Validity and reliability of the Tianyu climbing machine in maximal oxygen uptake testing

accurate assessment of maximum oxygen uptake (VO₂max) is fundamental to exercise physiology and cardiorespiratory fitness evaluation. While treadmills are the gold standard, there is a growing need for standardized vertical loading devices. This study aimed to evaluate the concurrent validity, construct validity, and reliability of the novel Tianyu climbing machine during progressive load exercise testing.

Thirty-one male physical education students (mean age: 20.45 years) were recruited to perform maximal graded exercise tests on both a treadmill (using the Bruce protocol) and the Tianyu climbing machine (starting at 0.05 m/s with 0.01 m/s increments every minute). Physiological indicators, including VO₂max, heart rate (HR), and respiratory exchange ratio (RER), were monitored. Concurrent validity was assessed using Bland-Altman plots and mean relative percentage error (MRPE), while construct validity was examined through canonical correlation analysis (CCA). Test-retest reliability of the machine's speed was evaluated via intraclass correlation coefficients (ICC).The climbing machine demonstrated high concurrent validity with the treadmill, with a mean relative percentage error (MRPE) of less than 10%.CCA revealed a significant linear relationship between physiological markers and climbing performance indicators (r = 0.779, P < 0.01). Furthermore, the device exhibited excellent speed accuracy (error < 1%) and high test-retest reliability (ICC = 0.74 - 0.85) across standardized speed ranges.

The Tianyu climbing machine is a scientifically valid and reliable tool for assessing cardiorespiratory function. Its ability to provide precise, controllable vertical loads makes it an effective alternative to traditional modalities for standardized metabolic testing in athletic and clinical settings.