The infinity test: a novel 3-minute all-out wheelchair field test for estimating VO₂peak in individuals with paraplegia.

Abstract

Methodological cross-sectional validation study with external validation. To develop and externally validate the Infinity Test, a 3-min all-out field protocol performed in the participant's own wheelchair with enforced synchronous propulsion, designed to estimate peak oxygen uptake (VO₂peak) in manual wheelchair users with chronic paraplegia. Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute École Bruxelles-Brabant (HE2B), Brussels, Belgium. Seventeen manual wheelchair users with chronic paraplegia completed both the Infinity Test and a laboratory arm-crank graded exercise test in counterbalanced order (development cohort). An independent cohort of 11 participants completed the Infinity Test only (external validation cohort). Breath-by-breath VO₂ was measured using a validated portable metabolimeter. Laps·min^-1 were derived from manual lap counting using standardized rounding rules and converted to predicted VO₂peak via a linear no-intercept model. Agreement with laboratory VO₂peakErgo was assessed using ICC, Bland-Altman analysis, Passing-Bablok regression, and ordinary least-products regression. Internal validity was evaluated using leave-one-out cross-validation; external validity via correlation and mean absolute error (MAE). Infinity Test VO₂peak∞ did not differ from laboratory VO₂peakErgo (mean bias + 25 mL·min^-1, 95% CI-360 to + 410; p = 0.89; ICC = 0.89, 95% CI 0.73-0.96). No fixed or proportional bias was detected. The no-intercept equation (VO₂peak∞ = 461 × laps·min^-1) explained 61% of variance in the development cohort (SEE = 517 mL·min^-1). External validation showed R² = 0.70 and MAE = 322 mL·min^-1 (14.8% of the mean). The protocol was well tolerated and completed in < 5 min including setup. The Infinity Test provides a feasible and ecologically valid field protocol for estimating VO₂peak in individuals with paraplegia. Its combination of predictive accuracy, operational simplicity, and use of personal wheelchairs, together with an open-source digital toolkit (interactive nomogram and automated clinical reporting), may support its integration into rehabilitation, high-performance, and community-based practice.