When using the CMC tool I get a warning for some muscles, e.g. "WARN - small force range for muscleX ( A to B )"
What exactly are numbers A and B and what muscle parameters do I need to be addressing to change this?
Thanks,
Moe
Small force range
RE: Small force range
Hi Moe,
I believe the way CMC works is at each time frame, given the current "pose" of the model, a check is done to see what force each muscle can produce with muscle excitation u = 0 (value A) and u = 1 (value B). If a muscle is operating at a "very short" or "very long" fiber length (away from it's optimal fiber length), it can not produce much force (even at full excitation u = 1), and hence it's force producing range is low. (A muscle's force producing range is also low if it is contracting at a velocity near Vmax).
A warning is issued, but this is not necessarily a bad thing: it is only a bad thing if that particular muscle is required to produce torque, but otherwise, it is just saying that no real control can be offered to that muscle at that time due to the "state" of the muscle.
Say for example say you are simulating an activity where there are high levels of hip flexion, your iliacus & psoas muscles at high hip flexion may be operating way in the low ascending of the F-L curve, hence unable to generate any active force. But if a hip extensor moment is required at that point in time to bring the thigh back, then it doesn't matter if the hip flexors have a small range because they will not be activated anyway.
Tim
I believe the way CMC works is at each time frame, given the current "pose" of the model, a check is done to see what force each muscle can produce with muscle excitation u = 0 (value A) and u = 1 (value B). If a muscle is operating at a "very short" or "very long" fiber length (away from it's optimal fiber length), it can not produce much force (even at full excitation u = 1), and hence it's force producing range is low. (A muscle's force producing range is also low if it is contracting at a velocity near Vmax).
A warning is issued, but this is not necessarily a bad thing: it is only a bad thing if that particular muscle is required to produce torque, but otherwise, it is just saying that no real control can be offered to that muscle at that time due to the "state" of the muscle.
Say for example say you are simulating an activity where there are high levels of hip flexion, your iliacus & psoas muscles at high hip flexion may be operating way in the low ascending of the F-L curve, hence unable to generate any active force. But if a hip extensor moment is required at that point in time to bring the thigh back, then it doesn't matter if the hip flexors have a small range because they will not be activated anyway.
Tim