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Related Experiment Videos

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

Y Haruna1, J R Styf, N Kahan

  • 1Gravitational Research Branch, NASA-Ames Research Center, Moffet Field, CA 94035-1000, USA.

Aviation, Space, and Environmental Medicine
|April 2, 1999
PubMed
Summary

Simulated microgravity delays nerve root function, specifically the Achilles tendon reflex. This study found that head-down tilt bed rest prolonged tibial H-reflex latency, suggesting spinal elongation impacts nerve function.

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Area of Science:

  • Neuroscience
  • Space Physiology
  • Biomechanics

Background:

  • Microgravity exposure can increase spinal height due to reduced axial compression.
  • This spinal elongation may affect neural structures, including nerve roots and paraspinal tissues.

Purpose of the Study:

  • To investigate the impact of simulated microgravity on nerve root function.
  • To determine if head-down tilt bed rest delays the synaptic portion of the Achilles tendon reflex.

Main Methods:

  • Six healthy males participated in a randomized crossover study.
  • Subjects underwent 3 days of horizontal bed rest (HBR) and 3 days of head-down tilt bed rest with traction (HDT), with a 2-week washout period.
  • Bilateral F waves and H-reflexes were measured daily in the prone position.
Keywords:
NASA Center ARCNASA Discipline Cardiopulmonary

Related Experiment Videos

Main Results:

  • Head-down tilt bed rest (HDT) significantly lengthened tibial H-reflex latency on days 2 and 3 compared to baseline.
  • ANOVA revealed differences between HDT and HBR in M-latency and F-ratio, but not F-latency, central latency, or H-latency.
  • Differences in M-latency and H-latency were observed during the course of bed rest.

Conclusions:

  • The H-reflex, a measure of monosynaptic reflex, was delayed during 6-degree HDT with traction.
  • The precise mechanism for this reflex delay requires further investigation.
  • It remains unclear if spinal lengthening is the primary cause of the observed nerve conduction changes.