Objective

Spine kinematics, kinetics, and trunk muscle activities were evaluated during different stages of a fatigue-induced symmetric lifting task over time.

Background

Due to neuromuscular adaptations, postural behaviors of workers during lifting tasks are affected by fatigue. Comprehensive aspects of these adaptations remain to be investigated.

Method

Eighteen volunteers repeatedly lifted a box until perceived exhaustion. Body center of mass (CoM), trunk and box kinematics, and feet center of pressure (CoP) were estimated by a motion capture system and force-plate. Electromyographic (EMG) signals of trunk/abdominal muscles were assessed using linear and nonlinear approaches. The L5-S1 compressive force (Fc) was predicted via a biomechanical model. A two-way multivariate analysis of variance (MANOVA) was performed to examine the effects of five blocks of lifting cycle (C1 to C5) and lifting trial (T1 to T5), as independent variables, on kinematic, kinetic, and EMG-related measures.

Results

Significant effects of lifting trial blocks were found for CoM and CoP shift in the anterior–posterior direction (respectively p < .001 and p = .014), trunk angle (p = .004), vertical box displacement (p < .001), and Fc (p = .005). EMG parameters indicated muscular fatigue with the extent of changes being muscle-specific.

Conclusion

Results emphasized variations in most kinematics/kinetics, and EMG-based indices, which further provided insight into the lifting behavior adaptations under dynamic fatiguing conditions.

Application

Movement and muscle-related variables, to a large extent, determine the magnitude of spinal loading, which is associated with low back pain.

中文翻译：

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疲劳诱发的重复举重过程中脊柱运动学、动力学和躯干肌肉活动的综合评价

客观的

随着时间的推移，在疲劳引起的对称举重任务的不同阶段评估了脊柱运动学、动力学和躯干肌肉活动。

背景

由于神经肌肉的适应，工人在起重任务中的姿势行为会受到疲劳的影响。这些适应的综合方面仍有待研究。

方法

十八名志愿者反复举起一个盒子，直到感到筋疲力尽。身体质心 (CoM)、躯干和箱体运动学以及足部压力中心 (CoP) 通过运动捕捉系统和测力板进行估计。使用线性和非线性方法评估躯干/腹部肌肉的肌电图 (EMG) 信号。通过生物力学模型预测 L5-S1 压缩力 (Fc)。进行了双向多变量方差分析 (MANOVA) 以检查提升循环 (C1 到 C5) 和提升试验 (T1 到 T5) 的五个模块作为独立变量对运动学、动力学和 EMG 相关的影响措施。

结果

举重试块对 CoM 和 CoP 在前后方向的偏移（分别为p < .001 和p = .014）、躯干角度（p = .004）、垂直盒位移（p < .001）有显着影响, 和 Fc ( p = .005)。EMG 参数表明肌肉疲劳，变化程度因肌肉而异。

结论

结果强调了大多数运动学/动力学和基于 EMG 的指数的变化，这进一步提供了对动态疲劳条件下提升行为适应的洞察。

应用

运动和肌肉相关变量在很大程度上决定了与腰痛相关的脊柱负荷的大小。