Problems of medical supervision and physiological validity encountered with fixed-rate step tests

Excerpt

Hansen et al. (2011) recently reported on their evaluation of a fixed-rate step test, hypothesizing that it would elicit low-to-moderate intensities (55–75% of \( \dot{V}{\text{O}}_{{ 2 { \max }}} \)). However, when they applied their test to a diverse population of ostensibly healthy adults (both men and women, ranging in age from 23 to 75 years), they noted that the work rate, as estimated relative to a cycle ergometer measurement of peak oxygen intake, averaged 85 ± 24% of these peak values; moreover, 41% of subjects reached levels that exceeded 95% of the peak oxygen intake. Note that I use the term “peak oxygen intake,” rather than the \( \dot{V}{\text{O}}_{{ 2 { \max }}} \) adopted by Hansen et al. (2011). The primary criterion for termination of their cycle ergometer test was subjective ((general/muscle fatigue, dyspnea), so it is likely that in many instances values were peak rather than maximal. Further, since some of the step tests of Hansen et al. (2011) had a duration as short as 45 s, alveolar oxygen concentrations will have been increasing during the measurement period, and the volume of oxygen taken into the lungs may substantially have exceeded that taken up by the circulation (Shephard 1955). …