The physiologic fallacy of adjusting for body weight in performance of the Master two-step test

Abstract

The physiologic load imposed by the double Master two-step test and by a similar step test in which work was carried out at a rate of 40 steps per 3 minutes was evaluated in 14 male subjects having a wide range of body weights. Gross oxygen consumption varied less among individuals during the Master procedure (the S.D. was 25.6 per cent of the mean) than during the 40-step test, in which all subjects worked at the same rate (the S.D. was 41.7 per cent of the mean). However, expression of energy requirements per unit of body weight decreased the coefficient of variation for the energy cost of the 40-step test (9.4 per cent) well below that of the Master test (26.7 per cent). Oxygen requirements per kilogram of body weight were very high for lighter subjects, reaching 38.6 ml. per minute, and very much less for heavy subjects (minimum, 19.1 ml. per minute). The lightest subjects were, therefore, approaching their maximal oxygen intakes while the heavier men were farthest from maximal. These data illustrate the error in decreasing the rate of work for heavier subjects performing the step test, and demonstrate that the Master procedure fails to provide a physiologically equivalent work load for individuals differing in body weight.