SPEED DEPENDENCE OF CRUTCH FORCE AND OXYGEN-UPTAKE - IMPLICATIONS FORDESIGN OF COMPARATIVE TRIALS ON ORTHOSES FOR PEOPLE WITH PARAPLEGIA

Objective: To determine speed dependence of crutch force and oxygen up take, and to discuss the implications of differences in self-selected walking speed between orthoses in a comparative trial. Design: Cross-s ectional comparison. Setting: Treadmill experiments and gait laborator y experiments were performed at five and three different imposed walki ng speeds, respectively. Patients: Five paraplegic subjects with lesio ns between T9 and T12 were included. All subjects had experience with ambulation using the advanced reciprocating gait orthosis (ARGO) as we ll as walking on a treadmill, Main Outcome Measures: Crutch force time integral (CFTI), crutch peak force on stance and swing side (CPFstanc e and CPFswing), oxygen uptake ((V) over dot o(2)), oxygen cost (Eo(2) ), Results: (V) over dot o(2), Eo(2), and CFTI were strongly dependent on walking speed. CPFstance and CPFswing were less dependent. However , depending on the clinically relevant difference that should be detec ted in a comparative trial, the peak forces can still be confounded by walking speed. Conclusion: CFTI, CPFswing, (V) over dot o(2), and Eo( 2) should be adjusted for walking speed if differences in walking spee d between orthoses are found, but this correction is relevant only if there is no effect modification. Such modification (different slopes b etween orthoses) cannot be excluded for the studied outcome measures. In addition, because determination of effect modification is difficult in small studies, standardization of walking speed, by means of a thr ee-point design, is recommended. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.