Dynamic "range of motion" hindlimb stretching disrupts locomotor function in rats with moderate subacute spinal cord injuries
Anastasia Valerievna Keller, Kathlene Marie Rees, Daniella Christina Prince, Johnny R Morehouse, Alice Shum-Siu, David Sk Magnuson
Journal of Neurotrauma 2017 March 13
Joint contractures and spasticity are two common secondary complications of a severe spinal cord injury (SCI) that can significantly reduce quality of life and stretching is one of the top strategies for rehabilitation of these complications. We have previously shown that a daily static stretching protocol administered to rats at either acute or chronic time points after a moderate or moderate-severe T10 SCI significantly disrupts their hindlimb locomotor function. The objective of the current study was to examine the effects of dynamic range of motion stretching on the locomotor function of rats with SCI as an alternative to static stretching. Starting at 6 weeks post-injury (T10 moderate contusion) eight adult Sprague Dawley rats were subjected to hindlimb stretching for 4 weeks. Our standard stretching protocol (6 maneuvers to stretch the major hindlimb muscle groups) was modified from 1 minute static stretch-and-hold at the end ROM of each stretch position to a dynamic 2 seconds hold, 1 second release rhythm repeated for a duration of 1 minute. Four weeks of daily (5 days/week) dynamic stretching led to significant disruption of locomotor function as assessed by the BBB Open Field Locomotor Scale and 3D kinematic and gait analyses. In addition, we identified and analyzed an apparently novel hindlimb response to dynamic stretch that resembles human clonus. The results of the current study extend the observation of the stretching phenomenon to a new modality of stretching that is also commonly used in SCI rehabilitation. While mechanisms and clinical relevance still need to be established, our findings continue to raise concerns that stretching as a therapy can potentially hinder aspects of locomotor recovery.
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