Changes in upper limb isometric strength and error tracking following training using iterative learning control (ILC) mediated by functional electrical stimulation (FES) (2008)

CHANGES IN UPPER LIMB ISOMETRIC STRENGTH AND ERROR TRACKING FOLLOWING TRAINING USING ITERATIVE LEARNING CONTROL (ILC) MEDIATED BY FUNCTIONAL ELECTRICAL STIMULATION (FES) <br/>Authors: Hughes, A. M. MSc1, Freeman, C. PhD2, Burridge, J. PhD1, Chappell, P. PhD2, Lewin, P. PhD2 and Rogers, E. PhD2 Affiliations: University of Southampton, Southampton, SO17 1BJ, UK <br/>1 School of Health Professions and Rehabilitation Sciences <br/>2 School of Electronics and Computer Science <br/>SUMMARY Based on existing motor control theory, an intervention involving a robot, ILC and FES was developed and tested on five chronic stroke patients. Improvements were seen in isometric strength and error tracking. <br/>CONCLUSIONS ILC mediated by FES enabled five chronic stroke subjects to accurately track a range of trajectories. Over time this related to an improvement in motor control reflected by increasing accuracy observed in unassisted tracking, and in isometric strength. <br/>INTRODUCTION Current opinion in motor learning, reinforced by clinical evidence, supports the use of FES and robot therapy to improve motor control [1-3]. ILC is a technique applicable to processes which repeatedly perform a task with a view to sequentially improving accuracy such as trajectory following in robots. The aim of this study is to test the feasibility of applying ILC to neurological rehabilitation. <br/>PATIENTS/MATERIALS and METHODS 5 hemiplegic stroke subjects underwent screening tests, and baseline assessments including isometric strength. Subjects used a robotic workstation to track 2 dimensional trajectories, over 18 intervention sessions within a 3 month period. At the beginning and end of each intervention session the ability of the stroke subject to track four trajectories without any FES or robot assistance was assessed. During the treatment sessions, ILC was used to modulate the FES applied to their triceps muscles in terms of timing and amplitude to improve tracking performance, whilst encouraging a maximal voluntary contribution to the task. Assessments of isometric muscle strength in six directions from a mid position were repeated after the eighteen sessions and for two subjects after an additional seven sessions. RESULTS Improvements in isometric strength were seen for all individual subjects after the intervention, with significant improvements for five out of six directions. Unassisted performance of the tracking tasks improved significantly for 3 out of the 4 tasks across the group. Subjects who performed poorly on the initial visit, showed the biggest improvements in tracking. DISCUSSION Analysis of the variability of the results may assist in the identification of good responders. Future work with the existing system includes assessing the potential for use with other neurological conditions, such as cerebral palsy and incomplete spinal cord injury. A subsequent study will develop a system for reaching in three dimensions and include opening the wrist and hand using ‘Smart glove’ as a position sensor. <br/>REFERENCES [1] De Kroon, J. R., van der Lee, J. H., Izerman, M. J., &amp; Lankhorst, G. J. 2002, Clinical Rehabilitation, vol. 16, pp. 350-360. [2] Schmidt, R. A. &amp; Lee, T. D. Motor control and learning a behavioural emphasis. 3rd Edition. 261-285. 1999. Human Kinetics. [3] Kwakkel, G., Kollen, B. J., &amp; Krebs H.I 2008, Neurorehabilitation and Neural Repair, vol. 22, pp. 111-121.