Limits of physical ability among individuals

Limits of physical ability among individuals are determined in part by body structure. Variations due to structure are exhibited when well-trained athletes perform ill competition. In the competitive situation the athletes have received motivation and training sufficient to enable them to approach the physiological limits of function of the critical organs. The difference ill performance then affected by differences in structure. Variations in structure which affect performance are found among different age groups, between the two sexes, among different body types and among different racial groups.

Individuals with wide differences in structure may all be able to execute the same kind of movement, but the difference in the quality of execution of the movement shown by the individuals results largely from variations in the amount of strength, speed, skill and endurance which is possessed by each. Furthermore, a piece of work which requires only a low grade of organic function does not differentiate individuals in a population. It is not until the work increased in intensity or complexity, requiring coordinate increases in strength, speed, skill or endurance that differences among individuals become apparent.

Responses of Young Ohildren to Exercise

Physiological studies of the responses of young children to exhaustive exercise are understandingly difficult to perform. Special exercise equipment which includes motivational devices must be constructed 1 since young children are usually unwilling to exert maximal effort. Difficulties in taking blood samples and fitting face masks for respiratory and metabolic determinations also complicate the collection of data. Furthermore, children are usually not readily available to physiological laboratories. The great mass of physiological data available to date has been collected predominantly from adult laboratory workers, medical and physical education students and athletes. At present, data on young children are insufficient to describe their physiological responses to strenuous exercise with a satisfactory degree of accuracy or completeness.

The physiological systems of younger children are apparently not so sufficiently developed to meet the demands of strenuous exercise as they become when puberty is reached. Children under 12 years of age possess a highly active sympathetic nervous system which predisposes to a high heart rate and an easily depleted capacity for endurance activities such as running. Children under 12 do not have the capacity to utilize oxygen that older boys do because of a relatively smaller stroke volume of the heart and a consequent smaller capacity for increased circulation of blood through the lungs. The younger boys also possess a lesser supply of carbohydrate fuel.