Lower extremity Fitts' task performance by patients with degenerative lumbar spinal stenosis: The application of induced strain

Fitts’ tasks are resistant to learning and have alterable task difficulty. The aforementioned combination makes Fitts’ tasks optimal for performance-based clinical outcome measure development. Degenerative lumbar spinal stenosis (LSS) patients report ambulation-induced strain. Our objective was to determine if a progressive exercise treadmill test (PETT) induces strain that impacts performance differentially than LSS presence. We compared LSS patients (N=16) and healthy individuals (N=16) on a lower-limb Fitts’ task before and after a 12-minute PETT.  Participants performed great toe pointing movements to squares projected on a platform with 4 possible indices of difficulty (ID). An Optotrak 3D Investigator (300Hz) recorded movement. Reaction time (RT), movement time (MT), peak velocity (PV) and peak acceleration (PA) were analyzed using 2 Group (Healthy, LSS) by 2 Strain (pre PETT, post PETT) by 4 ID?(3, 4a, 4b, 5) mixed ANOVA models with planned comparisons on variables related to strain. Replicating our previous work, a Group x ID interaction for MT provided evidence that LSS participants were impacted more adversely by increased task difficulty. A Group x ID interaction for PV revealed LSS patients did not scale movement execution to the same degree as healthy controls. Planned comparisons indicated that induced strain facilitates reaction to Fitts’ task stimuli, for both groups, but that effect disappears for the LSS group at the most challenging ID. Findings are discussed related to Fitts’ Law interpretation, and clinical implications for performance-based outcome measure development and application. Acknowledgments: Support for this research was provided by a grant from the Manitoba Medical Service Foundation (MMSF). Special thanks to Ran Zheng for assistance with data collection.