目的 观察躯干均匀负重和非负重状态下静态前屈和后伸时腰背部、腹部及臀中肌的肌电活动规律和运动学特征。方法6位正常健康的男性受试者直腿站立于特殊设计的试验框架和平台内做静态前屈和后伸的负重和非负重动作，每次试验持续4 s，重复3次。动作时，记录双侧腰臀部的10块肌肉：腹直肌、腹外斜肌、竖脊肌、多裂肌、臀中肌的肌电活动，以及三维角度运动轨迹和足底力系。计算标准化肌电、腰部躯干角和足底中心压力的位移。将所得数据作常规的统计分析。结果 负重和非负重前屈时，都是背侧肌活动较大(10.47~16.94)。非负重后伸时，腹侧肌活动也较大；负重后，背侧肌（3.70~17.95）和臀中肌（6.64~11.52）活动增加，腹肌活动减少（10.66~4.18）。后伸时，躯干的闪动次数随负重增加而增多，在3D角上增加1.55次；负重后，足底中心压力向前后的移动多于侧方移动，前屈的前后方移动（14.60）多于后伸的移动（7.65）。结论 后伸状态增加了背侧肌的活动，而且多裂肌更明显；同时，腰部角位移度和闪动次数增加，特别在后伸提重时更为显著。

Objective To observe the electromyography (EMG) activities and kinematic characteristics of the back, abdomen and hip muscles under the static symmetric loading and unloading with the flexion and extension posture. Methods Six healthy male subjects stood on a specially designed testing platform, doing flexion/extension under symmetric loading and unloading, respectively. Each trial lasted 4 seconds and was repeated 3 times. The EMG activities of 10 muscles(rectus abdominis，obliquus externus abdominis，erector spinae，multifidus，gluteus Medius), the 3D angular movement, the plantar COP (center of pressure) were recorded during the trial.The normalized EMG, trunk angle and COP displacement were calculated, and statistical analyses of all data were made. Results Muscle activities of the back were greater (10.47~16.94) with flexion both under loading and unloading. Muscle activities of the abdomen were greater with extension under unloading, and those of the back (3.70~17.95) and hip (6.64~11.52) were increasing under loading, with muscle activities of the abdomen decreasing (10.66~4.18). The flashing trunk numbers was increased with the increase of loading, especially 1.55-time increase in the trunk angle. The COP displacement in anterior posterior direction was shifted greater than that in lateral direction, and this shift was more during flexion (14.60) than that during extension (7.65).Conclusions Extension increases the activities of back muscles, especially for multifidus, and it also increases the torso angular displacement and flashing trunk numbers, especially under loading.

上海市自然科学基金项目（09ZR1430300），上海市人类运动能力开发与保障重点实验室项目资助（11DZ2261100）