The Effect of Body Composition on Physical Fitness and Motor Ability in Obese Boys 12 Through 14 Years of Age

Abstract

Excess body fat has generally been considered to influence physical fitness and motor ability in obese boys. However, very few studies have been done on the relationships of percent body fat (%fat), body fat and fat-free mass with physical fitness and motor ability. The purpose of this study was to clarify the relationships between body composition and selected physical fitness and motor ability elements in obese boys. The subjects were three hundreds and five boys aged 12-14 years. Eighteen physical fitness and motor ability elements were tested and skinfold thickness was measured at six sites using an Eiken-type caliper. Impedance (Z) was measured using a tetrapolar bioelectrical impedance plethysmograph (Selco SIF-891). Body density was calculated from the formula of Kim et al. Variables which represented muscular power and endurance were negatively affected by%fat, while muscular strength was positively related to%fat. Flexibility variables were found not to be affected by%fat. In order to further examine the effects of%fat on physical fitness and motor ability, the subjects were categorized into three groups according to%fat: lean= less than 12%(n=64), average12∼20% (n=192), and obese=greater than 20% (n=49). The results of comparison among groups clearly indicated that the obese group was significantly poorer in muscular power and endurance but was better in muscular strength than the other groups. To analyze the factorial structure in obese boys, principal factor analysis was applied tothe correlation matrix which was calculated with 18 variables, and then six factors were extracted. The differentiation and integration of factorial structure was investigated from the hierarchical factor model. Two factors (muscular power and speed, and flexibility) were extracted at a lower level oF rotation. The body fat was found to be one importantfactor that affects many physical fitness and motor ability elements. The relationships between physical fitness, motor ability and degree of fatness seem to be rather complicated, and a great deal of data should be accumulated for analysis of influence of body fatness in the obese. © 1992, The Japanese Society of Physical Fitness and Sports Medicine. All rights reserved.