Résumé
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.