Chest
Volume 101, Issue 3, March 1992, Pages 674-679
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Work Capacity and Cardiopulmonary Adaptation of the Obese Subject during Exercise Testing

https://doi.org/10.1378/chest.101.3.674Get rights and content

Twelve obese patients (six male subjects) aged 17 to 42 years with a mean body mass index (BMI) of 40 kg/m2 and 12 normal subjects (six male subjects) aged 19 to 39 years with a mean BMI of 22 kg/m2 underwent a cycloergometric test until exhaustion to assess work capacity and cardiopulmonary adaptations of the two groups. Minute ventilation, expiratory gas concentrations, and heart rate, together with anaerobic threshold (AT) were determined in each subject during the test. The same subjects were then submitted to normocapnic hyperpnea at rest to assess the oxygen cost of breathing. We found that in the obese patients, the maximal sustainable work rate was not different from that of controls (120 vs 136 W) while AT was significantly lower (78 vs 110 W). Nevertheless, there was no difference in maximum V˙o2 and in V˙o2 at AT levels (expressed in milliliters per minute) indicating that cardiac, pulmonary, vascular, and muscle performance did not differ from obese to normal subjects. Greater muscular effort was needed by obese patients when moving their heavier legs and less when doing external work with a decreased gross mechanical efficiency and an identical net mechanical efficiency between the two groups.

Section snippets

Subjects

We studied 12 obese patients and 12 normal subjects matched for age and sex, all employed as administrative or teaching staff, both groups being untrained and without cardiorespiratory disorders.

In the obese group there were six male and six female subjects whose mean age (±SE) was 25.9 ± 2.3 years (range, 17 to 42 years). The control group consisted of six male and six female subjects whose mean age was 27.7 ± 1.8 years (range, 19 to 39 years).

The body mass index (BMI, kg/m2) was taken as a

RESULTS

As shown in Table 1, the ERV and the FRC were significantly decreased in the obese patients. There was no significant difference in all the other lung function variables measured. The oxyhemoglobinic saturation was within normal limits in the obese and normal subjects both during rest and muscular exercise.

The peak work rate achieved did not differ significantly from normal to obese subjects (136 ± 11.6 W in controls, 120 ±9 W in the obese patients). The anaerobic threshold, expressed as work

DISCUSSION

Our results do not show a significant difference in the maximal sustainable work capacity between normal subjects and markedly obese patients (BMI: 39.9 ±1.1 kg/m2). The anaerobic threshold, however, was reached at a significantly lower work rate in the obese patients (p<0.05). According to Wasserman,21 this implies that the endurance time at maximal effort is less in obese patients than in normal subjects as a result of the increase in arterial lactate with subse-quent metabolic acidosis.

ACKNOWLEDGMENTS

The authors would like to thank Prof. J. Milic-Emili and Prof. D. Olivieri for their critical review of the manuscript.

REFERENCES (33)

  • WassermanK et al.

    Detecting the threshold of anaerobic metabolism in cardiac patients during exercise

    Am J Cardiol

    (1964)
  • CasaburiR et al.

    Effect of altering heart rate on oxygen uptake at exercise onset

    Chest

    (1989)
  • RayCS et al.

    Effect of obesity on respiratory function

    Am Rev Respir Dis

    (1983)
  • NaimarkA et al.

    Compliance of the respiratory system and its components in health and obesity

    J Appl Physiol

    (1960)
  • CherniackRM.

    The oxygen consumption and efficiency of the respiratory muscles in health and emphysema

    J Clin Invest

    (1959)
  • WhippBJ et al.

    The ventilatory stress of exercise in obesity

    Am Rev Respir Dis

    (1984)
  • MarkusJH et al.

    The threshold of anaerobic metabolism in chronic obstructive pulmonary disease: a promising index of evaluation

    Am Rev Respir Dis

    (1971)
  • MatsumuraN et al.

    Determination of anaerobic threshold for assessment of functional state in patients with chronic heart failure

    Circulation

    (1983)
  • WeberKT et al.

    Exercise testing in the evaluation of the patient with chronic cardiac failure

    Am Rev Respir Dis

    (1984)
  • DavisJA et al.

    Anaerobic threshold alterations caused by endurance training in middle-aged men

    J Appl Physiol

    (1979)
  • KindermanW et al.

    The significance of the aerobic-anaerobic threshold transition for the determination of work load intensities during endurance training

    Eur J Appl Physiol Occup Physiol

    (1979)
  • KumagaiS et al.

    Relationship of the anaerobic threshold with the 5 Km, 10 Km and 10 mile races

    Eur J Appl Physiol Occup Physiol

    (1982)
  • ReinhardU et al.

    Determination of anaerobic threshold by ventilation equivalent in normal individuals

    Respiration

    (1979)
  • SmithDA et al.

    The time course during 36 weeks' endurance training of changes in V˙o2 max and anaerobic threshold as determined with a new computerized method

    Cli Sci Lond

    (1984)
  • YoshidaT et al.

    Anaerobic threshold of middle and old aged men

  • EdwardsKDG et al.

    The simple measurement of obesity

    Cli Sci

    (1962)
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