Marchant Ashleigh, Ball Nick, Witchalls Jeremy, Waddington Gordon, Mulavara Ajitkumar P, Bloomberg Jacob J
Research Institute for Sport and Exercise, University of Canberra, Canberra, ACT, Australia.
KBRWyle, Houston, TX, United States.
Front Physiol. 2020 Apr 17;11:318. doi: 10.3389/fphys.2020.00318. eCollection 2020.
Evaluating countermeasures designed to reduce the impact of microgravity exposure on astronaut performance requires the development of effective methods of assessing changes to sensorimotor function in 1g analog systems. In this study, somatosensation at the ankle and fingers, lower leg muscle activity and visuomotor control were assessed using a full body loading and acute unloading model to simulate microgravity. It was hypothesized that the function of the hands and eyes are not constrained to 'weight bearing' postures for optimal function and would not differ between the loaded and acute unloaded conditions, whereas lower leg muscle activity and ankle somatosensation would be reduced in the acute unloaded condition. Somatosensation was recorded using the Active Movement Extent Discrimination Apparatus (AMEDA) protocol where participants were required to make an absolute judgment of joint position sense. A score closer to 1.0 demonstrates higher accuracy. Lower leg muscle activity was recorded using electromyography of major lower leg musculature to observe peak muscle activity and duration of contraction. The King Devick infrared eye tracking test was used to asses visuomotor control by monitoring saccade velocity and fixation time. In acute unloading, it was found that ankle somatosensation had decreased accuracy (loaded 0.68, unloaded 0.66, = 0.045) while finger somatosensation improved (loaded 0.77, unloaded 0.79, = 0.006). When acutely unloaded, peak lower leg muscle activation reduced ( > 27%) and total contraction time increased (2.02 × longer) compared to loading. Visuomotor assessment results did not vary between the loaded and acute unloaded postures, however the underlying techniques used by the participant to complete the task (saccade velocity and fixations time) did increase in acute unloaded conditions.
This research provides an insight to how to the human body responds immediately to acute changes of gravitational load direction. It provides insight to the acute affects' astronauts may encounter when in microgravity.
评估旨在减少微重力暴露对宇航员表现影响的对策，需要开发有效的方法来评估1g模拟系统中感觉运动功能的变化。在本研究中，使用全身加载和急性卸载模型来模拟微重力，评估了脚踝和手指的本体感觉、小腿肌肉活动以及视觉运动控制。研究假设，手和眼的功能并不局限于“负重”姿势以实现最佳功能，并且在加载和急性卸载条件下不会有所不同，而在急性卸载条件下小腿肌肉活动和脚踝本体感觉会降低。使用主动运动范围辨别仪（AMEDA）协议记录本体感觉，参与者需要对关节位置感进行绝对判断。分数越接近1.0表明准确性越高。使用小腿主要肌肉组织的肌电图记录小腿肌肉活动，以观察肌肉活动峰值和收缩持续时间。使用金德维克红外眼动追踪测试通过监测扫视速度和注视时间来评估视觉运动控制。在急性卸载时，发现脚踝本体感觉准确性降低（加载时为0.68，卸载时为0.66，P = 0.045），而手指本体感觉提高（加载时为0.77，卸载时为0.79，P = 0.006）。与加载相比，急性卸载时小腿肌肉激活峰值降低（>27%），总收缩时间增加（延长2.02倍）。视觉运动评估结果在加载和急性卸载姿势之间没有差异，然而参与者完成任务所使用的潜在技术（扫视速度和注视时间）在急性卸载条件下确实有所增加。
本研究为人体如何立即响应重力负荷方向的急性变化提供了见解。它为宇航员在微重力环境中可能遇到的急性影响提供了见解。
