The following is an exclusive excerpt from the book NSCA's Essentials of Personal Training, Second Edition, published by Human Kinetics. All text and images provided by Human Kinetics.

Respiratory Adaptations

With the respiratory system’s large capacity to increase ventilation in response to exercise, as well as the relatively low oxygen (or energy expenditure) cost of breathing in terms of percentage of total body oxygen cost, the demands of aerobic endurance training on the human respiratory system are not as great as they are for other systems. Consequently, chronic aerobic training produces considerably less adaptation than occurs in the cardiovascular system and skeletal muscle (39,46). For the great majority of healthy adults, the respiratory system is also not a limiting factor for performing maximal exercise (14,46,71). There are, however, several important adaptations in the respiratory system that relate to aerobic performance enhancement.

Adaptations in pulmonary minute ventilation (VE) in response to chronic aerobic training occur during submaximal and maximal exercise, with no changes at rest. With aerobic endurance training, VE values during a standardized submaximal work rate test may decrease by as much as 20% to 30% (71); in contrast, during maximal exercise, VE may increase 15% to 25% or more (39). With aerobic endurance training, adaptations during submaximal exercise generally include an increase in tidal volume and a decrease in breathing frequency, while during maximal exercise both tidal volume and breathing frequency increase.

During moderate-intensity aerobic exercise, the oxygen cost of breathing averages 3% to 5% of total body oxygen cost and increases to 8% to 10% of total body cost at VO₂max (15). With standardized submaximal exercise, after aerobic endurance training the percentage of the total body oxygen cost for breathing is reduced and the ventilatory equivalent for oxygen (VE/VO₂) is lowered, indicating improvements in ventilatory efficiency (39,46). This reduced oxygen cost for breathing enhances aerobic endurance performance by freeing more oxygen for use by exercising skeletal muscle (21) and by reducing the fatiguing effects of exercise on the diaphragm muscle (69). Specificity in respiratory training adaptations also occurs as can be illustrated through comparison of arm and leg aerobic training. Individuals performing arm training show an improvement in VE/VO₂ with arm exercise, but not with leg exercise; and the opposite occurs in individuals training with leg cycling (60). It thus appears that local adaptations in trained muscle are responsible for adaptations in VE/VO₂.

NSCA’s Essentials of Personal Training, Second Edition, is the authoritative text for personal trainers, health and fitness instructors, and other fitness professionals, as well as the primary preparation source for those taking the NSCA Certified Personal Trainer^® (NSCA-CPT^®) exam. The book is available in bookstores everywhere, as well as online at the NSCA Store.