Equilibrium Point Hypothesis (EPH)
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Transcript of Equilibrium Point Hypothesis (EPH)
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
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))
Torque
Angle1 2
i=1 f=2
Torque
Angle1
2
i=1 f=2
v
Td
βv = Θf - Td/σ Load EffectLoad Effect
Evidence for EPH Evidence for EPH ((Polit & Bizzi 1978-9Polit & Bizzi 1978-9))
EPH GeneralizationEPH Generalization
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?
Fitt’s Law Fitt’s Law Speed-Accuracy Trade-Speed-Accuracy Trade-
offoff
Fitt’s Law Fitt’s Law Speed-Accuracy Trade-Speed-Accuracy Trade-
offoff
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
Fitt’s Law Fitt’s Law (cont.)(cont.)
Fitt’s Fitt’s LawLaw
(cont.) (cont.)
-Larger limb showed Larger limb showed more sensitivitymore sensitivity
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.
Aging & Fitt’s Law (cont.)Aging & Fitt’s Law (cont.)Kelso (1984)Kelso (1984)
Aging increases the Aging increases the slopeslope
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%)