Academic journal article College Student Journal

Body Fat and Muscle Mass as Functions of Body Water

Academic journal article College Student Journal

Body Fat and Muscle Mass as Functions of Body Water

Article excerpt

Hydrostatic weighing and chemical dilution are well accepted methods for measuring body composition. Recently, Dual Energy X-ray Absorptiometry (DEXA) has become the preferred method. The two compartment algorithms used by these methods assume a fixed constant for lean body tissue. This constant has long been suspect of variations due to many reasons such as ethnic or racial differences, age, health, etc. Variations in muscle mass, however, are factors that affect every single subject. The study presented here includes muscle mass as one compartment of a three compartment body composition model. Each compartment is modeled as a function of body water measurements with hydrometric constants as parameters. A muscle mass algorithm is hypothesized and tested to support the authors' contention that muscle mass can be approximated by making body water measurements. It is demonstrated that, when muscle mass becomes a factor, the traditional two compartment models can overstate body fat ratios by as much as four percent.


This paper describes the development of a three compartment body composition model that includes muscle mass as a separate compartment. This model is hydrometric in that it is based on body water measurements. Hypothesis for the muscle mass component is corroborated using grip strength (as discussed by Rantanen, Guralnick, Foley et al, 1999) and body water data. The hydrometric constants of the model are determined by skin fold (as measured by Scherf, Franklin, Lucas et al, 1986, and Womersley, Durnin, Boddy et al, 1976), grip strength and body water measurements. Use of these constants is found to be consistent with the two compartment hydrometric constant for lean body tissue (developed by Garrow, 1982). Application of this model is used to demonstrate the representation of body composition in terms of body fat, muscle mass and other body organ components. This application demonstrates that the traditional, two compartment model overstates body fat ratios by as much as four percent. Industry acceptance of the three compartment model precludes application of the traditional two compartment model.



As is the case with body fat, muscle mass cannot be measured directly. Therefore the muscle mass component must be detected by measuring the effects of muscle mass variations. This study hypothesizes that, like body fat, muscle mass can also be approximated using body water measurements. This hypothesis is tested by correlating grip strength and body water measurements on thirty University of Montevallo students. The muscle mass approximation is then applied to a three compartment model by using multiple regression of grip strength, body water and skin fold measurements to determine the hydrostatic constants of the model.

Data Base

Thirty University of Montevallo students were measured for grip strength using the Smedley Hand Dynamometer. They were measured for body fat using the Lang Skin Fold Calipers along with the skin fold algorithms (developed by jackson and Pollock, 1978, and Jackson, Pollock and Ward, 19980). They were measured for body water and body weight using the Tanita Body composition Analyzer model TBF 300A along with the "athletic" body water and body weight algorithms that reside in the model TBF 300A Analyzer. The Tanita Body Composition Analyzer is a bioelectric device (as discussed by Kushner, 1992, and Thomas Cornish and Ward, 1992). The University of Montevallo student population consisted of eleven adult education students (six male and five female) and nine male and ten female athletic department students. The UM data base is shown in Table 1. Written informed consent was obtained from all of the subjects shown in Table 1. The consent forms and study plans were approved by the University of Montevallo Study Review Board.

Muscle Mass Hypothesis

It is well known that muscle mass contains larger portions of body water than do most other body organs. …

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