Lift‐to‐lift variability occurs in repetitive lifting tasks due to alterations in the lifting techniques used by the lifter, resulting in variability in lower back tissue loading. Understanding how trunk variability changes with time in the initial phases of a lifting bout may provide insights into the risk of injury during work startup. The purpose of this study was to quantify the variation of lifting kinematics and kinetics during the initial phase of a lifting bout. Twenty participants performed a repetitive lifting task continuously for 30 min. The load was equivalent to 10% of each participant's body weight and lifting was done at a rate of six lifts/min. Kinematic variables (three‐dimensional range of motion, angular velocity, and angular acceleration) of the trunk were measured using the Lumbar Motion Monitor and a dynamic biomechanical model estimated peak L5/S1 moment and spine compression. The variances of these variables were compared across 10‐min intervals: 0–10 min, 10–20 min, and 20–30 min. Results indicate a significant reduction in the variance of the peak sagittal acceleration, the sagittal range of motion, the transverse range of motion, peak sagittal moment, and peak spine compression between the first and second time intervals, followed by no significant change in variance between the second and third intervals. The downward trend in variation of these kinematic and kinetic variables suggests an initial adjustment period as the lifters reach a steady state of their lifting technique. The reduced variance of spinal loading may reduce the probability that a tissue tolerance is exceeded.

中文翻译：

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在重复提升任务的早期阶段，躯干运动变化随时间的变化

由于升降器使用的举升技术发生变化，因此在重复举升任务中举升动作会发生变化，从而导致下背部组织负荷的变化。了解举重训练初始阶段的躯干可变性如何随时间变化，可以提供有关工作启动过程中受伤风险的见解。这项研究的目的是量化举重比赛初期举重运动学和动力学的变化。20名参与者连续执行了30分钟的重复举重任务。负荷相当于每个参与者体重的10％，以每分钟6次提升的速度进行提升。运动学变量（三维运动范围，角速度，使用腰椎运动监测器和动态生物力学模型估计的躯干L5 / S1峰值和脊柱压缩力来测量躯干的强度和角加速度。这些变量的方差在10分钟的间隔内进行比较：0-10分钟，10-20分钟和20-30分钟。结果表明，在第一时间间隔和第二时间间隔之间，矢状加速度峰值，矢状运动范围，横向运动范围，矢状力矩峰值和脊柱压缩峰值的方差显着减小，随后之间的方差无明显变化。第二和第三间隔。这些运动学和动力学变量变化的下降趋势表明，起重器达到其起重技术的稳定状态时，将进入初始调整期。