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Correspondence |

Muscle Function in Smokers Response: Clearing Up the Smoke FREE TO VIEW

Rob C. I. Wüst, MSc; Hans Degens, PhD; David A. Jones, PhD
Author and Funding Information

Affiliations: Institute for Biomedical and Clinical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UK,  School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UK,  Universidad Central de Venezuela, Caracas, Venezuela

Correspondence to: Rob C. I. Wüst, MSc, Institute for Biomedical and Clinical Research Into Human Movement and Health, Manchester Metropolitan University, Manchester, UK; e-mail: r.wust@mmu.ac.uk


Chest. 2008;134(1):219-220. doi:10.1378/chest.08-0564
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Published online

We read with interest the article by Montes de Oca and colleagues,1 reporting that COPD smokers (without COPD) had a 22% lower fiber cross-sectional area of type I muscle fibers and a higher proportion of fibers with a low oxidative and high glycolytic capacity than the nonsmoking control group. The size of the type I muscle fibers in the control group was remarkably large (6,174 ± 1,807 μm2) compared with other studies (eg, 4,044 ± 846 μm2 and 4,591 ± 1,058 μm2 for women and men, respectively, in a large study by Simoneau and Bouchard,4). Taking these values as controls, the smokers reported by Montes de Oca and colleagues1 would appear unremarkable.

In an editorial2discussing this study, Peter Wagner points out that selecting a control group matched for physical activity levels is crucial when studying skeletal muscle function. Although the authors stated that smokers and nonsmokers had a similar sedentary lifestyle, they did not attempt to quantify this. Recently, we have shown in young healthy smokers, without signs of respiratory problems, that maximal strength and anatomical cross-sectional area were similar to those of physical activity-matched nonsmokers.3

Another question that was raised was how muscle changes affect exercise. Possibly relevant to this is a study we have completed looking at how muscle fatigue is affected by smoking. We observed that the development of fatigue elicited by electrically stimulated contractions occurred more rapidly in smokers than nonsmoking and physical activity-, age-, and sex-matched control subjects. Unpublished observations indicated that this lower fatigability was not related to the number of cigarettes or the total number of years smoked, indicating that rather than a cumulative effect of chronic smoking this is an acute effect of smoking. Certain substances in the smoke, such as carbon monoxide and cyanide, may directly inhibit muscle function; and in support of this we observed that 6% carboxyhemoglobin affected the outcomes of the fatigue test in a similar way.5Further support for the reversible nature of the muscle changes is the fact that COPD patients (39% FEV1 percentage of predicted) who had stopped smoking did not exhibit a reduced fatigue resistance in comparison with age- and activity-matched control subjects using the same fatigue protocol.6

The authors have reported that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Montes de Oca, M, Loeb, E, Torres, SH, et al (2008) Peripheral muscle alterations in non-COPD smokers.Chest133,13-18
 
Wagner, PD Cigarette smoking and the skeletal muscles.Chest2008;133,3-4
 
Morse, CI, Wust, RC, Jones, DA, et al Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.Acta Physiol (Oxf)2007;191,123-129
 
Simoneau, JA, Bouchard, C Human variation in skeletal muscle fiber-type proportion and enzyme activities.Am J Physiol1989;257,E567-E572
 
Morse, CI, Pritchard, LJ, Wust, RC, et al Carbon monoxide inhalation reduces skeletal muscle fatigue resistance.Acta Physiol (Oxf)2008;192,397-401
 
Degens, H, Sanchez Horneros, JM, Heijdra, YF, et al Skeletal muscle contractility is preserved in COPD patients with normal fat-free mass.Acta Physiol Scand2005;184,235-242
 
To the Editor:

We appreciate the interest in our study on smoker’s skeletal muscle characteristics that was recently published in CHEST (January 2008).1 Our aim was to assess the morphologic and inflammatory aspects of skeletal muscle in smokers and not to evaluate muscle function.1In their letter, Wüst et al mention that the cross-sectional area (CSA) of the type I fibers in our control group was larger compared to that reported in another study.2 In our article,1the CSA was measured using photographs of periodic acid-Schiff-stained sections and not in adenosine triphosphatase histochemical reaction. This may explain the differences in fiber size found by Simoneau and Bouchard.2 The issue is that both control subjects and smoker subjects were examined with the same techniques. In the smoker subjects, a significantly reduced CSA was found in type I fibers as well as a tendency for reduced CSA in type IIA fibers.

Although physical capacity was not tested in our study, none of the smokers and nonsmokers were engaged in any sport or exercise activity, and age was similar in both groups. These characteristics did not make us overlook individual differences, but they probably did not affect the muscle characteristic in the whole group.

Regarding the results in healthy smokers reported by Morse et al,3 it is not possible to extrapolate the effects of short-term and low exposures to tobacco in young adults (mean [± SD] age, 22.2 ± 2.5 years; mean smoking history, 2.5 ± 3.1 pack-years) to those in older subjects with long-term exposure (mean age, 55 ± 8 years; mean smoking history, 30 ± 10 pack-years). The damage on skeletal muscle may be a long-term effect that could be manifested by a change in fiber size.

References
Montes de Oca, M, Loeb, E, Torres, SH, et al Peripheral muscle alterations in non-COPD smokers.Chest2008;133,13-18
 
Simoneau, JA, Bouchard, C Human variation in skeletal muscle fiber-type proportion and enzyme activities.Am J Physiol1989;257,E567-E572
 
Morse, CI, Würst, RC, Jones, DA, et al Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.Acta Physiol (Oxf)2007;191,123-129
 

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Tables

References

Montes de Oca, M, Loeb, E, Torres, SH, et al (2008) Peripheral muscle alterations in non-COPD smokers.Chest133,13-18
 
Wagner, PD Cigarette smoking and the skeletal muscles.Chest2008;133,3-4
 
Morse, CI, Wust, RC, Jones, DA, et al Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.Acta Physiol (Oxf)2007;191,123-129
 
Simoneau, JA, Bouchard, C Human variation in skeletal muscle fiber-type proportion and enzyme activities.Am J Physiol1989;257,E567-E572
 
Morse, CI, Pritchard, LJ, Wust, RC, et al Carbon monoxide inhalation reduces skeletal muscle fatigue resistance.Acta Physiol (Oxf)2008;192,397-401
 
Degens, H, Sanchez Horneros, JM, Heijdra, YF, et al Skeletal muscle contractility is preserved in COPD patients with normal fat-free mass.Acta Physiol Scand2005;184,235-242
 
Montes de Oca, M, Loeb, E, Torres, SH, et al Peripheral muscle alterations in non-COPD smokers.Chest2008;133,13-18
 
Simoneau, JA, Bouchard, C Human variation in skeletal muscle fiber-type proportion and enzyme activities.Am J Physiol1989;257,E567-E572
 
Morse, CI, Würst, RC, Jones, DA, et al Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.Acta Physiol (Oxf)2007;191,123-129
 
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