The purpose of this study was to determine whether or not an erect and dynamic (facilitated) sitting posture demanded more work from the trunk musculature than a non-erect sitting posture (non-facilitated) when lower extremity movement occurred. EMG activity of the bilateral rectus abdominus and erector spinae was measured in 10 non-stroke and 5 stroke subjects ranging in age from 46 to 76 years of age. No significant differences in normalized EMG recordings were found between the two groups or between the muscle outputs elicited during facilitated, lower extremity movement and non-facilitated lower extremity movement. However, feedback from subjects suggest that it is possible that an erect and dynamic sitting posture can increase the tension generated by the trunk musculature in some individuals. Percents of maximal contraction were calculated for each muscle by dividing values obtained during facilitated and non-facilitated trails by the maximal recording obtained for each muscle. These percentages of maximal contraction were used for data analysis and revealed mean values over 100% which may suggest that lower extremity movement better recruits these muscles than volitional contractions. The variability in patterns of trunk muscle recruitment may indicate that there are a variety of patterns of muscle recruitment.
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