Effect of Eccentric and Concentric Muscle Conditioning on Tension and Electrical Activity of Human Muscle*

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Abstract
The effects of seven weeks of eccentric or concentric muscle conditioning on muscle tension and. integrated electrical activity (IEMG) were investigated on human subjects by using a special electrical dynamometer as a testing and training apparatus. The eccentric conditioning caused, on the average, a greater improvement in muscle tension than did the concentric conditioning. In early conditioning those in the eccentric group experienced soreness in their exercised muscles. This caused a concomitant drop in maximum strength. After the disappearance of pain symptoms, ability to develop tension increased in a linear fashion. Neither method was able to cause statistically significant changes in the maximum IEMG associated with any type of muscle contraction. The regression lino expressing the relationship between IEMG ( μ.v. per sec.) and isometric tension (in percent of maximal voluntary contraction) was parabolic. In this relationship muscle conditioning failed to cause any significant changes in IEMG per unit of tension. Although the IEMG changes due to conditioning were somewhat different in the two experimental groups, it could not be established that either type of conditioning caused increase in the desynchronized firing of motor units.

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