Equilibrium Point Hypothesis (EPH)

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Equilibrium Point Equilibrium Point Hypothesis Hypothesis (EPH) (EPH) F=0 : F=0 : ت ل ا در ح ت ل ا در حلدا ع تلد ا ع تFeldman (1966, 1986, …): Feldman (1966, 1986, …): λ λ - - Model Model Bizzi (1978, 1979, …): Bizzi (1978, 1979, …): α α - - Model Model

description

Equilibrium Point Hypothesis (EPH). Feldman (1966, 1986, …): λ - Model Bizzi (1978, 1979, …): α - Model. ∑ F=0 : در حالت تعادل. EPH and Muscle Stiffness. F = k ( X – X 0 ) : رابطه يك فنر (عضله). K = σ ( α ) X 0 = β ( λ ). Load Effect. β v = Θ f - Td/ σ. - PowerPoint PPT Presentation

Transcript of Equilibrium Point Hypothesis (EPH)

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Equilibrium Point Equilibrium Point HypothesisHypothesis

(EPH)(EPH)

∑∑F=0 : F=0 : در حالت در حالتتعادلتعادل

Feldman (1966, 1986, …): Feldman (1966, 1986, …): λλ--ModelModel

Bizzi (1978, 1979, …): Bizzi (1978, 1979, …): αα- Model- Model

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F = k ( X – XF = k ( X – X00) :) : رابطه يك فنر رابطه يك فنر(عضله)(عضله)

EPH and Muscle StiffnessEPH and Muscle Stiffness

K = K = σσ ( (αα ) ) XX00 = = ββ ( (λλ))

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Torque

Angle1 2

i=1 f=2

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Torque

Angle1

2

i=1 f=2

v

Td

βv = Θf - Td/σ Load EffectLoad Effect

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Evidence for EPH Evidence for EPH ((Polit & Bizzi 1978-9Polit & Bizzi 1978-9))

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EPH GeneralizationEPH Generalization

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Questions Questions Unanswered?Unanswered?

1- Role of Motor Centers in the 1- Role of Motor Centers in the Brain?Brain?

2- Motor Learning?2- Motor Learning?

3- Environmental Effects?3- Environmental Effects?

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Fitt’s Law Fitt’s Law Speed-Accuracy Trade-Speed-Accuracy Trade-

offoff

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Fitt’s Law Fitt’s Law Speed-Accuracy Trade-Speed-Accuracy Trade-

offoff

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Fitt’s Law (cont.)Fitt’s Law (cont.)

MT = a + b [ logMT = a + b [ log22 (2A/W) ] (2A/W) ] MT = Movement TimeMT = Movement Time

ID ( Index of Difficulty) = A/WID ( Index of Difficulty) = A/W

loglog22: Inspired from information : Inspired from information theorytheory

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Fitt’s Law Fitt’s Law (cont.)(cont.)

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Fitt’s Fitt’s LawLaw

(cont.) (cont.)

-Larger limb showed Larger limb showed more sensitivitymore sensitivity

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Learning & Fitt’s Law Learning & Fitt’s Law (cont.)(cont.)

Kelso (1984)Kelso (1984)

Slope was reduced to Slope was reduced to nearly zero following nearly zero following 40,000 trials. 40,000 trials.

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Aging & Fitt’s Law (cont.)Aging & Fitt’s Law (cont.)Kelso (1984)Kelso (1984)

Aging increases the Aging increases the slopeslope

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Modification to the Fitt’s Modification to the Fitt’s LawLaw

MT = a (A/W)MT = a (A/W)bb

Modification effectModification effect is minor (10%)is minor (10%)

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