Question

Many people think that their inability to do endurance work is related to an inability of their lungs to supply O2 to the blood. Provide a detailed explanation that you would give to an undergraduate exercise physiology class to help educate them why this idea is incorrect.

Answer 1

There are 3 systems that determine the endurance level. They are the respiratory system, cardiovascular system, and the musculoskeletal system. It is the cardiovascular system that totally controls the level of endurance to aerobic exercise in our body. It is the heart that supplies an enormous amount of oxygen to the skeletal muscles during endurance. This oxygen received is used for constant muscle contraction and for increasing the strength of muscles. As far as the respiratory system is concerned, they act my increasing more oxygen uptake thereby improving overall blood flow to the lung and would decrease both submaximal respiratory rate as well as pulmonary ventilation rate as to maximize the endurance capacity of muscle. The cardiovascular system acts by increasing the cardiac output, stroke volume, blood flow, blood volume, hemoglobin concentration, and finally decreased sub max heart rate. These synchronous activities from both respiratory and circulatory system will lead to increased size and density of mitochondria present in muscle cells and increased capillarization in the muscle cells. Thus, the overall endurance of muscle will increase leading to an increasing capability to do endurance workout.

From the above discussion we understand it is not the constant supply of oxygen by lung to tissues, but it is the oxygen supply to muscles by heart and a decrease in both submaximal respiratory and ventilation rate that leads to an increase in the endurance.