Expiratory flow limitation during exercise in competition cyclists

In some trained athletes, maximal exerciseventilation is believed to be constrained by expiratory flow limitation(FL). Using the negative expiratory pressure method, weassessed whether FL was reached during a progressive maximal exercisetest in 10 male competition cyclists. The cyclists reached an averagemaximal O₂ consumption of 72 ml · kg¹ · min¹(range: 67-82ml · kg¹ · min¹)and ventilation of 147 l/min (range: 122-180 l/min) (88% of preexercise maximal voluntary ventilation in 15 s). In nine subjects, FL was absent at all levels of exercise (i.e., expiratory flow increased with negative expiratory pressure over the entire tidal volume range). One subject, the oldest in the group, exhibited FLduring peak exercise. The group end-expiratory lung volume (EELV)decreased during light-to-moderate exercise by 13% (range: 5-33%) of forced vital capacity but increased as maximal exercise was approached. EELV at peak exercise and at rest were notsignificantly different. The end-inspiratory lung volume increasedprogressively throughout the exercise test. The conclusions reached areas follows: 1) most well-trainedyoung cyclists do not reach FL even during maximal exercise, and,hence, mechanical ventilatory constraint does not limit their aerobicexercise capacity, and 2) in absence of FL, EELV decreases initially but increases during heavy exercise.