Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Technical Report
  • Published:

The current standard measure of cardiorespiratory fitness introduces confounding by body mass: the DR's EXTRA study

International Journal of Obesity volume 36, pages 1135–1140 (2012)Cite this article

Subjects

Abstract

OBJECTIVE:

Cardiorespiratory fitness is currently estimated by dividing maximal oxygen consumption (VO2max) by body weight (per-weight standard). However, the statistically correct way to neutralize the effect of weight on VO2max in a given population is adjustment for body weight by regression techniques (adjusted standard). Our objective is to quantify the bias introduced by the per-weight standard in a population distributed across different categories of body mass.

DESIGN:

This is a cross-sectional study.

SUBJECTS AND METHODS:

Baseline measures from participants of the Dose-Responses to Exercise Training Study (DR's EXTRA), 635 men (body mass index (BMI): 19–47 kg m−2) and 638 women (BMI: 16–49 kg m−2) aged 57–78 years who performed oral glucose tolerance tests and maximal exercise stress tests with direct measurement of VO2max. We compare the increase in VO2max implied by the per-weight standard with the real increase of VO2max per kg body weight. A linear logistic regression model estimates odds for abnormal glucose metabolism (either impaired fasting glycemia or impaired glucose tolerance or Type 2 diabetes) of the least-fit versus most-fit quartile according to both per-weight standard and adjusted standard.

RESULTS:

The per-weight standard implies an increase of VO2max with 20.9 ml min−1 in women and 26.4 ml min−1 in men per additional kg body weight. The true increase per kg is only 7.0 ml min−1 (95% confidence interval: 5.3–8.8) and 8.0 ml min−1 (95% confidence interval: 5.3–10.7), respectively. Risk for abnormal glucose metabolism in the least-fit quartile of the population is overestimated by 52% if the per-weight standard is used.

CONCLUSIONS:

In comparisons across different categories of body mass, the per-weight standard systematically underestimates cardiorespiratory fitness in obese subjects. Use of the per-weight standard markedly inflates associations between poor fitness and co-morbidities of obesity.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1
Figure 2

Similar content being viewed by others

References

  1. Åstrand P-O, Rodahl K . Applied Sports Physiology. Textbook of Work Physiology 1986; 3: 646–679.

    Google Scholar 

  2. Mark DB, Lauer MS . Exercise capacity: the prognostic variable that doesn’t get enough respect. Circulation 2003; 108: 1534–1536.

    Article  Google Scholar 

  3. Franklin BA, McCullough PA . Cardiorespiratory fitness: an independent and additive marker of risk stratification and health outcomes. Mayo Clin Proc 2009; 84: 776–779.

    Article  Google Scholar 

  4. Heil DP . Body mass scaling of peak oxygen uptake in 20- to 79-yr-old adults. Med Sci Sports Exerc 1997; 29: 1602–1608.

    Article  CAS  Google Scholar 

  5. Balady GJ, Arena R, Sietsema K, Myers J, Coke L, Fletcher GF et al. Clinician's guide to cardiopulmonary exercise testing in adults: a scientific statement from the American Heart Association. Circulation 2010; 122: 191–225.

    Article  Google Scholar 

  6. Tanner JM . Fallacy of per-weight and per-surface area standards, and their relation to spurious correlation. J Appl Physiol 1949; 2: 1–15.

    Article  CAS  Google Scholar 

  7. Katch VL . Use of the oxygen-body weight ratio in correlational analyses: spurious correlations and statistical considerations. Med Sci Sports 1973; 5: 253–257.

    CAS  PubMed  Google Scholar 

  8. Nevill AM, Bate S, Holder RL . Modeling physiological and anthropometric variables known to vary with body size and other confounding variables. Am J Phys Anthropol 2005; 128 (Suppl 41): 141–153.

    Article  Google Scholar 

  9. Jensen K, Johansen L, Secher NH . Influence of body mass on maximal oxygen uptake: effect of sample size. Eur J Appl Physiol 2001; 84: 201–205.

    Article  CAS  Google Scholar 

  10. Buresh R, Berg K . Scaling oxygen uptake to body size and several practical applications. J Strength Cond Res 2002; 16: 461–465.

    PubMed  Google Scholar 

  11. Komulainen P, Kivipelto M, Lakka TA, Savonen K, Hassinen M, Kiviniemi V et al. Exercise, fitness and cognition—A randomised controlled trial in older individuals: The DR's EXTRA study. Eur Geriatr Med 2010; 1: 266–272.

    Article  Google Scholar 

  12. Brotman DJ . Mediators of the association between mortality risk and socioeconomic status. JAMA 2006; 296: 763–764.

    Article  CAS  Google Scholar 

  13. Wei M, Gibbons LW, Mitchell TL, Kampert JB, Lee CD, Blair SN . The association between cardiorespiratory fitness and impaired fasting glucose and type 2 diabetes mellitus in men. Ann Intern Med 1999; 130: 89–96.

    Article  CAS  Google Scholar 

  14. Sawada SS, Lee IM, Naito H, Noguchi J, Tsukamoto K, Muto T et al. Long-term trends in cardiorespiratory fitness and the incidence of type 2 diabetes. Diabetes Care 2010; 33: 1353–1357.

    Article  Google Scholar 

  15. Laaksonen DE, Lakka HM, Salonen JT, Niskanen LK, Rauramaa R, Lakka TA . Low levels of leisure-time physical activity and cardiorespiratory fitness predict development of the metabolic syndrome. Diabetes Care 2002; 25: 1612–1618.

    Article  Google Scholar 

  16. Hassinen M, Lakka TA, Savonen K, Litmanen H, Kiviaho L, Laaksonen DE et al. Cardiorespiratory fitness as a feature of metabolic syndrome in older men and women: the Dose-Responses to Exercise Training study (DR's EXTRA). Diabetes Care 2008; 31: 1242–1247.

    Article  CAS  Google Scholar 

  17. Wei M, Schwertner HA, Blair SN . The association between physical activity, physical fitness, and type 2 diabetes mellitus. Compr Ther 2000; 26: 176–182.

    Article  CAS  Google Scholar 

  18. Ekelund U, Brage S, Franks PW, Hennings S, Emms S, Wareham NJ . Physical activity energy expenditure predicts progression toward the metabolic syndrome independently of aerobic fitness in middle-aged healthy Caucasians: the Medical Research Council Ely Study. Diabetes Care 2005; 28: 1195–1200.

    Article  Google Scholar 

  19. Ekelund U, Franks PW, Sharp S, Brage S, Wareham NJ . Increase in physical activity energy expenditure is associated with reduced metabolic risk independent of change in fatness and fitness. Diabetes Care 2007; 30: 2101–2106.

    Article  CAS  Google Scholar 

  20. Ekelund U, Franks PW, Wareham NJ, Aman J . Oxygen uptakes adjusted for body composition in normal-weight and obese adolescents. Obes Res 2004; 12: 513–520.

    Article  Google Scholar 

  21. Goran M, Fields DA, Hunter GR, Herd SL, Weinsier RL . Total body fat does not influence maximal aerobic capacity. Int J Obes Relat Metab Disord 2000; 24: 841–848.

    Article  CAS  Google Scholar 

  22. Osman AF, Mehra MR, Lavie CJ, Nunez E, Milani RV . The incremental prognostic importance of body fat adjusted peak oxygen consumption in chronic heart failure. J Am Coll Cardiol 2000; 36: 2126–2131.

    Article  CAS  Google Scholar 

  23. Ross RM . ATS/ACCP statement on cardiopulmonary exercise testing. Am J Respir Crit Care Med 2003; 167: 211–277.

    Article  Google Scholar 

  24. Palange P, Ward SA, Carlsen KH, Casaburi R, Gallagher CG, Gosselink R et al. Recommendations on the use of exercise testing in clinical practice. Eur Respir J 2007; 29: 185–209.

    Article  CAS  Google Scholar 

Download references

Acknowledgements

The DR's EXTRA study was supported by grants from the Ministry of Education of Finland (116/722/2004, 134/627/2005, 44/627/2006, 113/627/2007, 41/627/2008), the Academy of Finland (104943, 211119, 123885), the European Commission FP6 Integrated Project (EXEGENESIS): LSHM-CT-2004-005272, the City of Kuopio, the Finnish Diabetes Association, the Finnish Heart Association, Kuopio University Hospital, Päivikki and Sakari Sohlberg Foundation and the Social Insurance Institution of Finland. KS was supported by a grant from the Finnish Medical Foundation; BK was supported by grants from Bruno Krachler and the Swedish Council for Working Life and Social Research. The funding sources had no role in the collection, analysis and interpretation of the data or in the decision to submit the manuscript for publication.

KS and BK contributed equally to data analysis and drafting of the manuscript. MH and PK collected and assembled data, participated in revision of manuscript. VK participated in data analysis. TL and RR are principal investigators of the DR's EXTRA study and participated in revision of manuscript.

Author information

Authors and Affiliations

  1. Kuopio Research Institute of Exercise Medicine, Kuopio, Finland

    K Savonen, B Krachler, M Hassinen, P Komulainen, T A Lakka & R Rauramaa

  2. Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland

    K Savonen & R Rauramaa

  3. Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, Sweden

    B Krachler

  4. Information Technology Centre, University of Eastern Finland, Kuopio, Finland

    V Kiviniemi

  5. Institute of Biomedicine/Physiology, University of Eastern Finland, Kuopio, Finland

    T A Lakka

Authors
  1. K Savonen
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. B Krachler
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. M Hassinen
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. P Komulainen
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. V Kiviniemi
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. T A Lakka
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. R Rauramaa
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to R Rauramaa.

Ethics declarations

Competing interests

The authors declare no conflict of interest.

Additional information

Supplementary Information accompanies the paper on International Journal of Obesity website

Supplementary information

Rights and permissions

Reprints and permissions

About this article

Cite this article

Savonen, K., Krachler, B., Hassinen, M. et al. The current standard measure of cardiorespiratory fitness introduces confounding by body mass: the DR's EXTRA study. Int J Obes 36, 1135–1140 (2012). https://doi.org/10.1038/ijo.2011.212

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/ijo.2011.212

Keywords

This article is cited by

Search

Advanced search

Quick links