Chest
Volume 96, Issue 6, December 1989, Pages 1312-1316
Journal home page for Chest

Clinical Investigations
Can Maximal Cardiopulmonary Capacity be Recognized by a Plateau in Oxygen Uptake?

https://doi.org/10.1378/chest.96.6.1312Get rights and content

The failure of oxygen uptake to increase with increasing work has been considered a marker of the limits of the cardiopulmonary system for many years. However, the concept has suffered from inconsistencies in definition, criteria, and data sampling, all of which affect the interpretation of the relation between changes in work and oxygen uptake. To evaluate the response and reproducibility of the slope in oxygen uptake at peak exercise, six subjects (mean age, 33±6 years) performed two individualized ramp treadmill tests on separate days. During exercise, oxygen uptake (for a given sample of 30 eight-breath running averages) was regressed with time and the slope was calculated. Maximal oxygen uptake, maximal heart rate and maximal perceived exertion were reproducible from day 1 to day 2 (mean difference, 0.4 ml/kg/min, 1.0 beats per minute, and 0.2 for maximal oxygen uptake, heart rate, and maximal perceived exertion, respectively [not significant]). Considerable variability in the slopes was observed during each test and from day to day. This occurred despite the use of large gas exchange samples, averaging techniques, and constant, consistent changes in external work. A plateau, defined as the slope of an oxygen uptake sample at peak exercise that did not differ significantly from a slope of zero, was not a consistent finding within subjects between days. We conclude that marked variability in the slope of the change in oxygen uptake occurs throughout progressive exercise, despite the use of large samples and a linear change in external work. These findings appear to preclude the determination of a plateau by common definitions.

Section snippets

Methods

Five healthy male subjects and one healthy female subject (mean [±SD] age, 33±6 years) participated in the study. None was taking any medication or had any remarkable medical history. All had at least average fitness; the mean (±SD) maximal oxygen uptake was 50.0±12 ml O2/kg/min.

Results

Differences between measurements made on day 1 and day 2 of heart rate, gas exchange, and perceptual responses are presented in Table 1. The slope of the change in oxygen uptake for subject 1 on day 1 and day 2 are illustrated in Figures 2 and 3, respectively.

The mean maximal oxygen uptake of the subjects was 50.0±11.7 ml/kg/min on day 1 and 49.6±11 ml/kg/min on day 2. This difference was not significant (NS). Accordingly, treadmill time was not different between day 1 (9.0±1.4 minutes) and day

Discussion

An important observation made from the present data was the variability in the slope of the change in oxygen uptake throughout progressive exercise, despite a constant, consistent change in external work and the use of large, averaged samples. A slope, in the present context, is defined as the change in oxygen uptake for a given sample associated with a unit change in external work. Thus, a slope not different from zero at peak exercise suggests that oxygen uptake was not increasing

Conclusion

Intuitively, the body's cardiorespiratory and metabolic systems must reach some finite limit beyond which oxygen uptake can no longer be increased. The factors that limit exercise capacity are not entirely clear, however, exercise capacity depends on disease, fitness, and the type and duration of exercise. The traditional interpretation of the plateau concept assumes oxygen delivery always limits exercise capacity. However, this may not be the case under all conditions.1 This may explain the

References (28)

  • JH Mitchell et al.

    The physiological meaning of the maximal oxygen intake test

    J Clin Invest

    (1958)
  • CG Cumming et al.

    Criteria for maximum oxygen uptake in men over 40 in a population survey

    Med Sci Sports

    (1972)
  • PO Astrand

    Experimental studies of physical work capacity in relation to sex and age

    (1952)
  • GR Cumming et al.

    Bicycle ergometer measurement of maximal oxygen uptake in children

    Can J Physiol Pharmacol

    (1967)
  • Cited by (69)

    • The effects of exercise modality on maximal and submaximal exercise parameters obtained by graded maximal exercise testing

      2016, International Journal of Cardiology
      Citation Excerpt :

      Derived parameters such as oxygen pulse (= VO2/HR), respiratory gas exchange ratio (RER = VCO2/VO2), ventilatory equivalent for O2 (EQO2 = VE/VO2), ventilatory equivalent for CO2 (EQCO2 = VE/VCO2) and ∆ VO2/∆Watt were calculated. Although VO2max is the most common used parameter to assess cardiorespiratory fitness the plateau concept has been questioned by different studies [42]. We calculated the OUES (= Oxygen uptake efficiency slope) according to Baba et al.

    • High prevalence of false-positive plateau phenomena during VO<inf>2max</inf> testing in adolescents

      2014, Journal of Science and Medicine in Sport
      Citation Excerpt :

      We also wished to identify whether criteria for accepting the “plateau phenomenon” could be fulfilled during sub-maximal exercise. By definition such plateaus must be “false”5 if the athlete is able to continue exercising to a higher VO2. Sixty-eight young male soccer players (age 14.3 ± 0.8 years, body mass 51.8 ± 9.5 kg, height 163 ± 9 cm) competing at the highest level for their age category in Hong Kong participated in the study.

    • Exercise performance and quality of life is more impaired in Eisenmenger syndrome than in complex cyanotic congenital heart disease with pulmonary stenosis

      2011, International Journal of Cardiology
      Citation Excerpt :

      However, as already mentioned as safety issue, CPET to maximum exhaustion to assess exercise capacity has important limitations. In our patient groups a plateau is rarely reached at peak exercise [18] due to muscular exhaustion of the legs or the feeling of discomfort in the severely cyanotic patient. [19] This discomfort cannot be differentiated whether it is a first neurological sign or simply a lack of motivation.

    View all citing articles on Scopus

    Manuscript received February 16; revision accepted June 12.

    View full text