ABSTRACT
The purpose of this study was to investigate the changes of electromyogram activity of trunk and lower leg muscles during dynamic balance control in 20 healthy adult subjects when various experimental visual conditions were applied. Surface electromyography system was used for recording of any signals produced by muscles. Muscle activity was recorded from muscles, of which left and right sides of rectus abdominis, external obliques, longissimus thoracis, multifidus, vastus medialis, biceps femoris, gastrocnemius medialis, and tibialis anterior, and then normalized as percentage of maximum voluntary isometric contraction. All data obtained from experiment were analyzed using SPSS ver. 20.0, and two-way analysis of variance were used to determine statistical significance between two factors (3x2 factorial analysis, visual conditions vs. leg conditions). Statistical significance levels were set at alpha=0.05. There were significant different in biceps femoris and external obliques muscle's activities between right and left leg, showing more prominent reduction in left leg when blind vision condition was given. Significantly higher muscle activities were shown in both sides of multifidus (p<0.05), vastus medialis (p<0.001), tibialis anterior (p<0.001) and gastrocnemius medialis (p<0.001) with sighted vision and blanking vision compared to the condition of blind vision. These results confirmed that muscle activity is prominently stimulated by visual information provision, and this implies that visual input may be a major factor for maintaining of the body's balance control.