Experimental Studies on Factors in Growth

Abstract

Among the factors influencing the growth of Japanese children (including heredity, infectious diseases, and climate), nutrition and physical exercise are of special interest (Nakajima 1964). Only limited information is available concerning the effects of different types of physical activity upon maturation and growth. A stimulating effect on bone development, resulting in an increase in height, is frequently postulated, but the documentation is scant. The influence of nutrition on growth, maturation, and life span has been studied extensively, but in most nutritional studies-including the studies on nutrition and life span-the influence of physical exercise has been neglected (Berg 1960; McCay et al. 1939; Ross 1961). To make a rigorous analysis of these problems, several animal experiments were carried out in our laboratory. In our first experiment, a total of 300 white rats of the Wistar strain were divided into three dietary groups for each sex. Each dietary group was subdivided into exercised animals and nonexercised controls. The diets (table 1) represented three patterns: (a) a high-carbohydrate diet characteristic of the Japanese rural population; (b) a high-protein, high-fat diet of the Western type; and (c) a balanced diet with a carbohydrate-proteinfat ratio that appears optimal. The three diets differed only with respect to these three dietary components, the vitamin and mineral content being kept constant. All animals were fed ad libitum.