Validation of a Novel Incremental Step Test for Assessment of Cardiopulmonary Fitness and Ventilatory Thresholds in Adults

Overview

The purpose of this single-group diagnostic validation and test-retest reliability study is to determine whether a novel Incremental Step Test (IST) can accurately assess cardiorespiratory fitness and ventilatory thresholds in healthy adults compared with an established laboratory-based cycle ergometer Cardiopulmonary Exercise Test (CPET). The main questions are whether the step test can elicit reliable physiological responses sufficient to identify the anaerobic threshold and respiratory compensation point, and whether it produces reproducible results when repeated under standardised conditions. The study will compare the incremental step test (IST) with CPET to assess whether the IST provides similar peak and submaximal physiological measures and agreement with CPET comparator. Participants will complete three laboratory exercise tests across separate visits: one maximal CPET on a cycle ergometer, followed by two repeated ISTs performed on a 25 cm step board following the audio metronome.

Participants will attend three laboratory visits separated by at least 3 days and conducted at similar times of the day. The first visit will include screening, anthropometric assessment, and a maximal CPET on an electronically braked cycle ergometer using a ramp protocol of 25 W/min for males and 20 W/min for females. Participants will complete 3 minutes of unloaded cycling followed by incremental protocol while maintaining the cadence at least 60 rpm, and the test will be terminated if they can no longer can sustain this cadence. Following CPET, participants will complete a 6-minute familiarisation session to practise the stepping activity, including the up-up-down-down stepping technique and alternation of the leading leg every 2 minutes. The second and third visits will involve repeated IST trials performed on 25 cm step board, with cadence progressed from 20 beats per minute and increased by 4 beats per minute every 20 seconds until volitional exhaustion. The IST will be terminated if the participant is unable to maintain the prescribed stepping rhythm for more than 15 seconds. Continuous breath-by-breath gas exchange, ECG, and heart rate monitoring will be used during testing to characterise peak performance and ventilatory threshold responses. Agreement between the step test and CPET, as well as test-retest reproducibility of the IST, will be evaluated to determine whether the new protocol could support more individualised exercise prescription in stepping-based activities.