Multi-digit maximum voluntary torque production on a circular object

Shim, Jae Kun; Huang, Junfeng; Hooke, Alexander W.; Latsh, Mark L.; Zatsiorsky, Vladimir M.

doi:10.1080/00140130601164516

Cited by 18 publications

(20 citation statements)

References 44 publications

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“…7% difference was observed in an anthropometric database (SizeKorea, 2012). In a previous study of twisting a circular object similar to door nap, clockwise torque with forearm supination was greater than counter-clockwise torque (Shim et al, 2007).…”

Section: )mentioning

confidence: 75%

Effect of Task Direction on the Maximal Pushing, Pulling, Twisting, and Grip Forces

Yoon¹

2016

Journal of the Ergonomics Society of Korea

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Objectiv e:The aims of this study are to understand the effects of task (pushing, pulling, and clockwise and counter clockwise twisting) direction on the maximal output and their grip forces and to explore the relationship between the maximal output and the grip forces.Background: Knowing the normative maximal grip force is not enough to design a good hand tool. The industrial designers should understand the required grip forces in various motions toward a specific direction to make an effective and efficient hand tool. Method:Eighteen healthy volunteers participated in the series of isometric maximal output force tests. A custom-made force measuring equipment collected the output and the grip forces for three seconds. Force measurements along the vertical, coronal and sagittal axes were randomly repeated three times. Results:The pulling was strongest and the pushing was weakest in all directions. The effect of motion on the output forces varied in different directions. The corresponding grip force increased in the order of pushing, pulling, clockwise twisting, and counter clockwise twisting in all directions. The maximal output and their grip forces were highly correlated but the relationship was affected by motion and direction. The regression coefficient was greatest in pulling and smallest in clockwise twisting. Conclusion:The effect of motion on the output forces varied in different directions. The maximal output and their grip forces were correlated but the relationship was affected by motion and direction.Application: Findings of this study can be valuable information for industrial designers to develop more productive hand tools and work stations to help preventing the musculoskeletal disorders at work.

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Section: )mentioning

confidence: 75%

Effect of Task Direction on the Maximal Pushing, Pulling, Twisting, and Grip Forces

Yoon¹

2016

Journal of the Ergonomics Society of Korea

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“…There have also been reports on possible differences in the neural control of tasks that require PR and SU efforts. In particular, higher peak moment magnitudes and higher synergy indices for the total moment of force have been reported for PR efforts, although in a different set of tasks that required moment of force production on a circular object (Shim et al 2007; Shim and Park 2007). During quick rotational actions at comparable speeds, higher normal forces were observed for actions into SU as compared to actions into PR (Zhang et al 2009).…”

Section: Discussionmentioning

confidence: 96%

Prehension synergies during smooth changes of the external torque

et al. 2011

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We studied characteristics of digit action and their co-variation patterns across trials (prehension synergies) during static holding of an object while the external torque could change slowly and smoothly. The subjects held in the air an instrumented handle with an attachment that allowed a smooth change in the external torque over about 12 s; the load was always kept constant. Series of trials were performed under three conditions: The torque could be zero throughout the trial or it could change slowly requiring a smooth change of the effort from a non-zero pronation value to zero (PR-0) or from a non-zero supination value to zero (SU-0). The handle was kept vertical at all times. Indices of variance and co-variation of elemental variables (forces and moments of force produced by individual digits) stabilizing such performance variables as total normal force, total tangential force, and total moment of force were computed at two levels of an assumed control hierarchy. At the upper level, the task is shared between the thumb and virtual finger (an imagined digit with the mechanical action equal to that of the four fingers), while at the lower level, action of the virtual finger is shared among the actual four fingers. We analyzed the total moment of force as the sum of the moments of force produced by the thumb and virtual finger and also as the sum of the moments of force produced by the normal forces and tangential forces. The results showed that the adjustments in the total moment of force were produced primarily with changes in the moment produced by the virtual finger and by changes in the moment produced by the normal forces. The normal force of the thumb at the final state (which was the same across conditions) was larger in the two conditions with changes in the external torque. The safety margin was significantly higher in the PR-0 condition, and it dropped with the decrease in the external torque. A co-contraction index was computed to reflect moment of force production by the fingers acting against the total moment produced by the virtual finger. It was higher for the SU-0 condition. Most variance indices dropped with a decrease in the external torque. The co-variation indices, however, remained unchanged over the trial duration. They showed signs of a trade-off between the two levels of the assumed hierarchy: Larger indices at the higher level corresponded to smaller indices at the lower level. This study and the previous one (Sun et al. 2011) document several previously unknown features of prehensile tasks. The results show that characteristics of digit action and interaction in such tasks depend not only on the magnitudes of external constraints but on a variety of other factors including time changes in the constraints and their history.

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“…Limitations in the control of individual fingers has been studied in both movement and force production tasks (Schieber 1991; Kilbreath and Gandevia 1994; Li et al 1998a, 2004; Zatsiorsky et al 2000; Shim et al 2007; Ingram et al 2008). In all these studies, finger motion or force production in a given direction was accompanied by unintentional motion (or force production) by other digits of the hand.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, we expected to see unintended forces not in the direction on the instructed force but in the opposite direction as well as substantial force production in directions orthogonal to the instructed direction. Our second main hypothesis has been based on earlier studies of multi-finger force production (Latash et al 2002a; Shim et al 2007; Gao et al 2005), which suggest that there may be strong multi-finger synergies stabilizing both magnitude and direction of the total force vector in three dimensions.…”

Section: Introductionmentioning

confidence: 99%

Finger interaction in a three-dimensional pressing task

et al. 2010

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Accurate control of forces produced by the fingers is essential for performing object manipulation. This study examines the indices of finger interaction when accurate time profiles of force are produced in different directions, while using one of the fingers or all four fingers of the hand. We hypothesized that patterns of unintended force production among shear force components may involve features not observed in the earlier studies of vertical force production. In particular, we expected to see unintended forces generated by non-task fingers not in the direction on the instructed force but in the opposite direction as well as substantial force production in directions orthogonal to the instructed direction. We also tested a hypothesis that multi-finger synergies, quantified using the framework of the uncontrolled manifold hypothesis, will help reduce across-trials variance of both total force magnitude and direction. Young, healthy subjects were required to produce accurate ramps of force in five different directions by pressing on force sensors with the fingers of the right (dominant) hand. The index finger induced the smallest unintended forces in non-task fingers. The little finger showed the smallest unintended forces when it was a non-task finger. Task fingers showed substantial force production in directions orthogonal to the intended force direction. During fourfinger tasks, individual force vectors typically pointed off the task direction, with these deviations nearly perfectly matched to produce a resultant force in the task direction. Multi-finger synergy indices reflected strong co-variation in the space of finger modes (commands to fingers) that reduced variability of the total force magnitude and direction across trials. The synergy indices increased in magnitude over the first 30% of the trial time and then stayed at a nearly constant level. The synergy index for stabilization of total force magnitude was higher for shear force components as compared to the downward pressing force component. The results suggest complex interactions between enslaving and synergic force adjustments, possibly reflecting the experience with everyday prehensile tasks. For the first time, the data document multi-finger synergies stabilizing both shear force magnitude and force vector direction. These synergies may play a major role in stabilizing the hand action during object manipulation.

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Multi-digit maximum voluntary torque production on a circular object

Cited by 18 publications

References 44 publications

Effect of Task Direction on the Maximal Pushing, Pulling, Twisting, and Grip Forces

Effect of Task Direction on the Maximal Pushing, Pulling, Twisting, and Grip Forces

Prehension synergies during smooth changes of the external torque

Finger interaction in a three-dimensional pressing task

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