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Dissertation

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by

Kerry Smith

on 16 June 2014

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Transcript of Dissertation

Background
Why look at plantaflexors?
Background
An investigation into the effect of multifidus vibration on ankle plantarflexor stretch reflex (PFSR) activity in healthy individuals

The reduction of the duration of the PFSR found was evident in the short latency (Ia afferent).

Clinically, this may be applicable to patients with spasticity .
Findings
Peak Muscle EMG
SUM Muscle EMG
Data not normally
distributed

Freidman: p= 0.393 (p>0.05)

Post-hoc analysis: n=41


SUM Torque
Data not normally
distributed

Friedman: p= 0.191 (p>0.05)

Post-hoc analysis: n=65
PFSR Duration
Data not normally distributed

Friedman: p= 0.039 (p<0.05)

Post-hoc analysis with one-tailed Wilcoxon test applied:
Contralateral and ipsilateral vibration, P=0.459 (P>0.0167)
Ipsilateral vibration and control, P=0.022 (P>0.0167)
Contralateral vibration and control, P=0.010 (P<0.0167)
Can vibratory stimulus to the multifidus modulate the plantaflexor stretch reflex?
Methodology
Outcome Measures
Tone can be defined as a resistance exhibited to passive stretch.
A mechanism that contributes to tone is stretch reflex (SR) activity.



Research Question
Different positions or postural sets can influence tone in different ways and is used clinically.

Is it possible to stimulate different sensory systems to influence tone in distant places?
Spasticity is the most common condition of increased muscle tone.

Traditionally, physiotherapists have used the Bobath concept to attempt breaking up spastic patterns.
Plantarflexors are commonly affected in people with spasticity. This results in an increased incidence of falls and decreased function.
Why use vibration?
Muscle vibration can induce the illusion of a muscle stretch.

Vibration is shown to modulate SRs at distal sites as demonstrated by seminal studies in the 1920s on decerebrate cats (Liddel et al, 1925).

Several studies have explored the effects of local vibration on SR size (Myriknas et al, 2000; Dimitrijevic et al. (1980)

Sasaki and Polus (2012) found that neck vibratory stimulus increased the excitability of the extensor muscles of the lower limbs.


Design
-A single-group repeated measure design

Participants
-21 healthy individuals

Position
-Participants were tested in a relaxed, prone position with their head turned to the right, the pelvis and right thigh strapped to the plinth, and shoulder pads adjusted appropriately.

Surface electromyogram (SEMG)
-Electrodes were positioned on tibialis anterior and medial head of gastrocnemius.

Ankle perturbatio
n-The right foot secured using two straps and the ankle axis was aligned to the axis of the customised servomotor
.

Vibratory Stimulus (0.5 s prior to stretch)-
Vibrators were applied 1cm either side of L2 spinous process.

Eighty stretches were randomly delivered

Data Analysis
Results

Following the stretch, muscle activation was seen.

Data normally distributed

ANOVA: p=0.227 (p>0.05)

Post hoc analysis: n=33488
Peak Torque (Nm)
Data normally distributed

ANOVA: p= 0.995 (p>0.05)

Post-hoc analysis: n=155,103
Normally Distributed Data
Parametric
Repeated Measure ANOVA
(mean and SD)
Level of Significance set at
P<0.05
Data not normally distributed
Non-parametric Friedman Test
(median and range)
Significance level set at P<0.05
Wilcoxon test
Level of significance set at P<0.0167 using a Bonferroni correction (0.05/3) to account for multiple comparisons


A Kolmogorov-Smirnov (KS) test analysed the normality of the data.
Discussion


Hypotheses partially accepted as statistically significant results were produced when modulating duration of SR of the contralateral multifidus muscle


Strengths


Standardised positioning.

Delivery of randomised stereotype stretch and vibration (to negate order effect and habituation).

SEMG was used as a direct measure of PFSR.

Analysed the onset of data using the mean +4 standard deviations .

Limitations


Multiple studies in the laboratory during data collection.

Multifidus is a deep muscle.

Adipose tissue.

Larger baseline (plus 4 standard deviations).
Did we succeed in modulating the PFSR
Further Research
Raw Data
Low pass filter
50 Hz Filter
Rectified
Chuang et al, 2012; Bobath, 1990
Marsden et al, 2012
Aim
Data was screened for artefact, filtered and rectified
To confirm the statistical significant finding of contralateral vibration on multifidus, further research is required with patients with PF spasticity
Larger study population of healthy individuals
Ipsilateral Vibration
Duration

SUM SEMG
SUM Torque
Conclusion
This study has identified for the first time that contralateral vibration of the lumbar multifidus reduces the duration of the PFSR in healthy individuals
Implication to Practice
Modulation of the SR can occur by pre and post-synaptic inhibition of neurons in the arc
We hypothesise that vibration stimulation of the contralateral multifidus muscle would reduce the size and/or duration of the PFSR and stretch-mediated ankle stiffness
Off Set
Full transcript