The General Effects of Muscular Exercise in the Trained and Untrained Person for Their Muscle Development

The greater strength and efficiency of the body, brought about by regular physical training, is the product of two processes which normally go hand in hand. One is the development of the muscular system as a whole, and more especially of the muscles employed in the form of exercise carried out; the other is an increase in the range and delicacy of the adjustments of the circulatory and respiratory systems whereby the supply of oxygen to the body is assured. The attention of trainers and athletes has naturally been directed almost exclusively to the first of these processes; and the traditional methods adopted in a regular course of training, for example, before a boat-race, are regular progressive muscle development exercise, and a particular form of diet, which includes the consumption of large quantities of meat.

The growth in the size of the muscles during muscle development training clearly demands the presence in the diet of a considerable amount of protein in order to provide the material required for this purpose. Possibly, also, in virtue of its specific dynamic action, protein may increase the intensity of the whole metabolic activities of the muscles, including those occurring during exercise. It may, in fact, lead to a more rapid combustion of the fat and carbohydrate, the oxidation of which provides the energy for muscular work, and may thereby increase the work of which the muscle is capable in a given time. On this view, a liberal protein diet, so to speak, makes the fire hotter in which the carbohydrate and fat are consumed.

There is no doubt, moreover, that many men have been successfully trained on a diet consisting largely of carbohydrate and eggs, and there is no consensus of opinion as to what form of diet is the most useful. Many athletes appear to find that a rigid or specialized training and diet are unnecessary, so long as the ordinary rules of health are observed and regular and progressively increasing muscle development exercise is taken.

The greater size and power of the skeletal muscles, which results from regular physical training, is accompanied by a similar development of the lungs and heart The greater expansion of the chest increases the vital capacity and the range of pulmonary ventilation, and these changes must be of value, not only in adding to the oxygen reserve in the lungs, but also in increasing the surface which the pulmonary capillaries offer to the alveolar air, and thereby raising the individual's coefficient of diffusion.

Regular and progressive exercise is the essential feature of muscle development, and the character of the diet, provided this is ample and is properly digested, is of subsidiary importance, and training develops not only the skeletal muscles, but also the heart, and, in a healthy man, the development of his heart corresponds with that of his muscular system. Owing to the increase in its contractile power, the output of the heart per beat is often larger, and the pulse-rate less frequent, in the trained, than in the untrained man, even during rest.

When a trained, and an untrained roan, takes the same amount of muscle development exercise, the pulse is less frequent, the arterial pressure is usually lower, and the minute volume of the heart is smaller in the former than in the latter. These differences are due partly to the fact that the output of the heart per beat is larger in the trained man and partly to the greater coefficient of utilization and oxygen-carrying power of the blood in the trained man, which lessen the output of the heart per minute necessary to provide a given supply of oxygen to muscle development. The better co-ordination of movement, which is brought about by training, also improves the mechanical efficiency of the body. The effect of these changes is not only to increase a man's power of doing muscular work, but also to enable such work, whether heavy or light, to be performed with the utmost economy of effort.

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