Predictors of Expiratory Flow Limitation during Exercise in Healthy Males and Females

Abstract

RationaleIt is unclear whether the frequency and mechanisms of expiratory flow limitation (EFL) during exercise differ between males and females.PurposeThis study aimed to determine which factors predispose individuals to EFL during exercise and whether these factors differ based on sex. We hypothesized that i) EFL frequency would be similar in males and females and ii) in females, EFL would be associated with indices of low ventilatory capacity, whereas in males, EFL would be associated with indices of high ventilatory demand.MethodsData from n = 126 healthy adults (20–45 y, n = 60 males, n = 66 females) with a wide range of cardiorespiratory fitness (81%–182% predicted maximal oxygen uptake) were included in the study. Participants performed spirometry and an incremental cycle exercise test to exhaustion. Standard cardiorespiratory variables were assessed throughout exercise. The tidal flow–volume overlap method was used to assess EFL based on a minimum threshold of 5% overlap between the tidal and the maximum expiratory flow–volume curves. Predictors of EFL during exercise were determined via multiple logistical regression using anthropometric, pulmonary function, and peak exercise data.ResultsDuring exercise, EFL occurred in 49% of participants and was similar between the sexes (females = 45%, males = 53%; P = 0.48). In males, low forced expired flow between 25% and 75% of forced vital capacity and high slope ratio as well as low end-expiratory lung volume, high breathing frequency, and high relative tidal volume at peak exercise were associated with EFL (P < 0.001; Nagelkerke R2 = 0.73). In females, high slope ratio, high breathing frequency, and tidal volume at peak exercise were associated with EFL (P < 0.001; Nagelkerke R2 = 0.61).ConclusionsDespite sex differences in respiratory system morphology, the frequency and the predictors of EFL during exercise do not substantially differ between the sexes.

Fitness Level– and Sex-Related Differences in Pulmonary Limitations to Maximal Exercise in Normoxia and Hypoxia

“…In the present study, ventilatory drive was evaluated through HVR at rest and during low-intensity exercise. A high variability in individual ventilatory responses has been observed in the present (30) 77.8% 37.5% Chi 2 (1) = 8.510, P = 0.004 Normoxia EFL (28) 70.4% 37.5% Normoxia non-EFL (23) 29.6% 62.5% Chi 2 (1) = 5.545, P = 0.019 study (Table 3). Such variability is commonly reported (44).…”

Functional assessment of respiratory muscles and lung capacity of CrossFit athletes

“…In within-group comparisons of this study, the CrossFit athlete group showed a high positive correlation, and the sedentary group without comorbidities showed a moderate positive correlation when FVC and FEV1 were analyzed; that is, despite these variables not being affected by the strength of the respiratory muscles, if the FVC increased, FEV1 was likely to increase. This observation is important because FEV1 is generally considered an effort-dependent pulmonary parameter, and higher values depend on the abdominal muscles, which are mainly active during expiration (Molgat-Seon et al, 2022). Although not similar, studies on the effect of exercise on lung function have been performed who observed improvement in FVC and FEV1 in participants with overweight and obese after 24 weeks of exposure to aerobic exercise (Azad et al, 2011).…”

Sex differences in the ventilatory responses to exercise in mild to moderate obesity

“…EFL, when present, was associated with lower peak $${\dot{V}}_{\rm{E}}$$ in females. Lower mid‐expiratory flows and lower expiratory reserve volume as a fraction of FVC (indicators of ventilatory capacity) and higher V T (%FVC) and f B (indicators of ventilatory demand) can help predict whether EFL occurs during exercise (Molgat‐Seon et al., 2022). However, a larger sample would be needed to explore sex differences in how ventilatory capacity and demand interact to produce EFL among males and females with obesity.…”