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Equilibrium Point Hypothesis (EPH)

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.

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Equilibrium Point Hypothesis (EPH)

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  1. Equilibrium Point Hypothesis(EPH) Feldman (1966, 1986, …): λ-Model Bizzi (1978, 1979, …): α- Model ∑F=0 : در حالت تعادل

  2. EPH and Muscle Stiffness F = k ( X – X0) :رابطه يك فنر (عضله) K = σ (α ) X0 = β (λ)

  3. Load Effect βv =Θf - Td/σ

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

  5. EPH Generalization

  6. Questions Unanswered? 1- Role of Motor Centers in the Brain? 2- Motor Learning? 3- Environmental Effects?

  7. Fitt’s Law Speed-Accuracy Trade-off

  8. Fitt’s Law Speed-Accuracy Trade-off

  9. Fitt’s Law (cont.) • MT = a + b [ log2 (2A/W) ] MT = Movement Time ID ( Index of Difficulty) = A/W log2: Inspired from information theory

  10. Fitt’s Law (cont.)

  11. Fitt’s Law (cont.) • Larger limb showed • more sensitivity

  12. Learning & Fitt’s Law (cont.)Kelso (1984) Slope was reduced to nearly zero following 40,000 trials.

  13. Aging & Fitt’s Law (cont.)Kelso (1984) Aging increases the slope

  14. Modification to the Fitt’s Law • MT = a (A/W)b Modification effectis minor (10%)

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