Finger coordination during moment production on a mechanically fixed object

Shim, Jae Kun; Latash, Mark L.; Zatsiorsky, Vladimir M.

doi:10.1007/s00221-004-1859-4

Cited by 36 publications

(43 citation statements)

References 18 publications

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“…In particular, Salter and Darcus (1952) report higher peak pronation torque magnitudes at some elbow flexion angles but not at others. A more recent study (Shim et al 2004b) reported somewhat higher torque magnitudes during supination efforts. To our knowledge, no study compared indices of variability in torque production tasks into pronation and supination.…”

Section: Moment Of Force Of Its Variabilitymentioning

confidence: 86%

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Accurate production of time-varying patterns of the moment of force in multi-finger tasks

2006

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We investigated the production of time profiles of the total moment of force produced in isometric conditions by the four fingers of a hand. We hypothesized that these tasks would be associated with multi-finger synergies stabilizing the time profile of the total moment across trials but not necessarily stabilizing the time profile of the total force produced by the fingers. We also expected the multifinger synergies to prevent an increase in the moment variability with its magnitude. Seated subjects pressed on force sensors with the four fingers of the right hand and produced two time profiles of the total moment of force, starting from a certain pronation effort, leading to a similar supination effort, and back to the initial pronation effort. One of the profiles was a sequence of straight lines (M-Ramp) while the other was a smooth curve (M-Sine). The subjects showed an increase in the total force during each task. This was accompanied by an increase in the force produced by the fingers opposing the required direction of the total moment-antagonist fingers. Variability of the total force and of the total moment showed complex, non-monotonic changes with the magnitude of the force and moment, respectively. In both tasks, the subjects showed patterns of co-variation of commands to fingers that stabilized the required moment profile over trials. The time profile of the total force was stabilized to a lesser degree or not stabilized at all. The share of fingers with larger moment arms (index finger for pronation efforts and little finger for supination efforts) was higher when the fingers acted to produce moments in a required direction but not necessarily when they acted as antagonists. The results demonstrate the existence of multi-finger synergies stabilizing the combined rotational action. They fit a hypothesis that stabilization of rotational actions may be a default strategy conditioned by everyday experience. The data also suggest that the mechanical advantage hypothesis is valid for sets of effectors that act in the required direction but not for sets of effectors that act as antagonists.

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Section: Moment Of Force Of Its Variabilitymentioning

confidence: 86%

“…Shim et al 2004b), and involvement of the thumb (Olatsdottir et al 2005). We would like to note, however, that at least one study reported high indices of moment-stabilizing synergies during more natural grasping tasks (Shim et al 2004a).…”

Section: Concluding Commentsmentioning

confidence: 97%

Accurate production of time-varying patterns of the moment of force in multi-finger tasks

2006

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“…Earlier studies have suggested the mechanical advantage hypothesis (Buchanan et al 1989;Prilutsky 2000;Zatsiorsky et al 2002;Shim et al 2004a), which states that effectors (muscles or digits) with longer lever arms contribute more to the total rotational action as compared to effectors with shorter lever arms. In our study, two fingers (I and M) produced PR moments (M PR ) while two other fingers (R and L) produced SU moments (M SU ).…”

Section: Moment Production By Individual Fingersmentioning

confidence: 99%

“…Only a handful of studies explicitly addressed the rotational action by the hand (e.g., Johansson et al 1999;Latash et al 2004). In particular, studies of finger force co-variation across static tasks withholding an object have suggested that the control of the hand action can be represented as a superposition of two processes, the control of the gripping action and the control of the rotational action (Shim et al 2003(Shim et al , 2004a). As such, hand control seems to obey the principle of superposition introduced in robotics (Arimoto et al 2000(Arimoto et al , 2001; according to this principle, some complex tasks performed by a set of effectors may be more efficiently controlled if they are decomposed into sub-tasks that have their own controllers with no interference with each other.…”

Section: Multi-finger Synergies Stabilizing Rotational Hand Actionmentioning

confidence: 99%

Finger synergies during multi-finger cyclic production of moment of force

2006

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We investigated multi-finger synergies stabilizing the total moment of force and the total force when the subjects produced a quick cyclic change in the total moment of force. The seated subjects performed the task with the fingers of the dominant arm while paced by the metronome at 1.33 Hz. They were required to produce a rhythmic, sine-like change in the total pronation-supination moment of force computed with respect to the midpoint between the middle and ring fingers. The framework of the uncontrolled manifold hypothesis was used to compute indices of stabilization of the total moment and of the total force across 20 cycles. Variance of the total moment showed a cyclic pattern with peaks close to the peak rate of the moment change. Variance of the total force was maximal close to peak moment into supination. Higher magnitudes of the moment directed against the required moment direction (antagonist moment) were produced by individual fingers during supination efforts as compared to pronation efforts. Indices of multi-finger synergies showed across-trials stabilization of the total moment over the whole cycle but not of the total force. These indices were smaller during supination efforts. We conclude that the central nervous system facilitates multi-finger synergies stabilizing the total rotational action across a variety of tasks. Synergies stabilizing the total force are not seen in tasks that do not explicitly require accurate force control. Pronation efforts are performed more efficiently and with better stabilization of the action.

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“…In particular, manipulative tasks have been investigated in order to understand this inherent trait of the neuromotor system [4][5][6][7][8] . Because of its singular mechanical structure, the hand stands out as a "convenient" tool in the study of the problem of motor redundancy 9 .…”

Section: Introductionmentioning

confidence: 99%

Efeito da posição da articulação do cotovelo no controle de torque de supinação do antebraço em jovens adultos

Borges¹,

Rodrigues²,

Loss³

et al. 2007

Rev. bras. fisioter.

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Background: large numbers of cases of pathological conditions in the forearm and elbow that have been reported in the literature are associated with tasks involving effort and repetitive movements of the arms and hands. Elbow position is known to affect the production of maximum forearm supination torque, and is a critical factor in designing appropriate therapeutic exercises. However, to our knowledge, there are no data on the effects of elbow position on tasks requiring control over submaximal torque levels. objective: this study investigated the effects of elbow position on the production of maximum isometric forearm supination torque, and on constant and continuous torque control at different submaximal torque levels. method: Sixteen young adults (24.7 ± 2.2 years old) were asked to perform two tasks: production of maximum lateral pinch torque (thumb and index finger) and controlled lateral pinch constant torque. Both tasks were evaluated at four different elbow positions (free position, 0°, 45° and 90° of elbow flexion) and three submaximal levels of lateral pinch torque production (20%, 40% and 60%). maximal torque, variability, irregularity and accuracy of the motor response were used as dependent variables. Results: greater torque values were found when the elbow joint was not restricted. the torque control tasks were not affected by the elbow position. However, greater variability and irregularity and lower accuracy in torque response were recorded with progressively increased submaximal torque levels. Conclusion: the results suggest that elbow position is not a determining factor for rehabilitation exercises that include torque control, in relation to forearm supination.

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Finger coordination during moment production on a mechanically fixed object

Cited by 36 publications

References 18 publications

Accurate production of time-varying patterns of the moment of force in multi-finger tasks

Accurate production of time-varying patterns of the moment of force in multi-finger tasks

Finger synergies during multi-finger cyclic production of moment of force

Efeito da posição da articulação do cotovelo no controle de torque de supinação do antebraço em jovens adultos

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