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Respir Med. 2007 Jun;101(6):1236-43. Epub 2006 Dec 14.

Skeletal muscle structure and function in response to electrical stimulation in moderately impaired COPD patients.

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1
Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respiratory Diseases, Department of Medicine, Federal University of São Paulo, São Paulo, SP, Brazil.

Abstract

STUDY OBJECTIVE:

To determine the structural and functional consequences of high-frequency neuromuscular electrical stimulation (hf-NMES) in a group of moderately impaired outpatients with chronic obstructive pulmonary disease (COPD).

DESIGN:

A prospective, cross-over randomized trial.

SETTING:

An university-based, tertiary center.

PATIENTS AND MATERIALS:

Seventeen patients (FEV(1)=49.6+/-13.4% predicted, Medical Research Council dyspnoea grades II-III) underwent 6-weeks hf-NMES (50Hz) and sham stimulation of the quadriceps femoris in a randomized, cross-over design. Knee strength was measured by isokinetic dynamometry (peak torque) and leg muscle mass (LMM) by DEXA; in addition, median cross-sectional area (CSA) of type I and II fibres and capillary-fibre ratio were evaluated in the vastus lateralis. The 6-min walking distance (6MWD) was also determined.

RESULTS:

At baseline, patients presented with well-preserved functional capacity, muscle strength and mass: there was a significant relationship between strength and type II CSA (P<0.05). NMES was not associated with significant changes in peak torque, LMM or 6MWD as compared to sham (P>0.05). At micro-structural level, however, electrical stimulation increased type II, but decreased type I, CSA; no change, however, was found in the relative fibre distribution or capillary:fibre ratio (P<0.05). There was no significant association between individual changes in structure and function with training (P>0.05). Post-NMES increase in type II CSA was inversely related to baseline mass and strength (P<0.05).

CONCLUSION:

NMES may promote a modest degree of type II muscle fibre hypertrophy in COPD patients with well-preserved functional status. These micro-structural changes, however, were not translated into increased volitional strength in this sub-population.

PMID:
17174082
DOI:
10.1016/j.rmed.2006.10.023
[Indexed for MEDLINE]
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