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1. XIX CONGRESS OF THE INTERNATIONAL SOCIETY OF ELECTROPHYSIOLOGY AND KINESIOLOGY Brisbane, Australia, 19-21 July 2012 An electromyographic study in vasti muscles during open kinetic and closed kinetic chain submaximal isometric exercises L. Spairani1, M. Barbero2, C. Cescon2, F. Combi3, T. Gemelli3, G. Giovanetti3,B. Magnani 3,4, G. D’Antona4,5 (1) Human Anatomy Unit, Department of Experimental Medicine, University of Pavia, Italy; (2) Department of Health Sciences, University of Applied Sciences and Arts of Southern Switzerland, SUPSI, Manno, Switzerland; (3) CRIAMS ,Interdepartmental Resource Center of Motor and Sports Activities, University of Pavia, Italy; (4) Institute of Motory Sciences, University of Pavia, Italy; (5) Human Physiology Unit, Department of Physiology & Interuniversity Institute of Myology, University of Pavia, Italy INTRODUCTION:The rehabilitation programs for patellofemoral dysfunction have been focused on vastusmedialisobliquus muscle training in an attempt to improve patellar tracking. Aim of the present study was to examine the myoelectric manifestations of muscle activation and fatigue in vastusmedialislongus (VML), vastusmedialisobliquus (VMO) and vastuslateralis (VL) at different knee joint angles during sustained isometric contractions using open kinetic chain knee extension and closed kinetic chain leg press. MATERIALS AND METHODS: Surface EMG signals were recorded with linear adhesive arrays of four electrodes from fourteen healthy young men (Age 23.5±3.2, meanSD) during isometric knee extension contractions at 10% and 60% of the maximum voluntary contraction (MVC) for 1 min and 20 s respectively at 30, 60 and 90 degrees knee joint angle. Initial values and rate of change (slope) of mean frequency (MNF), average rectified value (ARV) and conduction velocity (CV) of the EMG signal were calculated. RESULTS:Comparisons between the two force levels revealed that the initial values of ARV and CV for the VL, VML and VMO muscle were greater at 60% MVC compared to 10% MVC (3-way ANOVA; F=536; P<0.001, F=49: P<0.01 for ARV and CV respectively). Comparisons between the different muscles demonstrated lower initial values of CV for VMO compared to VL and VLM at 10% and 60% of MVC (F=15; P<0.05). In addition, initial estimates of ARV were higher for VMO compared to VML at both force levels (F=66; P<0.05). Comparisons between open and closed kinetic chain exercises revealed higher initial estimates of ARV for open kinetic chain knee extension at both force levels (F=62; P<0.01). In addition, the rate of change of MNF appeared to increase at higher angles for closed kinetic chain at 60% MVC while it was minimum at 60° degrees for open kinetic chain. No significant differences were observed in the rate of change of CV and MNF for the three muscles. CONCLUSIONS: These findings showed that both open and closed kinetic chain exercise activate equally the three portions of the quadriceps muscle, suggesting that selective training of the muscle is not achievable in these conditions. REFERENCES Haff, G.G., M. Stone, H. O'Bryant, E. Harman, C. Dinan, R. Jolmson, and K-H. Han. Force-time dependent char-acteristics of dynamic and isometric muscle actions. J. Strength and Cond. Res. 11(4):269-272. 1997 R. Sahaly, H. Vandewalle, T. Driss, H. Monod Maximal voluntary force and rate of force development in humans – importance of instructionEur J ApplPhysiol (2001) 85: 345–350 Bemben, M.G., Massey, B.H., Boileau, R.A. and J.E. Misner. Reliability of isometric force-time curve parameters for men aged 20 to 79 years. J. Appl. Sport Sci. Res. 6(3):158-164. 1992 G. J. Wilson and A. J. Murphy, The use of isometric tests of muscular function in athletic assessment, SportsMed.22(1), 19-37 (1996). HeliValkeinen, JariYlinen, EskoMalkia, MarkkuAlen, KeijoHakkinenMaximal force, force/time and activation/coactivation characteristics of the neck muscles in extension and flexion in healthy men and women at different ages Eur J ApplPhysiol (2002) 88: 247–254 Corresponding author: lorenzo.spairani@unipv.it