A multi-stage step test protocol for people with low exercise capacity

The objectives of this study were to: (a) develop a simple, safe, multi-stage step test protocol that accounts for differences in stature and is suitable for ambulatory people with low tolerance to exercise, and (b) test the validity of a standard equation for predicting VO₂using the developed protocol. The cohort consisted of 51 people (18 female, 33 male; mean ± SD age = 35 ± 11 years; 73.5 ± 14.2 kg; 171.7 ± 9.1 cm). Twenty-three of the group were currently undertaking exercise rehabilitation programs, while the remainder were free of disability or illness. Six healthy participants undertook the step protocol twice, one week apart, for the purpose of intra-subject test-retest comparisons. The six-minute step test on a step (height (cm) = 0.125 X the subject's height (cm)) began at a low cadence (14 cycles per minute, c.min^-1) and increased by 4 c.min^-1 to a peak cadence of 34 c.min^-1. At six minutes, V0₂ measured by expired gas analysis and heart rate were 27.6 ± 3.5 ml.kg^-1.min^-1 and 153 ± 19 b.min^-1, respectively. V02_-2 calculated from the predictive equation for step exercise (V0₂ = cadence (0.35 + step height (cm) × 2.394)) correlated with measured V0₂ (r = .90), but overestimated V0₂ by 8% (mean ± SD of the difference = 1.2 ± 2.6 ml.mm^-1.kg^-1; p < 0.001: coefficient of variation = 9.2%). The intra-individual test-retest reliability was high (r = .97; p < 0.001; mean ± SD of the test-retest difference = 1.7 ± 1.7 ml.min^-1.kg^-1; p < 0.001; coefficient of variation = 5.7%). The graded step test protocol is suitable and valid for functional capacity testing in people with low tolerance to exercise, particularly those undergoing exercise rehabilitation, but the standard predictive equation overestimates V0₂ by 8%.