Electrical Stimulation Of Triceps Surae For Muscular Strength Improvement In Volleyball Players

Abstract

In order to show the influence of muscle strength on jumping and to evaluate the difference between the athletes and the normal subjects, an experiment was carried out on a group of 5 volleyball players (athletes) during the championship. The results were compared with a previous experiment carried out on a group of 6 young healthy people not involved in any sporting activity (normal). All the subjects were treated by means of electrical stimulation of the triceps surae to increase muscle strength and to check variations in jumping capacity. In fact the triceps surae is one of the main muscles activated for jumping and it is concerned with the plantar flexion of the foot. A sinusoidal current at the frequency of 2500 Hz was used; a stimulation time of 10 s was chosen, followed by a rest period of 50 s to avoid a reduction of the subsequent contraction force. This stimulation procedure was applied for 20 minutes per day for 15 days, using a 4 channel ST.E.4C. stimulator. In order to transduce the maximum spontaneous force developed by the triceps surae a special bed, with movable pedals whose support rotated around an axis made coincident with the rotation axis of the foot, was built; behind each pedal a small hollow cylinder was fixed in position by way of a "Uniball" knickle joint; the cylinder was suitably shaped and a strain gauge, working in bridge type configuration, was fitted to the pedal to transduce the axial force in isometric conditions. At the beginning of the stimulation, after 9 days and after 15 days the following measurements were performed on both legs: the maximum spontaneous force, the jump index (using Abalakov method) and the maximum circumference of the limbs in the relaxed state and at maximum spontaneous contraction. The results are summarized in the table: [table] This study shows the efficiency of the electrical stimulation for muscle strength even on athletes in very good form. It has been also analyzed the effect of muscle strength increase on the asymmetry between the forces of the two legs.