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ADAPTATION AND RE-EDUCATION OF THE MOTOR SYSTEM
A BEHAVIOURAL, MOLECULAR AND CELLLULAR STUDY.
Soude J. (1), Grondard C. (1), Launay T. (1),
Gasc J. P. (2), Vidal P. P. (1), Gallien C.L.
(1), Chanoine C. (1) Charbonnier F. (1)
(1) LNRS, Paris, France (2) Lab. Anat. Comp,
Museum. Hist. Nat, Paris, France
Training Program
The mice were submitted to a training program of
12 weeks long. Three groups were formed 1
group of untrained mice (group 1) 1 group
trained during 6 weeks (group 2) 1 group
trained during 12 weeks (group 3)
Regular exercise has been shown to produce
improvement in health for both normal individuals
and patients affected of disease such as
cardiovascular disease, diabetes or obesity.
Recent studies have indicated that response to
exercise may be mediated enlarge part by
variation in genes, by local and/or systemic
ways. This suggests a role of the physical
activity in mechanisms of resistance to cell
ageing and death. Thus, the activation of several
genes encoding growth factors such as IGF-1 and
NT4 has been reported in muscles after exercise.
Overexpressed in the muscle, NT4 entails the
motor neuron sprouting and IGF-1 the
proliferation and the differentiation of Schwann
cells. Our research project is to
establish the relationship between physiological
adaptation to physical exercise with gene
expression, in relation to cellular and
behavioural adaptations to running. This
non-invasive methodology is based on a
combination of high speed cinematography (250
pictures/s) and X-ray photography. We have
specially designed several swimming pools to test
mice according to their age. Biomechanical
analyses include the precise determination of
the trajectory of each skeletal segment during a
jerk in a selected limb movement, the speed of
each segment in response to exercise, the
relative positions of segment with each other and
with respect to the body axis and the movement
axis. Cellular analysis include the determination
of muscle fiber transitions.
Biochemical index such as serum lactic acid
concentration was used to determine the
progressive effects of the training. The tests
were made after 5 minutes of forced swimming. The
serum lactic acid concentration decreased
significantly in the group 3. This results
suggested that the use of aerobic metabolism was
faster in the group 3 than in the other groups, a
classically observed effect in the endurance
training.
  Behavioral adaptation
Significant differences between the group 1 and
the groups 2/3 were found in the motion patterns
of the ankle during a swimming test. The ankle
motion pattern of the group1 was higher and ahead
of the motion pattern of the trained groups, in
regard of the coxo-femoral articulation. The
shape of the trajectory of the trained mice ankle
could be associated to an horizontal ellipse. The
shape of the ankle trajectory of the untrained
mice appeared to be more complex, since it was
composed of two ellipses, one horizontal ellipse,
resembling to the trained shape, and one second
more vertical. No differences were seen between
group 2 and group 3, suggesting that these
adaptations have occurred since 6 weeks of
training.
1
2
? Position of the body with regard to the
surface of the water  

Motion patterns of the ankle of the mice of the
groups 1 , 2, and 3.
To enable a more accurate comparison of the
motion patterns, four points in the ankle
trajectory were tracked down, forming four
segments Latency (point 1-point 2) power
stroke (point 2-point 3) - latency (point
3-point 4) - return stroke (point 3-point 4) The
duration of these segments was modified with the
training. A significant decrease of the time of
power stroke associated to an increase in the
following latent period was evidenced in the
trained groups. The time of return stroke was not
significantly different between the groups. It
was tempting to associate these micro-jerks,
evidenced inside a cycle of swimming, with
recovery periods that increase with the training.
Then, the training by swimming would generate a
more occasional locomotion.
? Position of the posterior paws with regard to
the body
The groups of mice were filmed during a round of
swimming exercise. Image 1 untrained mouse
(group 1) Image 2 trained mouse (group 3).
In blue, the angle corresponds to the angle of
the paws. The red axis corresponds to a mark of
the symmetry axis of the mouse. The training
by swimming improves the efficiency of the
gesture of swimming. The position of the mouse is
more hydrodynamic, the vertical position of
posterior paws allows a more efficient swimming.

The phases of a swimming cycle. The pink and
blue trajectories corresponds to the group 1 and
group 3 respectively. The coxo-femoral was shown
as a red point. The yellow zones correspond to
the phases of latency.   1 , 2 , 3 and 4
remarkable points of the cycle.
Biological adaptation
We also studied the adaptation to the
swimming program at a cellular level. The
muscular typology of two muscles of the calf, the
soleus and the plantaris, was analysed by
immunochemistry. The results showed that
comparable adaptations occurred for both the two
muscles. In the soleus, the proportion of fibers
IIa gradually increased and represented to 12
weeks of training the totality of fibers II of
the muscle. These results suggested a
fast-to-slow transition in this muscle. In a more
surprising way, after 12 weeks of training, a
decrease of the proportion of fibers I was also
noticed. This result suggested a slow-to-fast
transition, for the same exercise . Similar
results were found in the plantaris. An increased
population of fibers II was evidenced from 6
weeks of training. This was shown to be
associated to a decrease in the population of
fibers II b. This fast-to-slow transition
appeared to end at this time of training since no
more modification was detected even with the
follow-up training program. As seen in the
soleus, the population of fibers I decreased
with the training for the benefit of fibers II.
These anti-sense transitions of fibers in the
same exercise require to be confirmed on longer
times of training, notably in the soleus.
Analyses of gene expression will be performed by
comparing this expression in trained mice and
sedentary mice by gene arrays. This analysis will
be developed on the mutant mice designed as
genetic disease models of the human motor neuron
pathologies.