New article: Women and Men differ in Respiration during exercises read more at here http://www.spinonews.com/index.php/medical-news/item/3362-women-and-men-differ-in-respiration-during-exercises

In woman when workout intensity increased the respiratory muscles as diaphragm and muscles surrounding the ribcage take huge amount of oxygen than men. Woman need more energy in breathing because total amount of oxygen is sent to the respiratory muscles.

The researchers found the oxygen cost of breathing in healthy men and women over a range of exercise. Both Men and women together has undergone some tests. Cycle test is the first test completed with maximal breath to determine the movement of air and second test whole-body oxygen consumption associated with exercise. Each single breath with the coordination between inhalation rib cage muscles contract and abdominal muscles get relaxed where as in exhalation vice versa the abdominal muscles contract and rib cage muscles relax. This mechanism has several effects (i) it prevents rib cage distortion (ii) the diaphragm is unloaded and can act as a flow generator; and (iii) the volume of the abdomen is decreased below resting levels.

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Women have smaller lungs than men and women have a greater absolute oxygen cost of breathing and this represents a greater fraction of the total oxygen uptake compared to men. Although neither men nor women reach their maximal effective ventilation during exercise, women approach this value closer than men. Hence, the greater oxygen cost of breathing in women means that a greater fraction of total oxygen uptake and cardiac output is directed to the respiratory muscles influencing exercise performance.

The end pressure in lung volume is decreased during exercise. At each breath inhalation is stored in the form of elastic energy in previous exhalation. At maximal exercise, the oxygen consumed by the respiratory muscles to breath is only 10% of the total. In fact, in highly fit athletes the pressure produced by inhalation muscles can approach the maximum and exhalation pressures are increased to levels at which dynamic compression of the airways determines exhalation flow limitation.

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During heavy exercise, exhalation flow with no limit in time result in higher average positive pressures. But in normal condition flow slightly less than the atmospheric pressure known in negative pressures. These effects of respiratory muscles on the cardiovascular system understands systemic oxygen delivery and make the limb muscles even more influenced to tiredness.