J Orthop Sports Phys Ther. 2014 (Feb); 44 (2): 68–75 ~ FULL TEXT
Susan L. Edmond, PT, DSc, OCS, Guillermo Cutrone, PT, DSc, OCS, Cert MDT, FAAOMPT, Mark Werneke, PT, MS, Dip MDT, Jason Ward, MPT, MDT, Cert MDT, David Grigsby, MPT, MDT, Cert MDT, Jon Weinberg, PT, Dip MDT, William Oswald, DPT, Cert MDT, Dave Oliver, PT, Dip MDT, Troy McGill, PT, MS, Dip MDT, Dennis L. Hart, PT, PhD
The State University of New Jersey,
STUDY DESIGN: Retrospective cohort.
OBJECTIVES: In subjects with neck pain, the present study aimed (1) to describe the prevalence of centralization (CEN), noncentralization (non-CEN), directional preference (DP), and no directional preference (no DP); (2) to determine if age, sex, fear-avoidance beliefs about physical activity, number of comorbid conditions, or symptom duration varies among subjects who demonstrate CEN versus non-CEN and DP versus no DP; and (3) to determine if CEN and/or DP are associated with changes in function and pain.
BACKGROUND: CEN and DP are prevalent among patients with low back pain and should be considered when determining treatment strategies and predicting outcomes; however, these findings are not well investigated in patients with neck pain.
METHODS: Three hundred four subjects contributed data. CEN and DP prevalence were calculated, as was the association between CEN and DP, and age, sex, number of comorbid conditions, fear-avoidance beliefs, and symptom duration. Multivariate models assessed whether CEN and DP predicted change in function and pain.
RESULTS: CEN and DP prevalence were 0.4 and 0.7, respectively. Younger subjects and those with fewer comorbid conditions were more likely to centralize; however, subjects who demonstrated DP were more likely to have acute symptoms. Subjects who centralized experienced, on average, a 3.6-point (95% confidence interval: -0.3, 7.4) improvement in function scores, whereas subjects with a DP averaged a 5.4-point (95% confidence interval: 0.8, 10.0) improvement. Neither CEN nor DP was associated with pain outcomes.
CONCLUSION: directional preference (DP) and, to a lesser extent, centralization (CEN) represent evaluation categories that are associated with improvements in functional outcomes.
From the FULL TEXT Article:
Researchers have suggested that classifying patients into
subgroups based on clinical characteristics and matching
these subgroups to management strategies improve patient
outcomes of physical therapy interventions. [5, 10, 26, 37] Classification
of patients with neck pain has been recommended as a research
priority. [5, 16] Nevertheless, there is insufficient information regarding
how to classify these patients to inform
physical therapy interventions that optimize
Two examination procedures used to
classify patients with spinal pain have
been studied: centralization (CEN) and
directional preference (DP). These examination
procedures, which are derived
from Mechanical Diagnosis and Therapy
methods, inform clinical decisions and
guide patient management. A classification
method that combines CEN and DP
principles, called the “patient response
method,” has subsequently been proposed
and recommended for use with patients
with nonserious lumbar spine pain.36
A number of studies have demonstrated
that in relation to low back pain,
CEN and DP are of clinical value. CEN
has been shown to predict decreased disability, [9, 28, 32–34, 37]
return to work, [17, 23, 32, 35]
and reduced pain. [9, 23, 32–34, 37] In several
studies, prescribing exercises matched to
the patient’s DP has improved low back
pain outcomes. [2, 20–23] In 1 study (level 3
the authors suggested that
the patient response method delineated
and improved the prediction of pain and
function outcomes in patients with low
back pain. 
CEN is operationally defined as spinal
pain that is progressively abolished in a
distal-to-proximal direction in response
to therapeutic movement and positioning
strategies, without consideration of
intensity. [24, 26, 34, 37] DP is determined by
whether spine and/or referred spinal
pain located in the most distal body part
decreases in intensity, abolishes, or centralizes,
and/or whether subjects demonstrate
an improvement in range of motion
in response to a repeated-movement or
positional-loading strategy.  Individuals
not meeting these criteria are considered
to have non-CEN and no DP, respectively.
The decision rules for judging CEN
and DP are therefore similar but not
synonymous. When CEN is present, DP
must also be present. In contrast, DP
might occur in the absence of CEN (eg,
a patient’s lower-leg pain may decrease
in intensity but not change in location
with a specific repeated-movement or
positional-loading strategy). CEN has
also been shown to occur in the cervical
spine. The prevalence of CEN, identified
using the same operational definition described
above, was reported to be 0.3, 
0.4,  and 0.2  in prior studies. In the latter
study,  prevalence decreased among
more chronic and older subjects. The
prevalence of DP among subjects with
neck pain has not been reported in prior
literature and remains unknown.
Several studies have addressed the
predictive value of CEN, using the aforementioned
definition, in subjects with
cervical impairments. CEN has been
shown to be predictive of reduced disability [33, 34]
and pain. [33, 34, 37] In 1 of these
studies,  however, CEN was not associated
with changes in disability.
There are no studies that have examined
the clinical effectiveness of DP or
the patient response method in patients
with cervical impairments. It is therefore
unknown if subgrouping patients
by pain responses using CEN and DP
would improve the clinical interpretation
of patient outcomes, as previously
demonstrated in patients with lumbar
Based on the lack of information regarding
the prevalence and clinical utility
of DP in patients with neck pain and
previous recommendations for examining
both CEN and DP pain responses
when evaluating patients with low back
pain,  a logical next step would be to
investigate the clinical relevance of CEN
and DP as classification criteria for the
management of patients with cervical
impairments. Therefore, the objectives
of the present study were
(1) to describe
the prevalence of DP and no DP observed
during the initial evaluation of patients
with nonspecific neck pain whose symptoms
centralize versus those whose symptoms
do not centralize during their initial
(2) to explore whether the
prevalence of CEN and DP is affected
by age, sex, fear-avoidance beliefs about
physical activities, number of comorbid
conditions, and symptom duration; and
(3) to determine if classifying patients at
intake by DP or no DP, separately and in
combination with CEN or non-CEN, is
associated with changes in functional status
and pain intensity at discharge from
We hypothesized that the
prevalence of DP would be higher than
the prevalence of CEN, and that both
categorization strategies would be influenced
by the subject’s age and symptom
duration. In addition, we hypothesized
that classification by DP and CEN would
improve the ability to estimate prognosis
for function and pain outcomes, as previously
demonstrated in subjects with
lumbar impairments.  The present study
adds to the current literature by examining
the prevalence and characteristics
of CEN and DP, and the association between
changes in functional outcomes
and pain responses based on categorization
by CEN and DP, among patients
with neck pain.
This retrospective cohort study
analyzed data from 328 subjects
with neck pain who contributed
data to Focus On Therapeutic Outcomes,
Inc (Knoxville, TN), an international
medical rehabilitation data-management
company. [29, 30] Subjects represented a convenience
sample of patients seen from
July 2007 through December 2010 who
had complete data and could be classified
as having CEN or non-CEN at intake.
Subjects with no pain or relevant referred
symptoms immediately before repeatedmovement
testing were excluded from
our sample because they were not eligible
for categorization as CEN or non-CEN.
These 328 subjects were classified and
treated by 8 physical therapists (mean
age, 43 years; range, 32–61 years; 8
male) who routinely utilized Mechanical
Diagnosis and Therapy methods when
treating patients with spinal pain. Four
therapists had received additional postgraduate
training and had credentials
in Mechanical Diagnosis and Therapy.
The average number of years of clinical
experience was 16 (range, 9–41). Practice
settings were diverse: 3 therapists were
employed in hospital-based outpatient
clinics, 4 therapists worked in 3 different
private practices, and 1 therapist worked
in 2 military orthopaedic outpatient clinics.
Not all physical therapists collected
data during the entire study period, as 3
physical therapists started data collection
in the summer of 2009 and 4 were either
transferred between clinics or had nonpatient
responsibilities that interrupted
Subjects were classified as having CEN
or non-CEN at intake. These categories
have been recommended for routine use
and operationally described for patients
with lumbar impairments.  Briefly, patients
were classified by quantifying
changes in pain location observed during
the initial physical therapy visit. At this
time, they underwent a standard physical
examination according to Mechanical
Diagnosis and Therapy assessment methods, 
without consideration of symptom
intensity, using a body diagram and numeric
overlay template.  This template
has been previously described [9, 34] and
shown to have acceptable reliability (χ = 0.9–1.0).  Subjects were instructed by
the examiner to shade in all areas on a
body diagram where they were experiencing
spinal pain and referred symptoms.
Body diagrams were completed in sitting
before and after end-range, repeated
neck movements and/or positioning
techniques. The overlay template was
placed over the body diagrams, which
allowed quantification of the anatomical
location of pain. To be classified as having
CEN, a reduction of at least 1 pain location
level after testing was required. If
pain location increased or remained the
same after repeated-movement tests, the
pain response non-CEN was recorded.
Subjects with no pain or relevant referred
symptoms immediately before repeatedmovement
testing were excluded from
analyses because they were not eligible
for categorization as CEN or non-CEN.
Subjects were also classified by demonstration
of DP at intake. Specifically,
DP was present if the subject’s most distal
pain intensity decreased or abolished,
or the subject’s cervical range of motion
improved in response to repeated endrange
movement tests or positionalloading
strategies.  A subjective report
of a specific preference for activities and
movements, such as looking up (extension
preference) or looking down (flexion
preference), was used to guide the evaluation
process, but objective confirmation
during the initial evaluation was required
for DP classification.
The information on CEN and DP was
subsequently combined to determine
patient response method categories as
follows. A DP is always observed for patients
whose symptoms centralize. Therefore,
when categorizing subjects with DP
based on whether they also centralize,
a subject who centralized would be categorized
as having CEN/DP. For subjects
whose symptoms did not centralize, the
examination continued to judge DP using
additional criteria: if a DP was identified
under these circumstances, then the patient
was classified as having non-CEN/
DP. If no DP was identified, the subject
was classified as having non-CEN/no DP
Subjects classified as having DP irrespective
of CEN were treated with specifically
matched exercises and/or manual
techniques based on the subject’s DP. 
For example, if a subject’s symptoms centralized
using extension movements or
positioning in extension, the subject was
prescribed retraction stretches (a lower
cervical extension movement) and/or
global neck extension stretches. For subjects
who were categorized as non-CEN/
no DP, an individualized rehabilitation
plan was developed at the discretion of
the treating physical therapist. To improve
adherence to their home exercise
program and to enhance return to function
with good pain-control techniques,
all subjects, irrespective of categorization,
were encouraged to become actively
involved in their recovery process. No attempt
was made to standardize care beyond
Prior to the initial examination, all
subjects answered a series of questions,
including patient demographics, fearavoidance
beliefs about physical activity
assessed with the Fear-Avoidance
Beliefs Questionnaire physical activities
subscale (FABQ-PA), symptom duration,
functional status, and pain intensity.
This information was used to create
categories for age (18–44, 45–64, 65 or
greater years), FABQ-PA score (less than
15/24, 15/24 or greater),  and symptom
duration (calendar days between date of
condition onset and date of initial evaluation,
categorized as acute [0–21 days],
subacute [22–90 days], and chronic
[greater than 90 days]).
The subjects’ functional status was
quantified at intake and discharge with
the 36-item Functional Health Status
(FHS-36) questionnaire, a physical function
health status measure. The FHS-36
has been described in detail elsewhere. 
Measures range from 0 (low functioning)
to 100 (high functioning) on a linear
metric. Data support the empirical item
hierarchy, unidimensionality, reproducibility
of item calibrations, and content
and construct validity of the FHS-36. [13, 15]
In addition, 80% of the FHS-36 measures
had standard errors of 2 or 3 FHS36
units, or minimal detectable changes
of 5 to 7 units.  Furthermore, the FHS-36
was reported to be sensitive to functional
change during treatment for patients
with cervical impairments (effect size,
Maximal pain intensity reported by
the subject during the past 24 hours was
assessed using an 11–point numeric pain
rating scale, ranging from 0 (no pain) to
10 (worst imaginable pain). The numeric
pain rating scale has been reported to be
reliable and valid in this population, [7, 38]
and has been shown to have a minimal
detectable improvement of 4.1 points in
subjects with cervical radiculopathy. 
The Focus On Therapeutic Outcomes,
Inc Institutional Review Board for the
Protection of Human Subjects and the
Rutgers, The State University of New
Jersey Institutional Review Board approved
this project. The requirement for
informed consent was waived by both Institutional
Data were analyzed using SAS Version
9.2 (SAS Institute Inc, Cary, NC). Descriptive
statistics, the association between
CEN and DP, as well as age, sex,
number of comorbid conditions, FABQPA,
and symptom duration were calculated.
The association between each of
these demographic measures and CEN
and DP was evaluated using logistic regression
Linear regression models were used
to evaluate the association between CEN
and DP, and changes in function and
pain levels. For these analyses, we calculated
the prevalence of CEN and DP in
2 different ways. Subjects were first categorized
based on whether they demonstrated
CEN, then compared with those
who demonstrated non-CEN. Similarly,
subjects were categorized and compared
based on whether they demonstrated
DP or no DP. Subjects were also categorized
by combinations of CEN and DP,
based on the patient response method.
Because, by definition, subjects who
demonstrated CEN also had a DP, the
category representing combinations of
CEN and DP consisted of all subjects who
demonstrated CEN. Subjects who did
not demonstrate CEN were categorized
based on whether they demonstrated a
DP: non-CEN/DP or non-CEN/no DP
(FIGURE). When comparing across these 3
categories, the reference group consisted
of subjects who demonstrated CEN. An
improvement in FHS-36 scores of at least
5 points  and an improvement in pain
scores of at least 4.1  were considered
In relation to these analyses, we
evaluated for the following potential
confounders, which have been shown in
prior studies to be associated with outcomes
in subjects with neck pain:
age [1, 4, 12];
sex [3, 31];
fear-avoidance beliefs about physical activities [18, 19, 24];
number of comorbid conditions,  such as cardiac disease,
cancer, diabetes mellitus, and obesity;
and symptom duration. [1, 4]
were added to the linear regression models
in which the exposure was CEN and/
or DP and the outcomes were functional
status and pain, respectively. Age and
comorbidity were entered as continuous
variables, whereas FABQ-PA score
(dichotomized as elevated or not elevated)
and symptom duration (0–21 days,
22–90 days, greater than 90 days) were
collapsed, so as to more closely simulate
the manner in which this information is
used to make clinical decisions. Adding
age and symptom duration produced a
meaningful change (greater than 10%)
in the effect estimate,  and these 2 variables
were therefore retained in the final
Data were collected from a total
of 328 subjects, of whom 24 did
not contribute CEN data and 26
did not contribute DP data. Those who
contributed CEN data (n = 304) and
DP data (n = 302) did not differ significantly
from those who did not in relation
to age, FABQ-PA score, number of
comorbidities, sex, symptom duration,
and pain and function intake scores. Of
the subjects who contributed CEN and
DP data, 264 also contributed data on
function and 191 on pain at intake and
discharge. When comparing subjects who
contributed complete data on pain (the
outcome measure with the most missing
data) to those who did not, no significant
differences in age, FABQ-PA score,
number of comorbidities, symptom duration,
or pain or functional level intake
scores were found. There was, however, a
significant difference in sex, with males
significantly more likely to have missing
pain data than females (P<.01).
The prevalence of CEN and DP, both
separately and together, is provided in Table 1. The prevalence of CEN and DP
was 0.4 and 0.7, respectively. Among
subjects with a DP, 84% exhibited a DP
into extension. Because all subjects who
demonstrated CEN also had a DP, when
combining categorizations of CEN and
DP, the largest group consisted of those
who demonstrated both CEN and DP
Descriptive statistics on subjects who
contributed data on CEN and DP are provided
in Table 2. Sex was not associated
with CEN (P = .50; odds ratio [OR] =
1.18; 95% confidence interval [CI]: 0.73,
1.89) or DP (P = .53; OR = 0.85; 95% CI:
0.50, 1.43). Younger subjects (global P
= .01; OR = 1.93; 95% CI: 0.92, 4.05 or
OR = 2.91; 95% CI: 1.36, 6.21, depending
on comparison) and subjects with
fewer comorbidities (global P = .03; OR
= 1.13; 95% CI: 0.58, 2.19 to OR = 2.47;
95% CI: 1.25, 4.85, depending on comparison)
were significantly more likely
to demonstrate CEN than older subjects
and subjects with more comorbidities;
however, age (global P = .32; OR = 1.08;
95% CI: 0.52, 2.25 or OR = 1.60; 95%
CI: 0.74, 3.45, depending on comparison)
and comorbidity (global P = .11; OR
= 0.71; 95% CI: 0.36, 1.42 to OR = 2.49;
95% CI: 0.83, 7.44, depending on comparison)
were not associated with DP.
Conversely, symptom duration was not
associated with CEN (P = .07; OR = 1.15;
95% CI: 0.67, 1.99 to OR = 1.99; 95% CI:
1.11, 3.56, depending on comparison);
however, subjects who were more acute
were more likely to demonstrate a DP
(P<.01; OR = 1.93; 95% CI: 1.04, 3.58 or
OR = 3.55; 95% CI: 1.63, 7.70, depending
on comparison). Low FABQ-PA scores
were more common among subjects who
demonstrated CEN (P = .01; OR = 1.96;
95% CI: 1.18, 3.34) and those with a DP
(P<.01; OR = 2.50; 95% CI: 1.47, 4.35).
Results from regression models analyzing
the association between CEN and
DP and changes in function and pain
are presented in Tables 3 and 4, respectively.
In the multivariate model examining
change in functional status (Table 3), subjects who demonstrated CEN experienced,
on average, a 3.6–point (95%
CI: –0.3, 7.4) improvement in function
scores, whereas subjects with a DP had
an average improvement of 5.4 points
(95% CI: 0.8, 10.0), thereby exceeding
the minimal detectable change of 5
points.15 Compared with subjects classified
as non-CEN/DP and non-CEN/no
DP, subjects classified as CEN and DP reported
a 1.8–point (95% CI: -2.5, 6.2) and
a 6.2–point (95% CI: 1.3, 11.1) improvement
in function, respectively. Irrespective
of CEN or DP, most subjects (83%)
demonstrated improvements in function
that exceeded the minimal detectable
change for the FHS-36 of 5 points. 
Among subjects who demonstrated CEN,
86% exceeded this threshold, compared
with 80% of subjects who did not centralize.
In relation to DP, differences in
functional outcomes were similar: 84%
of those with a DP and 78% of those with
no DP exceeded the minimal detectable
change. In the multivariate models examining
pain intensity (Table 4), among
subjects who demonstrated CEN, DP, or
any of the combinations of CEN and DP,
there were no statistically significant differences,
based on a P value of .05 or less,
or clinically relevant changes, based on
the minimal detectable improvement of
4.1 points. 
The prevalence of centralization (CEN) among
subjects with neck pain in the present
study and that reported in 3 prior
studies [6, 34, 37] ranges from 0.2 to 0.4. In our
study, the prevalence of CEN was slightly
higher (0.4), despite similar definitions of
CEN. This variability in prevalence rates
across studies is likely attributable to differences
in the populations studied and
the assessment methods used to measure
CEN, as well as the exclusion from
our analyses of those subjects who could
not be classified. Ours is the first study
to describe the prevalence of directional preference (DP) among
subjects with neck pain. The difference
in prevalence rates between CEN and DP
was expected because of the additional
criteria used to determine DP. At 0.7, determining
DP has the potential to inform
interventions for a substantial number of
patients with neck pain. When pain responses
were classified using the patient
response method, the largest group was
CEN and DP; however, a substantial percentage
of patients (30%) were identified
as having DP in the absence of CEN.
We hypothesized that when comparing
CEN with non-CEN, and DP with
no DP, there would be differences in age
and symptom duration. In our study, age
was associated with CEN but not with
DP, whereas symptom duration was associated
with DP but not with CEN. One
other study has addressed the association
between CEN and age and symptom duration
in subjects with neck pain,  the
findings of which, in relation to age, are
consistent with ours. However, in that
study,  subjects who demonstrated CEN
were more likely to have acute symptoms
than those with non-CEN. We also
found that subjects with CEN had fewer
comorbid conditions, but there were no
differences in the number of comorbid
conditions among subjects with a DP.
Differences in age, number of comorbid
conditions, and symptom duration between
categories of CEN and DP provide
additional support for the assertion that
CEN and DP represent different clinical
We also hypothesized that CEN and
DP would predict changes in functional
outcomes and pain levels. When
combined with treatments consisting
of matched exercises and manual
techniques, in our study, DP compared
with no DP and CEN compared with
non-CEN/no DP predicted changes in
function but not pain. None of the categories
of CEN or DP, including the patient
response method, predicted pain
In 3 other studies, [33, 34, 37] investigators
reported on the association between CEN
and function and pain outcomes in patients
with cervical impairments, using
similar operational definitions for categorizing
CEN. In 2 of these studies, [33, 34]
results for subjects with low back pain
were combined with those for subjects
with neck pain. CEN was associated with
a greater reduction in disability and pain
in both studies. In the third study,  CEN
was associated with a greater reduction
in pain but not with functional levels
for subjects with cervical impairments.
These studies differ from ours, in which
CEN was not associated with changes
in function or pain, except in relation to
functional changes, and only when CEN
was compared with non-CEN/no DP.
This is the first study to address characteristics
of CEN and DP in subjects
with neck pain in the same study. In
relation to achieving a minimal detectable
improvement in function of at least
5 points,  our study results suggest that
DP compared with no DP and CEN/DP
compared with non-CEN/no DP predict
The association between functional
outcomes and CEN/DP and non-CEN/
DP categories was not significant, suggesting
that dividing DP into these 2
subcategories at intake may not be clinically
useful. If a patient demonstrates a
DP during the initial evaluation, further
delineation for a CEN pain response
does not appear useful to predict outcomes
from physical therapy interventions.
Therefore, evaluating patients with
neck pain solely for DP as operationally
defined in our study appears to be the
best strategy of those addressed in this
study to improve the interpretation of
functional outcomes. Future studies are
required to replicate our findings using
larger sample sizes and long-term outcome
We excluded patients who had no pain
or relevant referred symptoms immediately
before repeated-movement testing.
These subjects, although small in number
(n = 22) compared to our original sample,
might represent an important category of
patients to identify for effective treatment
Because all subjects who demonstrated
CEN or DP received matched treatments
based on DP, our study results
show that the categorizations of CEN and
DP were associated with improvements
in function when subjects with neck pain
also received treatment based on DP. It
is therefore possible that CEN and DP
predict better functional outcomes irrespective
of treatment. If research findings
in the lumbar spine are generalizable to
the cervical spine, this alternative explanation
is unlikely, because studies have
shown that matched treatments for patients
who demonstrate DP in the lumbar
spine are more effective than unmatched
treatments. [2, 20–23]
The present study has several limitations,
some pertaining to data acquisition.
Despite the fact that therapists participating
in data collection were instructed
to collect and record data on all subjects
with neck pain, 24 subjects with data on
neck pain had missing CEN data, and
26 had missing DP data. Therefore, the
subjects in the present study constitute a
sample of convenience. Additionally, we
were unable to control for all potential
confounding variables, as they were not
measured during data collection. Finally,
we made a determination regarding the
presence of DP by the end of the initial
visit. This protocol was implemented despite
recommendations  that subjects
who describe a subjective movement
preference but have no objective findings
indicative of a DP should be classified as
having a DP if the subjective findings
are confirmed during subsequent visits.
Identifying the specific criteria for classifying
DP to identify treatment strategies
and to optimize outcomes is a clinically
relevant question, and is planned for future
Study limitations also included those
related to study design. The FHS-36
questionnaire, which we used to measure
function, is not a commonly recognized
tool to measure function in patients with
neck pain, and was not designed to measure
the functional levels of specific body
parts. Also, the generalizability of our
study results might be impacted by the
utilization of therapists with advanced
training in Mechanical Diagnosis and
Therapy methods to collect data and treat
subjects. We believe, however, that therapists
can be trained easily to perform the
components of Mechanical Diagnosis and
Therapy methods that were incorporated
in this study, specifically the examination
techniques that used standardized operational
definitions of repeated-motion
testing and treatment strategies involving
repeated and progressive movements in a
specific direction based on DP.
Despite these limitations, our study
provides support for including DP in any
treatment-based classification system for
patients with neck pain, as it informs interventions
that result in improved functional
Directional preference (DP) is a prevalent evaluation category that, when combined with treatments consisting of matched exercises and manual techniques, can be used to predict changes in function, but not pain, in patients with neck pain.
FINDINGS: DP is a prevalent examination finding that predicts improvement
in function when combined with treatments matched to the direction of the DP.
IMPLICATIONS: The evaluation of DP should be a component of the physical
therapy examination of patients with neck pain and, when present, should
inform intervention strategies.
CAUTION: Criteria for identifying and categorizing DP in patients with
neck pain need further refinement.
A special acknowledgement
is dedicated to our coauthor Dr Dennis
Hart, who recently passed, for his guidance
and expertise in the study’s design. Dennis, you
will be greatly missed, and your contributions
to our research group and research initiatives
as well as to the physical therapy profession
will be long lasting
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