Multifinger Ab- and Adduction Strength and Coordination

Pataky, Todd C.; Latash, Mark L.; Zatsiorsky, Vladimir M.

doi:10.1197/j.jht.2008.02.002

Cited by 11 publications

(10 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There was no evident pattern of functional hand center being affected by torque. The results are similar to the data reported by Pataky et al (2008). Hence the location of the functional hand center in spreading/squeezing tasks is similar during pressing (Pataky et al, 2008) and grasping tasks (this study).…”

Section: Resultssupporting

confidence: 91%

“…Maximal strength in four-finger abduction/adduction during pressing tasks has previously been studied (Pataky et al, 2008) and the findings agree with our data: the absolute sum of forces is larger in adduction than abduction. The lateral fingers (I- and L-fingers) produced more force in both, the abduction and adduction, directions than the medial fingers (M- and R-fingers), on average the lateral fingers contributed 72.1 ± 27.9% of the total abduction/adduction force.…”

Section: Discussionsupporting

confidence: 92%

“…This was the same method used by Pataky et al (2008). It was assumed that the position of fingers was constant at x = 1, 2, 3, and 4 for the I-, M-, R-, and L-fingers, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Pataky et al (2008) studied the effects of maximal finger spreading and squeezing. A functional hand center was computed, which “represents an imaginary point of zero force from which the F t finger forces would originate.” During both tasks (spreading/squeezing) the functional hand center was between the index (I) and middle (M) fingers, which signifies that the I-finger produced force in opposite direction of those of the M-, ring- (R), and little (L)-fingers.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Coordination of Contact Forces During Multifinger Static Prehension

Martin¹,

Latash²,

Zatsiorsky³

2011

Journal of Applied Biomechanics

Self Cite

View full text Add to dashboard Cite

This study investigated the effects of modifying contact finger forces in one direction-normal or tangential-on the entire set of the contact forces, while statically holding an object. Subjects grasped a handle instrumented with finger force-moment sensors, maintained it at rest in the air, and then slowly: (1) increased the grasping force, (2) tried to spread fingers apart, and (3) tried to squeeze fingers together. Analysis was mostly performed at the virtual finger (VF) level (the VF is an imaginable finger that generates the same force and moment as the four fingers combined). For all three tasks there were statistically significant changes in the VF normal and tangential forces. For finger spreading/squeezing the tangential force neutral point was located between the index and middle fingers. We conclude that the internal forces are regulated as a whole, including adjustments in both normal and tangential force, instead of only a subset of forces (normal or tangential). The effects of such factors as EFFORT and TORQUE were additive; their interaction was not statistically significant, thus supporting the principle of superposition in human prehension. Keywordsprehension; grasping; motor control; occupational therapy To stably grasp an object the forces of all digits in contact with the object need to be coordinated to satisfy certain constraints. Often following an illness (e.g., a stroke) the ability to control fingers is impaired, making the simple task of holding an object statically in the air difficult or even impossible. Studies of unimpaired finger coordination during static prehension represent an important step toward developing rehabilitation strategies.The contact forces applied on the object during multifinger prehension are commonly divided into manipulation and internal forces (Kerr & Roth, 1986;Yoshikawa & Nagai, 1991;Gao et al., 2005). Manipulation forces disturb equilibrium and are necessitated by the mechanics of the task (i.e., magnitude and direction of the desired object's acceleration and its inertia). Internal forces are defined as the set of forces that do not disturb the equilibrium of the object (Mason & Salisbury, 1985;Murray et al., 1994;Gao et al., 2005). The elements of the internal force vector cancel each other out, resulting in zero net force and moment. Unlike manipulation forces, internal forces can vary substantially without influencing the performance outcome. Grasp mechanics allow for increasing or decreasing the normal forces-provided that the object is not dropped or crushed-without changing the manipulation force. In robotics, the manipulation and internal forces are controlled independently (Kerr & Roth, 1986;Yoshikawa & Nagai, 1991 (Smith & Soechting, 2005;Gao et al., 2005;Winges et al., 2007;Gorniak et al., 2010). For example, during vertical object manipulation the grasping pinch forces scale linearly with the effective load force, which depends on the acceleration (Johansson et al., 1992;Flanagan & Tresilian, 1994;Smith & Soechting, 2005). Regulating in...

show abstract

Section: Resultssupporting

confidence: 91%

Section: Discussionsupporting

confidence: 92%

“…This was the same method used by Pataky et al (2008). It was assumed that the position of fingers was constant at x = 1, 2, 3, and 4 for the I-, M-, R-, and L-fingers, respectively.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Coordination of Contact Forces During Multifinger Static Prehension

Martin¹,

Latash²,

Zatsiorsky³

2011

Journal of Applied Biomechanics

Self Cite

View full text Add to dashboard Cite

show abstract

“…It seems that finger opposition, i.e. spreading the fingers apart – abduction, or squeezing the fingers together – adduction (Pataky, Latash, Zatsiorsky 2007b), is used during prehension. The tangential forces generated due to the finger opposition are the internal forces, provided that they cancel each other.…”

Section: Manipulation Forcementioning

confidence: 99%

Multifinger Prehension: An Overview

Zatsiorsky

Latash

2008

Journal of Motor Behavior

Self Cite

139

128

View full text Add to dashboard Cite

This paper reviews the available experimental evidence on what people do when they grasp an object with several digits and then manipulate it. In addition to the Introduction, the paper includes three parts each addressing a specific aspect of multi-finger prehension. Part II discusses manipulation forces, i.e. the resultant force and moment of force exerted on the object, and the digits contribution to such force production. Part III deals with internal forces defined as forces that cancel each other and do not disturb object equilibrium. The role of the internal forces in maintaining the object stability is discussed with respect to such issues as slip prevention, tilt prevention and resistance to perturbations. Part IV is devoted to the motor control of prehension. It covers such topics as prehension synergies, chain effects, the principle of superposition, inter-finger connection matrices and reconstruction of neural commands, mechanical advantage of the fingers, and the simultaneous digit adjustment to several mutually reinforcing or conflicting demands.

show abstract