Specifications

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Pmt
The mechanical power of the entire muscle-tendon unit, i.e. the
rate of work performed on the skeleton. Notice that the power is
negative because the muscle is extending against the force.
Muscles behaving like this in the human body are often termed
antagonistic muscles.
Pmet
A crude estimate of the metabolism in the muscle. The estimate
is based on presumed efficiencies of the contractile element of
25% for concentric work and -120% for eccentric work. The
model does not take the metabolism of isometric force into
account.
Calibration
One of the practical challenges in working with detailed muscle models in complex musculoskeletal systems
is the dependency on defined tendon length, Lt0. A brief experiment with our model can reveal where the
difficulty lies. In the model we have just investigated, the activity of Muscle2 has the following development
over the movement:
But what would happen if our guess of tendon length, Lt0, in the muscle model definition was just slightly
off the correct value? Well if we change the current value from 0.5 m to 0.45 m, i.e. a reduction of 10%, we
get the following activity: