ELECTROSTIMULATION AND FORCE PRODUCTION

Abstract

INTRODUCTION For muscular and sport exercise, the force production is one of the first important parameter to control. It is always possible to regulate force production via the intensity, but in order to minimize fatigue phenomenon it may be interesting to have a better control of parameters of stimulation. The aim of this work is to determine the interest of multi-electrodes with a new current type. METHOD The experiment was conducted on 8 healthy male volunteer subjects (P.E. students, 1.72111, 75kg, 29 years). The subjects were seated with the knee flexed at 60degr. Trunk and thigh angle was fixed at 1 lode. A force transducer linked to a computer is fixed on the ankle. Electrostimulation was provided by mean of a SG4 apparatus. A reference electrode was secured over the femoral nerve and the active electrodes were put in regards of the motor point of VL,VM, and Vl muscle. Left and right legs are stimulated alternately. A symmetrical square wave signal with a 2 ms rest between positive and negative phase (150 s) was applied at 80 Hz frequency. RESULTS After an initial ramp a nearly flat curve corresponding to tetanos was reached. The stimulation procedure allows to reach 90% and 100% of MVC on the left and right leg respectively. After training session (18 periods) we got a similar result and force induced on the right leg about 110% of the force considered as MVC. DISCUSSION For beginners as well as after electrical training sessions inducing performance increase, the new muscular stimulation procedures proposed allow to get maximal contraction with a relative comfort. Most of the studies report that ES can induce nearly 70 to 80% of MVC. With the proposed technique we can reached quite easily 100% of MVC. This will be a powerful tool to improve maximal force.