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Evaluating the Accuracy of Using Fixed Ranges of METs to Categorize Exertional Intensity in a Heterogeneous Group of Healthy Individuals: Implications for Cardiorespiratory Fitness and Health Outcomes

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Abstract

Background

Appropriate quantification of exertional intensity remains elusive.

Objective

To compare, in a large and heterogeneous cohort of healthy females and males, the commonly used intensity classification system (i.e., light, moderate, vigorous, near-maximal) based on fixed ranges of metabolic equivalents (METs) to an individualized schema based on the exercise intensity domains (i.e., moderate, heavy, severe).

Methods

A heterogenous sample of 565 individuals (females 165; males 400; age range 18–83 years old) were included in the study. Individuals performed a ramp-incremental exercise test from which gas exchange threshold (GET), respiratory compensation point (RCP) and maximum oxygen uptake (VO2max) were determined to build the exercise intensity domain schema (moderate = METs ≤ GET; heavy = METs > GET but ≤ RCP; severe = METs > RCP) for each individual. Pearson’s chi-square tests over contingency tables were used to evaluate frequency distribution within intensity domains at each MET value. A multi-level regression model was performed to identify predictors of the amplitude of the exercise intensity domains.

Results

A critical discrepancy existed between the confines of the exercise intensity domains and the commonly used fixed MET classification system. Overall, the upper limit of the moderate-intensity domain ranged between 2 and 13 METs and of the heavy-intensity domain between 3 and 18 METs, whereas the severe-intensity domain included METs from 4 onward.

Conclusions

Findings show that the common practice of assigning fixed values of METs to relative categories of intensity risks misclassifications of the physiological stress imposed by exercise and physical activity. These misclassifications can lead to erroneous interpretations of the dose–response relationship of exercise and physical activity.

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Authors and Affiliations

  1. Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada

    Danilo Iannetta, Erin Calaine Inglis, Anmol T. Mattu & Juan M. Murias

  2. Toronto General Research Institute, University Health Network, Toronto, ON, Canada

    Daniel A. Keir

  3. School of Kinesiology, The University of Western Ontario, London, ON, Canada

    Daniel A. Keir & Donald H. Paterson

  4. Team Novo Nordisk Professional Cycling Team, Atlanta, GA, USA

    Federico Y. Fontana

  5. Department of Neurosciences, Biomedicine, and Movement Sciences, University of Verona, Verona, Italy

    Silvia Pogliaghi

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  1. Danilo Iannetta
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  2. Daniel A. Keir
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  3. Federico Y. Fontana
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  4. Erin Calaine Inglis
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  5. Anmol T. Mattu
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  7. Silvia Pogliaghi
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  8. Juan M. Murias
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Corresponding author

Correspondence to Juan M. Murias.

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Funding

Dr. Juan M. Murias was supported by NSERC Canada (RGPIN-2016-03698) and the Heart & Stroke Foundation of Canada (#1047725).

Conflict of interest

The authors declare no conflict of interest.

Ethical approval

All procedures performed were in accordance with the ethical standards outlined by the institutional research committees of the University of Calgary and University of Verona and in conformity with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Data availability

All data related to this study are presented within the manuscript.

Author contributions

DI, DAK, ECI, DHP, SP, and JMM conceived the study. DI, DAK, FYF, ECI, ATM and SP collected the data. DI, DAK, FYF, ECI, ATM, SP and JMM analyzed the data. All authors interpreted the data. DI wrote the first draft of the manuscript. All authors critically revised and contributed to the manuscript. All authors approved the final version of the manuscript.

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Iannetta, D., Keir, D.A., Fontana, F.Y. et al. Evaluating the Accuracy of Using Fixed Ranges of METs to Categorize Exertional Intensity in a Heterogeneous Group of Healthy Individuals: Implications for Cardiorespiratory Fitness and Health Outcomes. Sports Med 51, 2411–2421 (2021). https://doi.org/10.1007/s40279-021-01476-z

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