Vascular Dynamics and Peripheral Oxygen Uptake in Obese Individuals during Progressive Physical Exercise

Abstract

Background: Obese men show higher O₂ consumption than lean men during physical exercise, with a trend toward higher peripheral O₂ extraction; this is probably due to their larger muscle mass. Objectives: The aim of this study was to examine this phenomenon by measuring 2 vasoactive substances, endothelin-1 (ET-1) and nitric oxide (NO), during a progressive submaximal exercise. Methods: Seventeen obese (body mass index [BMI] 38.6) and 15 lean (BMI 22.5) men performed a maximal progressive cycle ergometer exercise to determine peak power output (PPO) and peak O₂ consumption (V∙O₂_peak); thereafter, they performed a submaximal cycle ergometer incremental test (every 6 min) at the same percentage of V∙O₂_peak until they reached 57.5% PPO. Blood samples were collected at rest and at the end of every step to measure ET-1 and NO concentrations. Results: At rest, the ET-1 and NO concentrations in obese men and lean controls were the same. However, during exercise, the ET-1 concentration at each step was significantly lower (p < 0.05) in the obese group. There was no significant difference in NO concentration between the 2 groups, although the increase at the beginning of the exercise session was faster in obese individuals. During submaximal exercise, end-tidal O₂ pressure (PETO₂) was lower in the obese group, with a significant difference in the PETO₂/fat-free mass ratio at each step. Conclusions: ET-1 and NO levels during physical exercise are different in obese versus lean men. This may support the notion that increased O₂ consumption in obesity is due to different behaviors of the cardiorespiratory and circulatory systems.

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“…The underlying mechanism involves a higher peripheral oxygen uptake in individuals with obesity than in controls. This is partly due to a different pattern in circulating endothelin-1/NO concentrations, with a decrease in the former and a higher level of the latter in subjects with obesity [13]. Exercising above AT increases the capacity of both lean subjects and individuals with obesity, to remove lactic acid from the circulation.…”

“…This means that endurance time at maximal effort is shorter, and therefore, that work capacity is lower [12]. Older subjects with obesity show a significant reduction in maximal sustainable work capacity and reach earlier AT, reflecting a more severe reduction in physical performance as compared to controls [13].…”

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“…In this issue of Respiration , Brunani and colleagues present additional data on comparative exercise physiology in obese and lean individuals [5]. Maximal cycle-ergometer exercise was performed by 17 obese and 15 lean male subjects, matched by age and height.…”