Submitted to: American Journal of Human Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/1999
Publication Date: N/A
Interpretive Summary: People with different body types (i.e., body sizes and shapes) tend to do different types of exercise or work. Generally, tall, thin people engage in activities that require endurance, whereas muscular people participate in activities that require strength and power. We sought to determine if these patterns of self selection of activity may be explained on the basis of diet or nutritional status or body composition. Young men who were provided nutritionally balanced diets underwent exercise tests on a cycle and specific examinations of body composition. Men who were tall and thin did the same amount of work as men who were muscular or mildly over fat. The tall, thin men, however, inhaled and exhaled more air to use the same volume of oxygen, relied more on the use of sugars stored in the body, and had greater accumulation of lactic acid (an indicator of stress during exercise) than the men in the other groups. The tall, thin men had less energy producing components of the body (muscle mass) than the men in the other groups. In addition, the tall, thin men had less muscle mass than was expected on the basis of their ages, height and weight. These findings provide the first evidence of the physiological basis for exercise or work performance deficits in men with this body type. This information will be useful to scientists who seek to determine the role of body composition and diet in regulating physical performance.
Technical Abstract: This study examined the hypothesis that somatotype determines body structure, functional responses during standardized exercise and nutritional status of 63 men aged 18 to 40-yr who lived under controlled conditions. Data were grouped by dominant somatotype to emphasize differences in body types. Dominant ectomorphs (n=19) had less (p<0.05) body weight, fat weight and percent body fat than endomorphs (n=14) and mesomorphs (n=30). Densitometrically-determined fat-free weight (FFW), total body potassium (TBK) and body cell mass (BCM), normalized for stature, were lower (p<0.05) in the ectomorphs than in the endomorphs and mesomorphs. Comparisons between measured and predicted FFW and TBK showed that only the ectomorphs had less (p<0.05) FFW and TBK than expected. Although all groups had the same peak power output, the ectomorphs had different functional responses during peak exercise. Ectomorphs had the greatest respiratory exchange ratio (p<0.05), ventilatory equivalent for oxygen and end-exercise plasma lactate concentrations (p<0.05), and lowest peak oxygen uptake (L/min; p<0.05). Nutrient intakes and blood biochemical markers of nutritional status were within the range of normal values in all groups. These data indicate that ectomorphs, as compared to endomorphs and mesomorphs, have deficits in FFW and BCM which are associated with differences in functional capacity during standardized exercise.