difference between Lfbar and PEFactor

Hi,

last year in August you explained what PEFactor is used for. You gave
me the example that if the PEFactor is 5 , i can theoretically pull
the muscle five times it’s fibre length before the F0 force is obtained.
That’s not difficult to understand.

Now i have the problem, that in your manual you write for PEFactor:
If we imagine a completely inactive muscle and load the muscle with a
force corresponding to the active strength of the muscle, F0, then the
length of the elongated muscle fibres will be PEFactor * Lfbar.

When i looked up Lfbar i found:
length of the contractile element at which the muscle has the strength
of F0.

What i’m looking for is the passive muscle force depending on the
length of the muscle. How do i have to calculate this?
Is the difference between the length calculated from PEFactor*Lfbar
and only Lfbar that in the first case the muscle is not contracted and
because of this it has to elongate for bringing up F0 force and in the
second case the muscle is contracted and so it is shorter even if it
carried forward F0 force?

So when i like to know passive force vs. muscle length (without any
contractions) as a function or for some different lengths, where do i
find this in the muscle model?

Thanks for your efforts, best regards, Maren

Hi Maren
The easiest way to obtain the passive force versus muscle length is
to equip the model with reaction forces in the all the human joints.
Then all muscles will become inactive and only the passive forces in
the muscles will remain.

Your description saying "If we imagine a completely inactive muscle
and load the muscle with a force corresponding to the active
strength of the muscle, F0, then the length of the elongated muscle
fibres will be PEFactor * Lfbar. " is correct.

The passive force as a function of length is calculated as an
exponential function which shape are controlled by the two points
(F0,LfbarPeFactor) and (0,LfBar) as I recall it. The length
calculated from LfBar
PeFactor is in other words just a point on the
force/length used for controlling the passive force/length curve. I
am not sure I fully understand the sentence “Is the difference â€¦.”.
I will try to explain; if you imagine a muscle with zero activation
and some passive force then activating this muscle will unload the
passive force to some extend, depending on the activation.

I am not sure if this answers your questions otherwise please write
again.

Best regards
SÃ¸ren, AnyBody Support

— In anyscript@yahoogroups.com, “Maren” <anystarter@…> wrote:
>
> Hi,
>
> last year in August you explained what PEFactor is used for. You
gave
> me the example that if the PEFactor is 5 , i can theoretically pull
> the muscle five times it’s fibre length before the F0 force is
obtained.
> That’s not difficult to understand.
>
> Now i have the problem, that in your manual you write for PEFactor:
> If we imagine a completely inactive muscle and load the muscle
with a
> force corresponding to the active strength of the muscle, F0, then
the
> length of the elongated muscle fibres will be PEFactor * Lfbar.
>
> When i looked up Lfbar i found:
> length of the contractile element at which the muscle has the
strength
> of F0.
>
> What i’m looking for is the passive muscle force depending on the
> length of the muscle. How do i have to calculate this?
> Is the difference between the length calculated from PEFactor*Lfbar
> and only Lfbar that in the first case the muscle is not contracted
and
> because of this it has to elongate for bringing up F0 force and in
the
> second case the muscle is contracted and so it is shorter even if
it
> carried forward F0 force?
>
> So when i like to know passive force vs. muscle length (without any
> contractions) as a function or for some different lengths, where
do i
> find this in the muscle model?
>
> Thanks for your efforts, best regards, Maren
>