RESEARCH REPORT POSTER DISPLAY

KNEE EXTENSOR FORCE CONTROL ABILITIES IN POST-STROKE HEMIPARESIS. Kiyama R, Tetsuo M, Kiyohiro F, Akihide U, Toshiki H, Yoichi Y; Course of Physical Therapy, School of Health Sciences, Faculty of Medicine, Kagoshima University. Rehabilitation Center, Kajiki-Onsen Hospital

PURPOSE: Since maximal strength is scarcely recruited in activities of daily living, sub-maximal force control may be a more meaningful parameter. To estimate force control ability, a force-tracking task in which the patient applies a target force according to the visual feedback is generally used.Evangelos found age effects on knee extensor force control during rapid discrete isometric task. Assessment of force control ability is expected to be useful for evaluation of lower extremity function in post-stroke hemiparesis.This study investigated the validity of sub-maximal isometric force control abilities of the knee extensors in post-stroke hemiparesis. RELEVANCE: Clinical evaluation of sub-maximal force control ability may contribute to the improvement of the physical therapy practice in stroke hemiparesis. PARTICIPANTS: Twenty patients with post-stroke hemi-paresis (mean 61.1 (SD 16.1) years of age, mean 6.1 (SD 4.8) years post-stroke) with the ability to walk volunteered for this study. In 13 cases, the patient’s right side was hemiplegic. METHODS: For testing, subjects were seated in the chair with the knee at a 90° angle. Strength data were measured using a hand-held dynamometer EG-230 (SAKAI Medical Corp., Tokyo, Japan). Sub-maximal voluntary isometric knee extensor force was obtained on the affected leg. The dynamometer was placed above the medial and lateral malleoli. The participant attempts to match the voluntary knee extensor strength with the target force represented by a bar chart for 60 seconds. The target force values during the trial period varied over two frequencies (0.3 Hz, 0.5 Hz), which ranged from 0% to 20% of the participant’s maximal isometric knee extensor strength. The strength data were transmitted to a computer at a sampling rate of 20Hz. The difference between the voluntary knee extensor strength and the target force was considered an estimate of force control ability. Smaller values indicated a better force control ability.We also assessed gait velocity with gait aids, and Brunnstrom Recovery Stage. ANALYSIS: The Spearman’s rank correlation was used to determine correlations of force control abilities and Brunnstrom Recovery Stage, gait velocity. RESULTS: The correlation between the force control ability at frequencies of 0.3 Hz and 0.5 Hz, and Brunnstrom Recovery Stage were −0.09 (n.s.) and −0.45 (p < 0.05), respectively. Similarly, the correlation between force control ability at frequencies of 0.3 Hz and 0.5 Hz, and gait velocity were −0.36 (n.s.) and −0.57 (p < 0.05), respectively. CONCLUSIONS: We found that knee force control ability at a frequency of 0.5 Hz correlated with Brunnstrom Recovery Stage and gait velocity. It may be that the knee force control ability kept pace qualitatively with motor recovery. The coordination of knee extensor force is important to control the center of gravity during gait, therefore knee extensor force control ability is associated with gait velocity. Measuring knee extensor force control ability may be available as a method of qualitatively evaluating motor recovery following stroke. IMPLICATIONS: Clinical evaluation of sub-maximal force control ability may contribute to the improvement of the physical therapy practice in stroke hemiparesis. KEYWORDS: force control ability, hemiparesis, gait velocity. FUNDING ACKNOWLEDGEMENTS: This work was supported by Grants-in-Aid for Scientific Research 2004-2005, Japanese Ministry of Education, Culture, Sports, Science and Technology. CONTACT: kiyama@health.nop.kagoshima-u.ac.jp

ETHICS COMMITTEE: The Institutional Review Board at the Kagoshima University approved the procedures used in this study.