Forelimb and hindlimb adjustments to treadmill speed during quadrupedal locomotion after a lateral spinal hemisection in adult cats.

The ability to attain and sustain moderately fast walking speeds is critically important for various locomotor tasks in animals, including humans. In animals, it is vital for survival, to capture prey or escape from predators and to find a mate. In humans, modulating walking speed is important for several activities, including sports, exercise and effective community ambulation, such as safely crossing a street. Following spinal cord injury (SCI), a common deficit includes an inability to attain and sustain moderately fast speeds. The goal of the present study was to describe adjustments to different speeds (0.4m/s-0.8m/s) before and after an incomplete SCI in the cat model. Experimental analyses were performed before, one week (H1) and eight weeks (H2) after a lateral spinal hemisection between the 5-6th thoracic vertebrae in 8 cats. We found that 4 cats were unable to perform 10-15 steps consistently on the treadmill at the fastest speeds (0.9m/s-1.0m/s) following hemisection (H1 and H2). Speed-dependent modulation of cycle, stance and swing durations were maintained in all cats, albeit with a significant decrease in forelimb cycle duration and increase in hindlimb cycle duration. The dissociation of fore-hindlimb rhythms lead to the appearance of 2-1 coordination which was not influenced by stepping speed. Step and stride length modulation was maintained after SCI, however, as speeds increased, hindlimb paw contact remained significantly more caudal relative to the hip at H1 and H2. Interlimb phase intervals were relatively unaffected by walking speed or lateral hemisection. Speed-dependent modulation of support period durations were conserved following SCI such that double support durations increased, while triple and quadruple support periods decreased with increasing speed. We did note a significant decrease in triple support period durations where two hindlimbs and one forelimb are in contact with the treadmill, along with a significant increase in quadruple support frequency and duration. As speeds increased, electromyographic (EMG) activity increased in all muscles tested, with the exception of the ipsilesional knee extensor, right vastus lateralis (RVL). We also noted a decreased RVL activation duration along with increased ipsilesional Sartorius (RSRT, hip flexor/knee extensor) burst duration across all speeds after hemisection. RSRT showed significant activation during the stance phase at both timepoints following hemisection, presumably to stabilize the knee post-SCI. Taken together, the present results demonstrate that felines can make the necessary adjustments to their locomotor pattern across a moderate range of speeds following hemisection at mid-thoracic levels. However, many of these cats could not attain the fastest speeds, which may be attributed to the various changes that occurred following hemisection. Future studies may seek to explore which adjustments limit SCI patients and quadrupeds most from attaining faster speeds to optimize recovery and ambulation after injury.

Name thesis:degree_name

M. Sc.

Level thesis:degree_level

Maîtrise

Discipline thesis:degree_discipline

Physiologie

Grantor dc:publisher

Université de Sherbrooke

Year dc:date.issued

2019

Author dc:creator

• Doelman, Adam

Advisor dc:contributor.advisor

• Frigon, Alain

• Locomotion
• Speed
• Spinal Cord Injury
• Vitesse
• Lésion incomplète à la moelle épinière

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nd/2.5/ca/

Language dc:language.iso

fr, en

Handle dc:identifier.uri

http://hdl.handle.net/11143/15799

OAI identifier oai:identifier

oai:usherbrooke.scholaris.ca:11143/15799