Equilibrium Point Hypothesis (EPH)

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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)

  • Equilibrium Point Hypothesis(EPH)F=0 : Feldman (1966, 1986, ): -Model

    Bizzi (1978, 1979, ): - Model

  • F = k ( X X0) : ()EPH and Muscle StiffnessK = ( ) X0 = ()

  • v = f - Td/ Load Effect

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

  • EPH Generalization

  • Questions Unanswered?1- Role of Motor Centers in the Brain?

    2- Motor Learning?

    3- Environmental Effects?

  • Fitts Law Speed-Accuracy Trade-off

  • Fitts Law Speed-Accuracy Trade-off

  • Fitts Law (cont.)MT = a + b [ log2 (2A/W) ] MT = Movement Time

    ID ( Index of Difficulty) = A/W

    log2: Inspired from information theory

  • Fitts Law (cont.)

  • Fitts Law (cont.)Larger limb showed more sensitivity

  • Learning & Fitts Law (cont.)Kelso (1984)Slope was reduced to nearly zero following 40,000 trials.

  • Aging & Fitts Law (cont.)Kelso (1984)Aging increases the slope

  • Modification to the Fitts LawMT = a (A/W)b

    Modification effect is minor (10%)