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


METHODS
A prospective, cross-over randomized trial.


METHODS
An university-based, tertiary center.


METHODS
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).


CONCLUSIONS
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.
Dal Corso
Simone
S
Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respiratory Diseases, Department of Medicine, Federal University of São Paulo, São Paulo, SP, Brazil.
Nápolis
Lara
L
Malaguti
Carla
C
Gimenes
Ana Cristina
AC
Albuquerque
André
A
Nogueira
Cristiano Rabelo
CR
De Fuccio
Marcelo Bicalho
MB
Pereira
Roberto D B
RD
Bulle
Acari
A
McFarlane
Niall
N
Nery
Luiz E
LE
Neder
J Alberto
JA
D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001823:Body Composition; D004599:Electric Stimulation Therapy / Q000379:methods*; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics; D016896:Treatment Outcome