Age is the main factor related to expiratory flow limitation during constant load exercise.

Objective: The objective of this study was to investigate the interaction among the determinants of expiratory flow limitation (EFL), peak oxygen uptake (VO2peak), dysanapsis ratio (DR) and age during cycling at different intensities in young and middle-aged men.
Methods: Twenty-two (11 young and 11 middle-aged) men were assessed. Pulmonary function tests (DR), cardiopulmonary exercise tests (VO2peak) and two constant load tests (CLTs) at 75% (moderate intensity) and 125% (high intensity) of the gas exchange threshold were performed to assess EFL. EFL was classified using the percentage of EFL determined from both CLTs (mild: 5%-30%, moderate: 30%-50%, severe: >50%).
Results: Only the middle-aged group displayed EFL at both exercise intensities (p<0.05). However, the number of participants with EFL and the percentage of EFL were only associated with age during high-intensity exercise.
Conclusions: There was no interaction between the determinants. However, age was the only factor that was related to the presence of EFL during exercise in the age groups studied.