Chest
Volume 141, Issue 4, April 2012, Pages 1031-1039
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Original Research
Pulmonary Physiology
Quantification of Cardiorespiratory Fitness in Healthy Nonobese and Obese Men and Women

https://doi.org/10.1378/chest.11-1147Get rights and content

Background

The quantification and interpretation of cardiorespiratory fitness (CRF) in obesity is important for adequately assessing cardiovascular conditioning, underlying comorbidities, and properly evaluating disease risk. We retrospectively compared peak oxygen uptake (

o2peak) (ie, CRF) in absolute terms, and relative terms (% predicted) using three currently suggested prediction equations (Equations R, W, and G).

Methods

There were 19 nonobese and 66 obese participants. Subjects underwent hydrostatic weighing and incremental cycling to exhaustion. Subject characteristics were analyzed by independent t test, and % predicted

o2peak by a two-way analysis of variance (group and equation) with repeated measures on one factor (equation).

Results

o2peak (L/min) was not different between nonobese and obese adults (2.35 ± 0.80 [SD] vs 2.39 ± 0.68 L/min).
o2peak was higher (P < .02) relative to body mass and lean body mass in the nonobese (34 ± 8 mL/min/kg vs 22 ± 5 mL/min/kg, 42 ± 9 mL/min/lean body mass vs 37 ± 6 mL/min/lean body mass). Cardiorespiratory fitness assessed as % predicted was not different in the nonobese and obese (91% ± 17% predicted vs 95% ± 15% predicted) using Equation R, while using Equation W and G, CRF was lower (P < .05) but within normal limits in the obese (94 ± 15 vs 87 ± 11; 101% ± 17% predicted vs 90% ± 12% predicted, respectively), depending somewhat on sex.

Conclusions

Traditional methods of reporting

o2peak do not allow adequate assessment and quantification of CRF in obese adults. Predicted
o2peak does allow a normalized evaluation of CRF in the obese, although care must be taken in selecting the most appropriate prediction equation, especially in women. In general, otherwise healthy obese are not grossly deconditioned as is commonly believed, although CRF may be slightly higher in nonobese subjects depending on the uniqueness of the prediction equation.

Section snippets

Materials and Methods

This is a retrospective study using subjects who took part in projects related to exercise and obesity in our laboratory.15, 16, 17, 18, 19, 20, 21 In accordance with the Institutional Review Board (University of Texas Southwestern Medical Center, STU 122010-108), all details of the experiments were discussed with the volunteers, and informed consent was obtained before participation. All subjects were selected using the same guidelines, were nonsmokers, and had the same exclusion criteria:

Results

Fifty-one men (11 nonobese, 40 obese) and 34 women (8 nonobese, 26 obese) comprised the cohort of 85 adults (Table 1).

There were no differences in maximal power output (W) or absolute

o2peak (L/min) between the nonobese and obese (Table 2). However,
o2peak relative to body mass (mL/min/kg) and LBM (mL/min/LBM) were lower (P < .01) in the obese. The effect of body mass on all traditional displays of
o2peak are shown in Figure 1.
o2peak (L/min) (Fig 1A) increases while
o2peak (mL/min/kg) (Fig 1B)

Discussion

Our main findings are as follows: (1) Traditional methods of reporting

o2peak (ie, L/min, mL/min/kg, mL/min/LBM) do not allow adequate assessment and quantification of CRF among obese and nonobese; (2) the use of a % predicted
o2peak enables a graded assessment and quantification of CRF in obese, although care must be taken in selecting the most appropriate prediction equation, especially in women; (3) quantifying CRF in obesity is a complex and extremely important issue that requires careful

Acknowledgments

Author contributions: Dr Babb had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Dr Lorenzo: contributed to data collection, data processing and analysis, critical input, and the writing of the manuscript.

Dr Babb: contributed to planning the project, supervising and assisting in data collection, directing data processing and analysis, and the writing of the manuscript.

Financial/nonfinancial disclosures:

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    Funding/Support: This work was supported by the King Charitable Foundation Trust, American Lung Association, American Heart Association, The Research and Education Institute at Texas Health Resources, Cain Foundation, National Institutes of Health [HL096782], and Texas Health Presbyterian Hospital Dallas.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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