Limited independent flexion of the thumb and fingers in human subjects.

Kilbreath, Sharon L.; Gandevia, Simon C.

doi:10.1113/jphysiol.1994.sp020312

Cited by 244 publications

(239 citation statements)

References 31 publications

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“…Some of these effects were described as "enslaving" (Kilbreath and Gandieva 1994;Zatsiorsky et al 2000;Schieber 2001) and were attributed to a feed-forward controller to physiologically connected effectors (Latash et al 1998a,b). Considering the current data, enslaving can account for neither the large internal force nor the change in normal force sharing across orientations (Fig.…”

Section: Mechanically Unnecessary Forcesmentioning

confidence: 99%

Prehension synergies during nonvertical grasping, I: experimental observations

2004

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The mechanical complexities of rotating an object through the gravity field present a formidable challenge to the human central nervous system (CNS). The current study documents the finger force patterns selected by the CNS when performing one-, two-, and four-finger grasping while holding an object statically at various orientations with respect to vertical. Numerous mechanically "unnecessary" behaviors were observed. These included: nonzero tangential forces for horizontal handle orientations, large internal forces (i.e., those in excess of equilibrium requirements) for all orientations, and safety margins between 50 and 90%. Additionally, none of the investigated measures were constant across orientations or could be represented as a simple trigonometric function of orientation. Nonetheless, all measures varied in systematic (and sometimes symmetric) ways with orientation. The results suggest that the CNS selects force patterns that are based on mechanical principles but also that are not simply related to object orientation. This study is complemented by a second paper that provides an in-depth analysis of the mechanics of nonvertical grasping and accounts for many of the observed results with numerical optimization (see Part II -current issue).Together, the papers demonstrate that the CNS is likely to utilize optimization processes when controlling prehensile actions.

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Section: Mechanically Unnecessary Forcesmentioning

confidence: 99%

Prehension synergies during nonvertical grasping, I: experimental observations

2004

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“…The result indicates that both instructed and uninstructed finger forces are perceived within the central nervous system (CNS) and that the absolute magnitude of total finger force is perceived and reproduced, i.e., absolute force matching, in the ipsilateral force matching paradigm. The phenomenon of uninstructed finger forces, name enslaving (Kilbreath and Gandevia 1994;Li et al 1998;Kilbreath et al 2002;Li et al 2003), is of central origin to a large degree Li et al 2000b;Latash et al 2002;Danion et al 2003;Li et al 2004). Similarly, in an ipsilateral matching task of an index finger reference force to be matched by a little finger, absolute force matching of finger forces and the enslaving effect on minimization of matching errors are also observed after an index finger fatiguing exercise (Park et al 2007).…”

Section: Introductionmentioning

confidence: 98%

Finger force perception during ipsilateral and contralateral force matching tasks

Park

Leonard

2008

Exp Brain Res

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The aims of the present study were to compare matching performance between ipsilateral and contralateral finger force matching tasks and to examine the effect of handedness on finger force perception. Eleven subjects were instructed to produce reference forces by an instructed finger (index -I or little -L finger) and to reproduce the same amount force by the same or a different finger within the hand (i.e., ipsilateral matching task), or by a finger of the other hand (i.e., contralateral matching task). The results of the ipsilateral and contralateral tasks in the present study commonly showed that 1) the reference and matching forces were matched closely when the two forces were produced by the same or homologous finger(s) such as I/I task; 2) the weaker little finger underestimated the magnitude of reference force of the index finger (I/L task), even with the higher level of effort (relative force), but the two forces were matched when considering total finger forces; 3) the stronger index finger closely matched the reference force of the little finger with the lower level of relative force (i.e., L/I task); 4) when considering the constant errors, I/L tasks showed an underestimation and L/I tasks showed an overestimation compared to I/I tasks. There was no handedness effect during ipsilateral tasks. During the contralateral task, the dominant hand overestimated the force of the non-dominant hand, while the non-dominant hand attempted to match the absolute force of the dominant hand. The overall results support the notion that the absolute, rather than relative, finger force is perceived and reproduced during ipsilateral and contralateral finger force matching tasks, indicating the uniqueness of finger force perception.

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“…Electromyographic studies of extrinsic finger muscles in humans, for example, typically describe a single MU as optimally activated during movement of a particular finger (Schmied et al, 1993;Kilbreath and Gandevia, 1994). Studies examining the discharge of single MUs during individuated movements of each finger reveal, however, that a MU optimally activated during movement of a particular finger typically discharges during movements of adjacent fingers as well, albeit at a lower discharge frequency or at a higher recruitment threshold (Schieber, 1993;Kilbreath and Gandevia, 1994). Furthermore, most single MUs in the EDC of the cat have been shown to exert tension on all four digital tendons .…”

Section: Introductionmentioning

confidence: 99%

Tension Distribution of Single Motor Units in Multitendoned Muscles: Comparison of a Homologous Digit Muscle in Cats and Monkeys

et al. 1997

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To determine whether single motor units (MUs) in multitendoned muscles distribute tension to multiple tendons or instead focus tension selectively on a single tendon, we examined the distribution of tension generated by single MUs in the cat extensor digitorum lateralis (EDLat), and in its macaque homolog, the extensor digiti quarti et quinti (ED45). General properties of MUs (maximal tetanic tension, axonal conduction velocity, and twitch rise time) were similar in these muscles to those reported for other limb muscles in cats and monkeys. Most cat EDLat MUs were found to exert tension rather selectively on one of the three tendons of the muscle. Fast fatigable MUs were slightly but significantly more selective than fast fatigue-resistant and slow MUs. In contrast, and contrary to expectation, the macaque ED45 contained a lower proportion of MUs that exerted tension selectively on one of the two tendons of the muscle, and a higher proportion of relatively nonselective MUs. These findings suggest that the cat EDLat may consist of three functional subdivisions, each acting preferentially on a different tendon, whereas the macaque ED45 is more likely to function as a single multitendoned muscle.

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Limited independent flexion of the thumb and fingers in human subjects.

Cited by 244 publications

References 31 publications

Prehension synergies during nonvertical grasping, I: experimental observations

Prehension synergies during nonvertical grasping, I: experimental observations

Finger force perception during ipsilateral and contralateral force matching tasks

Tension Distribution of Single Motor Units in Multitendoned Muscles: Comparison of a Homologous Digit Muscle in Cats and Monkeys

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