Mravcsik Mariann, Botzheim Lilla, Zentai Norbert, Piovesan Davide, Laczko Jozsef
Department of Computational Sciences, Wigner Research Centre for Physics, Budapest, H-1121 Hungary.
Department of Information Technology and Biorobotics, Faculty of Sciences, University of Pécs, H-7624 Hungary.
J Hum Kinet. 2021 Jan 29;76:175-189. doi: 10.2478/hukin-2021-0053. eCollection 2021 Jan.
Arm cycling on an ergometer is common in sports training and rehabilitation protocols. The hand movement is constrained along a circular path, and the user is working against a resistance, maintaining a cadence. Even if the desired hand trajectory is given, there is the flexibility to choose patterns of joint coordination and muscle activation, given the kinematic redundancy of the upper limb. With changing external load, motor noise and changing joint stiffness may affect the pose of the arm even though the endpoint trajectory is unchanged. The objective of this study was to examine how the crank resistance influences the variances of joint configuration and muscle activation. Fifteen healthy participants performed arm cranking on an arm-cycle ergometer both unimanually and bimanually with a cadence of 60 rpm against three crank resistances. Joint configuration was represented in a 3-dimensional joint space defined by inter-segmental joint angles, while muscle activation in a 4-dimensional "muscle activation space" defined by EMGs of 4 arm muscles. Joint configuration variance in the course of arm cranking was not affected by crank resistance, whereas muscle activation variance was proportional to the square of muscle activation. The shape of the variance time profiles for both joint configuration and muscle activation was not affected by crank resistance. Contrary to the prevailing assumption that an increased motor noise would affect the variance of auxiliary movements, the influence of noise doesn't appear at the joint configuration level even when the system is redundant. Our results suggest the separation of kinematic- and force-control, via mechanisms that are compensating for dynamic nonlinearities. Arm cranking may be suitable when the aim is to perform training under different load conditions, preserving stable and secure control of joint movements and muscle activations.
在运动训练和康复方案中,在测力计上进行手臂骑行运动很常见。手部运动沿圆形路径受限,使用者需克服阻力并保持一定节奏。即使给定了期望的手部轨迹,由于上肢的运动冗余性,仍有选择关节协调模式和肌肉激活模式的灵活性。随着外部负荷的变化,即使端点轨迹不变,运动噪声和关节刚度的变化也可能影响手臂姿势。本研究的目的是研究曲柄阻力如何影响关节构型和肌肉激活的方差。15名健康参与者在手臂骑行测力计上以60转/分钟的节奏单臂和双臂进行曲柄运动,对抗三种曲柄阻力。关节构型在由节段间关节角度定义的三维关节空间中表示,而肌肉激活在由四块手臂肌肉的肌电图定义的四维“肌肉激活空间”中表示。曲柄运动过程中的关节构型方差不受曲柄阻力影响,而肌肉激活方差与肌肉激活的平方成正比。关节构型和肌肉激活的方差时间曲线形状不受曲柄阻力影响。与普遍认为运动噪声增加会影响辅助运动方差的假设相反,即使系统具有冗余性,噪声的影响在关节构型层面也未出现。我们的结果表明,通过补偿动态非线性的机制,运动控制和力控制是分离的。当目标是在不同负荷条件下进行训练,同时保持对关节运动和肌肉激活的稳定和安全控制时,手臂曲柄运动可能是合适的。