腰痛性間欠跛行に伴う体幹前傾化に対する重錘負荷の影響

Effect of External Weights on Forward Bending Motion of the Trunk in Patients with Intermittent Claudication due to Low Back Pain

　高齢者には，歩行や立位で腰痛とともに体幹前傾化が発生し間欠跛行を呈する病態（腰痛性間欠跛行：ICLBP）が存在する．その病態解明のため，重錘負荷時の姿勢変化と体幹筋活動について検討した．その結果，健常者と比較して，体幹傾斜角度には顕著な前傾化が，角速度には有意な変動が認められた．一方，傍脊柱筋の平均筋電量には大きな活動（過活動現象）が，平均パワー周波数には周波数成分の徐波化（筋疲労現象）が認められた．すなわち，ICLBPに対する重錘負荷は傍脊柱筋の過活動と筋疲労を惹起して体幹前傾化を促進する．

　The pattern of motion of the trunk and the trunk muscle activity in patients with intermittent claudication due to low back pain (ICLBP) was simultaneously examined by imposing external weights to investigate the influence of ICLBP on forward bending motion of the trunk in the assessment of ability to maintain the trunk in the upright position. No significant forward bending motion occurred in the control group, and there were no differences in averaged EMG (AEMG) between the rectus abdominis muscles (RAMs) and the erector spinae muscles (ESMs) or in rate of change in the median power frequency (MPF). In the ICLBP group, there was a temporal increase in forward bending motion at various speeds in various time phases, and the AEMG of the ESMs was significantly higher than that of the RAMs. In addition, the rate of change in MPF of the ESMs had declined significantly, compared to the rate in the control group. The results of this study confirmed that overactivity and fatigue of back muscles associated with forward bending motion of the trunk are involved in chronic low back pain.