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2. Effect of vibrating proprioceptive activation on the
posture of patients after ACL-reconstruction
Brunetti O*, Liti A.***, Roscini M.*, Cerulli G.***, Pettorossi V.
E*. Filippi G.M.**,
Fisiologia Umana, Perugia* Università Cattolica, Roma**
Ortopedia, Perugia***
Vibration of muscles elicits short lasting effects, persisting
after vibration ending, on muscle tension and posture
reflexes. Beyond the increase of muscle tone (TVR), muscle
vibration has positive and persisting effects on motor system
in many different cases and experimental conditions. In fact,
following muscle vibration the performance of the muscles is
enhanced in healthy muscles (Bosco, C., M. Cardinale, and
O. Tsarpela. Influence of vibration on mechanical power and
electromyogram activity in human arm flexor muscles. Eur. J.
Appl. Physiol. Occup. Physiol. 79: 306-311, 1999), in palsy
neck muscles (Cannon, S. E., J. P. Rues, M. E. Melnick, and
D. Guess. Head-erect behavior among three preschool-aged
children with cerebral palsy. Phys. Ther. 67:1198-204, 1987),
in spasmodic torticollis (Karnath, H. O., J. Konczak, and J.
Dichgans. Effect of prolonged neck muscle vibration on lateral
head tilt in severe spasmodic torticollis J. Neurol. Neurosurg.
Psychiatry. 69:658-660, 2000). On the other hand,
proprioceptive training is reported to be able to induce
persisting improvements of motor control and body stability. In
addition, self motion perception and stepping in place are
influenced by neck muscle vibration for many days,
suggesting a long term effect of proprioceptors on the internal
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3. spatial representation. On this base, one can easily predict
that movements and body stability impaired by joints and
muscles pathology may be also improved by prolonged
vibratory stimulations. However, the challenge for the
researchers in this field is to find how to prolong the
positive effects of vibration and induce steady advantage.
Recently, we found that a brief sequence of low amplitude,
high frequency vibratory stimulation on isometric
contracted muscle (>20 micron, 75-120 Hz, 1-2 N, sul
ginocchio, 0.2 N sul collo), applied for few consecutive
days, 30 minutes each day, is able to prolong the motor
benefit of vibration for long period in healthy people. In
theory, this particular modality of muscle vibration could be
also useful in different pathologic condition concerning the
locomotor system and could help patients in recovering
correct movements and posture.
On this basis, we applied short lasting period of vibration to
the quadriceps muscle of subjects underwent anterior
cruciate ligament (ACL) reconstruction and we examined
their muscle power and equilibrium.
Methods. Twenty subjects underwent ACL reconstruction
have been studied in double blinded procedure. Informed
consent and local ethics committee approval were
obtained for all subjects. The subjects were separated in a
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4. stimulated group, receiving vibratory application and a
control group that underwent a slight rehabilitation period
instead of mechanical vibration
Stimulus paradigm. The experimental paradigm consisted
of applications of vibratory stimulation (100 Hz, >20 micron
peak-to-peak amplitude, 1-2 N force magnitude, by
NEMOCO srl Italy, International Patent Instrument) on the
skin overlying the distal part of quadriceps, on the operated
side, close to the tendon insertion of Intermedius Femoris,
Rectus Femoris and Vastus Medialis. Three applications of
mechanical vibration (duration of each application 10
minutes, time interval between two consecutive application
about 30 sec) were performed every day, in three
consecutive days, while Quadriceps was kept in isometric
contraction. The vibratory stimulation was applied one
month after the surgery and the recording sections were
done before and 10, 90 and 270 days after the application.
All subjects underwent conventional rehabilitation
programs. Recording paradigm: Equilibrium was
investigated using a balance platform open (OE) and closed
eyes (CE). The duration of each recording period was 51
sec. The parameters estimated were: length of trace, (LT)
in mm, mean speed of shifts (SM) in mm/sec., ellipse area
(AE) in mm2. The measure was performed with subjects
standing up on the operated and non operated leg
alternatively, after a brief period of training. The leg force
was measured during maximal isokinetic voluntary
contraction by using a conventional dynamometer.
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5. Data analysis. The evaluation of the effect on the length of
trace (LT), mean speed of shifts (SM) and ellipse area (EA)
was performed by comparing the pre-stimulation values and
the operated and not operated sides. Analyses of variance
(ANOVA) and Tukey’s post-hoc test were used to calculate
statistical significance.
Results.
Repeated applications of unilateral and protracted
mechanical perturbations on quadriceps of the knee caused
a clear improvement of subject’s equilibrium as shown by
the EA, SM, LT values by comparing normalised value of
subjects underwent vibration and control. This effect was
significantly different at 10 and 90 days after the vibratory
application. Later on, after 270 days, the difference became
less significant. Conversely, the analysis of Quadriceps
force did not showed a significantly difference between
treated and untreated subjects along the recovery period.
In spite of the significant improvement in the recovery of
body balance of treated subjects, there was a difference in
the recovery of balance values depending upon the leg the
subjects were using for standing up. The difference
between the two side was significantly different in treated
group, showing a large improvement on the operated side
compared to the unoperated side. The asymmetry in the
balance recovery suggests that treated subjects perceived
a major confidence in using the operated leg for body
balance, so that they learn easily the balance strategy when
they stand up on the operated leg rather than on the other
side.
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6. Discussion
The research shows the possibility of facilitate the normal
improving in the body balance after ACL reconstruction
simply by applying short period of muscle vibration on
selected muscles. The long lasting persistence of the
effects and the non invasive technique are important
factors that may lead to routinely use this vibratory pattern
in ACL reconstructed patients.
A trophic origin of the results is unlike since 10 days is a
too short time (Ahtiainen, J. P., A. Pakarinen, M. Alen, W.
J. Kraemer, and K. Hakkinen. Muscle hypertrophy,
hormonal adaptations and strength development during
strength training in strength-trained and untrained men.
Eur. J. Appl. Physiol. 89: 555-563, 2003) Moreover life style
of control and treated subjects was the same, thus an
improvement of muscle performance cannot be attributed
to a muscle exercise after treatment. In any case, the
monolateral presence of effects, ipsilateral to the treatment,
does not sustain the possibility of a muscle function
enhancement due to physical activity. Finally the absence
of any effect on the control group and the monolateral
improvement of muscle performance suggests a learning in
the proprioceptive system Even though mechanical
perturbations like vibration can alter muscle stiffness by a
mechanism localized inside the muscle and involving
cross-bridges, the origin of the reported results cannot be
ascribed to such alterations. Actually muscle stiffness
changes induced in sarcomeres by mechanical
perturbations are characterized by a very short duration
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7. limited to the time duration of the same perturbation.
In an attempt to explain the remarkable efficacy of the
pattern of vibratory stimulation we used, we considered
two factors: the characteristics of the vibration (small
amplitude and high frequency) and the combination of
contracting effort with the peripheral sensory activation.
The efficacy of high frequency stimulation could be
explained by taking into account that 100 Hz stimulation
has been reported to facilitate long term potentiation and
learning at the level of the central structures involved in
controlling balance (vestibular nuclei) (Grassi S., Pettorossi
V.E. and Zampolini M., Low frequency stimulation cancels
the high frequency-induced long lasting effects in the rat
medial vestibular nuclei. J. Neurosc., 16:(10): 3373-3380,
1996, Rosenkranz, K., J. C. Rothwell. Differential effect of
muscle vibration on intracortical inhibitory circuits in
humans. J. Physiol. 551.2:649-660, 2003; M. Steyvers,
O. Levin, M., Van Baelen, and
S. P. Swinnen Corticospinal excitability changes following
prolonged muscle vibration. Neuroreport., 14:1901-1905,
2003) while low frequency could cancel it. The explanation
of the efficacy of small amplitude is less obvious.
Proprioceptive network controlling a joint complex (muscle,
tendon and articular structures) is well known to be
powerful activated by mechanical stimulus . Moreover, it
has been reported that high threshold cutaneous and non
proprioceptive muscle afferents have an important role in
controlling the interneuronal activity at level of the spinal
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8. cord, modifying presynaptic inhibition and recurrent
inhibition. Particular combination of afferent inputs may lead
to remarkable difference in the network facilitation.
Finally, the combination of voluntary contraction and
peripheral activation may be efficacious because of
possibility that conditioning process could takes place in the
central nervous system.In fact, the experimental procedure
adopted in the present research could be considered a form
of associative conditioning induced by two temporally
associated stimuli impinging on the same neural network
(Kandel, E. R.. In: Principles of neurosciences. Kandel E.R.,
J.H. Schwartz, and T.M. Jessell (Eds.) Elsevier NY. 1991,
pp. 1009-1031). A powerful signal, generated by the trains
of mechanical perturbations is conveyed to the neural
network controlling the muscle and the joint involved. Since
the subject have to keep the quadriceps muscle in isometric
contraction, it implies that the same network, controlling the
muscle and the knee, is reached by two stimuli temporally
associated: i) the afferent signal elicited by the applied
mechanical perturbations and ii) the voluntary command
determined by the subject to maintain the requested
contraction. Such a situation might be considered a
paradigm of associative conditioning, and may explain the
long term effect of the vibratory stimulation.
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9. Efficacy of conditioning paradigms on proprioception was
clearly evidenced in animals (Wolpaw, J. R.. Acquisition and
maintenance of the simplest motor skill: investigation of CNS
mechanisms. Med. Sci. Sports Exerc. 26:1475-1479, 1994;
Wolpaw, J. R., A. M. Tennissen. Activity-dependent spinal cord
plasticity in health and disease. Annu. Rev. Neurosci. 24:807-
43, 2001 REVIEWS)
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