Cole K J, Abbs J H
J Neurophysiol. 1987 May;57(5):1498-510. doi: 10.1152/jn.1987.57.5.1498.
Kinematic and electromyographic responses of the thumb and index finger to load-induced extension of the thumb during a rapid precision grasp of the thumb and finger were studied in four human subjects. Angular position of the index finger metacarpophalangeal (MP) and proximal interphalangeal (PIP) joints was recorded along with the linear position of the thumb tip (TH). Myoelectric activity was recorded from flexor pollicis longus, flexor digitorum superficialis, first dorsal interosseous, and extensor digitorum communis. Loads that extended the thumb were applied ranging from 125 ms prior to movement onset to movement onset. For loads applied earlier than 50 ms before movement onset, the amount of flexion of TH was reduced compared with control trials. Contact between the finger and thumb was attained nonetheless due to an altered trajectory of the fingertip that was generated by reduced flexion of PIP and increased flexion of MP. These finger responses appear to be functional in that contact of the finger pulp on the more distal pulp of the thumb was preserved. With loads delivered near onset of the grasp, there was increased PIP flexion, rather than reduced PIP flexion. These responses to later loads occurred despite greatly reduced magnitudes of TH flexion compared with loads delivered well before onset of the gasp movements. Thus reduced PIP flexion observed with early loads was not simply the result of finger biomechanics. The thumb flexor muscle increased activity 45-55 ms after onset of the load, whereas responses of the finger flexors began 65 ms after load onset. Response magnitudes decreased as loads were introduced nearer to movement onset. Measured reaction times of the finger muscles to thumb extension stimuli averaged 154 ms, which indicated that the responses of the finger muscles were not voluntary responses to the thumb extension. Afferent information generated by perturbation of the thumb during a grasp movement can influence the activity of intrinsic and extrinsic muscles to yield apparently functional compensations in the closing movements. However, temporal limitations exist that appear to offer greater constraints on the use of afferent signals for controlling rapid movements than for sustained grasp.
在四名人类受试者中，研究了在拇指和手指快速精确抓握过程中，拇指和食指对由负载引起的拇指伸展的运动学和肌电图反应。记录了食指掌指（MP）关节和近端指间（PIP）关节的角位置以及拇指尖（TH）的线性位置。从拇长屈肌、指浅屈肌、第一背侧骨间肌和指总伸肌记录肌电活动。在运动开始前125毫秒至运动开始期间施加使拇指伸展的负载。对于在运动开始前50毫秒之前施加的负载，与对照试验相比，TH的屈曲量减少。尽管如此，由于PIP屈曲减少和MP屈曲增加所产生的指尖轨迹改变，手指与拇指之间仍实现了接触。这些手指反应似乎是有功能的，因为手指掌面与拇指更远端掌面的接触得以保留。在抓握开始时附近施加负载时，PIP屈曲增加，而不是减少。尽管与在抓握运动开始前很久施加的负载相比，TH屈曲的幅度大大减小，但对后期负载仍出现这些反应。因此，早期负载时观察到的PIP屈曲减少不仅仅是手指生物力学的结果。拇指屈肌在负载开始后45 - 55毫秒活动增加，而手指屈肌的反应在负载开始后65毫秒开始。随着负载在更接近运动开始时引入且反应幅度减小。手指肌肉对拇指伸展刺激的测量反应时间平均为154毫秒，这表明手指肌肉的反应不是对拇指伸展的自主反应。在抓握运动期间拇指扰动产生的传入信息可影响内在和外在肌肉的活动以在闭合运动中产生明显的功能补偿。然而，存在时间限制，这似乎对使用传入信号控制快速运动比控制持续抓握施加了更大的约束。
