Basic Concepts of Muscular
Conditioning
Frank J. Cerny, PhD
Increases in muscular strength or
endurance
• Neural
MOTOR UNIT
Basic Components
•
•
•
•
– Central output
– feedback
• Muscle
Nerve Cell Body
Axon
Neuromuscular Junction
Muscle Fiber
– Size
– Characteristics
Motor unit 1
Motor unit 1
+ or -
Motor
neurons
Motor
neurons
Motor unit 2
Motor unit 2
+ or -
Spinal
cord
Muscle fibers
Descending cortical inputs
(+ or -)
Spinal
cord
Sensory input
(feedback)
Muscle fibers
Motor unit recruitment
Motor unit 1
• Dependent on speed and force of
contraction
+ or -
Motor
neurons
– Think specificity
Motor unit 2
+ or -
Spinal
cord
Sensory input
(feedback)
Muscle fibers
1
Basic Concepts of Muscular
Conditioning
Frank J. Cerny, PhD
Gating by interneurons
Neural adaptations
Descending cortical inputs
(+ or -)
• MU activation
– Maximal = greater
– Submaximal = fewer
• MU Synchronization
– Fine motor
performance
– Decreased variability
Descending
control signal
Motor
neuron
-ve
Motor unit 1
+ or -
+ve
Motor
neurons
Sensory input
Motor unit 2
Interneuron
+ or -
• Muscular coordination
• Within a muscle
• Among muscles
Muscle fibers
Sensory input
(feedback)
Spinal
cord
“disinhibition” helps explain how a person
can get “stronger” with resistance training
without any change in size of the muscle
Muscle adaptations
Descending cortical inputs
(+ or -)
• Muscle fiber
characteristics
– “twitch” characteristics
– Metabolic characteristics
Motor unit 1
+ or -
Motor
neurons
Motor unit 2
+ or -
Spinal
cord
Muscle fibers
Sensory input
(feedback)
Motor Unit Heterogeneity
• Basic classification - Type I, IIa, IIb
• Oversimplification
• Human muscles have a variety of MU’s
all with different characteristics
• slow
fast, oxidative
glycolytic
• provides a functional continuum
Myosin ATPase
stain in acid to
show Type I
fibers
Myosin ATPase
stained alkaline
to show opposite
2
Basic Concepts of Muscular
Conditioning
Frank J. Cerny, PhD
Factors to Consider when
Developing a Training Program
• Training quality
• The specific effect of training on
the muscles is dependent on the
specific stimulus.
– specificity
• endurance
• strength
• Training quantity
–Determine the metabolic and
muscular demands and devise
strategies that target those specific
demands.
– intensity
– duration
– frequency
Training Overload
% CHANGE
TRAINING SPECIFICITY
• To obtain an change in structure
(strength) or function (endurance) the
muscle must be taxed beyond some
critical level
• Progressive
Increases in strength after
8 wks squat training
75
Specificity
50
25
SQUAT
LEG PRESS
KNEE EXTENSION
Maximal
Over training zone
Training
Rebuilding time
Upper
Threshold
• Need recovery time
Lower
Threshold
– The adaptive changes occur during periods
of rest.
• >24 hours for particularly strenuous
The Overload Principle
3
Basic Concepts of Muscular
Conditioning
Frank J. Cerny, PhD
Strength Training
Conclusion
Near maximum resistance
• Change, or improvement, of a particular
movement task
• 6 - 10 repeats for best results
• 2 - 4 sets for each muscle group or
specific motion
– Neural alterations
– Muscle alterations
• Specificity
• overload
4
What do we Know about Exercise
Based Treatments?
Use it or Lose it
Muscle Training Principles
Influence Voice, Speech & Cough
Failure to drive specific brain functions
through training can lead to the degradation
of that function
Failure to drive muscle activity results
in peripheral loss of function
Christine Sapienza, Ph.D.
University of Florida
Brain Rehabilitation Research
Center
Malcom Randall VA
z Kleim’
Kleim’s
group and others (e.g. Vaynman &
confirms that exercise
training impacts molecular systems
important for maintaining neural
function and plasticity.
z i.e. BDNF, survival and neurogenesis
GomezGomez-Pinilla., 2005)
But what about the science..
The concepts of strength training
The challenges of developing the
appropriate model to study training
z The design and delivery of our methods
and what we are measuring peripherally
z Future design for testing changes to brain
z
And if we could…
z
z
•
•
BUT EXERCISE IS NOT EXERCISE, IS NOT
EXERCISE
Results from limb and hand studies suggest
that resistance/strength training, in
particular,, changes the functional properties
of spinal cord circuitry in humans, but does
not substantially affect the organization of
the motor cortex.
z
“Revenge of the "sit": how lifestyle impacts
neuronal and cognitive health through molecular
systems that interface energy metabolism with
neuronal plasticity”
Gomez-Pinella, 2006)
plasticity” (Vaynman & Gomez“License to run: exercise impacts functional
plasticity in the intact and injured central nervous
system by using neurotrophins”
Gomezneurotrophins” (Vaynman & Gomez-
“Loud and Big, Keep on Talking and
Moving…
Moving…
z “License for loaded breathing..
z Strength training for swallowing survival…
survival….
z
Pinella, 2005)
z
“Motor training induces experience specific
patterns of plasticity across motor cortex and
spinal cord”
cord” (Adkins, Boychuk, Remple & Kleim, 2006 (eprint)
What’s potentially changing?
If this is true – should we not strength train
because it may not change the brain
z
z
z
z
z
z
z
Carroll, T.J., Riek, S., & Carson, R.G. (2002). J. Physiology,
544(pt2), 641641-652. and Adkins, Boychuk, Remple & Kleim
Don’t think so because even changes to corticospinal
drive, changes to muscle
are positive environmental changes
and there is still not enough evidence…..
Increased synchronization
Descending drive
Muscle activation
Motor unit firing rates
Strength
Glycolytic enzymes
Contractile properties of muscle including fiber
type, CSA, and inorganic phosphate content
(Leiber., 2002)
1
Multiple Levels of Plasticity
z
z
z
z
Multiple Populations of Interest to
Help and Study
In those with PD
That which changes brain (neural electromyographic evidence)
That which changes muscle (myogenic(myogenicstructural evidence
That which changes performance
(behavioral)
The clinical picture does not typically
implicate muscle weakness
z Yet, study outcomes show strength is
reduced even when ample time is
provided to generate force
z Results point to insufficient neural
activation as muscles during nerve
stimulation have normal strength
z
Identify which level you intend to study and
which mechanistic change you are defining
e.g.
Parkinson’
Parkinson’s disease, multiple sclerosis,
spinal cord injury, laryngeal airway
limitation, ataxia, TBI
z Singers
z Instrumentalists
z
z
Glendinning (1994;1997)
Forced Breathing
Quiet expiration: begins when gravity
and elastic forces act upon the ribcage,
decrease lung volume, increase
intrathoracic pressure (more
(more than the
atmospheric pressure)
z Air flows out of the lungs when a balance
is reached between the tendency of the
chestwall to expand and the lungs to
collapse.
z
How do we Breathe for Speech
and other Tasks?
Forced inspiration: accessory inspiratory
muscles are recruited to help the
diaphragm and the external intercostals
increase the lung volume
z Lung volume is increased, intrathoracic air
pressure is more decreased (Much
(Much less
than the atmospheric pressure)
pressure)
z
Respiratory System
Forced expiration: All expiratory
/abdominal muscles contract pushing
against the diaphragm, which is raised
z Decrease lung volume, increase
intrathoracic pressure (Much more than
the atmospheric pressure)
z
z
z
When we relax, diaphragm returns to its
natural position (domed)
The cycle is repeated-- increase in lung
volume----air flows into the lungs------
Subglottal
Pressure
Demand
Active Expiratory
Mechanism
2
What happens when you have
PD?
Motor unit discharge is irregular
z Larger number of motor units are recruited
at lower thresholds
z Antagonistic muscles are abnormally cocoactivated
z
The act of breathing is compromised by the disease state
affecting anatomical sites ranging from the cerebral
cortex, basal ganglia, brainstem to the alveolar sac.
z
Weakness of the respiratory muscles can dominate the
clinical manifestations in the later stages
z
Structural abnormalities of the thoracic cage interfere
with the action of the respiratory musclesmuscles-again in a
unique manner
z
The hyperinflation that accompanies diseases of the
airways interferes with the ability of the respiratory
muscles to generate subatmospheric pressure and it
increases the load on the respiratory muscles
z
(Glendinning & Enoka, 1994)
Laghi & Tobin (2003)
Reductions in Respiratory Muscle
Strength
z
Lower airway obstruction, lower airway
restriction, upper airway obstruction, and
muscle weakness
z Respiratory system involvement is REAL is more than what is perceived - and
pneumonia is one of the common causes of
death in this disorder.
z
z
Flow Volume Loops show:
Maximum Inspiratory and Expiratory Pressures
Alterations in Flow and Volume
250
cmH2O
200
150
100
50
0
Actual MEP
Predicted MEP
(Black & Hyatt, 1969)
Implementation of a Device
Driven Program
z
From Pump to Larynx
Supraglottal
Laryngeal
Healthy
Design
Intensity Matters
PD
Load versus No (Low) Load
z
Induction of plasticity (spinal
or cortical) requires sufficient
Is strength training with no load truly
strength training or just a practice effect?
z Respiratory Exercises
z Vocal
Exercises
Silverman Voice Treatment
z Expiratory Muscle Strength Training
z Lee
training intensity
z
Is it sensory or motor manipulation?
Respiratory
3
Provides specific, constant,pressure load (spring
loaded valve 00-150 cm/H20)
Loaded Spring
Hypothesized Target Muscles
z
Rectus abdominis, external abdominal
oblique, internal abdominal oblique and
transversus abdominis.
Adjustable Valve
Mouthpiece
EMG activation during MEP
Inductotrace (RC + AB)
signal
Result:
Adaptations
Defining changes?
z
Strength – defined by ability of muscle
to move weight
Progress
Strength
• Neural
adaptations
(6-8 weeks)
Hypertrophy
Rectus Abdominus
Neural adaptations
External Oblique
(with likely contribution from
Internal Obliques & Transverse
Abdominis)
• Myogenic
adaptations (5+
weeks)
Time
Design and Delivery
Current Study
Maximum Expiratory
Pressure
Strength Defined by Changes in
MEP
160
MEP
Pre
Post
140
200
180
160
140
120
100
80
60
40
MEP cmH20
120
Pre1
Pre2
1
2
3
4
Post (5)
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Last
cm H2O
90 Patients with PD
Stage II and III
Randomized
Two Group
Experimental (Device Driven)
Sham
(Modified from Sale, 1988)
Baselines
100
84% increase
80
60
40
20
0
1
2
3
4
5
6
7
Subject
4
Dyspnea Scale Rating
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Dyspnea
Physiologic Effort Significantly
Decreased
ƒ
Task Became Easier
ƒ
Improved Ability to Maintain High Levels
of Ventilation During High Expiratory
Loads
Pre
Post
1
2
3
4
5
6
7
Subglottal Pressure
ƒ
1 = None; 2 = Mild; 3 = Moderate; 4 = Mod-Sever; 5 = Severe-Profound
¾
PostPost-hoc analysis indicated that the ratio of Ps
to MEP decreased anywhere from 32 – 52%
¾
Proportion of subglottal pressure used
relative to the MEP generated by the subjects
decreased
¾
Decreased Ps/MEP ratio indicates less
physiological stress because there is more
reserve
¾
Relates to the decrease in sensation of
breathlessness
25
Subglottal Pressure
Maximizing the Container
MIP (cm H20)
Spinal Cord Injury
20
10
5
Tidal Volume (L)
0
ACOUSTIC CHANGE (Pre to Post IMST)
% Change
Sustained Vowel Production using Passy Muir
Spontaneously Breathing
10
0
-10
-20
-30
-40
-50
-60
-70
-80
FF
SDFF
Jit
Shim
NHR
Voice Handicap Index
48.5%
Increase
In MIP
15
1
2
3
1
2
3
4
Weeks
4
5
6
800
600
400
200
0
5
6
Age Matters Too
Pre
Post
Functional
20
25
Physical
18
25
Emotional
19
24
Total
57
74
Training induced plasticity occurs more
readily in the young brains and muscles
z But don’
don’t ignore the old?
Consider irreversible vs. reversible
changes
z
dB SPL
5
Maximizing Performance:
Reversible Muscle Changes
Muscle Mass loss due to individual
muscle fiber atrophy (Brooks, 2003)
z Reversible and preventable through
exercise
MEP AND MIP
Sedentary Elderly
Taking advantage of reversible muscle
changes
z
140
•10 week balance training only vs. resistance
training + balance training –
• Combined group- 52% increase in strength
F 1, 17 = 40.978, p < 0.001, 44%
Mean ± 2SE (cm H2O)
Mean +- 2 SE (cmH2O)
120
• Balance training only- 9% increase only
• Improved sensory orientation
• Improved balance with lesser falls
(Hirsch et al., 2003)
100
110.70 ± 26.12
80
60
F 1, 17 = 18.513, p < 0.001, 49%
77.32 ± 20.12
58.42 ± 18.71
•Possible neuromuscular adaptations to reduce
the abnormal agonist and antagonist muscle
activation patterns
40
39.08 ± 13.18
20
MEP Post
(Glendinning, 1997)
MEP Pre
MEP Post
MIP Pre
MIP Post
MEP Pre
MEP Pre
14
12
Cough
Flow (L/s)
10
MANOVA - Wilks’ Λ = 0.351, F 5, 13 = 4.803, p = 0.010
CPD
F 1, 17 = 13.590, p = 0.002, 53%
PEFR
F 1, 17 = 29.620, p < 0.001, 61%
6
Pre Strength
Training
Pre Strength
Training
z
2
0
-2
L/s
.3
10
-6
9
14
8
12
0.35 ± 0.19
5
.1
0.16 ± 0.17
0.0
Pre
Pre
Post
Training
Post
4
Post Strength
Training
8
8.00 ± 3.06
6
.2
Peak flow
Lose it
z Functional repercussions
z Progressive loss of muscle mass
z 30%
loss of muscle mass from 50-80 years
(Berger et al., 1988)
10
7
Pre
Flow (L/s)
.4
What if Nothing is Done at All?
4
-4
.5
milliseconds
Peak flow
8
Post
4.89 ± 2.18
3
loss of Strength (due to
force and power losses)
6
4
2
0
Pre
z Progressive
1
61 121 181 241 301 361 421 481 541 601 661 721 781 841 901 961102110811141120112611321
-2
Post
-4
-6
Time (msec)
Current Projects
Support for Cortical Plasticity
z
Neurogenic adaptations: TMS (Chhabra,
Chhabra, Kleim,
Kleim,
Atkins & Pringle, Sapienza)
z
Examining the effects of motor experience
(EMST) on the topography of movement
representations in the abdominal muscles
of healthy volunteers
z Hypothesis:
Increase in
corticospinal excitability will be
found with strength training
increase
6
Parkinson Induced Rats
Unilateral induced rats with 66-OHDA.
z Multiple Aims but one Aim is:
z
More…
z
Expose to a respiratory obstructive load, via
a tracheal occluder,
occluder, allowing training of the
respiratory muscles prior to lesion induction.
This paradigm examines the presence of
neuroprotective mechanisms.
z Brain function will be defined by
neuroanatomical analysis
z
IF IT WERE THIS EASY..
Future directions
Translational Research
Animal to Human
Bench Research
Exciting avenuesavenues- possibilitiespossibilities-different
animal models
z LimitationsLimitations- differences in fiber types of
humans versus animals
z How far can we stretch the animal model
to answer questions in humans…
humans…where do
we draw the line?
z
z
Thinking
Loud
Challenges (Animal)
Thinking
Loud
z
Say “ahhhh” for as
long as you can
Model Development
z Picking
the right animal
data from spinal to cranial
muscles
z Transferring
z Most
work done in upper and lower extremities
z Complexity of
measuring cortical plasticity
versus peripheral adaptations (special training
for us)
Say “ahhhh” for as
long as you can
Challenges (Human)
z
Model Development
z Understanding
the complexity of the disease
measuring cortical plasticity
versus peripheral adaptations
z Variability in performance
z Motivation
z Interference (Fine line between Training and
inducing Muscle Fatigue)
z Complexity of
7
Translation…
….
Team
z
z
z
z
z
z
SLP Colleagues (J. Rosenbek & N. Musson)
Study Coordinator (Michelle Troche, PhD student too)
Neurology (M. Okun & H. Fernandez)
Physiology & Physical Therapy (P. Davenport & D.
Bolser)
PostPost-Doc: Toni Chiara, Ph.D.
Doctoral Students
z Chris Carmichael
z Teresa Pitts
z Anuja Chhabra
8
Tongue Strengthening Exercises:
Oral Motor Exercise Which
Improves Swallowing
JoAnne Robbins, PhD
Professor, University of Wisconsin School of Medicine
and Public Health
Associate Director for Research
Geriatric Research Education and Clinical Center (GRECC)
William S. Middleton Memorial Veterans Hospital
American Speech Language Hearing Association
November 15, 2007
Swallowing Neural Control
Swallowing:
Moving food, liquid, secretions
or medications from the mouth
to the stomach, usually by a
series of muscle contractions
causing pressure changes in
the aero-digestive tract
Dysphagia
A swallowing disorder
characterized by difficulty…
Lungs Esophagus
Diagnostic Tools
Interventions
Until 1980’s:
Brainstem Reflex
• invariant
• output at a “local” level
Large scale distributed swallowing
neural network
Treatments Emerged:
For the Patient
through the environment
Food
Fluid
Positioning
By the Patient
Chin tuck
Head turn
Jaw extension (“jaw jut”)
Mendelsohn manuever
Exercise
Increasingly
demanding
(Zald & Pardo; Robbins, Annals of Neurology, 1999)
1
Exponential growth of the population of
older adults:
• As of July 1, 2005, there were an estimated 78.2
million American baby boomers (those born between
1946 & 1964)
• In 2006, baby boomers began turning 60 at a
rate of about 330 every hour
• Increase in longevity = potential for increase in Years
of Healthy Life (YHL)
(DHHS, PHS, 1996)
1991 - 1998
Hospitalization of elderly Medicare
beneficiaries for aspiration pneumonia
increased by 93.5%
WHY?
(Baine et al. Amer J of Pub Health, 2001)
Adults over age 65 swallow slower than
younger counterparts
Initiation of laryngeal & pharyngeal events,
including:
• laryngeal vestibule closure
• maximal hyolaryngeal excursion
• upper esophageal sphincter (UES) opening
Are all delayed significantly longer relative to oral
bolus transport than in younger adults.
™ Thus, the bolus is next to an open airway longer.
(Tracy et al, 1989; Robbins et al, 1992;
Shaw et al,1990; Shaw et al, 1995)
Neural Plasticity
PRESBYPHAGIA: age-related changes in
swallowing as demonstrated by healthy
older individuals
56 year old female
Changes in the functioning of a neural substrate and the possible alteration in
behavior can be secondary to influences such as:
•
•
•
•
•
•
•
•
Experience
Learning
Development
Aging
Change in use
Injury
Response to injury
REHABILITATION
(Tinazzi et al, Brain, 1998; Urasaki et al, J Clin Neurophysiol, 2005;
Ziemann et al, J Neurosci, 1998)
Grade = 0, Higher Cortical
Grade = 1, Lower Cortical
Single UBO with subcortical region
(white small)
(Levine, Robbins and Maser, Dysphagia, 1992)
2
Horizontal
Pressure applied
V
e
r
t
i
c
a
l
Hypothesize
that pressure
changes
with age
Strength as measured by pressure applied
to air-filled bulb
Isometric Lingual Resistance
Isometric Lingual Resistance
• Iowa Oral Performance Instrument (IOPI)
• Press tongue to roof of mouth (isometric)
• Anterior & posterior tongue
• Iowa Oral Performance Instrument (IOPI)
• Press tongue to roof of mouth (isometric)
• Anterior & posterior tongue
Isometric Pressures
IOPI Protocol
(3 Trials)
“Press your tongue against the bulb as hard as possible”
• Measured using the IOPI
• One repetition maximum:
highest value achieved one
time only
• 2 sets of 3 repetitions
• Average of sets do not differ
> 5%
Isometric Pressure
(kPa)
Set 1
Set 2
32
29
28
27
• press bulb with tongue as hard as possible
– maximum isometric pressure
• swallow with tongue bulb in place
– maximum swallow pressure
31
28
(Robbins et al, J of Gerontol, 1995)
3
Tongue Strength
Findings: Older adults
generate reduced isometric
pressures relative to their
younger counterparts…
But swallow pressures
remain the same as young
Swallowing Functional Reserve
Findings: max isometric pressure: swallowing pressures
• ability to adapt to stress
(Pendergast et al, 1993)
• decreases with age
• risk factor for dysphagia in elderly when
combined with poor medical condition,
chronic or acute illness, mechanical
perturbation
(Robbins et al, J of Gerontol, 1995; Nicosia et al, J of Gerontol, 2000)
Why does
lingual
strength
change with
age?
Anatomical MRI Data
Eight weeks of progressive resistance training on
skeletal muscle in the frail elderly population has
been associated with increased:
•
•
•
•
•
Gait speed
Activity level
Stair climbing
Endurance
Function
(Fiatarone et al., JAMA 1990; N Engl J Med, 1994)
38 Yr Old Female
81 Yr Old Female
Evidence in oropharynx
fat/connective tissue
cross-sectional area
fiber density
4
Lingual Resistance Exercise
(Non-Swallowing Specific)
¾ Iowa Oral Performance Instrument (IOPI)
¾ Press tongue to roof of mouth (isometric/static)
¾ Anterior and posterior tongue sites
Repetition Matters
American College of Sports Med, 2002:
Low repetition, high resistance builds strength
8-12 reps improves strength in older adults
8 weeks of exercise increases limb strength
10 repetitions per set
Intensity Matters
¾ One repetition maximum (1RM)
Highest amount that can be lifted one time
¾ 80% RM improves strength
¾ Duration of contraction is correlated with rate of
strength increase
60% RM Week 1
3 sets per day
80% RM Week 2-8
3 days per week for 8 weeks
3-5 sec. contraction
Healthy Normals (>65yo)
Healthy Normals (>65yo)
Change in Isometric Pressures
Change in Swallowing Pressures
Tongue
Tongue Blade
Blade
3mL Thin Liquid
50
50
35
Pressure (kPa)
40
40
Pressure (kPa)
(kPa)
Pressure
3mL Semi-Solid
40
30
30
20
20
10
10
30
25
20
15
10
5
00
0
Baseline
Baseline
Post-Exercise
Post-Exercise
(Robbins et al., JAGS, 2005)
Baseline
Post-Exercise
(Robbins et al., JAGS, 2005)
5
Magnetic Resonance Imaging
• Total Lingual Volume
• Fat fraction
4 Subjects 74-84 years old
Scanner
FOV
Thickness
Plane
Pulse
Sequence
ΔLingual
Volume
(Reeder, IDEAL)
Demographics of Stroke Subjects
1.5 Tesla GE
8 channel head coil
20 cm
3 mm
Coronal
T2 2D-FSE
•
•
•
•
•
•
N=10
Age (51-90yrs)
Ischemic stroke
Acute (6)
Chronic (4)
*acute:< 3 mos. post-stroke
↑ x 5.10 cm3
(Robbins et al, Arch Phys Med Rehabil, 2007)
Baseline Max Isometric Pressures
Time Matters
Posterior Tongue
Anterior Tongue
70
¾ Effects dependent on time post-lesion
Pressure (kPa)
¾ Plastic change depends upon time post-training
Neural changes may precede hypertrophy
Pressure (kPa)
70
50
30
10
Week 0
Data collected at 4 and 8
weeks post- exercise
10
Week 8
Week 0
Week 4
Week 8
(Robbins et al. JAGS, 2005)
Significant
Week 8 Max Isometric Pressures
Penetration/Asperation Scale Scores
10mL liquid (p=0.005) ; 3mL liquid (p=0.003)
Posterior Tongue
Anterior Tongue
70
50
*
30
Week 0
Week 4
Week 8
50
8
30
6
10
4
Week 0
Week 4
Week 8
Significant Change (p=0.0001)
in Anterior & Posterior Tongue Strength after
8 Weeks of Exercise
2
0
Aspiration
Penetration
Penetration-Aspiration Scale Score
Pressure (kPa)
70
Pressure (kPa)
30
Healthy Lingual Pressures (65+yrs)
40 kPa anterior, 39 kPa posterior
Chronic and acute stroke subjects
10
Week 4
50
Baseline
Week 4
= Mean
Pen/Asp
Score
(10mL
Liquid)
Week 8
(Rosenbek et al. 1996, Robbins et al., 1999)
6
Swallowing Pressures
Kay Swallowing Workstation
Isometric Exercise Increases Dynamic
Swallowing Pressures
(Kay Elemetrics Corp.)
Significance Levels:
™ 10mL liquid
(p=0.03)
™ 3mL liquid
(p=0.004)
™ 3mL semisolid
(p=0.02)
Anatomical Results
Muscles of Interest
Tongue
•
•
•
•
•
•
•
•
•
Longitudinal
Vertical
Transverse
Genioglossus
Hyoglossus
Styloglossus
Nasal conchae
Septum
Stroke Subject
Sample
Percent Change in Lingual
Volume
63 yo male
2%
54 yo female
6.7 %
Floor of mouth
Myohyoid
Geniohyoid
Anterior Bellies of the
Digastric
Epiglottis
Significant Increase in Lingual Volume
in 2 subjects
51 yr old stroke patient- acute post stroke
Weak image
Does a stronger muscular
framework make ALL the
difference for skilled movement?
(stronger/faster)
7
Stroke patient after 8 weeks lingual
strengthening exercise/Strong movie
10mm
10mm
Madison Oral
Strengthening
Therapeutic Device
(MOST)
6mm
8mm
Specificity:
Nature of the Experience Specifies the Plasticity
Isometric/Non-Specific
Swallow-Specific
Strength – Spinal
synaptogenesis
Skill – Cortical map reorganization
and Cortical synaptogenesis
8mm
Dynamic Cerebral Blood Flow
and Functional Synchrony in
Dysphagia
Functional Outcome Measures
Neural Plasticity…
Another level of
Influence/Evidence
? Fatigue
? Effort
? QOL
Physiological:
Oropharyngeal biomechanics
Temporospatial (duration, range of
motion)
Strength (pressure)
Bolus flow kinematics:
Direction
Duration
Clearance
Functional:
Swallowing Related QOL
Diet
Health status (respiration, hydration, nutrition)
The Future:
Neural Plasticity and Dysphagia
Rehabilitation
8
Acknowledgements
National Institutes of Health
Department of Veteran’s Affairs
Geriatric Research Education and Clinical Center (GRECC)
UW Graduate School
UW Institute on Aging
Jackie Hind, MS, CCC-SLP, BRS-S
Stephanie Kays, MS, CCC-SLP
Ianessa Humbert, PhD, CCC-SLP
Scott Reeder, MD, PhD
Sterling Johnson, PhD
Steven Barczi, MD
Andy Taylor, MD
Ross Levine, MD
Abby Duane, BS
Mark Nicosia, PhD
Angela Hewitt, MS
Eva Porcaro, MS
9
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Kays SA, Robbins JA. Framing oral motor exercise in principles of neural plasticity.
ASHA SID 2: Perspectives on Neurophysiology and Neurogenic Speech and Language
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Kraemer W et al. Progression models in resistance training for healthy adults. Med Sci
Sports Exerc 2002;34(2):364-380.
Lazarus C et al. Effects of two types of tongue strengthening exercises in young
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Levine R, Robbins JA, Maser A. Periventricular white matter changes and
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Luschei ES (1991). Development of objective standards of non-speech oral strength and
performance: An advocate's views. In Moore CA, Yorkston KM, & Beukelman DR
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Nicosia M et al. Age effects on the temporal evolution of isometric and swallowing
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Robbins J, Kays S, Gangnon R, Hewitt A, Hind J. The Effects of Lingual Exercise in
Stroke Patients with Dysphagia. Archives of Physical Medicine and Rehabilitation 88:
150-158, 2007
19. Robbins J et al. The effects of lingual exercise on swallowing in older adults. JAGS
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20. Robbins J. Invited Editorial: The evolution of swallowing neuroanatomy and physiology
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21. Robbins JA, Coyle J, Rosenbek J, et al. Differentiation of normal and abnormal airway
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somatosensory cortex during transient sensory deprivation: A preliminary study. Journal
of Clinical Neurophysiology 2002; 19:219-231.
33. Zald DH, Pardo JV. The functional neuroanatomy of voluntary swallowing. Annals of
Neurology 1999; 46:281-286.
34. Zeynep E et al. Effects of aging on motor-unit control properties. J Neurophysiol
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35. Ziemann U, Hallett M, Cohen LG. Mechanisms of deafferentation-induced plasticity in
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G. Lof
ASHA 2007: Why not strength exercises
Page 1
MUSCLE TRAINING PRINCIPLES AND RESULTING
CHANGES TO SPEECH AND SWALLOWING
(Invited Session)
2007 ASHA National Convention, Boston, MA
Strength Exercises:
Why not for Childhood Speech Sound Disorders
Gregory L. Lof, Ph.D., CCC-SLP
Graduate Program In Communication Sciences and Disorders
MGH Institute of Health Professions
Boston, MA
[email protected]
Is strength targeted by SLPS?
Nationwide survey of 537 SLPs by Lof & Watson (2004; 2008)
• Most frequently used exercises (in rank order): Blowing; Tongue Push-Ups; Pucker-Smile; Tongue
Wags; Big Smile; Tongue-to-Nose-to-Chin; Cheek Puffing; Blowing Kisses; Tongue Curling.
• Reported benefits (in rank order): Tongue Elevation; Awareness of Articulators; Tongue Strength; Lip
Strength; Lateral Tongue Movements; Jaw Stabilization; Lip/Tongue Protrusion; Drooling Control; VP
Competence; Sucking Ability.
Websites and self published materials encourages the use of strength exercises.
Question 1: How much strength is necessary for speaking?
•
•
•
•
Articulator strength needs are VERY low for speech and the speaking strength needs do not come
anywhere close to maximum strength abilities of the articulators. For example, lip muscle force for
speaking is only about 10-20% of the maximal capabilities for lip force, and the jaw uses only about 1115% of the available amount of force that can be produced (Forrest, 2002).
“…only a fraction of maximum tongue force is used in speech production, and such strength tasks are
not representative of the tongue's role during typical speaking. As a result, caution should be taken when
directly associating tongue strength to speech…” (Wenke, Goozee, Murdoch, & LaPointe, 2006).
Children with speech sound disorders actually had stronger tongues than typically developing
children (Sudberry, Wilson, Broaddus, & Potter, 2006).
Agility and fine articulatory movements, rather than strong articulators, are required for the ballistic
movements of speaking. Usually, non-speech exercises encourage gross and exaggerated ranges of
motion, not small, coordinated movements that are required for talking.
Question 2: Do typical non-speech oral motor exercises actually increase
strength?
•
These non-speech exercises may not actually increase articulator strength. To strengthen muscle,
the exercise must be done with multiple repetitions, against resistance, following a basic strengthtraining paradigm; there are probably no actual strength gains occurring due to these non-speech
exercises.
G. Lof
•
•
•
ASHA 2007: Why not strength exercises
Page 2
Articulators can be strengthened (e.g., the tongue for oral phase of swallowing or the VP complex)
but these strengthened articulators will probably not help with the production of speech.
Task specificity: The same structures used for speaking and other “mouth tasks” (e.g., feeding,
swallowing, sucking, breathing, etc.) function in different ways depending on the task and each task is
mediated by different parts of the brain. The organization of movements within the nervous system is not
the same for speech and non-speech gestures. Although identical structures are used, these structures
function differently for speech and for non-speech activities.
Non-speech motor movements elicit activation of different parts of the brain than do speech motor
movements (Bonilha, Moser, Rorden, Baylis, & Fridriksson, 2006; Stathopoulos & Duchane, 2006;
Weismer, 2006).
Question 3: How do speech-language pathologists objectively measure
strength?
•
•
Clinical measurements of strength are usually highly subjective (e.g., feeling the force of the tongue
pushing against a tongue depressor or against the cheek or just “observing” weakness), so clinicians
cannot initially verify that strength is actually diminished and then they cannot report increased strength
following NS-OME. Only objective measures (e.g., tongue force transducers) can corroborate statements
of strength needs and improvement. Without such objective measurements, testimonials of articulator
strength gains must be considered suspect.
Strength estimation is unreliable, with student clinicians actually better than practicing clinicians
(Solomon & Monson, 2004).
Why strength for certain speech sound disorders?
Cleft Lip and Palate
• The VP mechanism can be strengthened through exercise, but added strength will not improve speech
•
•
•
production. Blowing exercises for strength are not appropriate.
“Do not invest time or advise a parent to invest time and money addressing a muscle strength
problem that may not (and probably does not) exist. It is very frustrating to see clinicians working on
“exercises” to strengthen the lips and tongue tip when bilabial and lingua-alveolar sounds are
already evident in babble, or when bilabial and lingual/lingua-alveolar functions are completely
intact for feeding and other non-speech motor behaviors.” (Peterson-Falzone, Trost-Cardamone,
Karnell, Hardin-Jones, 2006).
“Having a repaired cleft does not mean a child will lack the muscle strength needed to produce
consonant sounds adequately. The presence of a cleft palate (repaired or unrepaired) has no bearing
on tongue strength or function (why would it?). The majority of children who demonstrate VPI do so
because their palate is too short to achieve VP closure. Muscle strength or lack thereof is not a
primary causal factor associated with phonological delays in this population.” (Peterson-Falzone,
Trost-Cardamone, Karnell, Hardin-Jones, 2006).
“…blowing should never be used to ‘strengthen’ labial or soft palate musculature; it does not work.
Children who appear to improve over time in therapy when using these tools are likely demonstrating
improvement related to maturation and to learning correct motor speech patterns. Had therapy
focused only on speech sound development, these children probably would have shown progress
much sooner.” (Peterson-Falzone, Trost-Cardamone, Karnell, Hardin-Jones, 2006).
G. Lof
ASHA 2007: Why not strength exercises
Page 3
Childhood Apraxia of Speech (CAS)
• By definition, children with CAS have adequate oral structure movements for non-speech activities
•
but not for volitional speech, and have adequate amounts of strength (Caruso & Strand, 1999).
The focus of intervention for the child diagnosed with CAS is on improving the planning, sequencing,
and coordination of muscle movements for speech. Isolated exercises designed to "strengthen" the
oral muscles will not help. CAS is a disorder of speech coordination, not strength.
(http://www.asha.org/public/speech/disorders/ChildhoodApraxia.htm#tx).
Language-Based Speech Sound Disorders
• It makes no sense that strengthening exercises could help improve the speech of children who have
non-motor problems, such as language-phonemic-phonological problems, for children in Early
Interventions diagnosed as late talkers. Why would children with a language-based sound problem
improve with strengthening exercises using a motor-based treatment approach?
References
ASHA: http://www.asha.org/public/speech/disorders/ChildhoodApraxia.htm#tx
Bonilha, L., Moser, D., Rorden, C., Baylis, G., & Fridriksson, J. (2006). Speech apraxia without oral apraxia:
Can normal brain function explain the physiopathology? Neuro Report, 17 (10), 1027-1031.
Caruso, A., & Strand, E. (1999). Clinical management of motor speech disorders in children. New York:
Thieme.
Davis, B., & Velleman, S. (2000). Differential diagnosis and treatment of developmental apraxia of speech in
infants and toddlers. Infant-Toddler Intervention, 10, 177-192.
Forrest, K. (2002). Are oral-motor exercises useful in the treatment of phonological/articulatory disorders?
Seminars in Speech and Language, 23, 15-25.
Golding-Kushner, K. (2001). Therapy techniques for cleft palate speech and related disorders. Clifton Park,
NY:Thompson/Delmar
Lof, G.L., & Watson, M. (in press 2008). A nationwide survey of non-speech oral motor exercise use:
Implications for evidence-based practice. Language, Speech, and Hearing Services in the Schools.
Peter-Falzone, S., Trost-Cardamone, J., Karnell, M., & Hardin-Jones, M. (2006). The clinician’s guide to
treating cleft palate speech. St. Louis, MO: Mosby.
Robbins, J., Gangnon, R., Theis, S., Kays, S., Hewitt, A., & Hind, J. (2005). The effects of lingual exercise on
swallowing in older adults. Journal of the American Geriatrics Society, 53, 1483-1489.
Solomon, N., & Munson, B. (2004). The effect of jaw position on measures of tongue strength and endurance,
Journal of Speech, Language, and Hearing Research, 47, 584-594.
Stathopoulous, E., & Duchan, J. (2006). History and principles of exercise-based therapy: How they inform our
current treatment. Seminars in Speech and Language, 24(4), 227-235.
Sudbery, A., Wilson, E, Broaddus, T., & Potter, N. (2006, November). Tongue strength in preschool children:
Measures, implications, and revelations. Poster presented at the annual meeting of the American SpeechLanguage-Hearing Association, Miami Beach, FL.
Weismer, G. (2006). Philosophy of research in motor speech disorders. Clinical Linguistics & Phonetics, 20,
315-349.
Wenke, R., Goozee, J., Murdoch, B., & LaPointe, L. (2006). Dynamic assessment of articulation during lingual
fatigue in myasthenia gravis. Journal of Medical Speech-Language Pathology, 14, 13-32.
Wide Smiles: Cleft Lip and Palate Resource. http://www.widesmiles.org/cleftlinks/WS-563.html.
The following article will be published in the December issue (Vol. 17, No. 4) of /Perspectives on Neurophysiology
and Neurogenic Speech and Language Disorders/, the peer-reviewed publication of ASHA Special Interest Division
2, Neurophysiology and Neurogenic Speech and Language Disorders. This article is being distributed at this ASHA
Convention forum with permission of the publisher, ASHA. It may not be reprinted, copied, or distributed by any
other individual or organization without express written permission from the publisher.
Framing Oral Motor Exercise in Principles of Neural Plasticity
Stephanie Kays
and
JoAnne Robbins
University of Wisconsin-Madison, Department of Medicine
and
William S. Middleton Memorial Veterans Hospital, Geriatric, Research, Education and Clinic
Center (GRECC)
Introduction
For decades the relationship between motor speech and swallowing production has been
debated, with the use of oral motor exercise to remediate speech and swallowing disorders
remaining a contentious issue. The field of speech pathology, which includes in its scope
swallowing and dysphagia, has evolved with two primary viewpoints. The task-specific or taskdependent model, which postulates that distinct neuromotor systems are responsible for specific
motor activities, suggests that speech or swallowing-specific tasks are the optimal stimuli for
influencing motor speech or swallowing production, respectively. In contrast, a non-specific or
task-independent model assumes that overlapping neuromotor systems comprise an integrated
sensorimotor network organized by general functions (e.g., force and timing), rather than specific
motor behaviors (e.g., speech or swallowing) (Ballard, Robin, & Folkin, 2003; Ziegler, 2003). In
this latter model, the use of volitional oral motor tasks is endorsed for promoting both speech and
swallowing rehabilitation (Ballard et al., 2003; Kent, 2004). While the theoretical debate over
task-specificity has received a great deal of attention in the field of communicative disorders,
speech-language pathologists have only recently been considering systematic treatment protocols
within a larger framework of principles shown to effect neural plasticity, the mechanism by
which the brain encodes, learns or relearns behaviors (Grossman, Churchill, Bates, Kleim, &
Greenough, 2002). As neuroscientists continue to elucidate the factors that guide brain recovery
through investigative activities such as animal research and neuroimaging, clinicians are
beginning to apply these principles in treatment designs and modes of delivery. Our profession
is just beginning to provide evidence to validate and establish treatment procedures by
understanding and systematically manipulating principles of exercise and neural plasticity.
Exercise physiology principles and techniques that were based on clinical intuition in the past are
now aligned with principles of neural plasticity and are leading to objective and quantifiable
measures for evidence-based treatment designs.
An understanding of fundamental processes that underlie motor learning is necessary in
order to translate the phenomenon of neural plasticity into speech and swallowing clinical
research and, ultimately, practice. Ten principles derived from animal research and neuroscience
have been identified by Kleim and Jones (in press) as being relevant to speech and swallowing
rehabilitation. Three of these principles that have received the most attention in efficacy-based
studies of therapy are repetition, intensity, and specificity.
Repetition
Animal research suggests that one mechanism critical for inducing neural plastic changes
in the central nervous system is repetitive performance of a skill even after the skill has been
acquired. For instance, although a patient may demonstrate correct performance of a behavior
such as a Mendelsohn maneuver (Kahrilas, Logemann, Krugler, & Flanagan, 1991) after one or
two therapy sessions, changes in neuronal synapses or cortical organization require continued
performance of the maneuver over time. It is hypothesized that plasticity influenced by repetition
results in an acquired behavior that is resistant to decay, such that the patient is able to continue
to use the function outside of therapy while maintaining and advancing gains (Kleim & Jones, in
press), (Monfils, Plautz, & Kleim, 2005).
Traditional treatment methods for motor speech disorders, such as childhood apraxia of
speech, are based on principles of motor learning, with one of the most important aspects being
the encouragement of a high number of responses within each therapy session. Yorkston and
colleagues stated that, “Probably the most common error made by speech-language pathologists
who treat motor speech disorders is failure to provide adequate practice in the form of hundreds
of trials or responses per session” (Yorkston, Beukelman, Strand, & Bell, 1991, p. 550). A high
frequency of practice was shown to facilitate phoneme acquisition in acquired apraxia of speech
in a recent single-subject design. However, minimal generalization of the trained behavior to
more complex behaviors was observed, despite the high number of repetitions within each
treatment session (Kendall, Rodriguez, Rosenbek, Conway, & Gonzalez Rothi, 2006). An
example of an exercise program that has incorporated the principle of repetition is provided by
Kuehn and colleagues in their study of patients with speech disorders secondary to structural
deviations (Kuehn et al., 2002). Results of this multi-center clinical trial with 43 children with
congenital cleft palate demonstrated that eight weeks of speaking against transnasal continuous
positive airway pressure (CPAP) resistance six days per week resulted in a significant reduction
in nasality during speech, although the response was variable across patients and centers. The
authors stated that the “response trend [was] minimal after four weeks of therapy with
accelerated benefit during the second month” (p. 273). This suggests that a certain level of
practice is necessary to induce robust skill acquisition.
The principle of repetition also is a key component of active resistance exercises, which
are more commonly being applied to the oropharyngeal musculature. Studies continue to emerge
demonstrating positive changes in strength and function subsequent to regimens that traditionally
have been reserved for the limb muscles. The concept of repetition has been incorporated as a
key principle of exercise for years, with the recognition that the outcome of a training program
can be manipulated by varying the number of repetitions with which an exercise is performed.
For instance, training programs designed to build muscle strength (force-generating capacity)
typically use a low number of repetitions against a near-maximal resistance. In contrast,
regimens designed to increase muscle endurance (fatigue-resistance) rely on a higher number of
repetitions with a sub-maximal load.
Robbins and colleagues developed an eight-week progressive resistance exercise regimen
that they applied to the lingual musculature. This regimen consists of 10 repetitions at two
tongue locations performed three times a day on three days of the week (Robbins et al., 2005;
Robbins et al., 2007). The American College of Sports Medicine confirms that eight to fifteen
repetitions performed one to three times a day is optimal for building strength in the limb
musculature (Kraemer et al., 2002). The most effective number of repetitions required to build
strength in the orofacial muscles remains to be discovered and likely varies with factors such as
age or underlying disease processes. However, healthy older adults and acute and chronic stroke
2
patients have demonstrated statistically significant improvements in lingual strength (pressure)
during a series of non-swallowing isometric lingual presses with spontaneous generalization to
natural swallowing tasks (Robbins et al., 2005). Moreover, stroke subjects demonstrated a
reduction in liquid aspiration and pharyngeal residue, likely related to a longer pharyngeal
response duration observed during liquid swallows (Robbins et al., 2007). After eight weeks of
exercise, stroke subjects continued to demonstrate improvements in isometric tongue strength,
suggesting that a longer program of exercise may yield even greater improvements in
swallowing function. Future studies incorporating anatomic magnetic resonance imaging (MRI)
to understand changes at the muscle level (e.g., lingual volume and tissue composition) and at
the neural level via functional MRI (fMRI) are underway (Humbert et al., in press; Kays et al., in
press) to confirm that these behavioral changes indeed represent neuromuscular changes in
response to repetitive exercise. Such study designs will incorporate measures at multiple time
points throughout an exercise program to determine patient response to various exercise doses.
Shaker and colleagues (Shaker et al., 1997; Shaker et al., 2002) similarly have
demonstrated an improvement in maximum anterior hyolaryngeal excursion and upper
esophageal sphincter opening during swallowing following a program of repetitive head lifting.
The Shaker protocol includes a dynamic component of 30 repetitive head lifts followed by three
sustained contractions, performed three times daily for six weeks. More recent findings by
Easterling, Grande, Kern, Sears, and Shaker (2005) demonstrate the importance of repetition
over time for skill acquisition, as participants who committed to the entire 6-week program were
more likely to attain the predetermined goals than those who discontinued within the first two
weeks. Continued work in this area is warranted to determine if the frequency of this regimen
and others is sufficient for eliciting changes in swallowing biomechanics that are resistant to
decay or if a maintenance program is necessary.
Recent findings by Sapienza and colleagues also have demonstrated a significant increase
in maximum expiratory pressure after four weeks of expiratory muscle strength training (EMST),
following a slightly different protocol of five repetitions, five times a day on five days of the
week (Sapienza & Wheeler, 2006). While short-term increases in electromyographic activity of
the anterior suprahyoid musculature have been measured during performance of EMST
(Wheeler, Chiara, & Sapienza, 2007), the optimal regimen for eliciting long-term changes
remains unknown. For example, a case study of an older patient with Parkinson disease revealed
continued improvements in maximum expiratory muscle strength over a period of 20 weeks of
EMST as opposed to the traditional regimen of four weeks (Saleem, Sapienza, & Okun, 2005).
The degree of repetition necessary to obtain a level of brain reorganization and skill acquisition
sufficient for a patient to maintain functional gains clearly requires more evidence.
One of the most well-known programs of therapy for improving speech and voice in
individuals with Parkinson disease is the Lee Silverman Voice Treatment® (LSVT/LOUD).
LSVT/LOUD utilizes highly-repetitive practice of a salient and simple treatment target (higheffort voice) to trigger system-wide effects across the speech and swallowing production
systems. The program requires an unprecedented amount of repetition that was not seen in
earlier models of speech and voice therapy, consisting of 16 individual 60-minute sessions
performed over a period of four weeks. LSVT/LOUD also promotes long-term maintenance of
the target speech behavior by including specific strategies for incorporating exercise into
repetitive or routine aspects of daily living (Fox et al., 2006; Ramig, Countryman, Thompson, &
Horii, 1995; Ramig, Countryman, O'Brien, Hoehn, & Thompson, 1996). The examples provided
clearly demonstrate that repetition is being recognized as a key component of treatments that
result in lasting changes hypothesized to represent neural plastic modifications. The optimal
frequency of repetition remains to be discovered and likely differs depending on variables such
as the desired behavior, treatment goals, and the patient population.
3
Intensity
In many cases, it is hypothesized that repetition alone generally is not adequate for
affecting sustainable neural modifications related to functional parameters, such as muscle
strength, endurance, or power. The intensity with which an exercise is performed also requires
consideration. Intensity is expressed by the overload principle, which states that the load placed
on a motor system must be progressively increased over time in order to increase demands as a
system adapts. Strength and endurance training protocols both incorporate the overload
principle, but use different levels of intensity, depending on whether the goal is to improve
muscle strength or endurance.
Strength Training
In order to build oropharyngeal muscle strength, clinical researchers have applied a
traditional load of 60% to 80% of an individual’s one repetition maximum (abbreviated 60-80%
RM), which refers to the highest amount of force that can be generated once. To build lingual
strength, Robbins and colleagues recommend an initial week of isometric exercise using a load
of 60% RM until proper technique and form are learned, followed by 7 weeks using an 80% RM
load that is progressively increased every 2 weeks relative to individual strength gains (Robbins
et al., 2005; Robbins et al., 2007). Sapienza and Wheeler (2006) follow a similar approach using
a load of 75% RM, and, unlike traditional breathing exercises that allow airflow rate to vary,
stress the importance of maintaining a consistent intensity throughout EMST.
Intensity is also emphasized in the LSVT/LOUD treatment program discussed earlier. A
hallmark of the LSVT/LOUD program is to encourage high-effort vocal loudness with increasing
demands for consistency and accuracy of loud performance in speech tasks (Ramig,
Countryman, Thompson, & Horii, 1995). Unlike the strengthening regimens discussed above,
LSVT does not specify a target value to apply across subjects but simply demands the highest
stimulable vocal effort while advancing the demands of the context. The positive effects, which
have shown to extend to articulatory precision (Sapir, Spielman, Ramig, Story, & Fox, 2007),
facial expression (Spielman, Borod, & Ramig, 2003) and swallowing (El Sharkawi et al., 2002),
are attributed in large part to the intensive delivery of this treatment. The findings from LSVT
also raise the appealing speculation that intensive stimulation of one sensorimotor system may
result in positive neural plastic changes in the brain that relate to other systems, a phenomenon
known as transference (Kleim and Jones, in press; Fox et al., 2006; Liotti et al., 2003).
Endurance Training
Depending on the goal of a program, a submaximal target load may be more effective
than a highly intense program. The principles of exercise recommend an intensity of 40 to 60%
RM performed with an increased number of repetitions to improve muscle endurance, as
opposed to muscle strength. Progressive exercises to improve the endurance of the speech and
swallowing systems have not been investigated over multiple time points, although a number of
studies exist that have devised methods of measuring the fatigue-resistance of the head and neck
musculature (Cahill et al., 2004; Goozee, Murdoch, & Theodoros, 2001; Lazarus, Logemann,
Huang, & Rademaker, 2003; McAuliffe, Ward, Murdoch, & Farrell, 2005; Solomon, 2004).
Solomon demonstrated a decrement in articulatory precision after exercising the tongue to the
point of fatigue; however, a strenuous fatigue-producing protocol involving repetitive maximal
force production was necessary to elicit changes in speech intelligibility, and no changes in
speaking rate were observed. This suggests that speech is a relatively robust system (Solomon,
2000). Preliminary work by Kays et al. (2007) taking a more functional approach, is beginning
to examine whether a similar relationship exists between ability of the tongue to withstand
fatigue during the sequential swallowing performed when consuming an entire meal, which may
be a challenging condition for frail elders and dysphagic individuals.
Specificity
4
Animal research has shown that experience is necessary, but not always sufficient, for
inducing long-lasting plasticity, and that the importance of a behavior to an individual is equally
as important as its frequency or intensity for stimulating learning (Kilgard & Merzenich, 1999).
For example, the proportion of motor cortex representing forelimb movement was shown to
increase in rats trained to perform skilled reaching (i.e., for a food reward) compared to nonskilled reaching. Moreover, the addition of a progressive resistance to the task did not affect the
cortical outcome despite improvements in forelimb strength. That is, both skilled reaching and
skilled reaching against a resistance equally resulted in cortical reorganization (Remple,
Bruneau, VandenBerg, Goertzen, & Kleim, 2001).
While this evidence may lead some to conclude that speech and swallowing can only be
improved through performance of the behavior itself, clinicians frequently are faced with the
dilemma that individuals lack the strength to even approximate an accurate or complete
production of the target behavior. In such cases, the value of practicing an incorrect target with
any degree of repetition or intensity is questionable. In some treatment models, basic resistance
exercises may be paired with more traditional treatments to build a foundation of strength
reserve, such that more dynamic, task-specific techniques can be successfully performed over
time. This is not unlike the theory underlying intensive speech therapies such as LSVT/LOUD,
in which a single, simplified component of speech production (vocal loudness) is emphasized
and enhanced in order to induce widespread system effects in progressively complex contexts
(Ramig et al., 1995).
Another example is a study of effortful swallowing, which indicated that middle-aged
adults were able to increase swallowing pressures to a greater degree than older adults when
cued to swallow hard (Hind, Nicosia, Roecker, Carnes, & Robbins, 2001), indicating that agerelated reductions in maximum isometric tongue strength may limit one’s ability to change
dynamic swallowing behavior. These findings suggest that a foundation of muscle strength may
increase the ability to utilize therapeutic strategies, thus improving prognostic outcomes.
Strengthening therefore may be a reasonable goal, particularly when performed in conjunction
with more skilled movements.
Finally, resistance training provides an effective means of stimulating orofacial muscle
and related neural pathways to maintain or build muscle strength without compromising patient
safety. For example, some dysphagic patients may be unable to safely perform swallowingspecific training due to the risk of aspiration. Resistance training also may be an important early
intervention for patients with muscle weakness secondary to disease-related weakness potentially
overlaid on the natural age-related loss of muscle mass and strength (sarcopenia). Such
treatments can maintain saliency by utilizing creative taste, temperature, and tactile inputs when
possible.
Although the interaction among systems of speech, swallowing and respiration remains
the focus of many researchers, several differences in these functions cannot be ignored and may
lead to divergent rehabilitation strategies. The muscles of speech are specialized to favor speed
over force. As Kent and others recognized (Kent, 2004; Adams, Weismer, & Kent, 1993),
studies show that normal speaking rates are more aligned in kinematic and force profiles with
fast speaking rates than slow rates. These findings suggest that the speech system is habitually
geared toward rapid production. Nonetheless, age-related changes in speech precision and
durations have been reported in adults over 60, suggesting that even though older adults may
produce speech that sounds normal, the manner of production may differ to account for
physiological age-related changes. Shawker and Sonies (1984) found significant differences in
the direction and extent of tongue movements in older versus younger speakers during
production of /a/. More recently, Goozee, Stephenson, Murdoch, Darnell, and LaPointe (2005)
demonstrated that older and younger adults used similar strategies to increase their speaking
5
rates, but that young adults were more likely to economize effort by reducing the distance
traveled by the tongue under very fast rate demands, while older adults showed smaller decreases
in distance and associated reductions in velocity. It was hypothesized that the smaller changes in
distance observed in older adults represent reduced neuromotor control, proprioception, or
stability of tongue movements. Swallowing, in contrast to speech, sacrifices a degree of speed
yet utilizes higher lingual contractile forces to prepare and propel a bolus. Also unlike speech,
swallowing durations have been shown to decrease with age relative to declines in lingual
muscle strength or force-generating capacity (Nicosia et al., 2000; Robbins, Levine, Wood,
Roecker, & Luschei, 1995). In addition, the sensory afferent pathways differ for speech and
swallowing, most notably in the undeniable importance of the auditory perceptual pathway in
speech development and rehabilitation and the consistency, temperature and taste inputs involved
in swallowing.
Luschei’s comments on the relationship between tongue strength and velocity of
movement remain relevant as the exploration of oral strengthening exercises grows (Luschei,
1991). He compared the motion of the lingual hydrostat to opening a door with a dashpot, a
device designed to keep the door from banging shut when released: “Although it does not take
much force to open the door slowly or hold it open, it requires a very large force to move the
door rapidly” (p. 8). Thus, there is reason to believe that the relationship between force, speed,
and accuracy of oral motor movements across the lifespan is still not well-understood and may
differ depending on the sensorimotor system in question. Evidence from higher levels of motor
control, available with innovative imaging techniques, will begin to elucidate the longstanding
question of whether oral neuromotor systems are topographically distinct or overlapping.
Summary
Recent imaging studies suggest that the speech, swallowing and respiratory systems may
be controlled by widespread cortical and subcortical networks with more shared regions than
traditionally predicted (Kern et al., 2001; Loucks, Poletto, Simonyan, Reynolds, & Ludlow,
2007; Riecker et al., 2005; Suzuki et al., 2003; Toogood et al., 2005; Zald & Pardo, 2000).
Martin and colleagues have begun to explore relationships between brain activity during tongue
elevation and saliva swallowing (Martin et al., 2004), demonstrating overlapping regions of
cortical activity (post central gyrus, cuneus and precuneus, supramarginal gyrus) that argues
against the existence of a “swallowing-specific” region. However, tongue elevation was
represented by distinctly larger cortical regions, indicating that the two behaviors also have
unique aspects of cortical control. Early PET imaging findings in individuals who have
completed LSVT reflect increased activity in neural systems that are hypothesized to be involved
in vocalization and loudness (basal ganglia, limbic system, prefrontal cortex, right hemispheric
cortex), yet decreased activity in the motor/pre-motor cortices (Liotti et al., 2003). Whether
decreased brain activity in this or other studies represents a “normalization” of brain effort
remains to be understood. Studies investigating changes in brain activity in response to various
intervention doses are on the horizon, and will depend on our ability to acquire and interpret
imaging data reliably. Advances in technology and neuroscience paired with lasting scientific
principles and therapy designs are leading the way to stimulate much-needed development in the
field of speech and swallowing rehabilitation. Much remains to be understood, including
interactions among age, disease, severity and cross-system impairments, such that only the
systematic application of interventions according to selected principles of neural plasticity will
yield outcomes that can be interpreted meaningfully and applied to patients efficaciously. Most
importantly, new levels of evidence are being pursued enthusiastically by teams of clinicians and
researchers, which will advance our understanding and discovery of critical patient-oriented
approaches to drive recovery.
6
Acknowledgements: This is GRECC manuscript #2007-19.
Stephanie Kays is a clinical and research speech-language pathologist at the University
of Wisconsin, Department of Medicine, and the Geriatric Research, Education and Clinical
Center (GRECC) of the William S. Middleton Memorial Veterans Hospital. She is a member of
the UW/VA Speech, Swallowing and Dining Enhancement Program and a primary contributor to
research on the effects of aging and lingual exercise on swallowing.
JoAnne Robbins is a Professor of Medicine and Radiology at the University of Wisconsin
School of Medicine and Public Health. She is also the Associate Director for Research at the
Geriatric Research, Education and Clinical Center at the William S. Middleton VA Hospital.
Her current research initiatives are examining the effects of oral motor exercise on swallowing
skills in the geriatric population.
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