Stretch reflex coupling between the hip and knee: implications for impaired gait following stroke

Abstract

Individuals with hemiparetic stroke often exhibit an abnormal coupling between the frontal plane of the hip and saggital plane of the knee during gait. The purpose of this study was to determine if stretch sensitive reflexes, which are known to be altered following stroke, exhibit similar coupling between the muscles of the hip and knee in the post-stroke population. Eighteen subjects were recruited for this study including ten with hemiparesis resulting from stroke and eight unimpaired, age-matched controls. A servomotor was used to apply ramp and hold perturbations to both the hip and knee joints in separate sessions and electromyographic activity was recorded in eight muscles of the lower limb. Hip abduction perturbations elicited abnormal activation in rectus femoris (RF) in seven of ten stroke subjects with amplitudes ranging from 3.2 to 12.5% of the maximum voluntary contraction (MVC). Only two of eight control subjects exhibited any activity in RF and these responses were only 2.1 and 2.7% of MVC. To determine if the responses in the stroke group were a result of muscle stretch, a musculoskeletal model was used to simulate the experimental abduction perturbations and estimate muscle length changes. The simulation revealed that RF should be shortened by the perturbations and this suggests that the response was not likely due to direct stretch. Moreover, knee flexion perturbations elicited responses in the hip adductors (AL) with a mean amplitude of 5.1 ± 3.8% of MVC across all stroke subjects while no significant responses were recorded in controls. The presence of a reciprocal, reflex-mediated coupling between RF and AL following stroke suggests

Quadrupedal coordination of bipedal gait: implications for movement disorders

“…As a functional consequence, a defective sensori-motor integration, which is assumed to be responsible for the disturbed inter-and intralimb coupling [47,58], could essentially be due to the impaired processing of afferent input described here. The novel aspect of this research is that the reflex effects evoked by a non-noxious afferent volley concerns both the affected and unaffected arm of stroke subjects.…”

“…Nevertheless, an abnormal coupling of upper and lower limb muscles was described in subjects following stroke [43][44][45][46] or cervical spinal cord lesions [19]. The disturbed inter-and intralimb coupling is assumed to contribute to falls in post-stroke subjects [47][48][49][50][51][52].…”

The basic mechanics of bipedal walking lead to asymmetric behavior

“…For example, the stereotypical behavior of leg circumduction has been attributed to torque coupling between hip adduction and knee extension [10], [11]. Asymmetries also result from apparent bilateral impairments, a common example being cerebral palsy [3].…”

Using fuzzy logic for diagnosis and classification of spasticity

“…During the passive movements of muscle activities, it has been reported that besides muscle activities producing increased resistance against passive extension, other mechanisms were responsible (13,28). Thus, the excessive extension or flexor reflexes that emerge in the muscles, especially with UMN syndrome, can contribute to spastic muscle tonus and to secondary changes in the internal and external muscle features, such as different muscle lengths, as well as the increasing resistance of a spastic muscle against extension (29). The surface EMG values measured in the DF and PF positions were higher than those for resting and standing positions of the patients.…”