Simulated obesity-related restrictive ventilatory load impairs moderate exercise sustainability in nonobese men

This study aims in investigating the effects of simulating obesity-related restrictive ventilatory load (RVL) with external thoracic restriction (ETR) on sustaining moderate exercise and on associated cardio-respiratory responses, perceived breathlessness sensation and ventilatory muscle fatigue in nonobese men. Seven male adults with body fat <15% performed two identical exhaustive constant-load moderate cycle exercises with their resting total respiratory elastance either increased twofold by the ETR, with concomitant reduction in functional residual capacity in the RVL trial, or not manipulated in the control trial. In RVL condition, the ETR induced inspiratory muscle fatigue (as indicated by the reduction in post-exercise static maximum mouth pressure) and shortened the exercise time to exhaustion in all subjects (p < 0.05). At exhaustion, hyperventilation composed of rapid and shallow breathing pattern and decreased end-tidal CO₂ tension occurred, while arterial O ₂ saturation and whole-body O₂ consumption were maintained in the control group. Subjective rating of perceived breathlessness sensation (RPB) was increased in the RVL condition (p < 0.05). The increase in RPB was correlated to the reduction in exercise sustainability (r = -0.83). Such findings implied that the perceived sensation of breathlessness in obesity mediated by obesity-related RVL during moderate exercise might contribute to their inferior exercise tolerance.