FiberVelocityInfo contains velocity quantities related to the velocity of the muscle (fiber + tendon) complex.
The function that populates this struct, calcFiberVelocityInfo, is called when position and velocity information is known. This function is the second function that is called of these related functions:calcMuscleLengthInfo,calcFiberVelocityInfo and calcMuscleDynamicInfo. When calcFiberVelocity is called the acceleration of the muscle path, and any forces the muscle experiences will not be known.
NAME DIMENSION UNITS
fiberVelocity length/time m/s
fiberVelocityAlongTendon length/time m/s [1]
normFiberVelocity (length/time)/Vmax NA [2]
pennationAngularVelocity angle/time rad/s [3]
tendonVelocity length/time m/s
normTendonVelocity (length/time)/length (m/s)/m [4]
fiberForceVelocityMultiplier force/force NA [5]
userDefinedVelocityExtras NA NA [6]
[1] fiberVelocityAlongTendon is the first derivative of the symbolic equation that defines the fiberLengthAlongTendon.
[2] normFiberVelocity is the fiberVelocity normalized with respect to the optimal fiber length of the fiber and the maximum fiber velocity defined in fiber-lengths/s.
[3] The sign of the angular velocity is defined using the right hand rule.
[4] normTendonVelocity is the tendonVelocity (the lengthening velocity of the tendon) divided by its resting length
[5] The fiberForceVelocityMultiplier is the scaling factor that represents how a muscle fiber's force generating capacity is modulated by the contraction (concentric or eccentric) velocity of the fiber. Generally this curve has a value of 1 at a fiber velocity of 0, has a value of between 1.4-1.8 at the maximum eccentric contraction velocity and a value of 0 at the maximum concentric contraction velocity. The force velocit curve, which computes this term, is usually an interpolation of an experimental curve.
[6] This vector is left for the muscle modeler to populate with any computationally expensive quantities that are computed in calcFiberVelocityInfo, and required for use in the user defined function calcMuscleDynamicsInfo. None of the parent classes make any assumptions about what is or isn't in this field
1.8.1.2 
