Hoffmann-reflex is delayed during 6 degree head-down tilt with balanced traction

Haruna, Y.; Styf, J. R.; Kahan, N.; Hargens, A. R.

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NASA NTRS · 20040142021

Hoffmann-reflex is delayed during 6 degree head-down tilt with balanced traction

Haruna, Y.·Styf, J. R.·Kahan, N.·Hargens, A. R.

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Abstract

BACKGROUND: Increased spinal height due to the lack of of axial compression on spinal structures in microgravity may stretch the spinal cord, cauda equina, nerve roots, and paraspinal tissues. HYPOTHESIS: Exposure to simulated microgravity causes dysfunction of nerve roots so that the synaptic portion of the Achilles tendon reflex is delayed. METHODS: Six healthy male subjects were randomly divided into two groups with three in each group. The subjects in the first group underwent horizontal bed rest (HBR) for three days. After a two week interval they underwent bed rest in a position of head-down tilt with balanced traction (HDT). So that each subject could serve as his own control, the second group was treated identically but in opposite order. Bilateral F waves and H-reflexes were measured daily (18:30-20:30) on all subjects placed in a prone position. RESULTS: By means of ANOVA, differences between HDT and HBR were observed only in M-latency and F-ratio, not in F-latency, central latency, and H-latency. Differences during the course of the bed rest were observed in M-latency and H-latency only. Tibial H latency was significantly lengthened in HDT group on day 2 and 3, although no significant difference between HDT and HBR was observed. CONCLUSION: The monosynaptic reflex assessed by H-reflex was delayed during 6 degree HDT with traction. The exact mechanism of this delay and whether the change was due to lengthening of the lower part of the vertebrae remain to be clarified.

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Randomized Controlled Trial Clinical Trial NASA Discipline Cardiopulmonary NASA Center ARC Head-Down Tilt H-Reflex/physiology Tibial Nerve/physiology Bed Rest Support, U.S. Gov't, Non-P.H.S Action Potentials Neural Conduction Support, Non-U.S. Gov't Adult Electromyography Reaction Time Male Peroneal Nerve/physiology Human

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Haruna, Y., Styf, J. R., Kahan, N., Hargens, A. R.. 1999-03-01. Hoffmann-reflex is delayed during 6 degree head-down tilt with balanced traction. https://ntrs.nasa.gov/citations/20040142021

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