Journal article
Low frequency depression of H-reflexes in humans with acute and chronic spinal-cord injury
Experimental brain research, Vol.133(2), pp.233-241
07/2000
DOI: 10.1007/s002210000377
PMCID: PMC4034370
PMID: 10968224
Abstract
We measured low-frequency depression of soleus H-reflexes in individuals with acute (
n
=5) and chronic (
n
=7) spinal-cord injury and in able-bodied controls (
n
=7). In one acute subject, we monitored longitudinal changes in low-frequency depression of H-reflexes over 44 weeks and examined the relationship between H-reflex depression and soleus-muscle fatigue properties. Soleus H-reflexes were elicited at 0.1, 0.2, 1, 5, and 10 Hz. The mean peak-to-peak amplitude of ten reflexes at each frequency was calculated, and values obtained at each frequency were normalized to 0.1 Hz. H-reflex amplitude decreased with increasing stimulation frequency in all three groups, but H-reflex suppression was significantly larger in the able-bodied and acute groups than in the chronic group. The acute subject who was monitored longitudinally displayed reduced low-frequency depression with increasing time post injury. At 44 weeks post injury, the acute subject’s H-reflex depression was similar to that of chronic subjects, and his soleus fatigue index (assessed with a modified Burke fatigue protocol) dropped substantially, consistent with transformation to faster muscle. There was a significant inverse correlation over the 44 weeks between the fatigue index and the mean normalized H-reflex amplitude at 1, 5, and 10 Hz. We conclude that: (1) the chronically paralyzed soleus muscle displays impaired low-frequency depression of H-reflexes, (2) attenuation of rate-sensitive depression in humans with spinal-cord injury occurs gradually, and (3) changes in H-reflex excitability are generally correlated with adaptation of the neuromuscular system. Possible mechanisms underlying changes in low-frequency depression and their association with neuromuscular adaptation are discussed.
Details
- Title: Subtitle
- Low frequency depression of H-reflexes in humans with acute and chronic spinal-cord injury
- Creators
- Sheila Schindler-IvensRichard K Shields
- Resource Type
- Journal article
- Publication Details
- Experimental brain research, Vol.133(2), pp.233-241
- DOI
- 10.1007/s002210000377
- PMID
- 10968224
- PMCID
- PMC4034370
- NLM abbreviation
- Exp Brain Res
- ISSN
- 0014-4819
- eISSN
- 1432-1106
- Language
- English
- Date published
- 07/2000
- Academic Unit
- Orthopedics and Rehabilitation; Physical Therapy and Rehabilitation Science
- Record Identifier
- 9984047644702771
Metrics
20 Record Views