Department of Physical Medicine and Rehabilitation, Michigan Medicine, Ann Arbor, MI, USA; Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
Department of Physical Medicine and Rehabilitation, Michigan Medicine, Ann Arbor, MI, USA; Michigan Robotics Institute, University of Michigan, Ann Arbor, MI, USA.
Gait Posture. 2021 Oct;90:334-339. doi: 10.1016/j.gaitpost.2021.09.189. Epub 2021 Sep 20.
Functional resistance training is frequently applied to rehabilitate individuals with neuromusculoskeletal injuries. It is performed by applying resistance in conjunction with a task-specific training, such as walking. However, the benefits of this training may be limited by motor slacking, a phenomenon in which the human body attempts to reduce muscle activation levels or movement excursions to minimize metabolic- or movement-related costs. While kinematic feedback could reduce one's tendency to minimize effort during training, this has not been verified experimentally.
Does functional resistance training during walking lead to motor slacking, and can techniques such as visual feedback be used to reduce these effects?
Fourteen able-bodied individuals participated in this experiment. Participants were trained by walking on a treadmill while a bidirectional resistance was applied to the knee using a robotic knee exoskeleton. During training, participants were either instructed to walk in a manner that felt natural or were provided real-time visual feedback of their kinematics. Electromyography and knee kinematics were measured to determine if adding resistance to the limb induced slacking and if feedback could reduce slacking behavior. Kinematic aftereffects were measured after training bouts to gauge adaptation.
Functional resistance training without feedback significantly reduced knee flexion when compared to baseline walking, indicating that participants were slacking. This reduction in knee flexion did not improve with continued training. Providing visual feedback of knee joint kinematics during training significantly increased knee muscle activation and kinematic aftereffects.
The findings indicate that individuals are susceptible to motor slacking during functional resistance training, which could affect outcomes of this training. However, motor slacking can be reduced if training is provided in conjunction with a feedback paradigm. This finding underscores the importance of using additional methods that externally motivate motor adaptation when the body is not intrinsically motivated to do so.
功能性抗阻训练常用于康复神经肌肉骨骼损伤患者。它通过结合特定任务的训练（如行走）来施加阻力。然而，这种训练的益处可能会受到运动松弛的限制，即人体试图降低肌肉激活水平或运动幅度，以最小化代谢或运动相关的成本。虽然运动学反馈可以减少训练过程中最小化努力的趋势，但这尚未通过实验验证。
行走时进行功能性抗阻训练是否会导致运动松弛，视觉反馈等技术是否可以用来减少这种影响？
14 名健康个体参与了这项实验。参与者在跑步机上行走时，使用机器人膝关节矫形器对膝关节施加双向阻力。在训练过程中，参与者被指示以自然的方式行走，或者实时反馈他们的运动学信息。肌电图和膝关节运动学被测量，以确定向肢体施加阻力是否会导致松弛，以及反馈是否可以减少松弛行为。在训练回合后测量运动学后效，以评估适应情况。
与基线行走相比，无反馈的功能性抗阻训练显著降低了膝关节的屈曲，这表明参与者存在运动松弛。这种膝关节屈曲的减少并没有随着持续的训练而改善。在训练过程中提供膝关节运动学的视觉反馈显著增加了膝关节肌肉的激活和运动学后效。
这些发现表明，个体在进行功能性抗阻训练时容易出现运动松弛，这可能会影响这种训练的效果。然而，如果在训练过程中结合反馈范式，可以减少运动松弛。这一发现强调了在身体没有内在动机时，使用额外的方法来外部激发运动适应的重要性，因为这些方法可以激发运动适应。
