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Original Research: Pulmonary Physiology |

Ventilatory Responses at Peak Exercise in Endurance-Trained Obese AdultsVentilatory Responses in Endurance-trained Obese

Santiago Lorenzo, PhD; Tony G. Babb, PhD
Author and Funding Information

From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and The University of Texas Southwestern Medical Center, Dallas, TX.

Correspondence to: Tony G. Babb, PhD, Institute for Exercise and Environmental Medicine, 7232 Greenville Ave, Ste 435, Dallas, TX 75231; e-mail: TonyBabb@TexasHealth.org


This study was presented in abstract form at the American College of Sports Medicine Annual Meeting, San Francisco, CA, May 2012. (Lorenzo S, Bassett JT, Moran RB, Pineda J, and Babb TG.)

Funding/Support: This work was supported by the American Heart Association [11POST4920002], the National Institutes of Health [HL096782 to Dr Babb], the King Charitable Foundation Trust, an American Lung Association Career Investigator Award, an American Heart Association Grant in Aid, The Research and Education Institute at Texas Health Resources, the Cain Foundation, and Texas Health Presbyterian Hospital Dallas.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2013;144(4):1330-1339. doi:10.1378/chest.12-3022
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Background:  Alterations in respiratory mechanics predispose healthy obese individuals to low lung volume breathing, which places them at risk of developing expiratory flow limitation (EFL). The high ventilatory demand in endurance-trained obese adults further increases their risk of developing EFL and increases their work of breathing. The objective of this study was to investigate the prevalence and magnitude of EFL in fit obese (FO) adults via measurements of breathing mechanics and ventilatory dynamics during exercise.

Methods:  Ten (seven women and three men) FO (mean ± SD, 38 ± 5 years, 38% ± 5% body fat) and 10 (seven women and three men) control obese (CO) (38 ± 5 years, 39% ± 5% body fat) subjects underwent hydrostatic weighing, pulmonary function testing, cycle exercise testing, and the determination of the oxygen cost of breathing during eucapnic voluntary hyperpnea.

Results:  There were no differences in functional residual capacity (43% ± 6% vs 40% ± 9% total lung capacity [TLC]), residual volume (21% ± 4% vs 21% ± 4% TLC), or FVC (111% ± 13% vs 104% ± 15% predicted) between FO and CO subjects, respectively. FO subjects had higher FEV1 (111% ± 13% vs 99% ± 11% predicted), TLC (106% ± 14% vs 94% ± 7% predicted), peak expiratory flow (123% ± 14% vs 106% ± 13% predicted), and maximal voluntary ventilation (128% ± 15% vs 106% ± 13% predicted) than did CO subjects. Peak oxygen uptake (129% ± 16% vs 86% ± 15% predicted), minute ventilation (128 ± 35 L/min vs 92 ± 25 L/min), and work rate (229 ± 54 W vs 166 ± 55 W) were higher in FO subjects. Mean inspiratory (4.65 ± 1.09 L/s vs 3.06 ± 1.21 L/s) and expiratory (4.15 ± 0.95 L/s vs 2.98 ± 0.76L/s) flows were greater in FO subjects, which yielded a greater breathing frequency (51 ± 8 breaths/min vs 41 ± 10 breaths/min) at peak exercise in FO subjects. Mechanical ventilatory constraints in FO subjects were similar to those in CO subjects despite the greater ventilatory demand in FO subjects.

Conclusion:  FO individuals achieve high ventilations by increasing breathing frequency, matching the elevated metabolic demand associated with high fitness. They do this without developing meaningful ventilatory constraints. Therefore, endurance-trained obese individuals with higher lung function are not limited by breathing mechanics during peak exercise, which may allow healthy obese adults to participate in vigorous exercise training.

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