Cardiopulmonary exercise testing during body weight supported treadmill exercise in incomplete spinal cord injury: A feasibility study

Abstract

Body weight supported (BWS) treadmill exercise could potentially improve the cardiopulmonary fitness of those with an incomplete spinal cord injury (SCI). Despite this, methods for estimating key cardiopulmonary performance parameters have not been investigated. We investigated whether new exercise test protocols for BWS treadmill exercise in incomplete SCI enable accurate determination of key cardiopulmonary performance parameters and examined how these parameters change with training. Two subjects with incomplete SCI carried out 20 weeks of BWS treadmill training (BWSTT). They performed an incremental exercise test (IET) and constant load step exercise test (SET) at baseline and 4-week intervals. After training, peak work rate had increased from 1.41 to 9.37 W in subject A and from 6.22 to 43.99 W in subject B. Peak oxygen uptake changed in subject A from 8.23 to 10.19 ml.kg^-1.min^-1 and from 13.84 to 13.91 ml.kg^-1.min^-1 in subject B. Dynamic O₂ cost decreased from 115 to 29.03 ml.min^-1.W^-1 (subject A) and from 66.57 to 4.52 ml.min^-1.W^-1 (subject B). Gas exchange thresholds could not be identified from the IETs. V̇O₂ kinetics could be identified during only 2 of subject B's SETs. Accurate estimation of key cardiopulmonary performance parameters was limited. The new protocols have the potential to characterise cardiopulmonary status and monitor adaptations to training interventions, but require testing with a larger subject cohort.