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Table 1 Definition of symbols used in the model.

From: Development of a mathematical model for predicting electrically elicited quadriceps femoris muscle forces during isovelocity knee joint motion

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
τ 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 τ2 (see Eqn. 20)
K m --- sensitivity of strongly bound cross-bridges to C N
τ 1 ms time constant of force decline in the absence of strongly bound cross-bridges
τ 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