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Title: Reflex control of human trunk muscles
Author: Beith, Iain David
ISNI:       0000 0001 3454 0855
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2002
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Muscles of the human trunk are arranged in layers and attach either to the vertebral column or to the pelvis and thorax. Present understanding suggests the deeper muscles, attached to the vertebral column, stabilise the spine, whereas the more superficial muscles, attached to the thorax and pelvis, produce and control trunk movement. If so, the control of these two groups may differ, with deeper muscles working synergistically and those more superficially located acting antagonistically to one another. To this end the role that reflex connections between the different muscles may play in mediating either synergistic or antagonistic roles was investigated. Muscle afferent activity was evoked via a series of mechanical taps applied to individual muscle/tendon complexes of three abdominal and two paraspinal muscles by means of a mechanical tapping device. The resultant reflex responses were recorded by surface electromyography in the same five muscles, both ipsilateral and contralateral to the applied tap. This allowed analysis of the effect of muscle afferents from any one muscle to all the others. Short latency, (less than 25ms) heteronymous muscle afferent connections are excitatory and widespread between the abdominal muscles. They are also excitatory between ipsilateral paraspinal muscles, but inhibitory between these muscles contralaterally. Reflexes are mostly absent between abdominal and paraspinal muscles. Specifically, connections both to and from the internal oblique muscle (IO), the deepest abdominal muscle studied, were the most widespread and potent, with the connection from one IO to the other being of similar amplitude and minimal difference in latency. It is suggested that at least the earliest part of the short latency excitatory crossed reflexes observed here, are monosynaptically mediated. In addition, there is evidence of asymmetry in the presence and strength of these reflexes between the left and right sides. Longer latency reflexes with latencies of between 40 and 50ms were also observed between all muscle groups studied. These were excitatory within the abdominal and paraspinal groups, but inhibitory between them. However, whether these originate from muscle or cutaneous afferents is unclear.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available