The current notion of spasticity as a velocity-dependent increase of muscle response to imposed stretch was mainly derived from studies performed under stationary experimental conditions. To address the issue of a spastic muscle behaviour under dynamic conditions, we conceived a novel approach, aimed at quantitatively assessing motor output over the lengthening periods which take place during unperturbed functional movements. Application to the analysis of overground walking in children with spastic cerebral palsy (CP) revealed that, for representative lower limb muscles, the relationship between EMG levels and estimated muscle lengthening rate displays either increased gain or reduced velocity threshold. Parallel measurement of gait kinetics frequently showed congruent increase of the mechanical resistance to joint rotation. Abnormalities preferentially targeted the lengthening contractions occurring around the ground contact period of the stride. The pathophysiological profile of what is clinically defined as 'spastic' gait in CP children did not only consist of dynamic spasticity, as described above. Most often it resulted from the simultaneous contribution of other factors, including paresis, co-contraction, immature and non-neural components. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
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Shanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R ChinaShanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R China
Fang, Xi
Xu, Chunxin
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Shanghai Rehabil Ctr Special Children, Shanghai 200127, Peoples R ChinaShanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R China
Xu, Chunxin
Mi, Yunhui
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Shanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R ChinaShanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R China
Mi, Yunhui
Sun, Kexing
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Shanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R ChinaShanghai Jiao Tong Univ, Sch Med, Shanghai Childrens Med Ctr, Shanghai 200127, Peoples R China