Exercises of strength lead rapidly to an increase in the size of the thorax. It is the same with exercises of speed when they need very energetic movements. No exercise develops the chest as rapidly as does running, unless it be wrestling.
Mountaineers all have large chests, and the Indians who live on the high plateaus of the Cordillera in the Andes have been noted for the extraordinary size of their chests. This great development in mountaineers is due to two causes which act in the same direction: frequent ascent of steep inclines, and constant residence at great heights at which the air is rarefied. The climbing of these slopes needs a great quantity of work, which causes increase of the respiratory need; respiration in a rarefied atmosphere obliges a man to take deeper breaths in order to supplement, by the quantity of air breathed, the insufficiency of its vivifying properties.
Singers, with no other exercise but singing, acquire great respiratory power and a remarkable increase in the dimensions of their chests.
Numerous observations prove that it is enough voluntarily to take a certain number of deep breaths every day, to produce, in a short time, an increase in the circumference of the chest which may amount to two or three centimetres.
If we wish to gain the same result from muscular exercise, we must choose a form of work which will increase the intensity of the respiratory effort—that is, an exercise which brings powerful muscular masses into action. We shall thus perform a great quantity of work in a short time without producing fatigue. Now the legs, which possess three times as much muscle as the arms, can perform thrice the quantity of work before being fatigued. The lower limbs are, then, more capable than the arms of awakening the respiratory need, which is proportional to the expenditure of force.
Thus it is an error to demand from gymnastic exercises practiced with appliances, exercises of suspension or support, any development of the chest. The trapeze, the rings, the parallel bars, quicken respiration much less than running. These exercises cause an increase in the size of the muscles, and even of the bones of the regions which work, but they cause very little increase in the dimensions of the thorax.
Men who do much work with their arms have often a conformation which is very imposing at the first glance. They have sometimes broad shoulders; but if the arms have done the work alone, without the assistance of the muscles of the trunk, we easily see that the apparently large size of the thorax is due to an excessive development of the muscles about the shoulder-joint, and not to raising of the ribs.
