The respiratory system as an exercise limiting factor in normal trained subjects.

Area of Science:

• Exercise Physiology
• Respiratory Muscle Physiology

Background:

• Untrained respiratory systems limit submaximal exercise endurance in sedentary individuals.
• Isolated respiratory training significantly improves breathing and cycling endurance in sedentary subjects.

Purpose of the Study:

• To investigate if endurance-trained individuals also benefit from respiratory muscle training.
• To determine the effects of respiratory training on breathing and cycle endurance, maximal oxygen consumption (VO2max), and anaerobic threshold in trained subjects.

Main Methods:

• Eight endurance-trained subjects underwent 4 weeks of daily respiratory muscle training.
• Performance tests including breathing and cycle endurance, VO2max, and anaerobic threshold were measured before and after training.
• Subjects maintained their habitual endurance training throughout the study.

Main Results:

• Respiratory training increased breathing endurance from 6.1 to 40 minutes.
• Cycle endurance at the anaerobic threshold improved by over 35% (22.8 to 31.5 minutes).
• VO2max and anaerobic threshold remained unchanged, while minute ventilation at submaximal intensities decreased post-training.

Conclusions:

• Respiratory muscle training can markedly improve endurance even in already trained individuals.
• Respiratory muscle fatigue and associated hyperventilation limit exercise performance at the anaerobic threshold in trained subjects.
• The respiratory system is a significant exercise-limiting factor in normal, endurance-trained individuals.