Rhythmic Auditory Stimulation
(RAS)
 Developed primarily by Thaut, McIntosh, & Rice
at the CBRM at Colorado State University
 NMT technique utilizing the physiological effects
of rhythm on the motor system to increase the
efficiency of controlled movement patterns
during rehabilitation.
 Enhancement of gait is mediated by an
entrainment effect where movement frequencies
and motor programs entrain to rhythm through
anticipatory cuing of functional movement
patterns.
RAS Uses
 Immediate entrainment
stimulus providing
rhythmic cues during
movement.
 Listen to music with
strong rhythmic pulse
while walking to enhance
walking tempo, balance,
and control of muscles
and limbs.
 Stimulus for training
where patients train with
RAS for a prescribed
period of time in order to
achieve more functional
gait patterns which they
then transfer to walking
without rhythmic
facilitation.
Mechanisms
 Rhythmic Entrainment
 Priming of the Auditory Pathway
 Cuing of the Movement Period
 Step-Wise Limit Cycle Entrainment
Rhythmic Entrainment
 Physiological basis for the perception of
rhythm is the detection of periodicity
patterns in amplitude modulations of sound
 External rhythm serves as an external
oscillator which has a “magnet” effect on
one’s internal timekeeper.
 Strength of the effect is substantiated by
the observation that motor responses can
be entrained by rhythmic patterns even at
levels that are imperceptible.
Auditory-Spinal Facilitation
 Physiological entrainment of muscle activation through
rhythm perception takes place via reticulospinal
pathways.
 Neurons in the spinal cord become excited as a result of
auditory perception.
 Support for these concepts were observed in research
when many components of the neural synchronization
network were already activated and “entrained” simply by
listening to rhythm.
 One result of neuronal excitement is the “priming” or
“readying” of muscle groups utilized in movement, which
has a facilitative effect on subsequent motor functioning.
Cuing of the Movement Period
 Period Synchronization - adaptation of the movement
duration to the rhythmic stimulus duration
 Phase Synchronization - ISI and IRI are closely matched
although period synchronization is not behaviorally
observable.
 Kinematic models show that period (or frequency)
entrainment results in enhanced kinematic stability
through the stabilization of the following parameters:
acceleration, velocity, trajectory).
Step-Wise Limit Cycle Entrainment
(SLICE)
 RAS frequencies (tempi) need to be set initially
at a pt.s ‘resonant’ (current or intrinsic) frequency
of movement.
 Limit cycles are frequencies at which any moving
system performs optimally (developed in the
fields of engineering, physics)
 Hence, RAS frequencies should be adapted to a
person’s current limit cycle, i.e. the current step
cadence.
SLICE cont’d
 Initial purpose of RAS is to stabilize movement
parameters at a pt.s current limit-cycle.
 New limit cycles can be gradually entrained
through a step-wide incremental process to
approximate a pt.s pre-morbid limit-cycle.
 Ex. When using RAS to increase cadence of PD
pt.s, stride lengths will increase also due to the
mechanical properties of the gait generating
system.
SLICE cont’d
 In the case of pt. who has a nearly normal
cadence with shortened stride length, RAS is
used to match the current cadence or a slightly
slower one in order to increase stride length
through added kinematic stability which is
present due to the entrainment process.
 SLICE - most commonly used RAS protocol in
the treatment of gait disorders.
RAS Gait Training Procedures
 Assessment
 Resonant Frequency Entrainment
 Frequency Modulation
 Advanced Adaptive Gait
 Fading
 Reassessment
Cadence Assessment
 Cadence - steps/minute
 Client walks for 60 seconds while you
count each step; walks for 30 seconds then
multiply steps by 2)
 This is unaccompanied by music.
 Avg. cadence for an adult is 105-120
steps/min but is age related.
Velocity Assessment
 Velocity - Meters/minute or feet/minute
 Measure distance across time
 Pt. walks for 60 seconds and you measure how
many meters or feet they walked (multiply by 2 if
walking for only 30 seconds)
 Difficult to do because of space limitations.
 Hospitals usually have 1-foot floor tiles. Count
the tiles to get a feet/min measurement, then
divide by 3.281 for meters/min (1 meter = 3.281
ft.)
Velocity Assessment cont’d
 Measure off 10 meters on the floor.
 Time the number of seconds it takes a pt. to walk 10
meters. *Have them start a few ft. before and continue
going for a few ft. past the line.
 Divide the number of seconds by 60 (60 sec/min)
 Divide 10 meters by the number of minutes which gives
you the meters/minute value.
 Ex. Pt. walks 10 meters in 7 seconds
 7 sec/60 sec/min = .117 minutes
 10 meters/.117 minutes = 85.5 meters/minute
 Avg. normal velocity in adults is 80 m/m, but is age
dependent.
Stride Length
 Divide velocity by cadence.
 This will provide the number of meters for each
step. (*This in inaccurate if there is uneven step
length between the right and left legs)
 Multiply this figure by 2 and this will give you
the average stride length.
 Ex. 70 meters/min (velocity) / 80 steps/min
(cadence) = .875 meters/step
 .875 meters/step x 2 steps/stride = 1.75 meters
avg. stride length.
Step 2 Resonant Frequency Entrainment
 Match RAS frequency (music tempo) to gait
cadence and walk with patient.
 Pt.s who are not ready for sustained walking
exercises can practice specific pre-gait exercises,
e.g. weight shifting - front to back, side to side,
etc. 6/8 tempo usually more preferable
 Therapist may need to cue proper gait mechanics,
e.g. stride length, arm swing, posture, toe
clearance, heel strike, etc.
Step 3 Frequency Modulation
 Increase tempo by no less than 5% ~ an increase that still
allows them to maintain proper mechanics.
 Again use verbal cues, but feedback should be kept to a
minimum as you may interfere with rhythm perception
and its subsequent effects
 Clients who have attention problems may need enhancing
verbal cues initially, e.g. left-right, 1-2
 Generally, frequencies (tempi) that are more closely
aligned with a pt.s pre-morbid state tend to more have the
strongest effect on overall gait patterns.
 In some cases, a deceleration in RAS frequency is
indicated for pt. groups who have the proclivity for
unsafe walking patterns.
Considerations
 2/4 or 4/4 meter with strong beat accents (1 & 3)
 If a pt. utilizes an assistive device, cane or
walker, a 3-step pattern may be more useful, e.g.
step, step, walker
 The motivational quality of music is a bonus
secondary effect ~ client preferences. Note that
some diagnoses do not perceive complex acoustic
patterns well so very simple music or simply a
metronomic click would work best.