Lower Extremity Fitts’ Task Performance by Patients with Degenerative Lumbar Spinal Stenosis: The Application of Induced Strain Steven R Passmore; Valerie Pelleck; Yasmine Amad; Erica Ramos; Michael Johnson; Cheryl M Glazebrook University of Manitoba, Winnipeg, Manitoba DISCUSSION RESULTS INTRODUCTION METHOD A common cause of low back pain is lumbar spinal stenosis (LSS). LSS is a narrowing of the central canal and/or intervertebral foramen through which the spinal cord and/or nerve roots traverse. Impoverished lower limb movement is among the first symptoms LSS patients note and many patients report ambulation-induced strain (Katz and Harris 2008). In order to effectively examine the abilities and limitations of LSS patients, the conditions of examination should not be static. To determine function, testing should be completed while the patient is under strain (Barz et al., 2008). Treadmill walking typically induces sensations that mimic the strain felt during activities of daily living for LSS patients (Deen et al, 2000). Previous investigation using a cross-sectional approach with Fitts’ Law identified specific differences between LSS and healthy populations. Increases in task difficulty (ID) had a more adverse impact on lower limb movement planning and execution in LSS patients than individuals in a healthy population (Passmore et al., 2013). The present study builds on findings by Passmore et al. (2013) by utilizing a foot movement Fitts’ task with LSS and control groups, but with the novel introduction of movement-induced strain. Using a before-and-after design, a progressive exercise treadmill test (PETT) was added to investigate the role of strain in performance-based outcome measurement. • Analysis of behavioral and kinematic variables replicated previous lower extremity Fitts’ task findings consistent with Passmore et. al (2013) • Increases in task difficulty led to performance decreases in: • movement preparation (reaction time), speed-accuracy performance trade off (movement time), online control of movement (peak velocity). • LSS participants: • Significantly longer time to plan movements • More adversely impacted by task difficulty increases • May reflect the anticipatory postural adjustments (APAs) associated with performance of a lower-limb pointing task (Bertucco, Cesair, Latash, 2013). • Treadmill walking facilitated reaction time for both groups • May indicate the effect of acute exercise known to facilitate RT (Davranche et al, 2009). • Shorter reaction times in Fitts’ trials with a precue reflect preprogramming of limb movement. • APAs occur 80-100 ms prior to a predictable stimulus and have an impact on reaction time. Participants may anticipate limb movements when precue is present. (Bertucco, Cesair, Latash, 2013). • Effect should have been minimal as variable foreperiod following the precue should have limited anticipation. • Treadmill task induced strain in the LSS group • Time spent on the treadmill was significantly shorter in the LSS group than the control group. • Presence of LSS appeared to negate performance improvements in the efficiency/consistency of the ballistic phase of lower limb movements. • Participants • 16 healthy participants (9 females; mean age= 58.4 [6.3]) • 16 participants with LSS (10 females; mean age= 62.8 [10.4]) • Baseline Questionnaires • Waterloo Footedness Questionnaire- Revised (WFQ-R) • LSS participants also completed the Swiss Spinal Stenosis score (SSS) • Bilateral leg and low back Quadruple Numeric Rating Scales (QNRS) • Fitts’ Task • Participants pointed with their great toe to a 2.5cm or 5cm square target that appeared at a distance of 20 or 40 cm from the home position (IDs= 3b, 4a, 4b, 5) • The four combinations were presented in a random order, with each combination being presented 10 times. Once completed, the procedure was repeated with the opposite foot (80 trials total). • Participants performed two blocks of 10 trials of each ID using each foot for a total of 80 pointing movements • Pointing movements were collected using 3D motion analysis (3D Investigator, Northern Digital Instruments, Waterloo, ON) • Behavioural and kinematic measures were applied to evaluate performance • Progressive Exercise Treadmill Test (PETT) • Following the first block of trials, participants completed a 12-minute progressive exercise treadmill test (PETT), or walked until they chose to discontinue the test due to an onset of clinical symptoms • LSS participants completed an abbreviated version of the QNRS immediately after finishing the PETT • A second block of trials was then completed with both feet • Analysis • Means for Reaction Time (RT), Movement Time (MT), Peak Velocity (PV), Time to Peak Velocity (ttPV) and Standard Deviation (Variability) of Time to Peak Velocity (SDttPV) were analyzed • 2 groups (Healthy, LSS) x 4 ID (3b, 4a, 4b, 5) x 2 conditions of strain (pre-PETT, post-PETT) • Mixed ANOVA models were applied for behavioral and kinematic analysis • All significant effects with more two means were further analyzed using Tukey’s HSD, p < 0.05 • Reaction Time: • Main effect for ID F(3,372)=6.725, p<.001; and group F(1,124)=5.872, p=0.017 • Group x ID interaction, F(3,372)=4.207;p=.006 • Both groups’ reaction times (RT) increased with task difficulty. • The PETT facilitated RT for both groups, F(1,124)=5.105;p=0.026. • Movement Time: • Main effect for ID, F(3,372)=444.394, p<.001 • Group by ID interaction F(3,372)=6.724, p<.001. • Replicating our previous work, LSS participants were impacted more adversely by increased task difficulty. • Peak Velocity: • Main effects for ID, F(3,372)=1654.455, p<.001 and group, F(1,124)=7.852, p=.006. • Group by ID interaction, F(3,372)=8.428 p<.001 • LSS participants had lower PVs than healthy participants and longer amplitudes to the target negatively impacted PV performance more than target size • LSS group had significantly lower PV at higher IDs. • Variability of Time to Peak Velocity: • Significant main effect for group F(1,124) = 18.61 p<.001. • LSS group was significantly more variable than the control group in their time to peak velocity • significant effect for strain in the control group at the lowest ID, t(31)=2.149; p=0.040. • Control participants were less variable in their time to peak velocity post strain, a benefit not seen in the LSS group. CONCLUSION A lower extremity movement task captured differences under strain between healthy and LSS populations. The role of strain was explored and was sufficient to prevent LSS participants from demonstrating improvement in the variability of the ballistic phase of movement execution. To enhance performance-based outcome measurement, future LSS clinical intervention studies may consider strain induction. • Fitts’ Law: • Movement Time = a + b(ID) • a = y intercept • b = slope • Index of Difficulty (ID) = log2(2A/W) • A = amplitude to target • W= target width REFERENCES Barz, T., Melloh, M., Staub, L., Roeder, C., Lange, J., Smiszek, F.G., Theis, J.C., and Merk, H.R. (2008). The diagnostic value of a treadmill test in predicting lumbar spinal stenosis. European Spine Journal, 17(5):686-690. Bertucco, M., Cesari, P., and Latash, M.L. (2013). Fitts’ Law in early postural adjustments. Neuroscience, 231:61-69. Davranche, K., Hall, B., and McMorris, T. (2009). Effect of acute exercise on cognitive control required during an Eriksen flanker task. Journal of Sport and Exercise Psychology. 31, 628–639. Deen, H.G., Zimmerman, R.S., Lyons, M.K., McPhee, M.C., Verheijde, J.L., and Lemens, S.M. (2000). Test-retest reproducibility of the exercise treadmill examination in lumbar spinal stenosis. Mayo Clinic Proceedings, 75(10):1002-1007. Katz, J.N., and Harris, M.B. (2008). Clinical practice: Lumbar spinal stenosis. New England Journal of Medicine, 358(8), 818-825. Passmore, S.R., Pelleck, V., Gysel, A., Johnson, M., Kriellaars, D., Glazebrook, C. (2013). The impact of lumbar spinal stenosis on lower extremity motor control: using movement to measure function. Journal of Chiropractic Education, 27(1), 75. OBJECTIVES Index of Difficulty (ID) • Objectives of this study were to improve our understanding of performance-based outcome measurement for lumbar spinal stenosis (LSS) patients under conditions of strain, and no strain. • Quantify the lower extremity motor strategies and capabilities of a population with LSS compared to healthy matched controls under conditions of strain, and no strain. • Identify challenging movement conditions for a population with LSS, on a lower limb aiming task with alterable levels of difficulty, compared to healthy matched controls under conditions of strain, and no strain. ACKNOWLEDGEMENTS 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 and Taylor Post with data analysis. ONE UNIVERSITY. MANY FUTURES.