The influence of electrical stimulation on strength and swimming performance

Abstract

s-International Society of Biomechanics XIV Congress 1993 683 THE INFLUENCE OF ELECIXICAL STIh4ULATION ON STRENGTH AND SWIMMING PERFORMANCE Florence Pichon and Gillea Cometti Laboratoire d’Etude et de Recherche sur la Performance Sportive UFR-STAPS, Universitt! de Bourgogne, B.P 138,210OO Dijon, France. This study aims to examine the influence of a three week’s cycle of electrical stimulation on latissimus dorsi on strength development and swimming performance. Eighteen regional and national standard sprint swimmers were divided into two groups : the control group (N=8) and the study group (N=8) underwent with electrostimulation sessions (three sessions a week during three weeks) in addition to swimming training. Sessions are carried out using a portable stimulator (stywel) and lasted 12 minutes, the contraction time was five seconds and the rest one was 15 seconds. A biodex type (Biodex Corporation, Shirley, NY, USA) isokinetic ergometer was used to measure the maximum torque values developed over the arm flexion-extension movement at different velocities (-120, -6O,O, 60, 120, 180,240,300, 360%). Therefore, special tests in the pool (50 meters arms only and full movement) were carried out. At the end of training, the results for electrostimulated swimmers show a significant difference in peak torque concentrically at velocity of 180/s and 36O”/s and in peak torque isometrically (with ~4~05). Moreover an improvement of 0,44 s (p&,05) is recorded for the 50 meters full movement. While the control group showed no significant difference for all tests. A electrostimulation training for three weeks could be the consequence of a preferential solicitation of muscular type IIb fibres. The important improvements find in swimming indicate that electrostimulation training must be used in planning of swimmers. AN ATHLETIC SHOE AGAINST HYPERINVERSION IN THE ANKLE DURING HIGH LOAD PERFORMANCE Mark R.Pitkin Iv2 1 Department of Rehabilitation Medicine Tufts University, Boston, MA 02111, USA. ’ Newman Laboratory for Biomechanics and Human Rehabilitation, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. This work relates to an athletic shoe design made to reduce the risk of injury of the subt,alar joint. Said injury occurs when the ankle moves in frontal plane from neutral to the inverted position and the bending torque of the external forces becomes more than the counterresistance of the joint,‘s ligaments. Biomechanical analysis of the incorporation of the borders, wrapping, torsion sole, flaring, various midsole hardness did not prove their effectiveness in protection of l igaments in t,he subtalar joint. A model of the subtalar joint r&istance has been developed, which enabled to propose a new design of the athletic shoe, protecting subtalar joint from hyperinversion. The shoe has two soles having the shape of the controversial wedges in the frontal cross section, which are elastically connected. A shift of the upper sole in the lateral direction provides the lifting of its lateral upper edge, while its medial upper edge goes down. MUSCULAR SYNERGY PATTERNS IN WEIGHTLImING. A FOLLOW-UP STUDY R.Pozzo, M.Jahn, Institute of Biomechanics, Cologne, Germany In order to identify individual and general strategies in the motor control, combined analysis of EMG and of the biomechanical structure (Ground Reaction Forces, barbell kinematics) of the movement ( competitive movements and assistant exercises) were carried out during the training (5 months) of 6 elite weightlifters. AAer recording of myoelectrical potentials (CMRR r 70 db, BP= 1OHz lKHz, Zin= 1,s MQ , gain= 1000) EMG signals were full wave rectified, root mean squared and low-pass filtered (70 Hz). The intermuscular activity patterns (IMAP) of VM, BF, TR and BB are representative of the main characteristics of the movement sequences. For the pull phase of snatch and clean two main patterns were identified. By comparing the kinematics and kinetics of the movements with the EMG patterns, indicators of the “technique” goodness are indentified. By means of regression analysis the individual adaptation processes with respect to the variation of the load and to the type of exercise were determined in terms of traning induced effects. Differences in the IMAP are not necessarily matching similar variations in the GRF and barbell kinematics. This is essential for the usefullness of GRF as interpretative and diagnostic indicator in training. The analysis of the interphasic relations between the peak values of GRF, barbell velocity and EMG amplitude and between the EMG onset of different muscles permits to compare the neuromuscular strategies of these multi-joint movements with theoretical models (equlibrium-point hypothesis, speed strategy).