Respiratory ability is very important for the maximal performance in endurance sportive events.
The oxygen consumption & total pulmonary ventilation has a linear relationship with levels of exercise. Both can increase, in a well trained person, in maximal intensity of exercise to 20 times the value at resting state. Physical training is important as oxygen consumption under maximal conditions in a well trained person can be increased to 1.4-2 times the highest for an untrained average person.
The intense ventilation during exercise results mainly from neurogenic signals transmitted directly into the brain stem respiratory center as a collateral impulse when the brain is transmitting motor impulse to the exercising muscles (much like the stimulation of the vasomotor center in the brain stem during exercise causes a simultaneous rise in blood pressure),& partly form sensory signals from contracting muscles & moving joints.
This neurogenic anticipatory stimulation of the respiration at the onset of exercise, even before it is needed, is used to supply the extra oxygen required for the exercise & also to blows off extra carbon dioxide. The chemical factor & the thermal factor do the required fine adjustment in the respiration initiated by the neurogenic factor to keep the oxygen, carbon dioxide, pH of body fluids as normal as possible.
This neurogenic factor is now shown be partly a learned response; i.e; with repeated periods of exercise, the brain becomes progressively more able to provide the proper signal to keep the Pco2 in body fluids (direct function of amount of carbon dioxide) etc at its normal levels.
This again shows the importance of physical & breathing training. One important thing is that the maximal breathing capacity (voluntary) is about 50% greater than the actual pulmonary ventilation during maximal exercise. This means that respiratory system is not normally the limiting factor in delivery of oxygen to the exercising muscles.
The rate of oxygen utilization under maximal aerobic metabolism (Vo2max) increases only 10 ter short term athletic training, but may increases more after years of training.Vo2max on the other hand is largely determined genetically-people with grater chest sizes in relation to body size, & stronger respiratory muscles have more Vo2max, & hence such person are more successful as marathoners etc.
The oxygen diffusing capacity of lungs increases above 3 times during maximal exercise. The maximum diffusing capacity of a trained person is almost 2 times that of a nonathlete during maximal exercise. This lays the importance of physical training, specially the endurance training. Genetics is also an important determining factor of maximal oxygen diffusing capacity.
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