Electromyographic patterns of the rat hindlimb in response to muscle stretch after spinal cord injury.

STUDY DESIGN: Experimental Study. OBJECTIVES: To characterize the specific hindlimb electromyographic (EMG) patterns in response to muscle stretch and to measure the applied forces during stretching in the rat model of moderate SCI. SETTING: Kentucky Spinal Cord Injury Research Center, Louisville, KY, USA. METHODS: Female Sprague Dawley rats (n = 4) were instrumented for telemetry-based EMG recording (right rectus femoris and biceps femoris) and received a moderate T10 spinal cord injury (SCI). The major hindlimb muscle groups were stretched using our clinically modeled protocol. The EMG responses were recorded biweekly for 8 weeks. The forces applied during stretching were measured using a custom-designed glove. Locomotor function was assessed using the BBB Open Field Locomotor Scale, 3D kinematics and gait analysis. RESULTS: Three main EMG patterns in response to stretch were identified: clonic-like, air-stepping, and spasms. Torques applied during stretching ranged from 0.4-8 N•cm, and with the exception of the quadriceps, did not change significantly over the weeks of stretching. Two stretching sessions a week did not result in a significant disruption to locomotor function. CONCLUSIONS: Stretching evokes EMG patterns in rats similar to those reported in humans including clonus and spasms. The torques used during stretching are comparable, based on the ratio of torque to body weight, to the few previously published studies that measured the forces and/or torques applied by physical therapists when stretching patients. Future studies are warranted to fully explore the impact of muscle stretch on spinal cord function after injury. SPONSORSHIP: DoD, KSCHIRT, NIH.

Hindlimb stretching alters locomotor function after spinal cord injury in the adult rat.

BACKGROUND: Stretching is a widely accepted standard-of-care therapy following spinal cord injury (SCI) that has not been systematically studied in animal models. OBJECTIVE: To investigate the influence of a daily stretch-based physical therapy program on locomotor recovery in adult rats with moderate T9 contusive SCI. METHODS: A randomized treatment and control study of stretching in an animal model of acute SCI. Moderate SCIs were delivered with the NYU Impactor. Daily stretching (30 min/day, 5 days/wk for 8 weeks) was provided by a team of animal handlers. Hindlimb function was assessed using the BBB Open Field Locomotor Scale and kinematically. Passive range-of-motion for each joint was determined weekly using a goniometer. RESULTS: Declines in hindlimb function during overground stepping were observed for the first 4 weeks for stretched animals. BBB scores improved weeks 5 to 10 but remained below the control group. Stretched animals had significant deficits in knee passive range of motion starting at week 4 and for the duration of the study. Kinematic assessment showed decreased joint excursion during stepping that partially recovered beginning at week 5. CONCLUSION: Stretch-based therapy significantly impaired functional recovery in adult rats with a moderate contusive SCI at T10. The negative impact on function was greatest acutely but persisted even after the stretching ceased at 8 weeks postinjury.