Association of Step Count with Cardiorespiratory Fitness: Results from the Virtual 2-Minute Step Test.

Abstract

Objective: To test the hypothesis that step count based on a virtual 2-minute step test (2MST) predicts cardiorespiratory fitness (CRF).

Design: Cross-sectional study.

Setting: Veteran Affairs Medical Centers participating in a randomized trial of functional exercise training delivered by videoconferencing.

Participants: People with human immunodeficiency virus (HIV) (PWH) who were aged ≥50 years and clinically stable on antiretroviral therapy were eligible for the trial. Consecutive male participants who were enrolled prior to November 9, 2023 and completed a baseline 2MST and cardiopulmonary exercise test (CPET) were included in the cross-sectional study (N=74).

Intervention: None.

Main outcome measures: Step count was measured by a 2MST performed by live videoconferencing using the Rikli and Jones protocol. CRF was measured by peak oxygen utilization (VO₂peak) during a modified Bruce cardiopulmonary exercise testing.

Results: Most participants (62.2%) were ≥60 years of age. The mean (SD) VO₂peak was 23.6 (5.7) mL/kg/min, which represented 72.4% (SD, 14.1) of expected VO₂peak. Step count correlated with VO₂peak (r=0.47, P<.001). Multivariable linear regression showed that step count was significantly associated with VO₂peak independently of age and body mass index. Based on this model, the prediction of VO₂peak based on step count explained 60% of the variance in VO₂peak. A Bland-Altman plot showed good agreement between predicated and measured VO₂peak without heteroscedasticity.

Conclusions: The virtual 2MST predicted VO₂peak independently of age and body mass index in men with well-controlled HIV. In ambulatory populations with known impaired cardiorespiratory fitness, the virtual 2MST may be a feasible and valid estimate of VO₂peak that can be used in the telerehabilitation setting. Future work is required in more demographically diverse individuals with various chronic conditions.