Document Detail

Doublet stimulation protocol to minimize musculoskeletal stress during paralyzed quadriceps muscle testing.
MedLine Citation:
PMID:  18436697     Owner:  NLM     Status:  MEDLINE    
With long-term electrical stimulation training, paralyzed muscle can serve as an effective load delivery agent for the skeletal system. Muscle adaptations to training, however, will almost certainly outstrip bone adaptations, exposing participants in training protocols to an elevated risk for fracture. Assessing the physiological properties of the chronically paralyzed quadriceps may transmit unacceptably high shear forces to the osteoporotic distal femur. We devised a two-pulse doublet strategy to measure quadriceps physiological properties while minimizing the peak muscle force. The purposes of the study were 1) to determine the repeatability of the doublet stimulation protocol, and 2) to compare this protocol among individuals with and without spinal cord injury (SCI). Eight individuals with SCI and four individuals without SCI underwent testing. The doublet force-frequency relationship shifted to the left after SCI, likely reflecting enhancements in the twitch-to-tetanus ratio known to exist in paralyzed muscle. Posttetanic potentiation occurred to a greater degree in subjects with SCI (20%) than in non-SCI subjects (7%). Potentiation of contractile rate occurred in both subject groups (14% and 23% for SCI and non-SCI, respectively). Normalized contractile speed (rate of force rise, rate of force fall) reflected well-known adaptations of paralyzed muscle toward a fast fatigable muscle. The doublet stimulation strategy provided repeatable and sensitive measurements of muscle force and speed properties that revealed meaningful differences between subjects with and without SCI. Doublet stimulation may offer a unique way to test muscle physiological parameters of the quadriceps in subjects with uncertain musculoskeletal integrity.
Shauna Dudley-Javoroski; Andrew E Littmann; Masaki Iguchi; Richard K Shields
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2008-04-24
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  104     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2008 Jun 
Date Detail:
Created Date:  2008-06-04     Completed Date:  2008-08-20     Revised Date:  2014-09-20    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1574-82     Citation Subset:  IM    
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MeSH Terms
Adaptation, Physiological
Electric Stimulation* / adverse effects
Exercise Test / adverse effects,  methods*
Femoral Fractures / etiology,  physiopathology,  prevention & control*
Middle Aged
Muscle Contraction*
Muscle Strength*
Paralysis / etiology,  physiopathology*
Quadriceps Muscle / physiopathology*
Reproducibility of Results
Spinal Cord Injuries / complications*,  physiopathology
Stress, Mechanical
Grant Support
R01 NR010285/NR/NINR NIH HHS; R01 NR010285-05/NR/NINR NIH HHS; R01-NR010285-05/NR/NINR NIH HHS

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