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Sigmund Alfred Anderssen, PhD; Elisabeth Edvardsen, MSc; Bjørge Herman Hansen, PhD; Ingar Morten Holme, PhD; Sindre Mikael Dyrstad, PhD
Author and Funding Information

From the Department of Sports Medicine (Drs Anderssen, Hansen, and Holme and Ms Edvardsen), The Norwegian School of Sport Sciences; the Department of Pulmonary Medicine (Ms Edvardsen), Oslo University Hospital; and the Department of Education and Sport Science (Dr Dyrstad), University of Stavanger.

Correspondence to: Sigmund Alfred Anderssen, PhD, Department of Sports Medicine, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Station, Oslo 0806, Norway; e-mail: s.a.anderssen@nih.no


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

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


Chest. 2014;146(1):e30-e31. doi:10.1378/chest.14-0712
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To the Editor:

To conduct studies on the cardiorespiratory response during maximal exercise testing in population-based samples is complicated. To compare the results with those obtained by others is even more challenging. In our article in CHEST1 we made an effort to do so, and in a single paragraph we compared our results with those from the HUNT Fitness study.2 Dr Nes and colleagues comment on our discussion points concerning why maximal oxygen uptake (V˙ o2max) was 9% lower in our study1 compared with the mean values from the HUNT Fitness study.2 They provide good arguments that we, in retrospect, should have considered when we discussed our results originally.1

There are indeed several reasons why differences across studies occur. Among them are differences in study population, test protocol, exclusion criteria prior to testing, criteria for terminating the test, and type of equipment used.

The participants included in our cardiopulmonary exercise testing study were recruited from a population-based sample in which several individuals reported asthma, cardiovascular disease, cancer, or type 2 diabetes. Hence, it may be argued that the health status of the original study population included in our study and that of those in the HUNT Fitness study were different. However, only a few individuals who reported underlying disease were included in the exercise test in the cardiopulmonary exercise testing study, suggesting that this is not the main explanation for the differences observed in V˙ o2max between the studies. Further, the difference in V˙ o2max between the studies was consistent across age strata, implying that the health aspect may be less important. Nevertheless, the differences between the study populations may still explain the differences observed in V˙ o2max between the HUNT Fitness study and ours, for instance, with respect to differences in exercise habits and physical activity. When discussing our observations, we mentioned “level of exhaustion” as one of the possible reasons for the different results between studies. Even though maximal heart rate (HRmax) is not a variable that predicts maximal effort well, it may provide a picture of the degree of fatigue in larger groups. Unfortunately, to our knowledge, the information about HRmax from the HUNT Fitness study3 was not publicly available when we submitted our manuscript. In retrospect, the higher observed HRmax values in the HUNT Fitness study may well partly explain the difference in V˙ o2max between the study populations.

However, it is equally reasonable to argue that the precision and accuracy of the measurement instrument may play a pivotal role when it comes to comparing results across studies, regardless of the outcome in question. However, with belated wisdom, we realize that we pinpointed too strongly the differences in the equipment as one possible explanation for differences between studies. It was our intention to provide a balanced and reasonable discussion with respect to the difference in results between the two studies.

References

Edvardsen E, Hansen BH, Holme IM, Dyrstad SM, Anderssen SA. Reference values for cardiorespiratory response and fitness on the treadmill in a 20- to 85-year-old population. Chest. 2013;144(1):241-248. [PubMed]
 
Aspenes ST, Nilsen TI, Skaug EA, et al. Peak oxygen uptake and cardiovascular risk factors in 4631 healthy women and men. Med Sci Sports Exerc. 2011;43(8):1465-1473. [PubMed]
 
Loe H, Rognmo O, Saltin B, Wisløff U. Aerobic capacity reference data in 3816 healthy men and women 20-90 years. PLoS ONE. 2013;8(5):e64319. [PubMed]
 

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References

Edvardsen E, Hansen BH, Holme IM, Dyrstad SM, Anderssen SA. Reference values for cardiorespiratory response and fitness on the treadmill in a 20- to 85-year-old population. Chest. 2013;144(1):241-248. [PubMed]
 
Aspenes ST, Nilsen TI, Skaug EA, et al. Peak oxygen uptake and cardiovascular risk factors in 4631 healthy women and men. Med Sci Sports Exerc. 2011;43(8):1465-1473. [PubMed]
 
Loe H, Rognmo O, Saltin B, Wisløff U. Aerobic capacity reference data in 3816 healthy men and women 20-90 years. PLoS ONE. 2013;8(5):e64319. [PubMed]
 
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