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

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 (VOpeak) during a modified Bruce cardiopulmonary exercise testing.

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

Conclusions: The virtual 2MST predicted VOpeak 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 VOpeak that can be used in the telerehabilitation setting. Future work is required in more demographically diverse individuals with various chronic conditions.