COMPARISON OF A MUSCLE STRENGTHENING METHOD USING ECCENTRIC CONTRACTION TO OTHER METHODS WITH ISOMETRIC OR CONCENTRIC CONTRACTION

Abstract

As the general principle of muscle strengthening, there is the overload principle as reported by Hellebrandt. But in two usual kinds of muscle contraction (isometric and concentric) it is difficult to overload the muscle, while eccentric contraction seems to be more appropriate for that purpose.
The eccentric contraction is a muscle contraction where, in spite of contraction, the muscle is ellongated by a load which is beyond the muscle force.
When this is utilized to muscle strengthening, the muscle that is contracting with maximum force is stretched by a load which exceeds the force exerted by the muscle.
As to the comparison of eccentric contraction to other training methods, there are reports by Akashi (1967), Doss Karpovichi (1968) and Olson (1972), but the muscles used and the methods of measurements do not seem appropriate.
The present study was conducted for two purposes: to compare these three muscle contraction methods, and to elucidate the degree of overload on eccentric contraction.
The musculus abductor digiti minimi of 40 normal individuals were tested.
The subjects were divided into 4 groups: group A (eccentric contraction against a load 200g over the maximum force), group B (eccentric contraction against a load 500g over the maximum force), group C (DeLorme-Watkins method), and group D (isometric contraction).
Each group underwent muscle training for 8 weeks.
In order to measure the muscle force, a goniometer and a tension meter were attached to an analyzer for the recording of muscle and joint angle.
The results are briefly summarized as follows:
1) The increase of muscle force was marked in group A as 224±48.5% and the similar tendency was observed with respect to the work and the power as well.
2) It seems that the proper overload of eccentric contraction is about 200g added to the maximum force. Considering the initial measurement, the whole overload amounts to 120-130% of maximum force.
3) In the case of eccentric contraction sufficient training effects were obtained by five contractions of 6 sec/day.
4) As to the relation of maximum force to the joint angle, the dynamic training (group A, B, C) gave the greatest force at angle of 40-50° and the static training (group D) at angle of 0-20°.
5) Cross education effect was recognized in the dynamic training while it was not observed in the static training.
6) The integrated EMG potential by surface electrodes showed neither correlation with the muscle strengthening nor difference due to the training methods.