Maximal aerobic capacity in ageing subjects: actual measurements versus predicted values

Abstract

We evaluated the impact of selection of reference values on the categorisation of measured maximal oxygen consumption (V'_O2peak) as "normal" or "abnormal" in an ageing population. We compared measured V'_O2peak with predicted values and the lower limit of normal (LLN) calculated with five equations. 99 (58 males and 41 females) disease-free subjects aged ≥70 years completed an incremental maximal exercise test on a cycle ergometer. Mean V'_O2peak was 1.88 L·min^-1 in men and 1.26 L·min^-1 in women. V'_O2peak ranged from 89% to 108% of predicted in men, and from 88% to 164% of predicted in women, depending on the reference equation used. The proportion of subjects below the LLN ranged from 5% to 14% in men and 0-22% in women, depending on the reference equation. The LLN was lacking in one study, and was unsuitable for women in another. Most LLNs ranged between 53% and 73% of predicted. Therefore, choosing an 80% cut-off leads to overestimation of the proportion of "abnormal" subjects. To conclude, the proportion of subjects aged ≥70 years with a "low" V'_O2peak differs markedly according to the chosen reference equations. In clinical practice, it is still relevant to test a sample of healthy volunteers and select the reference equations that better characterise this sample.

FIGURE 1

Measured maximal oxygen consumption (V′_O2peak) in a) 58 men and b) 41 women, aged >70 years and free of chronic diseases. Predicted maximal oxygen consumption (V′_O2max) reference values and their changes with age were calculated using reference equations by Wasserman et al. [11], Jones et al. [8], Blackie et al. [12], Hakola et al. [13] and Koch et al. [17] for an illustrative individual (male: 80 kg and 172 cm; female: 67 kg and 160 cm; mean heights and weights in our study).