Document Detail


The role of pulse duration and stimulation duration in maximizing the normalized torque during neuromuscular electrical stimulation.
MedLine Citation:
PMID:  18678958     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
STUDY DESIGN: Controlled laboratory study OBJECTIVES: To determine the effects of pulse duration and stimulation duration on the evoked torque after controlling for the activated area by using magnetic resonance imaging (MRI). BACKGROUND: Neuromuscular electrical stimulation (NMES) is commonly used in the clinic without considering the physiological implications of its parameters. METHODS AND MEASURES: Seven able-bodied, college students (mean +/- SD age, 28 +/- 4 years) participated in this study. Two NMES protocols were applied to the knee extensor muscle group in a random order. Protocol A applied 100-Hz, 450-microsecond pulses for 5 minutes in a 3-seconds-on 3-seconds-off duty cycle. Protocol B applied 60-Hz, 250-microsecond pulses for 5 minutes in a 10-seconds-on 20-seconds-off duty cycle. The amplitude of the current was similar in both protocols. Torque, torque time integral, and normalized torque for the knee extensors were measured for both protocols. MRI scans were taken prior to, and immediately after, each protocol to measure the cross-sectional area of the stimulated muscle. RESULTS: The skeletal muscle cross-sectional areas activated after both protocols were similar. The longer pulse duration in protocol A elicited 22% greater torque output than that of protocol B (P<.05). After considering the activated area in both protocols, the normalized torque with protocol A was 38% greater than that with protocol B (P<.05). Torque time integral was 21% greater with protocol A (P = .029). Protocol B failed to maintain torque at the start and the end of the 10-second activation. CONCLUSIONS: Longer pulse duration, but not stimulation duration, resulted in a greater evoked and normalized torque compared to the shorter pulse duration, even after controlling for the activated muscular cross-sectional areas with both protocols. LEVEL OF EVIDENCE: Therapy, level 5.
Authors:
Ashraf S Gorgey; Gary A Dudley
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, N.I.H., Extramural     Date:  2008-08-01
Journal Detail:
Title:  The Journal of orthopaedic and sports physical therapy     Volume:  38     ISSN:  0190-6011     ISO Abbreviation:  J Orthop Sports Phys Ther     Publication Date:  2008 Aug 
Date Detail:
Created Date:  2008-08-05     Completed Date:  2008-12-09     Revised Date:  2010-09-22    
Medline Journal Info:
Nlm Unique ID:  7908150     Medline TA:  J Orthop Sports Phys Ther     Country:  United States    
Other Details:
Languages:  eng     Pagination:  508-16     Citation Subset:  IM    
Affiliation:
Department of Physical Therapy, Indiana University, Indianapolis, IN 46202-5119, USA. agorgey@gmail.com
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MeSH Terms
Descriptor/Qualifier:
Adult
Electric Stimulation Therapy / methods*
Female
Humans
Knee Joint / physiopathology*
Magnetic Resonance Imaging
Male
Muscle Strength Dynamometer
Muscle Weakness
Muscular Atrophy / therapy
Torque
Young Adult
Grant Support
ID/Acronym/Agency:
HD39676S2/HD/NICHD NIH HHS; HD39679/HD/NICHD NIH HHS; R01 HD039676-02S1/HD/NICHD NIH HHS
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