According to authors Jack H. Wilmore and David L. Costill in their book, "Physiology of Sports and Exercise," exercise performance is largely determined by maximal oxygen consumption. Maximal oxygen refers to the body's ability to process and deliver oxygen to working muscles, and it is determined by both cardiac output and arteriovenous difference. Cardiac output is the amount of blood delivered by the heart to the body and arteriovenous difference refers to the oxygen content in the bloodstream. Exercise of short duration is fuelled through chemicals and is referred to as anaerobic. Longer exercise bouts are fuelled through oxygen and are termed aerobic.
The cardiac and respiratory systems work together to supply the body with blood and oxygen it needs to meet the increased demands of physical stress. Therefore, exercise scientists refer to the harmonious adaptations of these two systems as the cardiorespiratory system. According to the National Strength and Conditioning Association, or NSCA, an increase in breathing rate during exercise will produce changes in cardiac output, and vice versa. Though the largest adaptation to exercise is increased cardiac output, increased oxygen supply through breathing also plays a key role, Wilmore and Costill report.
Acute anaerobic effects
The NSCA says that during anaerobic exercise, ventilation is greatly increased. Ventilation is greater during recovery periods than actual exercise, and the degree to which ventilation increases is related to the intensity of the exercise. The most substantial elevations have been reported when rest periods are one minute or less, the NSCA explains. In addition to increased breathing rate, increases in tidal, or lung, volume have been observed as well.
Chronic anaerobic effects
The NSCA reports that because anaerobic exercise is fuelled chemically, long-term respiratory adaptations are minimal in healthy adults. Exercisers who are relatively untrained, however, may experience some improvement. The NSCA asserts that 5 to 8 per cent improvement in maximal oxygen consumption has been observed in untrained individuals. These improvements are more likely to occur when exercise periods are longer than rest periods, perhaps 30 seconds or less.
Acute aerobic effects
According to the NSCA, aerobic exercise has the most significant effect on maximal oxygen consumption as compared to other forms. Aerobic exercise is associated with both increased rate of breathing and increased volume of air breathed. Aerobic exercise can produce breathing rates of three times the resting rate, while volume of air breathed can increase more than 20 times.
Chronic aerobic effects
The NSCA explains that, whilst exercise produces an increase in ventilation, long-term training only moderately affects breathing. Adaptations are highly particular to the type of exercise performed. For example, training at higher intensities will primarily improve ventilation during high-intensity exercise. Despite this specificity, the NSCA reports that increased tidal volume and breathing frequency are improved during exercise, whilst they are both reduced during sub-maximal intensity or at rest.
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