Abstract
[Purpose] We investigated the characteristics of electromyographic trunk muscle activities and the relationship between the trunk muscle activities and postural sway during unstable sitting. [Subjects] Ten people (25.1 ± 4.4 years old) participated in this study. [Methods] Electromyographic trunk muscle activities and postural sway were evaluated during unstable sitting and stable sitting. [Results] Abdominal muscles were activated significantly more higher in unstable sitting than in stable sitting. Also, rectus abdominis, thoracic and lumbar erector spinae muscles activities that could be classified as global muscle activity and postural sway correlated significantly, but local muscle activity did not. [Conclusion] The results suggest that rectus abdominis, thoracic and lumbar erector spinae muscle activities that can be classified as global muscle activity influence the balance ability during unstable sitting.
