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.
