Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
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©Journal of Sports Science and Medicine (2005) 04, 395 - 405

Research article
Tolerance and Conditioning to Neuro-Muscular Electrical Stimulation Within and Between Sessions and Gender
Gad Alon1, , Gerald V. Smith1,2
Author Information
1 University of Maryland, School of Medicine, Department of Physical Therapy & Rehabilitation Science, Baltimore, MD 21201, USA.
2 University of Central Florida, College of Health and Public Affairs, Department of Health Professions, Orlando, FL 32816, USA.

Gad Alon
✉ Department of Physical Therapy and Rehabilitation Science, University of Maryland School of Medicine 100 Penn Street - Suite 107, Baltimore MD 21201, USA
Email: galon@som.umaryland.edu
Publish Date
Received: 04-07-2005
Accepted: 22-08-2005
Published (online): 01-12-2005
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ABSTRACT

This study was conducted to determine: 1) If healthy subjects can be conditioned to tolerate clinically useful electrically induced muscle contraction; and 2) If there is a gender difference in response to such conditioning. Healthy volunteers (10 males, 11 females, mean age of 27.6 ± 5.8 yrs) were tested during each of 6 testing sessions. Maximal voluntary isometric contractions (MVIC) of the right quadriceps femoris (RQF) recorded by a computerized dynamometer. Electrical stimulation delivered through two surface electrodes and stimulation amplitude increased until the subject indicated to stop. After a 1 min rest the amplitude increased again to the same phase charge level, and the electrically induced contraction (EIC) was recorded by the dynamometer. Measurements of stimulation amplitude were repeated in each of 10 stimulation bouts per session. Measurements of EIC were repeated in session six. Statistical analyses included Multivariate ANOVAs, and Newman-Kuel’s post-hoc tests (p < 0.01). Mean values of phase charge increased from session 1 to 6 for all subjects. Males tolerated significantly higher phase charge. The mean %MVIC torque generated by female subjects was initially only 11.2 ± 21.6% but reached 42.9 ± 25.4% at the end of the 6th session. Males’ %MVIC torque values were significantly higher reaching 49.0 ± 41.6% and 73.5 ± 18.7% in the first and last trials respectively. Using the criterion that electrically induced contractions must be at least 25% of MVIC to be considered clinically useful, 36% of females were below this threshold at the end of the last session. In contrast, all males exceeded the 25% MVIC threshold at the end of the study. Most healthy subjects can be conditioned to electrical stimulation of the quadriceps, but depending on the criteria of therapeutic value and gender, some males and even more females may not reach the desired stimulation goal in 6 sessions. Females may require more conditioning sessions to reach contraction levels of therapeutic benefits. The reason(s) for the confounding factor of gender remains unknown.

Key words: Neuromuscular electrical stimulation, tolerance, conditioning, gender


           Key Points
  • Neuromuscular electrical stimulation (NMES) can strengthen skeletal muscles
  • Tolerance to NMES improves within 6 sessions
  • Conditioning is a key to eliciting stronger contraction and to increasing the number of subjects that can benefit from NMES
  • Healthy males can tolerate higher stimulusintensity and higher electrically induced quadriceps femoris contraction.
 
 
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