05-04-2002, 08:45 AM
I am working on this Biomechanics assignment given to me from my
biomechanics professor as part of my final project for the course. And I
am having a little trouble with some of the calculations.

Anyway, the assignment is this. We (the class) were each given the same
standardized hypothetical lizard model. And my specific part of this
model is to vary the rate of muscle contraction (muscle shortening) on
this lizard to see how it would affect the following:

(1) velocity of locomotion (speed),
(2) stride length (length of a stride for one leg - foot down to foot
down for same foot)
(3) stride frequency (rate at which feet are moving - number of strides
per second)
(4) power.

I have calculated the distance the muscle shortens (the muscle in
question is the caudofemoralis muscle which connects to the femur), but
now I am having trouble calculating the rate at which this muscle
contracts. I was wondering if you could look at the model, which is
typed down at the end of this e-mail and possibly give some ideas on how
to calculate standard speed on muscle contraction. Thanks!

* * * *

Calculations that I made:

I figured out that the length of muscle contraction for this muscle
(caudofemoralis muscle) is 15.3 mm. I also figured
out that the femoral contribution to a step (foot down to foot up), not
a stride (which is foot down to foot down) is 6.93 cm. Does this make
any sense?

* * * *

Standardized Lizard Model

Mass = 700 grams
SVL (snout vent length - measured from snout to anal pore) = 280 mm
femur length = 45 mm
tibia length = 45 mm
limb mass = 1

Vo (initial velocity) = 157cm/sec = 5.6SVL/sec
SLo (initial stride length) = 27.5cm/stride
SFo (initial stride frequency) = 5.7 stride/sec
DFo (duft factor - amount of stride which foot is on ground) = 40% of

Io (initial insertion site of caudofemoralis muscle) = 10 mm
Lo (initial resting length of muscle fibres) = 5 mm
Lmin (final contracted length of muscle fibres) = 0.5 of Lo
Ao (initial muscle fiber pinnation angle) = 45 degrees
N (initial number of muscle fibres) = 10,000
Fmax (maximum force of caudofemoralis) = 100 newtons
Fo (initial muscle force) = 0.4 of Fmax
Vfmax = maximum contraction velocity of muscle fibres
Vfi (initial contraction velocity of muscle fibres) = 0.5 of Vfmax

* * * * *

Thank you so much for atleast trying! I really appreciate it!

-mary alice allen

I used to be a SuperHero.....



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