Background: In obesity, the addition of mass loading of the chest wall by adipose tissue decreases compliance, but its ventilation does not seem to be a limiting factor to physical performance. Plasma K+ and lactic acid are considered important determinants of ventilation during exercise. Obesity is characterized by insulin resistance. Objectives: The aim of this study was to assess ventilatory adaptations to sustained effort and the effects of lactic acid and potassium in young obese subjects. Methods: Twelve obese subjects with a body mass index of 40 (mean age 27 years, 6 males) and 12 normal subjects with a body mass index of 22 (aged 28 years, 6 males) performed a progressive cycloergometric test with increases of 20 W every 4 min to exhaustion while minute ventilation, oxygen consumption, carbon dioxide production, end-tidal oxygen pressure, and end-tidal carbon dioxide pressure were measured. Blood samples were collected at the end of every step to determine plasma K +. Lactic acid was measured at rest, 40, 80, 120 W and peak exercise (or only at peak exercise if 2 increase but less appropriate for the increased O2 consumption. Both K+ and lactic acid increased less in the obese group. Conclusions: In our obese subjects, ventilation was not a limiting factor during exercise. Its lower increase may be due, in addition to the characteristics of their chest walls, to insulin resistance which may limit the increase in lactic acid during effort, and to the hypertrophy of muscle fibers previously noted, which may be linked to a lower increase in plasma K+ during physical exercise.
- Insulin resistance
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine