Oxygen delivery and the restoration of the muscle energetic balance following exercise: implications for delayed muscle recovery in patients with COPD

Am J Physiol Endocrinol Metab. 2017 Jul 1;313(1):E94-E104. doi: 10.1152/ajpendo.00462.2016. Epub 2017 Mar 14.

Abstract

Patients with chronic obstructive pulmonary disease (COPD) experience a delayed recovery from skeletal muscle fatigue following exhaustive exercise that likely contributes to their progressive loss of mobility. As this phenomenon is not well understood, this study sought to examine postexercise peripheral oxygen (O2) transport and muscle metabolism dynamics in patients with COPD, two important determinants of muscle recovery. Twenty-four subjects, 12 nonhypoxemic patients with COPD and 12 healthy subjects with a sedentary lifestyle, performed dynamic plantar flexion exercise at 40% of the maximal work rate (WRmax) with phosphorus magnetic resonance spectroscopy (31P-MRS), near-infrared spectroscopy (NIRS), and vascular Doppler ultrasound assessments. The mean response time of limb blood flow at the offset of exercise was significantly prolonged in patients with COPD (controls: 56 ± 27 s; COPD: 120 ± 87 s; P < 0.05). In contrast, the postexercise time constant for capillary blood flow was not significantly different between groups (controls: 49 ± 23 s; COPD: 51 ± 21 s; P > 0.05). The initial postexercise convective O2 delivery (controls: 0.15 ± 0.06 l/min; COPD: 0.15 ± 0.06 l/min) and the corresponding oxidative adenosine triphosphate (ATP) demand (controls: 14 ± 6 mM/min; COPD: 14 ± 6 mM/min) in the calf were not significantly different between controls and patients with COPD (P > 0.05). The phosphocreatine resynthesis time constant (controls: 46 ± 20 s; COPD: 49 ± 21 s), peak mitochondrial phosphorylation rate, and initial proton efflux were also not significantly different between groups (P > 0.05). Therefore, despite perturbed peripheral hemodynamics, intracellular O2 availability, proton efflux, and aerobic metabolism recovery in the skeletal muscle of nonhypoxemic patients with COPD are preserved following plantar flexion exercise and thus are unlikely to contribute to the delayed recovery from exercise in this population.

Keywords: 31P-MRS; COPD; O2 availability; PCr recovery kinetics; mitochondrial function; muscle fatigue.

Publication types

  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aged
  • Energy Metabolism
  • Exercise Therapy / methods
  • Exercise Tolerance*
  • Exercise*
  • Female
  • Humans
  • Male
  • Muscle Fatigue
  • Muscle Strength
  • Muscle, Skeletal / physiopathology*
  • Oxygen Consumption*
  • Pulmonary Disease, Chronic Obstructive / physiopathology*
  • Recovery of Function / physiology*