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Voluntary and electromyostimulation forces in trained and untrained men
T Hortobágyi1, N J Lambert, C Tracy
1Human Performance Laboratory, East Carolina University, Greenville, NC 27858.
Medicine and Science in Sports and Exercise
|June 1, 1992
Summary
Percutaneous electrical muscle stimulation (EMS) did not enhance maximal voluntary contraction forces in elbow flexors for either trained or untrained individuals. The study suggests EMS may not be effective for strength development or atrophy prevention in upper limbs.
Area of Science:
- Sports Medicine
- Neuromuscular Physiology
- Rehabilitation Science
Background:
- Electromyostimulation (EMS) is widely used for lower extremity muscle strength and atrophy prevention in sedentary or disabled individuals.
- Its efficacy in upper extremity muscles, particularly in athletes, remains less understood.
Purpose of the Study:
- To compare the effects of percutaneous EMS on elbow flexor muscles in strength-trained versus untrained healthy men.
- To evaluate EMS-evoked tetanic force and its impact when superimposed on maximal voluntary contraction (MVC).
Main Methods:
- Six strength-trained and six untrained men underwent percutaneous EMS.
- Maximal voluntary isometric contraction (MVC) forces, EMS-evoked tetanus, and superimposed EMS on MVC were measured.
- Stimulation used a 2.5-kHz alternating current sine wave modulated at 50 bursts/s with a 50% duty cycle.
Main Results:
- Strength-trained men exhibited 29% higher MVC than untrained controls.
- Despite differences in tolerated EMS current, tetanic forces were similar between groups (92.5 N untrained vs. 96.0 N trained).
- EMS superimposed on MVC significantly reduced voluntary force by 10% (untrained) and 13% (trained).
Conclusions:
- Percutaneous EMS appears to reduce maximal voluntary elbow flexion force, irrespective of training status.
- The tetanic forces evoked by EMS may be insufficient for effective muscular strength development or atrophy prevention in the upper limbs.