Keep your leg at a 90-degree angle and your knee and foot at the same height. Avoid rotating your spine at any point during the exercise. Pause at the top for two seconds before lowering your knee to the floor. Repeat 15-25 times before performing the exercises with the other leg.
Inhaled air is about 20-percent oxygen. Exhaled air is about 15-percent oxygen. Therefore, about 5-percent of breathed air is consumed in each breath. That air is converted to carbon dioxide. So, as far as how much air is actually used, human beings take in about 550 liters of pure oxygen per day. A person who is exercising uses a lot more oxygen than that.
The air in the lung is divided into four compartments: tidal vol-. umeâair exhaled during quiet breathing; inspiratory reserve vol-. umeâmaximal air inhaled above tidal volume; expiratory reserve. volumeâmaximum air exhaled below tidal volume; and residual. volumeâair remaining in the lung after maximal exhalation. The.