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Abstract

The kinematics of the hand and fingers were studied during various keystrokes in typing. These movements were defined by 17 degrees of freedom of motion, and methods were developed to identify simplifying strategies in the execution of the task. Most of the analysis was restricted to the 11 degrees of freedom of the fingers, neglecting thumb and wrist motion. Temporal characteristics of the motion were defined by computing principal components, and it was found that only a few (two to four) principal components were needed to characterize motion of each of the degrees of freedom. Hierarchical relationships among patterns within and between different degrees of freedom were identified using cluster analysis. There was a considerable amount of consistency each time a given keystroke was executed by a subject, and this repeatability may imply a reduction in the number of degrees of freedom independently controlled by the nervous system. However, there also appears to be considerable flexibility in the coordination of the many joints of the hand when examined across different keys and across different subjects.

Decoding of human hand actions to handle missing limbs in neuroprosthetics

“…These are just a few of the countless gestures we can use and learn. Anatomically, the hand comprises a total of 27 bones, 18 joints, and 39 muscles (Tubiana, 1981), which afford over 20 degrees of freedom (DOF) (Stockwell, 1981; Soechting and Flanders, 1997; Jones and Lederman, 2006). The number of degrees of freedom is an important characterization of the human hand because it defines the dimensionality of the control problem that has to be solved by the motor system.…”

Grasp-Based Functional Coupling Between Reach- and Grasp-Related Components of Forelimb Muscle Activity

“…The hand is the fore-limb's end effector; therefore, hand use essentially determines how we engage with our environment. Moreover, the hand encompasses the largest number of independent degrees of freedom in the forelimb (Soechting & Flanders, 1997), which makes it most efficient for the neuromotor control system to plan forelimb movements according to how hand-related degrees of freedom must be engaged to accomplish behavioral goals. Furthermore, most forelimb reaching movements involve precise manipulation of hand joints while proximal muscles transport, orient, or stabilize the hand, making it essential to control proximal forelimb muscles in the context of hand use.…”

Analyzing finger interdependencies during the Purdue Pegboard Test and comparative activities of daily living

“…Thus the proficient grasping of an object entails simultaneous motion at multiple joints, with correlated rotations 13 . Simultaneous correlated motion at multiple joints has been studied during more dexterous uses of the hand, such as typing 16 , playing the piano 17 , and haptic interactions 18 , but a standard procedure to assess such movement synergies has not been developed. Moreover, previous studies involved sets of tasks and hand postures or force patterns that were not specific enough to be immediately translated into assessment practice [19][20][21] .…”

“…More precisely, it assesses proficiency of one particular grasping pattern, the precision grip 16 . It has been shown, however, that there are several factors that account for hand manipulative task performance 5,[22][23][24][25] , and the degree with which the Purdue Pegboard Test assesses individual factors has yet to be investigated.…”