Biomedical Engineering Reference
In-Depth Information
force of a muscle. Proportionality between the tensile stress r
m
and model
parameters k
t1
(case E) could not be ascertained. This case was subsequently
neglected since the effect of the transverse stiffness k
t1
of the Pectoralis major on
the transverse force F
T
was small compared to the effect of the stress r
m
on F
T
.
With proportionality for four out of the five significant pairs of morphometric
and model parameter and one pair deemed negligible, the intra-species correlation
in the baboon was considered sufficiently robust and valid for larger sample sizes,
in terms of a wider range of body mass M
b
, under similar conditions. Physiological
parameters not included in Eq. (
4
) had a negligible effect on F
T
and thus did not
affect the robustness of the intra-species correlation.
4.4 Intra-Species and Inter-Species Evaluation of Model
Parameters
The intra-species correlation of morphometric parameters and F
IL
with the
transverse force on the pacemaker, F
T
, was derived and formulated in Eq. (
4
)as
follows:
F
T
¼
1055
:
78
0
:
24 F
IL
þ
3
:
24 L
m
þ
5
:
95 w
m
þ
434
:
62 r
m
The difference of morphometric and mechanical parameters between subjects
and the influence of the model parameters on F
T
were evaluated intra-specifically
(between baboons) and inter-specifically (between baboons and humans). The
following subject populations were considered:
• Baboons: adult males, M
b
& 24 kg [
10
],
• Humans: adult males, M
b
& 90 kg [
35
].
Musculoskeletal material parameters were comparable between baboons and
humans based on similarity of mammalian musculoskeletal tissue [
3
]. The eval-
uation of each model parameter for the intra-species and inter-species effect on F
T
was conducted by assuming that all model parameters, except the one under
evaluation, remained constant, and ascertaining whether the influence of the var-
iance of this parameter within the subject population had a strong (significant) or
weak (insignificant) effect on the magnitude of F
T
.
For the intra-species baboon case, the strength of the effect (weak or strong) of a
parameter on F
T
was based on: (a) whether or not it was represented in Eq. (
4
), (b)
experimental findings and/or (c) data from literature. For model parameters not
studied in our intra-species MLR analysis [
10
], weak intra-species influence on F
T
was assigned based on the following considerations:
• t
mu
and r
mu
: Due to the non-linear elastic properties of passive muscle and
F
Trest
[ 0, a sufficiently high stiffness k
t2
was assumed, minimizing a change of
t
mu
during contraction of Pectoralis major. Combined with the indication that
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