The influence of skin thickness on the determination of the percentage of body fat (skinfolds and ultrasound)

Breytenbach, Johannes Gerhardus (1996-03)

Thesis (M. in Human Movement Studies)--University of Stellenbosch, 1996.

Thesis

ENGLISH SUMMARY: There are several ways to assess the body composition of young men in a laboratory setting. However, due to the invasiveness, expense, time, specialised equipment, extensive instrumentation and level of skilled personnel required to perform these methods, they are generally not used in a clinical setting. New methods are being developed for clinical use, which may offer the potential for non-invasive, not too costly in terms of time and equipment, reliable and easy body composition estimate. These methods involve the development of formulae which relate skinfold or circumference measurements, or a combination of both, to indirect estimates of body fat (Drinkwater, 1984: 17). Since many of these methods involve the determination of the adipose tissue in vivo, most techniques rely on external body measurements through the skin. The importance of the influence or contribution of the actual skin thickness on the determination of the caliper skinfold thickness has rarely been investigated. Ultrasound or sonar scans proved to be a fairly non-invasive and inexpensive, not too time consuming, yet accurate method to determine the skin and subcutaneous fat layer individually in human beings. Various tests were performed on the subjects, such as hydrostatic weighing, lung functions, bio-electrical impedance analysis and a vast range of anthropometrical measurements including weight, stature, diameter, girth and skinfold (caliper), skin and fat (sonar) on fourteen body locations were recorded. The body density values (skinfolds), according to Durnin & Rahaman (1967) and Jackson & Pollock (1978), were individually applied to the formulae of Brozek (1953) and Siri (1961) to calculate the percentage body fat. Correlations with hydrodensitometry were high, ranging from r=O,81499 (for Durnin & Rahaman and Brozek) to r=O,82338 (Jackson & Pollock and Siri) (see Figures 10 to 13). The same procedure was followed with the sonar measurements and different combinations such as fat, 1x skin + fat and 2x skin + fat, were used. Correlations with hycfrodensitometry were remarkably high, seeing that these formulae were developed for the use of skinfold calipers, and ranged from r=O,77198 (Durnin &' Rahaman and Brozek) to r=O,84545 (Jackson & Pollock and Siri) (see Figures 14a to 17c). When applying the sonar (fat) measurements to the formula of Jackson & Pollock, it resulted in a relatively higher correlation (r=0,8455), as when compared to other combinations of sonar measurements, namely sonar (1 x skin + fat) and sonar (2x skin + fat), which resulted r=0,83697 and r=0,81987 respectively. When substituting the supra iliac (anterior) and medial thigh body locations with the supra iliac (posterior) and anterior thigh values respectively, a good correlation (r=0,83575) was found. Although all of these variations yielded good results, it can be seen that the formula of Jackson & Pollock was developed for the use of skinfolds (r=0,89224). When substituting the supra iliac (anterior) and anterior thigh body locations with the supra iliac (posterior) and medial thigh values respectively, a good correlation (r=0,86924) was found. This indicated that more attention should be given to these areas of fat deposits formerly not investigated, especially the medial thigh for females, and the posterior supra iliac for males. Each of the 14 body locations was individually correlated with body density via three different methods, namely skinfold measurements (Harpenden caliper), fat measurements (sonar) and 2x Skin and fat: (sonar). Skinfolds correlated the highest with body density, ranging from r=0,827 (abdomen) to r=0,615 (bicep). The second highest correlations were found to be that of fat thickness, varying from r=0,791 (tricep) to r=0,237 (chin). The sonar measurements (2x skin + fat) correlated third highest ranging from r=0,754 (chest) to r=0,239 (chin). Subsequently no ultrasound formulae were available to compare this population group and a new regression equation, using seven sonar fat values, was developed to indirectly estimate the body density. These findings were compared to and correlated with hydrodensitometry (r=0,86784) (see Fig, 29). A further regression equation was developed, using the sum of seven skinfolds as measured by caliper, in order to predict body density. This equation was also compared to hydrodensitometry and yielded a correlation of r=0,86936 (Fig 30). Either method of measurement and accompanying formula yielded good results when compared to hydrodensitometry providing that the subject qualifies for the 18 to 30 year old endo-mesomorphic category. This study provides the health professional with alternatives where a choice between sonar and skinfold measurements can be made, depending on the preference of the patient and clinician or the time and apparatus available.

AFRIKAANSE OPSOMMING: Daar bestaan verskeie maniere om die liggaamsamestelling van jong mans in 'n laboratorium milieu te bepaal. Weens die finansiele implikasies, gespesialiseerde toerusting, hoogs opgeleide personeel, ingrypende prosedure en tyd daaraan verbonde, word die meeste van hierdie metodes beperk tot navorsingsfasiliteite en derhalwe nie aangewend in 'n kliniese omgewing nie. Nuwe metodes word voortdurend ontwikkel ten einde 'n nie-ingrypende, bekostigbare, eenvoudige, dog akkurate alternatief daar te stel waarvolgens die mens se liggaamsamestelling bepaal kan word. Die meeste van hierdie metodes behels die ontwikkeling van vergelykings waar sekere antropometriese metings soos velvoumate, omtrekke en deursneemate van die ligaam en ledemate aangewend word om die liggaamsamestelling indirek te voorspel (Drinkwater, 1984: 17). Aangesien die meeste van hierdie metodes die bepaling van liggaamsvet in vivo behels, word hierdie metings uitwendig deur die vel geneem. Die belangrikheid van die invloed van die werklike veldikte se bydrae tot die velvoumeting, soos bepaal deur die velvouknyper, is nog weinig vantevore ondersoek. Ultraklank of sonar skanderings het getoon om 'n vinnige, relatief bekostigbare, nie ingrypende, dog akkurate bepalingsmetode van die dikte van die vel en onderhuidse vetlaag te wees. Verskeie toetse en metings is op die proefpersone uitgevoer, wat onderwaterweging, bio-elektriese impedansie analise, longfunksies en breedvoerige antropometriese opmetings, met velvouknypers en sonar, op veertien verskillende liggaamsareas ingesluit het. Die liggaamdigtheidwaardes (velvoue), soos bepaal met die formules van Durnin & Rahaman (1967) en Jackson & Pollock (1978), was elkeen ingestel in die formules van Brozek (1953) en Siri (1961) om die persentasie liggaamsvet te bereken. Korrellasies met onderwaterweging was hoog en het gewissel van r=O,81499 (Durnin & Rahaman en Brozek) tot r=O,82338 (Jackson & Pollock en Siri) (sien fig 10 tot 13). Dieselfde prosedure is gevolg vir die sonarmetings met verskillende kombinasies soos vet, 1 x vel + vet en 2x vel + vet. Korrellasies met onderwaterweging was verbasend hoog, r=O,77198 en r=O,84545 vir Durnin & Rahaman en Brozek en Jackson & Pollock en Siri onderskeidelik. Aangesien bogenoemde formules ontwerp en ontwikkel is vir (vet) waardes wat ingestel word in die formule van Jackson & Pollock, lewer dit 'n hoer korrrellasie (r=O,8455) as wanneer daar van die ander kombinasies 5005 sonar (1x vel + vet) (r=O,83697) of sonar (2xvel + vet) (r=O,81987) gebruikgemaak word. Wanneer die waardes van die suprailiaca (anterior) en anterior dy liggaamsareas vervang word met supra iliaca (posterior) en mediale dy waardes, word 'n goeie korrellasie van r=O,83575 verkry. Alhoewel al bogenoemde moontlikes goeie resultate en ooreenkomste getoon het, word daar duidelik getoon dat die formule van Jackson & Pollock ontwikkel was vir die aanwending van velvoumate (r=O,89224). Weer eens word gesien dat wanneer die waardes van die supra iliaca (anterior) en anterior dy liggaamsareas vervang word met supra iliaca (posterior) en mediale dy waardes vervang word, word 'n goeie korrellasie van r=O,869224 verkry. Dit dui daarop dat hierdie vetdeposito areas meer aandag kan geniet, veral die mediale dy vir dames en die posterior supra iliaca in die geval van mans. Verder was elkeen van die veertien liggaamsareas op drie wyses, naamlik velvoumates (Harpenden knyper), vetwaardes (sonar) en 2x vel + vet (sonar) afsonderlik met liggaamsdigheid, soos bepaal deur middel van die onderwatermetode, vergelyk. Velvoue het die hoogste korrellasie met liggaamsdigtheid getoon en het gewissel van r=0,827 (abdomen) tot r=0,615 (bicep). Die tweede hoogste korrellasie was die van sonar vetwaardes, waar die tricep (r=O, 791) die hoogste en ken (r=0,237) die laagste waardes getoon het. Laastens het die sonarwaardes (2x vel + vet), bors (r=0,754) tot ken (r=0,239), korrellasies getoon met die onderwaterweging. Aangesien geen formules vir sonarmetings beskikbaar was om hierdie groep mee te vergelyk nie, is daar 'n nuwe regressievergelyking, met behulp van sewe sonar vetwaardes, ontwikkel om liggaamsdigtheid indirek te kon bepaal. Hierdie bevindings is vergelyk met onderwaterweging en 'n korrellasie van r=0,86784 is gevind (Fig 29). 'n Verdere regressievergelyking is ontwikkel waar die som van sewe velvoue, soos gemeet met die velvouknyper, aangewend word om liggaamsdigtheid te bepaal. Laasgenoemde vergelyking is ook met onderwaterweging vergelyk en toon 'n korrellasie van r=0,86936 (sien Figuur 30). Enige van die bogenoemde metodes het goeie resultate getoon in vergelyking met die onderwaterweegmetode met die voorbehoud dat die persoon kwalifiseer as 'n 18 tot 30 jarige endo-mesomorfiese man. Hierdie studie dui daarop dat diegene in die mediese milieu en gesondheidsberoepe, naas die velvoumetode, ook die sonarmetode vir die akkurate bepaling van die liggaamsdigtheid en persentasie liggaamsvet kan gebruik.

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