The assessment of walking capacity using the walking index for spinal cord injury: Self-selected versus maximal levels

Objectives: To assess (1) the frequency and magnitude of differences between self-selected and maximal walking capacity following spinal cord injury (SCI) by using the Walking Index for Spinal Cord Injury (WISCI) and (2) how these levels differ in efficiency and velocity. Design: Prospective cohort. Setting: Academic medical center. Participants: Fifty people with chronic incomplete SCI. Interventions: Not applicable. Main Outcome Measures: Subjects ambulated at the level used in the community (self-selected WISCI) and the highest level possible (maximal WISCI). Velocity (in m/s), Physiological Cost Index (PCI), and Total Heart Beat Index (THBI) were calculated. Differences were compared using the paired t test (parametric) or Wilcoxon signed-rank test (non parametric). Results: For 36 subjects, maximal WISCI was higher than self-selected WISCI; 21 subjects showed an increase of 3 levels or more. Ambulatory velocity was higher for self-selected WISCI compared with maximal WISCI (.68 m/s vs .56 m/s, P <.001). PCI and THBI at self-selected WISCI were lower than at maximal WISCI (PCI, 0.99 beats/m vs 1.48 beats/m, P <.001; THBI, 3.39 beats/m vs 4.75 beats/m, P <.001). Conclusions: Many people with chronic SCI are capable of ambulating at multiple levels. For these people, ambulation at self-selected WISCI was more efficient as evidenced by greater velocity and decreased PCI and THBI. The findings have implications for assessing walking capacity within the context of clinical trials.