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

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.

Inclusion criteria

• Healthy adults aged 18 to 55 years.
• Body mass index between 18.5 and 29.9 kg/m².
• Non-smoker.
• No known cardiovascular, respiratory, metabolic, neurological, or musculoskeletal conditions that would contraindicate maximal exercise testing.
• Able to provide written informed consent.
• Willing and able to complete one Cardiopulmonary Exercise Test and two Incremental Step Test sessions.

Exclusion criteria

• Age younger than 18 years or older than 55 years.
• Body mass index below 18.5 kg/m² or above 29.9 kg/m².
• Current smoker or use of nicotine products.
• Known cardiovascular, respiratory, metabolic, neurological, or musculoskeletal conditions that may affect exercise performance or make maximal exercise testing unsafe.
• Any contraindication to maximal exercise testing according to established exercise testing guidelines.
• Use of medications known to significantly affect cardiovascular, respiratory, or metabolic responses to exercise.
• Current injury, illness, or infection that may limit participation in exercise testing.
• Pregnancy.
• Inability to provide informed consent.
• Inability to complete study procedures or attend all required study visits.

-