EUR MED PHYS 2003;39:19-25
Mechanical vibration in the rehabilitation of patients
with reconstructed anterior cruciate ligament
A. SALVARANI 1, M. AGOSTI 1, A. ZANRÈ 1, A. AMPOLLINI 2, L. MONTAGNA 3, M. FRANCESCHINI 1
Aim. More and more, mechanical vibration exercise is
being used in both sports training and rehabilitation
therapy. Many studies have reported an increase in
the muscle performance of subjects after whole-body
vibration, but so far none have evaluated the possibility to improve the recovery of muscle strength after
anterior cruciate ligament reconstruction. The contraindications to this type of treatment are related to
the administration of higher vibration frequency for
periods much longer than those foreseen by our protocol. However, numerous studies have found this
treatment can offer the benefit of reduced frequency
and intensity of the electromyographic tracing,
accompanied by an increase in muscle strenght similar to that obtained after strength training with overload. Hormonal response was also seen to differ from
that after strength training with overload because of a
major increase in blood concentrations of growth
hormone and a reduction of cortisol. The aim of our
study was to evaluate the usefulness of mechanical
vibration in the rehabilitation of patients who
received reconstruction of the anterior cruciate ligament.
Methods. In this study 20 subjects were enrolled and
randomly divided into 2 groups (10 patients and 10
control subjects). The subjects received 5 daily
administrations of whole-body vibration (30 Hz frequency for 1 minute) over a 2-week period. Muscle
force during extension of both lower limbs was evaluated by isometric contraction for 5 seconds.
Results. Different results were obtained: the treatSubmitted for publication November 18, 2002.
Accepted December 27, 2002.
Address reprint requests to: A. Salvarani, UO di Medicina Riabilitativa, Azienda Ospedaliera di Parma, Via Abbeveratoia 8/A, 43100
Parma (Italy). E-mail: [email protected]
Vol. 39 - No. 1
1Rehabilitation Department
Parma Hospital, Parma, Italy
2Casa di Cura “Città di Parma”, Parma, Italy
3Centro Parmense Riabilitativo, Parma, Italy
ment group showed a mean increase in muscle
strength and in mean force peaks, both statistically
significant (p<0.001), compared with the control
group (p<0.005).
Conclusion. The benefits this treatment affords, comprising rapid administration time and ease of application, indicate that it can be useful in the rehabilitation of subjects who receive reconstruction of the
anterior cruciate ligament.
Key words: Vibration - Anterior cruciate ligament, surgery - Rehabilitation.
I
n northern European countries, mechanical
vibration is used in the prevention and treatment
of osteoporosis. In a study conducted by Flieger to
evaluate the effect of whole-body vibratory stimulation to prevent the loss of bone concentration,
differences were found between rats treated with
vibration and controls. Results showed that this
method is efficacious in the prevention of bone
density loss in animal models.1 A study conducted
by Bovenzi on contraindications to the method
showed that the contraindications are closely
linked to repeated administration of vibrations for
prolonged periods at frequencies above those used
in rehabilitation protocols; this finding agrees with
evidence from other studies on hand-held vibrating
tools.2-6
EUROPA MEDICOPHYSICA
19
SALVARANI
MECHANICAL VIBRATION IN THE REHABILITATION OF PATIENTS WITH RECONSTRUCTED ANTERIOR CRUCIATE LIGAMENT
TABLE I.—Rehabilitation protocol after reconstruction of the
anterior cruciate ligament.
Week
1-2
2 Crutches
1 Crutch
Mobilization of knee and patella
Isometric exercise
Electrostimulation
Stretching
Ischiocrural
Quadriceps
Cryotherapy
Weight shifting
Isotonic exercises
Hip
Ischiocrural
Quadriceps
Hydrokinesitherapy
Shoulder massage
Waist massage
Proprioception
Bipedal
Monopedal
Exercise bike
Walking, cycling, swimming
Isokinetics
Running
3-4
5-8
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
9-12
13-16
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
In Italy, fitness centers and sports teams exploit
the effect of whole-body mechanical vibration to
integrate or substitute muscle strength training sessions. The rationale for this practice comes from
studies that have demonstrated that whole-body
vibration can reduce the frequency and intensity of
electromyographic activity,7-14 while obtaining an
increase in muscle force similar to that achieved
with muscle strength training.
The device used in this treatment method is a
force platform on which the subject stands upright,
with a unit that generates vibrations whose frequency and duration the trainer can set to achieve
the desired results. In a study conducted by Bosco
on 12 boxers of the Italian national boxing team,
one arm received 5 one-minute vibration sessions
and the opposite arm performed the same exercise
sets using isometric contraction but without vibratory mechanical stimulation.15 A strength test of isometric muscle contraction in both arms before and
after treatment was performed. The results showed
a statistically significant increase in the muscle
strength of the treated arm, without significant
changes in the strength of the untreated arm. It
20
was also observed that during vibratory stimulation
electromyographic activity augmented, whereas at
the end of treatment it was lower.
In addition, Bosco measured the blood concentration of several hormones in the 14 male study
subjects, all of which regularly practiced sports 3
times a week. After vibratory stimulation, testosterone and growth hormone levels increased, whereas cortisol concentrations decreased. This change
was accompanied by an increase in quadriceps
muscle strength and a decrease in electromyographic activity.16, 17
Moreover, mechanical vibration can be used as
pre-training warm-up or post-training cool-down.
One of the most studied benefits is the enhancement of muscle strength, without the need to overload the joints or the muscle-tendon attachments of
the limbs being trained. Recently, this method has
been adopted by high-profile sports teams in
response to the needs of athletes in intensive
weekly training for participating in more and more
competitive events. The teams also use mechanical
vibration as part of postcompetition cool-down for
muscle recovery and to enhance muscle flexibility,
which greater decreases with fatigue.15
The aim of our study was to evaluate the usefulness of mechanical vibration in the rehabilitation of
patients who received reconstruction of the anterior cruciate ligament.
Materials and methods
Twenty subjects (17 male, 3 female) were included in the study. After informed consent on study
purpose and procedures was obtained, the subjects
were randomly assigned by computer to the treatment or the control group. The treatment group
comprised 10 subjects (mean age 29.7 years±7.8;
mean height 174.1 cm±7.7; mean body weight 72.0
kg±7.6). The control group comprised 10 subjects
(mean age 26.8 years±5.2; mean height 175.2 cm±
8.3; mean body weight 73.2 kg±7.9).
All subjects had received reconstruction of the
anterior cruciate ligament (autologous transplant of
the patellar tendon) performed by the same orthopedic surgeon using the half-tunnel technique. All
subjects followed the same rehabilitation program
(Table I).
After the 1 st evaluation (V1) performed one
EUROPA MEDICOPHYSICA
March 2003
MECHANICAL VIBRATION IN THE REHABILITATION OF PATIENTS WITH RECONSTRUCTED ANTERIOR CRUCIATE LIGAMENT
month after surgery, the treatment group received
mechanical vibration. The protocol provided for one
daily session of 5 one-minute administrations with 1
minute of rest between administrations. The device
(Neuromuscular Mechanical Stimulation - NEMES
Bosco-System®) was set to a frequency of 30 Hz for
the entire duration of stimulation (Figure 1). The
subjects were requested to remain standing upright
on the platform, with knees slightly bent to
approximately 25°, and arms hanging at the sides
of the body. Treatment comprised 10 sessions
spaced out over a 2-week period.
The control group received standard treatment
plus isometric training, with knees bent at approximately 25°, in 10 sessions spaced out over a 2week period, but without mechanical stimulation.
At the end of the treatment period, the subjects
underwent an isokinetic test of knee flexion-extension to evaluate whether the subject was able to
return to preinjury activity levels. After a training
period, all subjects were reassessed (V2), and 2
weeks later evaluated a 3rd time (V3). The purpose
of the tests was to measure lower limb muscle
strength during isometric contraction with extension
of the hip, knee and ankle while standing erect.
The subjects wore a rock climbing harness padded
to protect the skin and connected to the force platform. The distance to the platform could be varied;
at the lower end a steel chain was attached. The
chain was connected to a load cell which was in
turn connected to the force platform. So arranged,
the system could be regulated with a draw chain to
allow maintenance of the knee position flexed at
approximately 25°. Muscle activity of both legs during exertion was recorded on a electromyographic
tracing. The muscles tested comprised the oblique
medial vastus, the biceps femoris and the soleus.
On the signal given by the operator, the subject had
to extend the legs, while exerting maximum muscle
contraction against the constraint of the chain for 5
seconds. The test consisted of 5 leg extensions,
with a 1-minute pause between each.
The load cell (FN3030®) had a range of 500 daN
and a sensitivity of 1.834 mV/V. The system was
powered with a voltage stabilized at 10 Vdc, an
impedance of 351 Ohm in input and output, linearity plus hysteresis was below 0.03% of the upper
limit, the zero offset was less than 5% of the upper
limit. Operation temperature ranged between 0 °C
and +60 °C, isolation was greater than 1 000 MΩ.
Vol. 39 - No. 1
SALVARANI
Fig. 1.—NEMES Bosco-System® force platform.
To telemetrically detect electrical muscle activity,
a multichannel electromyograph (TELEMG) consisting of a patient unit and a base unit was used.
Onboard software (AcqKnowledge3.5.3®) was used
for acquisition, processing and analysis of the electromyographic signals and the signals of the load
cell generated during limb extension.
The test was performed using a closed kinetic
chain, an important factor in this postoperative
phase, to reduce transverse forces on the knee joint.
Isometric contraction was chosen because, in the
presence of movement, surface electromyography
may also record values altered by the skin sliding
over the underlying tissues. The weighted bipedal set
up allowed the subjects to perform the test with only
minor pain and anxiety. Another important consideration was that the test is more accurate the more
closely it reproduces the characteristics of training.
For each group, the increase in force of each
EUROPA MEDICOPHYSICA
21
SALVARANI
MECHANICAL VIBRATION IN THE REHABILITATION OF PATIENTS WITH RECONSTRUCTED ANTERIOR CRUCIATE LIGAMENT
TABLE II.—Strenght measurement (in kg) of treatment (T) and
control (C) groups on evaluation (V1, V2, V3).
F∆t
F∆tc
V1
V2
V3
V1
V2
V3
V1
V2
V3
T
(mean±SD)
C
(mean±SD)
400
249.9±91.7
318.1±98.1
321.4±122.6
172.0±65.4
220.3±72.4
220.2±80.3
226.4±86.7
290.0±95.5
286.2±110.2
195.5±89.0
241.9±94.4
258.0±95.2
142.3±63.5
168.7±67.8
173.0±68.9
179.5±83.0
213.4±88.2
219.4±91.1
300
Mean
P
500
200
100
0
1
2
3
4
V1
6
7
8
9
10
V3
V2
Fig. 2.—Mean of peak forces (P) exerted by treatment group.
400
300
Mean
individual exerted against himself was calculated,
taking into account the mean peak force values (P)
measured during the 5 contractions of each evaluation (V1). The P values were then compared with
the mean values of the subsequent evaluations (V2
and V3). In addition, the length of time each subject needed to perform contraction was recorded,
calculating the mean value of the applied force
(F∆t). The 3rd parameter was the mean value of the
force applied during the mid-second of contraction
∆t (F∆tc).
5
200
100
Statistical analysis
The hospital ethics committee approved the study.
0
1
2
V1
Results
4
5
V2
6
7
8
9
10
V3
Fig. 3.—Mean of peak forces (P) exerted by control group.
The mean values calculated from the evaluation
of the subjects are listed in Table II. Statistical analysis of peak forces was performed using Student’s t
test for dependent samples. The treatment group
showed a highly significant increase in strength
(Figure 2) (p=0.0018) between P1 and P2; significance remained high between P1 and P3
(p=0.0051), whereas peak forces were not significant between P2 and P3 (p=0.8214).
The control group showed a significant increase
in strength (Figure 3) (p=0.017) between P1 and
P2; the significance remained between P1 and P3
(p=0.0121), but peak forces between P2 and P3
were not significant (p=0.0856).
Friedman ANOVA and Kendall’s coefficient of
concordance, which takes into account P in all 3
evaluations, indicated a higher significance of the
22
3
treatment group than the control group (p=0.0023 vs
p=0.0075).
The 2nd parameter studied was F∆t (Figures 4, 5).
The mean force values were analyzed using the
ANOVA test, which showed a high significance for
the treatment group (p=0.0023), whereas, the control
attained threshold significance (p=0.0451). By applying the same test to F∆tc (Figures 6, 7), one can note
that the treatment group maintained significance
(p=0.0203), unlike the values of the control group
which did not achieve significance (p=0.1496).
In our sample, sex, age, body weight and height
did not affect the final result and so were not significant.
In the patients who underwent isometric strength
testing, a common characteristic emerged from the
EUROPA MEDICOPHYSICA
March 2003
MECHANICAL VIBRATION IN THE REHABILITATION OF PATIENTS WITH RECONSTRUCTED ANTERIOR CRUCIATE LIGAMENT
350
SALVARANI
500
300
400
200
Mean
Mean
250
150
300
200
100
100
50
0
1
2
3
4
V1
5
6
7
8
9
0
10
1
V3
V2
2
3
4
V1
5
6
7
8
9
10
V3
V2
Fig. 6.—Mean force exerted by treatment group during midsecond contraction (F∆tc).
Fig. 4.—Mean force exerted by treatment group (F∆t).
300
400
250
300
150
Mean
Mean
200
100
100
50
0
200
1
2
V1
3
4
5
6
7
V2
8
9
10
0
1
2
3
4
5
6
7
8
9
10
V3
V1
Fig. 5.—Mean force exerted by control group (F∆t).
V2
V3
Fig. 7.—Mean force exerted by control group during mid-second
contraction (F∆tc).
analysis of the electromyographic trace (Figure 8).
The trace of the operated medial vastus showed
lower intensity and frequency than the contralateral
medial vastus. This finding is associated with an
inverse tendency of the other 2 muscles studied. In
fact, both the biceps femoris and the soleus of the
operated limb had electromyographic tracings with
a greater discharge frequency than the muscles of
the opposite limb.
Discussion
The results showed that all subjects increased
their peak force values between V1 and V2; however, no significant improvement occurred over the
Vol. 39 - No. 1
subsequent 15 days. If, instead, the increase in
strength between V1 and V3 is compared, it can be
noted that they maintained significance levels in
increase of strength compared with baseline values, indicating that the improvement achieved during the 1st phase was maintained. It should also be
noted that the patients in the treatment group differed from the controls. The increase in strength in
both groups had a P value less than 0.05, whereas
in the treatment group it was more significant in
both comparisons (p<0.01). The significance
remained different also when F∆t was analyzed. In
fact, the treatment group had values with P<0.0023,
compared with the P value of the control group,
EUROPA MEDICOPHYSICA
23
Cell
1.0000
2.0000
3.0000
Volts
Volts
Volts
Volts
Volts
VM_DX BF_DX SOL_DX SOL_SX BF_SX
VM_SX
4.00000
2.00000
0.00000
-2.00000
-4.00000
4.00000
2.00000
0.00000
-2.00000
-4.00000
4.00000
2.00000
0.00000
-2.00000
-4.00000
4.00000
2.00000
0.00000
-2.00000
-4.00000
4.00000
2.00000
0.00000
-2.00000
-4.00000
6.00000
4.00000
2.00000
0.00000
-2.00000
400.000
200.000
0.00000
-200.000
-400.000
Volts
MECHANICAL VIBRATION IN THE REHABILITATION OF PATIENTS WITH RECONSTRUCTED ANTERIOR CRUCIATE LIGAMENT
kg
SALVARANI
4.0000
5.0000
6.0000
7.0000
8.0000
Seconds
Fig. 8.—Electromyographic tracing of patient operated on right knee. The first 3 traces of the left lower limb: medial vastus, biceps femoris,
soleus. The next 3 traces of the right lower limb: soleus, biceps femoris, medial vastus. The last trace shows the load cell expressed in kg.
which was much closer to the threshold value,
demonstrating a positive influence of mechanical
vibration from V1 to V3. Importantly, the force
applied during the mid-second of the test (F∆tc)
was not significant for the values of the control
group (p=0.1496), whereas the treatment group
showed a significant increase in F∆tc.
The scheme of neuromuscular activation
revealed by the electromyographic tracing can be
explained by the compensatory movement the subjects adopted to avoid anterior translation of the
tibia and to better stabilize the knee by substituting
the activity of the anterior cruciate ligament with
the biceps femoris. The major recruitment of the
soleus of the operated limb is used to shift the
weight to the healthy limb.
Conclusions
Rehabilitation plays an important role in facilitating the recovery of muscle strength in subjects who
24
receive reconstruction of the anterior cruciate ligament. Significant improvement was observed in
both groups. Mechanical vibration treatment incorporated within the rehabilitation protocol positively
influenced the recovery of muscle strength.
Improvement was observed in peak force and in
the mean force exerted during isometric testing;
however, improvement was particularly noted in
the mean force of the mid-second of contraction,
which did not occur in the control group, thus
demonstrating better resistance to fatigue.
Other authors have examined changes in electromyographic tracing of muscle activity after
mechanical vibration. If the phenomenon is accompanied by an increase in muscle performance, as
demonstrated in this study, the hypothesis can be
made that neural adaptation takes place in
response to mechanical vibration, with an improvement in neuromuscular efficiency. Hence, the high
significance may be attributed to a better recruitment of the motor units.
A comparison of the benefits gained from the
EUROPA MEDICOPHYSICA
March 2003
MECHANICAL VIBRATION IN THE REHABILITATION OF PATIENTS WITH RECONSTRUCTED ANTERIOR CRUCIATE LIGAMENT
use of this method, with short administration time
(10 minutes per day) and ease of application, suggests that it can be useful in the rehabilitation of
subjects who receive reconstruction of the anterior
cruciate ligament.
SALVARANI
Riassunto
stimolazioni vibratorie inducono sul tracciato elettromiografico. Associando questo fenomeno all’aumentata forza muscolare post-trattamento, l’ipotesi più ovvia è quella di un
miglior reclutamento delle unità motorie, per cui le vibrazioni inducono un incremento dell’efficienza neuromuscolare.
Se si confrontano i benefici apportati da tale metodica,
con il tempo speso per la somministrazione e la semplicità
di applicazione, risulta positivo disporre di tale strumento
nel trattamento riabilitativo dei soggetti sottoposti a intervento di ricostruzione del legamento crociato anteriore.
L’utilizzo delle vibrazioni nella rieducazione di pazienti operati per lesione del legamento crociato anteriore
Parole chiave: Vibrazioni - Legamento crociato anteriore Riabilitazione.
Obiettivo. Le vibrazioni sono utilizzate sempre maggiormente sia nel campo sportivo, sia per trattare alcune patologie. In letteratura sono presenti numerose ricerche riguardo
l’aumento delle prestazioni muscolari in soggetti sottoposti
alle vibrazioni applicate al corpo intero, tuttavia, non esistono studi eseguiti per valutare se sia possibile migliorare il
recupero della forza muscolare in soggetti sottoposti a intervento di ricostruzione del legamento crociato anteriore. Le
controindicazioni di questa metodica sono legate a una somministrazione di vibrazioni di frequenza maggiore e per un
periodo molto superiore rispetto al nostro protocollo. I vantaggi trovati nelle numerose ricerche sono legati ad una riduzione della frequenza e dell’intensità del tracciato elettromiografico, accompagnata da un aumento della potenza muscolare, simile a quella ottenuta dopo un allenamento con resistenze. La risposta ormonale è risultata essere differente
rispetto a quella ottenuta in seguito ad allenamento con resistenza, sia per un maggior aumento dell’ormone della crescita e del testosterone, sia per una riduzione del cortisolo.
Scopo del nostro lavoro è stato valutare l’utilità delle vibrazioni nella riabilitazione di soggetti operati per rottura del
legamento crociato anteriore.
Metodi. Sono stati arruolati 20 pazienti e randomizzati in 2
gruppi: casi, 10 pazienti e controlli, 10 pazienti.
I soggetti sono stati sottoposti, per un periodo di 2 settimane, a 5 somministrazioni giornaliere di una vibrazione di
30 Hz, della durata di 1 minuto. La valutazione della forza,
espressa dall’estensione di entrambi gli arti inferiori, è stata
effettuata mediante una contrazione isometrica, della durata
di circa 5 secondi.
Risultati. Il gruppo sperimentale ha ottenuto risultati differenti dal gruppo di controllo, in quanto l’incremento della
forza media, espressa durante tutto il periodo di contrazione,
e l’aumento della media dei picchi di forza, raggiunti durante
ogni valutazione, sono risultati altamente significativi
(p<0,01), contro la significatività dei dati del gruppo di controllo (p<0,05 ma non p<0,01). Di grande importanza è la
forza espressa durante il secondo centrale della contrazione,
perché non esiste significatività tra i valori registrati nel gruppo di controllo, mentre il gruppo trattato si distingue grazie a
un incremento significativo di forza.
Conclusioni. Altre ricerche trattano le modificazioni che le
Vol. 39 - No. 1
References
1. Flieger J. Mechanical stimulation in the form of vibration prevents postmenopausal bone loss in ovariectomized rats. Calcif
Tissue Int 1998;63:510-4.
2. Bovenzi M. Exposure-response relationship in the hand-arm
vibration syndrome: an overview of current epidemiology
research. Int Arch Occup Environ Health 1998;71:509-19.
3. Gemne G. Bone and joint pathology in workers using handheld vibrating tools. Scand J Work Environ Health 1987;13:290300.
4. Griffin MJ. Handbook of human vibration. London: Academic
Press; 1990.
5. Nakamura N. Change in digital blood flow with simultaneous
in plasma endothelin induced by end-arm vibration. Int Arch
Occup Environ Health 1996;68:115-9.
6. Necking LE. Vibration-induced muscle injury. J Hand Surg
1992;17B:270-4.
7. Bongiovanni LG. Prolonged muscle vibration reducing motor
output in maximal voluntary contractions in man. London: J
Physiol 1990;423:15-26.
8. Gandevia SC. Fusimotor reflexes in relaxed forearm muscles
produced by cutaneous afferents from the human hand. J
Physiol 1994;479:499-508.
9. Kodaki K. Difference in electromyographic response of finger
flexion muscles between tonic vibration reflex and finger flexion reflex induced by finger tip vibration. Neurosci Lett
1987;75:303-7.
10. Lebedev MA. Analysis of the interference electromyogram of
human soleus muscle after exposure to vibration. Neirofiziologiia 1991;23:57-65.
11. Ribot-Cyscar E. Muscle spindle activity following muscle tendon vibration in man. Neurosci Lett 1998;258:147-50.
12. Rittweger J. Acute physiological effects of exhaustive wholebody vibration exercise in man. Clin Physiol 2000;20:134-42.
13. Seidel H. Myoelectric reactions to ultra-low frequency and lowfrequency whole body vibration. Eur J Appl Physiol 1988;57:
558-62.
14. Kasai T. The effects of wrist muscle vibration on human voluntary elbow flexion-extension movements. Exp Brain Res 1992;
90:217-20.
15. Bosco C. Influence of vibration on mechanical power and electromyogram activity in human arm flexor muscles. Eur J Appl
Physiol 1999;79:306-11.
16. Bosco C. Hormonal responses to whole-body vibration in men.
Eur J Appl Physiol 2000;81:449-54.
17. Bosco C. Monitoring strength training: Neuromuscular and hormonal profile. Med Sci Sport Exerc 1998;32:202-8.
EUROPA MEDICOPHYSICA
25