Human spinal cord injury: motor unit properties and behaviour

Area of Science:

• Neuroscience
• Physiology
• Rehabilitation Science

Background:

• Spinal cord injury (SCI) causes significant alterations in muscle function.
• Changes in excitatory and inhibitory inputs to motoneurons are key consequences of SCI.
• Understanding these changes is crucial for developing effective rehabilitation strategies.

Purpose of the Study:

• To review motor unit data and analyze how SCI affects motoneuron management.
• To investigate the impact of SCI on muscle properties, including weakness and fatigability.
• To explore species-specific differences in SCI-induced muscle dysfunction to inform recovery efforts.

Main Methods:

• Review of existing motor unit data related to spinal cord injury.
• Analysis of changes in motoneuron input and output.
• Comparison of muscle property alterations across different muscles and species.

Main Results:

• SCI alters motoneuron recruitment and firing rates, impacting force production and precision.
• Reduced motor unit numbers and altered twitch/tetanic force ratios contribute to weakness.
• Muscle weakness, fatigability, and reduced contractile speed are common post-SCI, though variations exist.

Conclusions:

• SCI profoundly affects motor unit control and muscle physiology, leading to functional deficits.
• Species and injury-specific factors influence the manifestation of muscle dysfunction after SCI.
• Further exploration of these diverse effects is essential for improving recovery of desired functions in individuals with SCI.