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

We evaluated the impact of selection of reference values on the categorisation of measured maximal oxygen consumption (V'_Opeak) as "normal" or "abnormal" in an ageing population. We compared measured V'_Opeak 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'_Opeak was 1.88 L·min^-1 in men and 1.26 L·min^-1 in women. V'_Opeak 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'_Opeak 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.