Muscle Mechanics and Forward Simulation

Question 1

What are the three components in the Hill-Muscle model? And what do each represent?

Answer 1

Contractile Element - a damper in parallel with an active (force generating) component.

Parallel Elastic Component - a spring in parallel with the contractile element, representing properties of connective tissue

Series Elastic Component - a spring in series with the other components, representing series elastic tissue

Question 2

What are the additional terms in the Hill-Muscle model?

Answer 2

L = length of muscle tendon
Fb and Fp are forces due to the damper and spring
x = displacement of parallel components (approx muscle) from the equilibrium position
Ft = overal muscle-tendon force

Question 3

what does positive and negative work mean for muscles?

Answer 3

Positive work:

• during concentric contraction
• muscle moment acts in the same direction as the angular velocity of the joint

Negative work:

• during eccentric contraction
• muscle moment acts in opposite direction to angular velocity at joint

Question 4

What is the equations for muscle power Pm

Answer 4

Product of the net muscle moment M and the joint angular velocity:

Pm = Mω (Watts)

Question 5

Assuming linear damper and springs - what is the equation for the Hill-Muscle model?

Answer 5

Ft = bx(dot)+ kx + Fa

Question 6

How to solve the muscle hill model first order differential equation:

Answer 6

sub in ft = ks(L-lo-x) and use data book.