NEURAL INHIBITION DURING ECCENTRIC AND CONCENTRIC QUADRICEPS CONTRACTION: EFFECTS OF RESISTANCE TRAINING

Abstract

1178 The aim of this study was to examine the degree of neural inhibition during maximal volitional quadriceps activation, hypothesizing a diminished inhibition after resistance training. Quadriceps EMG and Moment of Force(KinCom) were obtained (1 kHz) during maximal isokinetic knee extensions in young sedentary males (n=15) pre and post 12 wks of heavy resistance training(36 sessions). Slow (30 °·s-1) and fast (240°·s-1) concentric and eccentric quadriceps contractions were tested between 90 ° and 10 ° knee joint angle (0 °=full extension). EMG of the lateral and medial vastii (VL,VM) and rectus femoris(RF) were rectified and smoothed by zero-lag, 4th order Butterworth filter. Subsequently, the average EMG between 30 ° and 70 ° joint angle was computed (iEMG divided by integration time). Prior to training EMG was lower(p<0.0001) in slow concentric, eccentric (30CON, 30ECC) and fast eccentric contraction (240ECC) compared to fast concentric contraction (240CON), indicating significant neural inhibition to appear. To quantify the degree of inhibition, EMG at 30CON, 30ECC, 240ECC were expressed relative to EMG obtained at 240CON: TableTableIn conclusion, substantial neural inhibition was observed for the quadriceps muscle. Post training this inhibition was reduced (VL,VM) or even completely removed (RF).