THE EFFECTS OF ABDOMINAL BRACING MANEUVER ON QUADRICEPS MUSCLE TORQUE, TIME TO PEAK TORQUE AND MUSCLE ACTIVATION LEVELS AT DIFFERENT KNEE FLEXION ANGLES

Purpose: The aim of the present study was to investigate the effects of abdominal bracing maneuver (ABM) on quadriceps peak torque (PT), time to peak torque (TTPT) and muscle activation levels during maximal strength testing of the quadriceps muscle in healthy individuals. Methods: Sixteen healthy individuals (Age: 24.63 +/- 1.67 years) participated in the present study. Each participant was taught ABM technique by a physical therapist's guidance. Surface electromyography was used to measure internal oblique/transversus abdominis, vastus medialis, vastus lateralis, and rectus femoris activation levels. Isokinetic dynamometry was used to measure quadriceps PT and TTPT during maximum isometric muscle testing at 60 degrees and 90 degrees of knee flexion angles with and without ABM. Repeated measures of ANOVA was performed for statistical analysis. Results: There was a significant angle by condition interaction for quadriceps PT (F(1,15)=5.30, p=0.04). PT decreased when ABM was performed, but the decrease was greater at 600 compared to 900 of knee flexion (60 degrees: p=0.001, ES=0.68; 90 degrees: p=0.008, ES=0.33). Quadriceps activation levels also decreased during ABM (p=0.04) regardless of knee flexion angle. Conclusion: The present study revealed that ABM may decrease muscle activation levels and peak torque during maximal quadriceps strength testing. Researchers should evaluate compensatory movements of the lumbopelvic region in order to prevent the error of force transfer in test results