, and innovative approaches to analysis and

interpretation of results served as an inspiration to those who followed. His highly innovative

and lucid use of anthropometry renewed interest in somatotyping and paved the way for others,

especially Heath and Carter whose first modifications were derived from Parnell's M.4 approach

(Carter and Heath, 1986).

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Heath-Carter somatotype method

The Heath-Carter somatotype method is a modification of the system developed by Sheldon and

his colleagues. It uses much of the original vocabulary and employs the criteria of their basic

approach, which are objective and straightforward. In modifying Sheldons method, Heath and

Carter (1967) recognized that somatotype rating is a phenotype rating, which allows for changes

over time. The rating scales for the three components were opened and redefined so as to apply

to the physique of both sexes at all ages. Selected anthropometric ratings were used to objectify

the somatotype ratings. The component terms were redefined to reflect the conceptualmodifications thus:

Endomorphy - (relative fatness) is derived from the sum of three skinfolds namely triceps,

subscapular and supraspinale skinfolds, after adjustments are made for stature.

Mesomorphy (relative musculo- skeletal robustness) is derived from the humerus and femur

width, flexed arm girth (corrected for the thickness of the triceps skinfold) and calf girth

(corrected for the thickness of medial calf skinfold). These four measurements are adjusted for

stature. Carter and Heath (1990) viewed this second component as expressing fat-free mass

relative to stature.

Ectomorphy third component (relative linearity or slenderness of build) is based on stature

divided by the cube root of the body mass.

Each component contributes variably to the somatotype hence it is relative fatness, relative

musculo- skeletal robustness and relative linearity or slenderness with reference to the entire

physique, which is a composite. Although the three components are related, they are

conceptually and methodologically quite different (Carter and Heath, 1990; Malina et al., 2004).

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The Heath-Carter photoscopic somatotype ratings are based upon the standard somatotype

photographs of Sheldon et al. (1940) together with a record of age, present height

and weight of the subject (Heath and Carter, 1967). Accurate ratings depend upon

skill in recognizing the probable ratings for each component and in reconciling

photoscopic impression with appropriate somatotype (de Ridder, 2003). The Heath-

Carteranthropometric somatotype method allows anthropometric measurements to

be assessed as well as to distinguish between differences in a given subjects

somatotype components (Carter, 1996). Furthermore, it provides an objective

prelude for an anthropometric-cum-photoscopic rating when a photograph isavailable (Claessens et al., 1986). The Heath- Carter method provides the data for

reliable somatotype ratings when minimal clothing is desirable. Measurements can

be used for other analyses as well as evaluation of body structure and somatotype

ratings (Carter and Heath, 1990).

Correlates of the Somatotype in human biology

The protocols for specific measurements as well as the algorithms for estimation of the

somatotype by the Heath-Carter anthropometric method have been elaborated by Lohman et al.

(1988), Carter and Heath (1990), Norton and Olds (1996) and the International Society for the

Advancement of Kinanthropometry (2001).

Studies of physique changes during growth permit a better understanding of the variations in theadult physique. Physique has been related to a variety of behavioral, occupational, performance

and disease variables primarily in adults (Hunt, 1981; Malina, 1969; Malina and Katzmarzyk

1999). However, the influences on the development of the physique during adolescence, and its

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relationships with other variables such as biologic maturity, performance and behavior have been

studied less extensively (Parnell, 1958; Sheldon et al., 1969; Malina and Rarick, 1973).

Relationships between components of the physique and risk factors for cardiovascular disease

evident in adults may be evident in adolescents (Malina et al., 1997; Katzmarzyket al., 1998),

and relationships between physique and performance have been shown to be generally similar in

youth and adults (Malina and Rarick, 1973; Malina, 1992). Data for young athletes in gymnastics

and diving, for example, indicate that those who are successful tend to have physiques that are

similar to adult athletes in these sports (Carter and Heath, 1990), which suggests that physique is

a selection factor and perhaps a significant contributor to success in some sports (Carter, 1996).The methods used for the assessment of physique and their applicability to adolescents have been

described primarily within the context of the somatotype (Sheldon et al., 1940; Sheldon et al.,

1954; Parnell, 1958; Barton and Hunt, 1962; Heath, 1963; Heath and Carter, 1967; Claessens et

al., 1980; Carter and Heath, 1986). Somatotype is the quantitative assessment of the physique of

an individual at a given point in time (Ross and Marfell-Jones, 1991). Variation in somatotype

among adolescents is known to be considerable (Tanner, 1953; Zuk, 1958; Hunt and Barton,

1959; Walker, 1962; Petersen, 1967; Tanner and Whitehouse, 1982) and the difference between

sexes is especially apparent in the distribution of somatotypes in reasonably large samples of

children. Changes in somatotype from childhood through adolescence have been described on

the basis of observations from several cross-sectional and longitudinal studies (Walker, 1962;

Petersen 1967; Carter and Parizkova, 1978; Tanner and Whitehouse, 1982; Carteret al., 1997).

The somatotype appears to be a moderately stable characteristic of the individual from late

childhood on (Parizkova and Carter, 1976; Claessens et al., 1986; Hebbelincket al., 1995). The

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wide variation in somatotype during adolescence may be associated with individual differences

in the timing and tempo of the adolescent growth spurt and sexual maturation.

Changes in somatotype during growth

Anthropometric estimates of endomorphy from previous studies are generally lower than those

based on the photoscopic method (Claessens et al., 1986), whereas estimates of ectomorphy are

generally similar because both the photoscopic and anthropometric methods used the same

stature/ weight ratio (Tanner and Whitehouse, 1982). In comparison between the photoscopic

and anthropometric methods, mesomorphy appears to be the component that varies the most. The

photoscopic method gives a higher estimate of mesomorphy. This observation was especially

apparent in Belgian boys followed from 13 to 18 years of age (Claessens et al., 1986).

Somatotypes of this longitudinal sample were estimated with a modification of Sheldons

original procedures and with the Heath-Carter anthropometric method. In modifying the Sheldon

procedures, the Parnell scale for endomorphy i.e. sum of triceps, suprascapular and suprailiac

skinfolds (Parnell, 1954) and the Heath-Carter scale (Heath and Carter, 1967) for ectomorphy

(height divided by the cube root of weight) were used to derive preliminary estimates of the first

and third components, respectively. These estimates were then used as guides in photoscopically

rating endomorphy and ectomorphy from the somatotype photographs of each boy relative to

photographs in theAtlas of Men (Sheldon et al., 1954). Each boys somatotype photographs were

compared with those of young male adults (16 to 24 years of age) in the Atlas to derive a

photoscopic rating of somatotype. The method of this study is thus basically photoscopic but

used anthropometric data only as a guide in the process.

Estimates of somatotype based on modification of the photoscopic method and on the Heath-

Carter anthropometric method yield different estimates in adolescent boys. Heath- Carter

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anthropometric somatotypes are generally lower in endomorphy at most ages. A similar trend

was observed in Czech boys compared with the others (Parizkova and Carter, 1976). This

sample, however, was engaged in regular physical activity during the course of the study, which

may be related to the lower endomorphy ratings.

Changes in mean components appear to be relatively small from childhood through adolescence

(Walker and Tanner, 1980; Malina et al., 2004). Allowing for variation among samples for

which data are available, several trends have been suggested, particularly in the anthropometric

estimates of somatotypes. Endomorphy tends to increase with age in girls and to decrease with

age in boys, especially during adolescence (Hebbelinck et al., 1995). Ectomorphy appears toincrease with age up to the age of maximum growth in height (about 12 years of age) in girls,

and then declines (Bouchard, 2004). Ectomorphy tends to increase with age from childhood into

adolescence in boys, and then declines in late adolescence. Mesomorphy appears to decline with

age in girls and to increase gradually with age in males; the increase is especially apparent in late

adolescence (Claessens, 2004). The late adolescent decline in ectomorphy in males is probably

related to late adolescence increase in mesomorphy, which is illustrated in the generally higher

values for mesomorphy at 18 years of age (Carteret al., 1997).

Somatotypes of two samples of boys and one sample of girls were also estimated in adulthood,

thus permitting comparison of different stages of the maturation period i.e. early adolescence and

late adolescence to adulthood (Zuk, 1958, Carter and Parizkova, 1978). The Czech sample of

males was studied at 24 years of age, and the California sample of males and females was

studied at 33 years of age. The two samples of males show an increase in mesomorphy and a

decline in ectomorphy between late adolescence and adulthood. In the Czech sample of males,

mean endomorphy and ectomorphy increase from 11 to 15 years, whereas mean ectomorphy

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decreases from 17 to 18 years of age. The trends changed during the second stage (from 18 to 24

years of age) in which ectomorphy and endomorphy declined and mesomorphy increased.

However, the sample subjects were actively training during most of adolescence, so some of the

changes in late adulthood may reflect changes in the pattern of habitual physical activity,

especially the effects of training on subcutaneous fatness. On the other hand, mean endomorphy

remains rather stable in the sample of California males. In the females, mean endomorphy and

mesomorphy increase, whereas mean ectomorphy declines between 17 and 33 years of age.

Influence of socioeconomic status on somatotype

Studies have been published in central Europe (Farkas, 1986; Eiben, 1994; Romon et al., 2005),

the United States (Mayeret al., 2005; Rouse and Barrow, 2006), the United Kingdom (Saxena et

al., 2004; Wardle et al., 2006), the Mediterranean (Rosique and Rebato, 1995; Rebato et al.,

2003), Australia (Marks et al., 2000; Adams et al., 2002) central Asia (Singh and Singh, 1991;Wang, 2001; Ghosh and Malik, 2004), Latin America (Martorell et al., 1989; Malina, 1990;

Malina and Pena Reyes, 2002) and Africa (Janes, 1970; Toriola, 1990; Pawloski, 2002; Gillett

and Tobias, 2002; Prista et al., 2003) that demonstrate and analyze the relationship between

environmental factors such as nutrition, energy expenditure associated with physical work, the

sociocultural lifestyle and the childs physical development suggesting that remarkable

differences in body dimensions and physique may exist between children when their social

background is dissimilar. Established indicators of socio-economic status (SES) include mothers

level of education, fathers occupation, family size, per-capita income, the grade of modern

conveniences in the habitat, the settlements level of urbanization, the population the community,

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the quality of health care and access to medical services (Townsend et al., 1998). The different

types of instruments used for assessing SES among adolescents have been reviewed by Wardle

et al. (2002) including the home affluence scale, a popular questionnaire-based instrument

listing household material items which is known to have adequate internal reliability and good

external validity. There isevidence that students with poorer material circumstances areless able

to report parental education and occupation whereasmaterial-based questions showed less bias.

Furthermore, the non-applicability of some of the indices of socioeconomic status to many

developing countries has been highlighted by Onwujekwe et al. (2006) suggesting the need to

adopt simpler and easily-verifiable criteria. The use of proxies of SES such as area of residenceand the type of school attended has been reviewed in Wardle et al. (2006) The socio-economic

status of the family is often reflected in the type of school attended by the children since

economically advantaged families often prefer fee-paying, private school to minimal-fee paying

public school because they are better funding to provide superior educational facilities and a

more positive learning environment (McMurray et al., 2002; Prista et al., 2003). Thus, the type

of school attended by a child (school type) is a reliable proxy indicator of the socio-economic

status of adolescent urban Nigerian children in Lagos.

RATIONALE FOR THE STUDY

The current non-availability of a comprehensive anthropometric database for adolescent growth

developed for African populations is a major challenge for growth research (Carter, 1996).

Human biologic diversity in Africa today appears to reflect more the diversity of the continents

many environments rather than the variability inherent in its peoples (Cameron, 1991). This adult

diversity, while having a major genetic component, has been interpreted as the result of the

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impoverished environment endemic to African countries (Cameron, 1992). The effects of

malnutrition and disease probably combine to mask the underlying growth pattern hence much of

what is currently known of the growth of African children is based on data that are tainted by the

adverse environment endemic to Africa (Cameron et al., 1998).

Although anthropometry is the single most portable, universally applicable, inexpensive and

non-invasive technique for assessing the size, proportions, and composition of the human body,

reflecting both health and nutritional status and predicting performance, health and survival, it is

still an underused tool for guiding public health policy and clinical decisions (WHO, 1995).

While height, weight, and the body mass index (BMI) have been used in many nutritional

surveys, corresponding data for other body dimensions and indices are very limited (Carter,

1996).

Furthermore, the reports of several studies reviewed in Ukoli et al. (1993), and Spiegel et al.

(2004) comparing the United States Center for Disease Control and Prevention (CDC) Growth

Charts reference data with data from other countries and continents suggest that the American

reference data may not adequately describe non-US populations. Thus it is recommended that

individual countries develop databases describing their local situations (de Onis and Habicht,

1996).

Majority norms of body dimensions for Nigerian adolescent schoolchildren are not readily

available at the present time. It may be surprising to note that the available scientific literature

suggests that the earlier cross-sectional studies of Johnson (1970, 1971 and 1972) in the urban

Lagos area are yet to be complimented by more recent data. These data sets have been included

in the global survey report by the FAO (2000) earlier referred to in this report. The survey report,

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however, noted that the small sample sizes of the datasets were a major constraint to their

acceptability as representative of the population from which they were drawn (Marshall, 1981).

Other related adolescent studies by Omololu et al. (1981) carried out at Ile-Ife, Osun state, Ukoliet al. (1993) at Benin, Edo state and Ukegbu et al. (2007) at Umuahia, Abia state, however,

represent other geographical locations outside the Lagos area. The efforts of Toriola and

Igbokwe (1985) in determining the relationship between perceived physique and somatotype

characteristics of adolescent boys and girls in Iseyin, a semi-rural community in Osun state,

southwest Nigeria and Salokun (1991) on theperceived somatotype as related to self-concept in

Nigerian adolescent students at a secondary school in Ibadan, an urban metropolis in Oyo state,

southwest Nigeria have yet to be complimented by studies of the influence of the widely varied

socioeconomic circumstances on the physical growth of the urban adolescent population.

STATEMENT OF THE PROBLEM

The literature has documented several studies, reviewed in Carter (2006), describing andanalyzing the somatotypes of adolescent children from around the world and from other regions

in Nigeria. However, there remains, still, a dearth of scientific literature on the somatotypes of

the urban Lagos adolescent population. The status and pattern of growth among adolescent

school children in urban Lagos have yet to be described and documented using an internationally

acceptable procedure that could produce norm-reference data for this population.

SIGNIFICANCE OF THE STUDY

The results of this study will provide verifiable information regarding size, body composition

and body build distribution patterns of the urban Nigerian adolescent population. At a glance, it

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will be possible to identify the malnourished individuals as well as their location in the

community.

The data will be a reliable normative reference data set useful in the determination of appropriate

age- and size-related medication dosages and nutritional requirements.

The identification of the segments of the adolescent population that is at risk for adult health

disorders in this age group will improve prognosis following early intervention. This may be

useful to health professionals and insurance policy managers.

Dress-makers and manufacturers in the garment industry will benefit from data that will enhanceaccurate determination of appropriate sizing and fitting of clothes for the rapidly growing

adolescents.

The results may further provide useful baseline data for sports and fitness coaches interested in

the physical characteristics of the adolescent youth for the purposes of talent identification, the

monitoring of training programmes and the scientific prediction of adult performance that arespecific to their sport.

Parents, clinical and sport psychologists may find the results of somatotype distribution useful

for body-image analysis of adolescent children with various kinds of psychological disorders

arising from their perception of the changes in their physical appearance during their growing

years. This would positively impact on their self-confidence and performance.

The potential of this study to advance into a longitudinal study at the school, university, city,

state and nationwide levels with the possible consequence of a study comparable with the

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Ellisras, Nijmegen, Harpenden, Fels and Harvard projects is considerable. In that likely

eventuality, the cohort of this study should form the baseline or reference group.

AIM OF STUDY

The overall aims of this study are to characterize, describe and analyze the morphology and the

somatotype distribution patterns in terms of absolute body size, body proportion and the

somatotypes of adolescent children in urban Lagos.

OBJECTIVES OF THE STUDY

The specific objectives of this study are to:

1. Assess the physical status of adolescent Nigerian boys and girls attending both private and

public secondary schools in urban Lagos.

2. Measure the body composition indices of adolescent Nigerian boys and girls attending both

private and public secondary schools in urban Lagos

3. Describe the somatotype distribution of adolescent boys and girls attending private and public

secondary schools in urban Lagos.

4. Analyze the body size and somatotype data itemized in 1-3 above.

5. Compare the data derived from 1-4 above with those derived from other populations around

Nigeria and the world.

HYPOTHESES

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The null hypothesis is that there is no significant difference in the stature, body mass, body mass

index, height weight ratio and somatotype characteristics between the private school and public

schoolchildren in urban Lagos.

DEFINITION OF TERMS

Growth: An increase in the size of the body as a whole and or the size attained by specific parts

of the body.

Postnatallife: Life after birth. It is commonly, although somewhat arbitrarily, divided into three

or four age periods.

Neonatal period: The first month after birth.

Infancy: The first year of life from the end of the first month up to but not including the first

birthday.

Childhood: Extends from the end of infancy (the first birthday) to the start of adolescence.

Early childhood: Includes the preschool years. It extends from the first birthday up to but not

including age 5.0 years (i.e. 1.0 to 4.99 years).

Middle childhood: Extends from 5.0 years to the beginning of adolescence. It includes the

elementary school years into primary five and six.

Adolescence: World Health Organization (WHO, 1995) defines the age of adolescence as

between 10 and 18 years. However,certain authorities regard the age ranges of8 to 19 years in

girls and 10 and 22 years in boys as more appropriate limits for normal variation in the onset

and termination of adolescence.

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Adulthood: The attainment of full structural and functional maturity. The definition of18 years

as age of full maturity of an individual is legal and notbiological.

Physical status: The size attained at a given point in time.

Maturity status: The state of maturation attained at a given point in time.

Somatic growth: Growth of the external body structure including skin, subcutaneous tissue,

skeletal muscles and bones.

Frankfort plane: A horizontal plane passing through the superior limb of the tragus of the ear-

the tragion landmark- and the lower border of the eye socket- the orbitale landmark.

ICH/PC: Institute of Child Health and Primary Care of the College of Medicine of the

University of Lagos, Idi-Araba.

MATERIALS AND METHODS

Study Description

The study was a cross-sectional survey conducted among adolescent Nigerian schoolchildren

resident in urban Lagos.

The sample

The Mendelian nature of the study population was assessed. Oral interview results indicated that

the subjects in the sample were from Christian, Moslem or traditional African religious and

sociocultural backgrounds. The caste system of marriage, which restricts intermarrying across

caste barriers, is rarely practiced in West Africa and marriage laws in Nigeria do not restrict

conjugal relationships across ethnic groups or social class (Hedrick, 2000; Ghosh and Malik,

2004). It was, therefore established that the subjects were born through conjugal relationships

that do not restrict transmission of genetic traits from parent to offspring in any specifically

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defined manner. The subject population may thus be considered a heterogeneous Mendelian

population.

Inclusion Criteria

School records and the response to individualized questioning established that the subjects were

normally resident in metropolitan Lagos. The ethno-cultural distribution of the biological

parentage of the subjects is given in table 1 below. The Nigerian ethnic groups represented in the

sample included Yoruba, Ibo, Edo, Urhobo, Itsekiri, Ijaw, Ibibio, Efik, Annang, Igala, Hausa-

Fulani, Nupe, Idoma and Tiv.

Table 1

Ethnic distribution of subject population

ETHNIC CATEGORY OF SUBJECTS

PARENTAGE

PROPORTION OF SAMPLE

REPRESENTED (%)Mono-ethnic Nigerian (e.g. Ibo versus Ibo) 61

Mixed Nigerian national (e.g. Ibo versus Yoruba) 36

Mixed Nigerian transnational (Nigerian to non-Nigerian)


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children with poor health conditions that manifested with overt signs of stunted growth or

physical emaciation; grotesquely obese children to avoid potentially excessive errors in

measurement and also for whom exposure before other children might cause undue

embarrassment (ISAK, 2001).

Sampling procedure

Sampling technique The subjects for this study were selected using a systematic, multistage,

randomized stratified sampling technique to arrive at the final sample for the study. The

arguments for this choice have been elaborated in Kalton (1983) and Rumsey (2003).The full co-operation of the school authorities enabled free access to the class lists before the

sampling commenced. Dates of birth of subjects were collected from the school registers, and

confirmed from the subjects individually. In case of an anomaly, subjects were requested to

confirm from their parents. Decimal age of each subject was calculated by subtracting the date of

birth of the subject from the date of data collection, using decimal age calendar (Marshall and

Tanner, 1969, 1970). All subjects between 13.51 and 14.50 years were classified in the age group

14 years, while those falling between 14.51 and 15.50 were included in the age group of 15

years. The same principle was applied throughout to classify subjects in appropriate age groups.

The sample consisted of 3498 volunteer males and females (1565 males, 1933 females) aged

between 10-16 years drawn from a total of eight secondary schools with a total population size of

11,600. These were four private, school fee-paying schools representing the high and middle

income class and four public, non-school fee-paying schools representing the low income class.

The private schools charged a minimum of fifty thousand naira (N50, 000.00) per term as tuition

fees. All schools were located within five randomly selected local government areas in

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metropolitan or urban Lagos. These were: Surulere, Mushin, Lagos Mainland, Kosofe and Ikeja.

The list of all secondary schools (including registered private and public) located in Lagos State

was obtained from the State Schools Management Board. This list, serialized by local

government area and wards, permitted quick identification and the development of the

appropriate sampling frame to select the schools.

Sample stratification The method used for the distribution of the subjects into gender, age-

range and socioeconomic status stratum sample units is the Neymans Optimum Allocation

(Neyman, 1958). This procedure, a special kind of the Optimal Allocation method, enables the

selection of the best sample size per stratum to achieve the maximum precision for a fixedsample size at the least cost. I sought to maximize the information gathered through the

systematic and randomized stratified sampling procedure and to guarantee adequate

representation to each stratum of the sample.

The equation for Neymans Allocation is given in equation (1) below as:

nh = n * (Nh * Sh ) / [ ( Ni * Si ) ] (1)

where nhis the sample size for the stratum h, n is the total sample size, Nh is the population size

for the stratum h, and Sh is the standard deviation of stratum h. Accordingly, the minimum

sample size per stratum was computed to achieve maximum precision at a predetermined

confidence level of 95%. A previous study of adolescent children similarly stratified by age

group, gender and socioeconomic status (Prista et al., 2003) had selected 81 boys and 131 girls at

age group of 10- years with a mean stature of 139.3 cm 7.4 for boys and 139.5 cm 7.7 for

girls. Assuming the entire population of 11,600 schoolchildren has equal proportions of boys and

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girls in the 8 secondary schools, the minimum number of boys (nb) to be allocated to each

stratum by the Neyman criteria is given in equation (2) by:

n b = 222 * (5800 * 7.4) / [ ( 5800 * 7.4) + (5800 * 7.7 ) ] = 109 boys (2)

The minimum number of girls (n g) to be allocated to the group of 10-year old girls is given in

equation (3) as:

n g = 222-109 = 113 girls (3)

The sample size allocation design has been compared with the allocation procedures adopted forrecently reported cross-sectional studies and shown to be valid and consistent (Meszaros et al.,

2002; Prista et al., 2003). The results are reported in table 1 of the results section.

Institutional Approval for the Study

Ethical Clearance

To conduct this study ethical clearance was obtained from the Research Grants and

Experimentation Ethics Committee of the College of Medicine of the University of Lagos

(CMUL) prior to the commencement of sampling and measurements in all the schools (see

appendix 1). Also approval was obtained from the authorities at the Local Education Districts

supervising the administration of the selected public secondary schools and from the proprietors

of the participating private schools.

Informed Consent

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Consent was obtained from each subject that participated in the study and their parents (see

appendix 2). This was after the purpose and procedure of measurement had been carefully

explained to them. A clear indication of full comprehension and acceptance to participate was

received from them. Strict compliance with local or institutional rules regarding consent for

every individual subject was ensured. All subjects received a guarantee of preservation of their

personal space throughout the measurement exercise. Their right to withdraw- if so desired- at

any stage of the study was also stated clearly to them. All measurements recorded belong to only

those who gave full consent.

Anthropometry

Tester/ measurer selection

The preparations for anthropometry involved the training of volunteer measurers in

anthropometric measurements according to ISAKs protocol to the standard of level 1

Technician (ISAK, 2001) in the Department of Anatomy, CMUL by the researcher, an ISAK-

certified anthropometrist, with the assistance of a female ISAK-certified anthropometrist. The

volunteers were:1) post-graduate Masters of Science (M.Sc) students in the Department of

Anatomy and 2) 600 level medical students at ICH/PC postings in Maternal and Child Health.

Each measurer was required to undertake reliability testing as part of their training and to

achieve technical errors within internationally accepted limits (Ross, 1984; Mueller and

Martorell, 1988; De Ridder, 2003; Carter and Ackland, 1994; Monyeki, 2003). This procedure

has been validated by previous work (Adams et al., 2002; Prista et al., 2003).

Measurement protocol

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A total of 10 measurements were taken according to the protocols recommended in the

International Standards for Anthropometric Assessment published by the International Society

for the Advancement of Kinanthropometry (ISAK, 2001). The measurements included:

1) Two basic: - body mass and stature

2) Four skinfolds: - triceps, subscapular, supraspinale and medial calf skinfolds

3) Two bone breadths: - humerus and femur

4) Two maximum girths: - upper-arm (flexed and tensed) and calf.

A full description of each measurement is given herein. They complied strictly with those

described in the ISAK manual (ISAK, 2001). All anthropometric measurements were taken bythe select trained field testers with the exception of the skinfold measurement which were done

by the certified anthropometrists only, the researcher attending all the male subjects while the

female assistant certified anthropometrist attended all the female subjects.

Measurement procedure

Subject selection for the study was done at the various school locations. The measurements were

taken in carefully selected clean, well-lit and well-ventilated rooms within the school premises

between 9.00 a.m. and 1.00 p.m. each day. The measurement stations were arranged in the

steeplechase format, allowing for quicker movements and fewer delays between

measurements. Personnel consisting of one measurer, an observer and one recorder manned each

station. At the outset of measurements, all anatomical sites for measurements of skinfolds and

limb segment circumference or girth and bone breadths were determined and marked using a

felt-tipped, non-toxic and non-permanent marker. Each subject was required to rotate through the

steeplechase twice so that the measurer repeated each measurement blind. This was to allow

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for the determination of the intra-observer (intra-class) technical error of measurement or intra-

class correlation (ICC) for each measurement. This exercise served the additional role of a dress

rehearsal of the procedure to be used in all the school locations.

Equipment for anthropometry

1. Stadiometer: GPM Anthropometer from Siber-Hegner customized with adapted foot plate.

2. Broca plane: A customized triangular head board.

3. Anthropometric tape: The Lufkin specialty Executive Diameter flexible steel measuring tape

(W606PM)

4. Bone caliper: From Siber-Hegner which has extended branches with round pressure plates.

5. Skinfold caliper: The Slim Guide skinfold calipers (Creative Health Products, Plymouth,

Michigan, USA).

6. Weighing machine: The spring type balance (SECA alpha model 770, Germany) with an

electronic meter calibrated in kilograms and tenths of kilograms (full capacity scale -150 kg).

7. Measuring platform: A one-foot-square plywood platform or foot-plate leveled by wooden

vertical shims was customized and utilized throughout the study.

8. Personnel five persons: the tester/measurer, the observer, the recorder, two supervising

certified anthropometrists and quality assurance persons

Measurement techniques

Basic measurements

Stature (height): This was taken against a stadiometer or height scale calibrated to the accuracy

of 1mm. Stature was taken with the subject in full inspiration standing straight, against the

stadiometer, touching the wall with heels, buttocks and back, the head orientated in the Frankfort

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plane with the foot-heels kept together while a headboard (Brocas plane) was lowered until it

firmly touched the vertex of the head.

Body mass (weight): This was taken with the subject, wearing minimal clothing i.e. the school

uniform without shoes, standing in the center of the scale platform. Body mass was recorded to

the nearest tenth of a kilogram. To determine the nude body mass for subsequent calculations,

a correction in body mass was made for the subjects clothing by deducting a mass equal to the

mean of a small number of sample uniforms belonging to children of the same age-range.

Furthermore, the subject was known to have had the last meal at least two hours before

commencement of measurement.

Skinfolds thickness

At the previously marked anatomical site, a fold of skin and subcutaneous tissue was firmly

raised between thumb and forefinger of the left hand and away from the underlying muscle. The

edges of the skinfold plate were applied on the caliper branches 1 cm below the fingers of the left

hand and then allowed to exert their full pressure before reading off within two seconds the

thickness of the fold. All skinfolds were taken on the right side of the body. The subject stood

relaxed, except for the calf skinfold, which was taken with the subject seated.

Triceps skinfold: With the subject's arm hanging loosely in The Anatomical Position, the

tester raised a fold at the back of the arm at a marked site located halfway down a line

connecting the acromiale landmark and the radiale landmark.

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Subscapular skinfold: The tester raised the subscapular skinfold at a marked site located 2cm

down a line from the inferior angle of the scapula in a direction that is obliquely downwards and

laterally at 45 degrees.

Supraspinale skinfold: The skinfold was raised at a marked point above the anterior superior

iliac spine where a marked diagonal line going downwards and medially at approximately 45

degrees from the anterior axillary border meets with another marked horizontal line drawn from

the tubercle of the iliac crest. This skinfold was formerly called suprailiac (Tanner, 1962) or

anterior suprailiac (Parnell, 1958). The name has been changed to distinguish it from other

skinfolds called "suprailiac", but taken at different locations (Carter and Heath, 1990).Medial calf skinfold: The tester raised a vertical skinfold at a marked site located on the medial

side of the leg, at the level of the maximum girth of the calf.

Biepicondylar breadth

1. Humerus. This is the width between the medial and lateral epicondyles of the humerus,

with the shoulder and elbow flexed to 90 degrees. The bone caliper was applied at an angle

approximately bisecting the angle of the elbow. Firm pressure was placed on the crossbars in

order to compress the subcutaneous tissue.

2. Femur. The subject was seated with knee bent at a right angle. The tester measured the

greatest distance between the lateral and medial epicondyles of the femur with firm pressure on

the crossbars in order to compress the subcutaneous tissue.

Girths

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1. Upper arm girth (elbow flexed and tensed) The subject flexed the shoulder to 90 degrees

and the elbow to 45 degrees, clenched the hand, and maximally contracted the elbow flexors and

extensors. The measurement was taken at the greatest girth of the arm.

2.Calf girth (right). The subject stood with feet slightly apart. The tester placed the tape around

the calf and measured the maximum circumference.

Stature and girths were read off to the nearest mm, biepicondylar diameters to the nearest 0.5

mm, and skinfolds to the nearest 0.5 mm. All measurements (including skinfolds) were taken on

the right side as is traditionally recommended for large surveys (Norton and Olds, 1996; ISAK,

2001).

Quality Control

Measurement Error

The validity of the somatotype rating depends on the reliability of the measurements used. To

determine measurement error intrinsic to this study, the two measures of validity given below

were used:

Technical error of measurement (TEM)

Intra-class Correlation Coefficient (ICC)

The procedures used are described briefly below.

The technical error of Measurement (TEM)

A measure of precision or replicability (Malina et al., 1973), this included:

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Intratester TEM: Six measurements, taken by each tester on the same set of subjects, were

repeated blind. The six pairs of measurement were then compared using the equation (4)

given as follows:

TEM = [d2/2n] 0.5 (4)

Where d = difference between the first and second measures of each measurement used and n =

number of measurement sites on the subjects (Cameron, 1984, Norton and Olds, 1996). This test

is the most basic indicator of the individual testers expertise at taking precise measurement.

Intertester TEM: Six measurements were each taken by both the tester and the quality

assurance person (certified anthropometrist). This pair of measurements was also comparedusing the equation given above.

The subjects, variables and measurement procedures used for the two types of TEM were the

same and the tests had to be carried out independently. Since one of the testers is a certified

anthropometrist, the intertester TEM can be used as a measure of accuracy. The TEM provides

an estimate of the measurement error that is in the units of measurement of the variable. This

value indicates that two thirds of the time a measurement should come within +/- of the TEM

(Mueller and Martorell, 1988).

Intraclass Correlation Coefficient (ICC): this is a measure of accuracy of the test

measurements. Accuracy is the degree to which repeated measurements of the same variable

approximate those of a standard of reference under the same measurement conditions. It is the

proportion of the observed measurement variance that is accounted for by the true score variance

(de Ridder, 2003; Malina et al., 2004).

The equation for intra-class correlation coefficient of reliability, r, is given as equation (5) below:

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r = (so2 - se2)/so2 (5) where

so is the observed measurement variance and se is the error variance. In this equation, the factor

(so2 - se2) represents the true measurement variance.

Data collation and presentation

Data collation

All data was entered into a desktop personal computer installed with Microsoft Windows XP

unlimited operational system located in the Department of Anatomy, College of Medicine of the

University of Lagos. Sorting was carried out using Microsoft Excel software package. This

package has been shown to be adequate for the storage of anthropometric data. This enabled theorganization of all data prior to analysis. All the measurement data were thereafter used either

singularly or in combination and with the appropriate algorithms (equations) to determine the

following morphologic characteristics:

Physical status indices include the following:

1. Stature (height)

2. Body mass (weight)

Body composition indices include the following:

1. Body mass index (BMI) - Quetelet index

2. Height-weight Ratio (HWR) - Reciprocal of Ponderal Index (Sheldon index)

The algorithm for HWR and BMI are given as equations (6) and (7) below:

Height- weight ratio (HWR) = stature (cm)

Body mass (kg) 0.333 (6)

Body mass index (BMI) = body mass (kg)

Stature (m)2 (7)

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Data presentation

The physical structure and body composition characteristics are presented as tables of descriptive

statistics showing the variation of each characteristic with chronological age, gender and

socioeconomic status. Tables for the characteristics presented include:

1. Stature

2. Body mass

3. Body mass index (BMI)

4. Height-Weight Ratio (HWR)

For inferential statistics, all statistical analyses were performed using the SPSS 11.0 forWindows statistical software package. This package has been shown to be adequate for use in the

analysis of anthropometric data. The analyzed data were thereafter double-checked for

systematic and random errors by comparing the results with the same data analyzed manually.

Descriptive statistics for the subjects attending both public and private schools were calculated

for the relevant variables for this study. The Students t-statistic was used to compute the

statistical significance of differences observed among the boys and girls of either category of

schools.

Somatotypes

The following algorithms were used in the calculation and analysis of somatotype data.

The anthropometric somatotype components

Endomorphy = - 0.7182 + 0.1451*(X) - 0.00068 *(X2) + 0.0000014*(X3) (8)

Mesomorphy = (0.858 HB + 0.601 FB +0.188 CAG + 0.161 CCG) - (0.131 H) + 4.5 (9)

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Ectomorphy: If HWR 40.75, then

1. Ectomorphy = 0.732 HWR - 28.58 (10)

If HWR < 40.75 and > 38.25, then

2. Ectomorphy = 0.463 HWR-17.63 (11)

If HWR < 38.25, then

3. Ectomorphy = 0.1 (or recorded as ) (12)

Where: X = (sum of triceps, subscapular and supraspinale skinfolds) multiplied by

(170.18/height in cm); HB = humerus breadth; FB = femur breadth; CAG = corrected arm girth;

CCG = corrected calf girth; H = height; HWR = height (cm) / cube root of weight.CAG and CCG are the girths corrected for the triceps or calf skinfolds respectively as follows:

CAG = flexed arm girth - triceps skinfold/10; CCG = maximal calf girth - calf skinfold/10.

Plotting somatotypes on the 2-D somatochart

X-coordinate = ectomorphy endomorphy --------- (13)

Y-coordinate = 2 x mesomorphy - (endomorphy + ectomorphy) --------- (14)

Somatotype frequency categories

The plotting of the somatochart displays the individual somatotypes within specific somatotype

categories on the chart. Sheldon et al. (1940) originally conceived of nineteen categories of

somatotype. These were later redefined and reduced to thirteen by Heath and Carter (1967). The

thirteen categories have been defined in Carter and Heath (1990). The latter based the definition

of these categories on the somatochart as follows:

1. Balance endomorph - endomorphy is dominant and mesomorphy and ectomorphy are

equal (or do not differ by more than one half unit).

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2. Mesomorphic endomorph - endomorphy is dominant and mesomorphy is greater than

ectomorphy.

3. Mesomorph endomorph - endomorphy and mesomorphy are equal or do not differ by

more than one half unit and ectomorphy is less.

4. Endomorphic mesomorph - mesomorphy is dominant and endomorphy is greater than

ectomorphy.

5. Balanced mesomorphy - mesomorphy is dominant and endomorphy and ectomorphy are

equal or do not differ by more than one half unit.

6. Ectomorphic mesomorph - mesomorphy is dominant and ectomorphy is greater thanendomorphy.

7. Mesomorph ectomorph - mesomorphy and ectomorphy are equal or do not differ by more

than one half unit and endomorphy is lower.

8. Mesomorphic ectomorph - ectomorphy is dominant and mesomorphy is greater than

endomorphy.

9. Balanced ectomorph - ectomorphy is dominant and endomorphy and mesomorphy are

equal or do not differ by more than one half unit.

10. Endomorphic ectomorph - ectomorphy is dominant and endomorphy is greater than

mesomorphy.

11. Endomorph ectomorph - endomorphy and ectomorphy are equal or do not differ by more

than one half unit and mesomorphy is lower.

12. Ectomorphic endomorph - endomorphy is dominant and ectomorph is greater than

mesomorphy.

13. Central - no components differ from the other by more than one unit.

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Somatotype categories are reported in category charts (tables) presented immediately below the

corresponding somatochart.

Somatotype analysis

Two-dimensional analyses

1. Somatotype attitudinal distance (SAD).

The SAD is the exact difference, in component units between two somatotypes (A, an individual

or group and B, an individual or group), or between two somatotype group means (e.g. A and B),

or between a subject and a group mean (e.g. subject A and group mean B). For the purpose of

this study, the third situation is applicable as shown in equation (15) thus:

SAD A;B = [(ENDO A - ENDO B)2 + (MESO A - MESO B) 2 + (ECTO A - ECTO B) 2 ] (15)

Where: ENDO = endomorphy; MESO = mesomorphy; ECTO = ectomorphy; A = each

individual somatotype, B = sub-group mean somatotype for each age group/stratum.

2. The somatotype attitudinal means (SAM)

The somatotypes attitudinal mean (SAM) is the mean of a group of somatotypes and is given by

the equation (16) below:

SAM = SADi / nX (16)

where: SADi = somatotype of each subject minus the mean somatotype of the group; nx is the

number in the group x.

The somatotype attitudinal variance (SAV) is the variance of the group.

SAV = SAD2i / nx (17)

The standard deviation of the somatotypes about SAM is given by the equation

SAM = SAV (18)

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3. Somatotype Analysis of Variance (SANOVA)

Comparisons between independent samples

Sample groups (strata) would be compared either as pairs of independent samples or as multiple

groups or samples. In the former situation, somatotype analysis for two-dimensional distributions

(SADs and SAMs) will be carried out with the aid of the t-statistic. Differences between

independent pairs of sample were assessed using the t-ratio. The algorithm for calculating the t-

ratio is given below:

1. t-ratio:

t = 1 - 2 / 0.5[ (SAD21) + (SAD22) / (n1 + n2 - 2) * (1/n1 + 1/n2)] (19)

Where: 1 = mean of group 1, 2 = mean of group 2; SAD1 and n1, and SAD2 and n2, refer to

groups 1 and 2 respectively.

When multiple sample groups were to be compared, a special type of analysis of variance known

as somatotype analysis of variance (SANOVA) that was developed to analyze whole

somatotypes (Carteret al.1983; Carter and Heath, 1990) was utilized and the table of F-statistic

was used to determine statistically significant differences. The algorithms for SANOVA are

given below:

2. F-ratio:

F = (SS t / dft) / (SS e / dfe) = MS t / MS e (20)

SS t = nj (j - Mo) 2, and SS e = (SAD2j) (21)

SS t1 = n1 (1 - Mo) 2, and SS t2 = n2 (2 - Mo)2 (22) where

the subscripts t = treatment; e = error; j = j groups; Mo = overall mean somatotype for combined

groups; MS = mean square; SS = sum of squares; 1, 2 = group labels

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4. Somatotype frequency analysis

This involves the comparison of Category charts. For analysis of the frequencies and relative

frequencies of somatotype in each category chart, non-parametric tests including comparative

ratio analysis and the chi-square statistic will be used to determine the difference between age,

gender and school type groups.

RESULTS

Sampling Distribution

This study involved a total of 3498 subjects, 1565 males and 1933 females, classified into strata

by Neyman Optimum Allocation procedure to ensure that the sample sizes for the males were

not less than 109. However, availability of subjects permitted sample sizes that were greater than

113 for the females (see table 2).

Table 2 Stratified sampling distribution of all subjects by age range, gender and school

type into strata After the Optimal Allocation procedure of Neyman (1958)

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Age Range

(years)

Age

groups

Private

schoolboys

(PRB)

Public

schoolboys

(PUB)

Private

schoolgirls

(PRG)

Public

schoolgirls

(PUG)

Total

9.51-10.50 10 0.5 113 112 118 129 47210.51-11.50 11 0.5 116 110 135 127 488

11.51-12.50 12 0.5 115 113 140 149 51712.51-13.50 13 0.5 109 112 142 146 60913.51-14.50 14 0.5 110 109 135 147 60114.51-15.50 15 0.5 113 111 142 148 51415.51-16.50 16 0.5 112 110 134 141 497Total 7 788 777 946 987 3498

Stature

The descriptive and inferential statistical data for stature (height) are summarized in table 3. The

data is presented as mean and standard deviation (mean SD). The large standard deviations in

all groups indicate wide variation in measurement sizes. The mean stature of private school boys

(PRB) increased consistently from 143.1(7.3) cm at 10 years to 172.8 (8.2) cm at 16 years while

the mean stature of the public school boys (PUB) also increased steadily from 135.9 (7.9) cm at

age 10 years to attain 167.6 (8.0) cm at age 16 years. The mean difference between the school

types per age group was statistically significant at all ages (p< 0.05). The mean stature of private

school girls (PRG) increased from 143.7 (8.1) cm at age 10 years to 162.0 (6.0) cm at 16 years.

The mean difference at all age groups compared was statistically significant (p


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tallest (172.8 cm) at 16 years. By 16 years, both male groups had attained to a taller stature than

the two female groups.

Body mass

The descriptive and inferential statistical data for body mass (weight) are summarized in table 4.

The mean body mass for private school boys (PRB) increased from 35.2 (7.8) kg at 10 years to

reach a mean body mass of 60.5 (10.5) kg at 16 years. The mean body mass of public school

boys (PUB) increased from 28.8 (4.1) kg at 10 years to attain to 56.4 (8.7) kg at 16 years. At all

ages from 10 to 16 years, the mean difference between PRB and PUB was highly significanteven at p< 0.01.

Table 3 Descriptive and inferential statisti

completed thesis for approval

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