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.
Adult ; Electromyography ; Humans ; Isometric Contraction ; Leg* ; Muscles* ; Paraspinal Muscles ; Quadriceps Muscle ; Rectus Abdominis

PURPOSE: The aim of this study was to investigate the changes of contraction patterns and the differences of activities in trunk muscles during dynamic balance (multidirectional tilting exercise). METHODS: Eight physically active male subjects participated in the study. Tilting exercises were included by four directions (i.e., forward, backward, left, and right side), and were undertaken at three different tilting degrees (i.e., 10°, 20°, and 30°). They performed two occasions of tilting exercise, separated by 6-week time interval. Surface electromyography system was used for record of any signals produced by muscles which normalized as percentage of maximum voluntary isometric contraction. RESULTS: There were no statistically significant different interactive effects in any of muscles between two factors (time vs. degree). However, we identified significant main effects of degrees (among 10°, 20°, and 30°) in muscle activations during maintaining with forward tilting (left and right longissimus, multifidus), backward tilting (left and right rectus abdominis, external oblique), left side tilting (right rectus abdominis, external oblique, longissimus, multifidus), right side tilting (left rectus abdominis, external oblique, longissimus, multifidus). CONCLUSION: Findings from this study allow the multidirectional tilting exercise to be considered as suitable for ameliorate muscle balance by inducing co-contraction in trunk muscles.
Electromyography ; Exercise ; Humans ; Isometric Contraction ; Male ; Muscles ; Rectus Abdominis