In humans, the lungs occupy about 6% of the body volume regardless of their weight. Thorax changes in volume, due to its structure. The largest amplitude of ribs is possible if during inspiration the spine extends, and during exhalation – spine flexes. Movement of the upper ribs changes thorax in the anteroposterior direction, and the lower ones – in the frontal plane.
Lung volume changes during inspiration but nor regularly in all its parts. For this there are three main reasons: firstly, the thoracic cavity increases irregularly in all directions, and secondly, not all parts of the lung are equally extensible. Thirdly, we assume the existence of the gravitational effect which promotes downward displacement of lung.
At rest an adult breathes 16-20 times per minute. In children same breath is more frequent – up to 60 breaths per minute.
During tidal respiration a human inhales and exhales about 500 ml of air. This amount is called the tidal volume.
With a deep breath, you can inhale additional 1,500 ml of air. This volume of air is called the reserve inspiratory volume.
After the tidal exhalation a human can further exhale another 1,500 ml of air. This volume of air is called reserve expiratory volume.
The sum of these three volumes constitutes vital lungs capacity (VC). In adult this capac- ity is approximately 3500 ml. VC depends on age, sex, physical fitness of a human.
Moreover, even after the deepest expiration approximately 1,000 ml of air remain in human lungs. This volume of air is called residual volume, and even more air remains in the airways (about 150 ml) which do not participate in gas exchange.
The sum of Reserve Inspiratory Volume, Reserve Expiratory Volume, and Residual Vol- ume (RV) is the Total Lung Capacity (TLC). In these contexts, a capacity can be broken down into two or more volumes.
Physical exercises have more than a beneficial effect on the entire respiratory system and redundant capabilities of the organism, i.e., the reserve of health, directly depend on the reserve possibilities of the respiratory system.