Skeletal muscle oxygen uptake in obese patients: functional evaluation by knee-extension exercise

Abstract

We hypothesized, in a group of obese women (OB), a more significant impairment of aerobic metabolism during knee extension (KE) exercise vs. that described during cycle ergometer exercise, lending support to the role of skeletal muscles in limiting exercise tolerance in OB. Eleven OB (age 29.5 ± 5.5 years, body mass index 43.2 ± 5.4 kg m(-2)) and 10 non-obese controls (CTRL) women were tested. Fat-free mass of a lower-limb (FFMLL) was assessed by a densitometer. Heart rate (HR) and pulmonary O2 uptake (VO2) were determined during incremental exercise tests to voluntary exhaustion carried out on a custom-built KE ergometer and on a cycle ergometer (CE). FFMLL and maximal isometric force of KE muscles were higher in OB vs. CTRL (+42.4 and +46.2 %, respectively). Peak work rate was significantly lower in OB (-18.4 %) vs. CTRL in CE, but not in KE. Expressed in mL min(-1), peak VO2 was not different in OB vs. CTRL in CE and in KE. After it was divided per unit of FFM involved in the exercises, peak VO2 was significantly lower in OB vs. CTRL, both for CE (-19 %) and KE (-33 %). Expressed per unit of exercising muscle mass, peak oxidative function is impaired in OB. The impairment is more pronounced after limitations related to cardiovascular O2 delivery are reduced. In OB muscle hypertrophy and the increased muscle force allow to preserve exercise tolerance during aerobic exercises carried out by relatively small muscle masses.

Aging, Obesity and Beyond

“…Findings indicate lower cardiorespiratory capacity and impaired task performance related to obesity. Results from these lifting tasks are consistent with the findings of previous studies that have investigated obesity-related differences in standard aerobic function tests, standardized cycling and treadmill walking tasks (Lafortuna et al, 2008;Lazzer et al, 2013;Salvadori et al, 1999), indicating that the relationship between obesity and impairment carries over to an occupationally-relevant task as well.…”

Ergogenic effects of beetroot juice supplementation during severe-intensity exercise in obese adolescents

“…Obesity, also in adolescence, is usually associated with reduced cardiorespiratory fitness and exercise intolerance (30,33). Whereas V O 2peak , expressed in absolute units (e.g., l/min), is usually normal compared with normal-weight controls, when it is normalized per unit of BM (ml·kg Ϫ1 ·min Ϫ1 ) values in obese patients are~40% lower than in controls (23,30). Other factors contributing to the impaired exercise tolerance in obesity include a higher O 2 cost for submaximal exercise (30,33,37), which is at least in part attributable to an increased O 2 cost of breathing (31,32), a lower GET, slower adjustment of the fundamental component of V O 2 kinetics (30), and a more pronounced amplitude of the slow component of V O 2 kinetics during heavy-intensity exercise (30).…”

“…The reduced exercise tolerance is associated with a higher O 2 cost for submaximal exercise (30,33,37), a lower gas exchange threshold, slower adjustment of the fundamental component of oxygen consumption (V O 2 ) kinetics (30), and a more pronounced amplitude of the slow component of V O 2 kinetics during heavy intensity exercise (30). These impairments are attributable to cardiovascular (33), respiratory (31,32), and skeletal muscle factors (23,30). In a vicious circle, the impaired exercise tolerance and the associated reduced level of physical activity worsen obesity and interfere with interventions (such as exercise prescription) aimed at its control.…”

Cardiopulmonary Exercise Testing in Children and Adolescents with High Body Mass Index

“…Moreover, Sunagawa and coworkers (39) suggested in 1984 that an abnormal VO 2 -HR slope could indicate cardiac impairment during exercise in children. Data from both human and animal models indicate that this impairment results from interrelated mechanisms of chronic inflammation, neuroadrenergic dysregulation, altered fiber-type distribution in skeletal muscle, and endothelial damage (17,20,26). Brun and coworkers (7) demonstrated interactions between abdominal obesity, circulating lipids, and increased blood viscosity.…”