Table 1 Definition of symbols used in the model.
Symbol | Unit | Definition |
|---|---|---|
C N | --- | normalized amount of Ca2+-troponin complex |
t | ms | time since the beginning of the stimulation |
t i | ms | time when the i th pulse is delivered |
Ï„ c | ms | time constant controlling the rise and decay of C N |
R 0 | ---- | term characterizing the magnitude of enhancement in C N from the following stimuli |
F | N | instantaneous force due to stimulation |
k s | N/m | spring stiffness |
b | Ns/m | damping coefficient |
V | m/s | shortening velocity of motor |
A 40 | N/ms | scaling factor for force at 40° of knee flexion |
a | N/ms-deg2 | scaling factor to account for force at each knee flexion angle |
b | N/ms-deg | scaling factor to account for force at each knee flexion angle |
θ | deg | knee flexion angle |
H | Nm | resistance moment knee extension |
l | m | distance between knee center of rotation and center of mass of leg |
L | M | length of lever arm from center of force transducer to center of knee rotation |
V 1 | N/deg2 | scaling factor in the term G(θ) |
T STIM | Nm | knee joint torque due to stimulation |
mg | N | weight of the tibia and foot |
V 2 | 1/deg | constant that is linearly realted to Ï„2 (see Eqn. 20) |
K m | --- | sensitivity of strongly bound cross-bridges to C N |
Ï„ 1 | ms | time constant of force decline in the absence of strongly bound cross-bridges |
Ï„ 2 | ms | time constant of force decline due to the extra friction between actin and myosin resulting from the presence of strongly bound cross-bridges |
M | N | resistance to knee extension |
F EXT | N | experimental force measured by the KinCom dynamometer |