1243
Continuous-Scale Physical Functional Performance
Healthy Older Adults: A Validation Study
in
M. Elaine Cress, PhD, David M. Buchner, MD, Kent A. Questad, PhD, Peter C. Esselinan, MD,
Barbara J. delateur, MD, Robert S. Schwartz, MD
ABSTRACT.
Cress ME, Buchner DM, Questad KA, Esselman PC, deLateur BJ, Schwartz RS. Continuous-scale
physical
functional performance
in healthy older adults: a validation
study. Arch Phys Med Rehabil 1996;77: 1243-50.
Objective: The continuous-scale
physical functional performance test (CS-PFP) is an original instrument designed to provide a comprehensive,
in-depth measure of physical function
that reflects abilities in several separate physical domains. It is
based on a concept of physical function as the integration of
physiological
capacity, physical performance, and psychosocial
factors.
Setting: The test was administered under standard conditions
in a hospital facility with a neighborhood setting. The CS-PFP
consists of a battery of 1.5 everyday tasks, ranging from easy
to demanding, that sample the physical domains of upper and
lower body strength, upper body flexibility, balance and coordination, and endurance. Participants are told to work safely but
at maximal effort, and physical functional performance
was
measured as weight, time, or distance. Scores were standardized
and scaled 0 to 12. The test yields a total score and separate
physical domain scores.
Design: The CS-PFP was evaluated using 148 older adults78 community dwellers, 31 long-term care facility residents
living independently,
and 39 residents with some dependence.
Main Outcome Measures: Maximal physical performance
assessment included measures of maximal oxygen consumption
(Vozmax), isokinetic strength, range of motion, gait, and balance. Psychosocial factors were measured as self-defined health
status using the Sickness Impact Profile (SIP), self-perceived
function using the Health Survey (SF36), and Instrumental Activities of Daily Living (IADL).
Results: IADL scores were not significantly different among
the groups. Test-retest correlations ranged from .84 to .97 and
inter-rater reliability
from .92 to .99 for the CS-PFP total and
5 domains. Internal consistency was high (Cronbach’s (Y, .74 to
.97). Both total and individual
domain CS-PFP scores were
significantly different for the three groups of study participants,
From the Department of Medicine, Division of Gerontology
& Geriatric Medicine (Dr. Cress), the Department of Rehabilitation Medicine (Drs. Questad, Esselman), and the Departdent
of Health Services and Community
Medicine (Dr.
Buchner), University
of Washington,
Seattle; the Northwest HSR&D Field Program, Seattle Veterans Affairs Medical Center (Dr. Buchner); and the Department
of Physical Medicine and Rehabilitation, Johns Hopkins University (Dr. delateur),
Baltimore, MD.
Submitted for publication November 9, 1995. Accepted in revised form April
17, 1996.
Sunoorted bv National Institutes of Health srant 1 R29 AG10267. Centers for
Dises;sk Control grant U48-CCUO09654,
Natiokl
Institutes of Heal& grant 1 R01
AG10853, and National Institutes of Health grant R010943.
Presented in part at the 1994 annual meeting of the Gerontological
Society of
America, Atlanta. GA.
No commercial
oar& havine a direct tinancial interest in the results of the
research supporting this article has or will confer a benefit upon the authors or
upon any organization with which the authors are associated.
Reprint requests to M. Elaine Cress, PhD, University
of Washington,
Box
358852, Seattle, WA 98195.
0 1996 by the American Congress of Rehabilitation Medicine and the American
Academy of Physical Medicine and Rehabilitation
0003-9993/96/7712-3762$3.00/O
increasing with higher levels of independence, supporting construct validity. CS-PFP domain scores were significantly correlated with measures of maximal physical performance (Vozmax,
strength, etc) and with physical but not emotional aspects of
self-perceived function.
Conclusions:
The CS-PFP is a valid, reliable measure of
physical function, applicable to a wide range of functional levels, and having minimal floor and ceiling effect. The total and
physical domains may be used to evaluate, discriminate, and
predict physical functional performance for both research and
clinical purposes.
0 1996 by the American Congress of Rehabilitation
Medicine
and the American Academy of Physical Medicine and Rehabilitation
P
HYSICAL
PERFORMANCE
tests have become popular
because of research concerns that self-reported function provides insufficient information about the type of impairment and
lacks sensitivity to change.’ Many investigators and clinicians
find physical performance measures appealing because of their
potential for insight into the site and severity of functional
impairment,
sensitivity to change, and face validity. Several
new performance tests have been published in recent years.2-6
With one exception,5 they focus on mobility dysfunction or on
people having severe limitations. Our aim was to develop a
reliable measure of physical functional performance that was
not constrained by ceiling or floor effects, used several physical
domains, and applied to a broad spectrum of abilities. A secondary goal was to develop an instrument that provides insight into
causes of poor physical functional performance.
Although there is no gold standard for the measurement of
physical function, several instruments are available to assess
factors that contribute to physical function in varying degrees.
The Venn diagram in figure 1 represents a conceptual model
of the physical and psychological
spheres affecting physical
function. The physiological
capacities of the cardiovascular,
musculoskeletal, and neuromuscular systems are primary determinants of function. In this model, “physiological
capacity”
refers to the basic cellular and anatomic function such as cardiac
ejection fraction, nerve conduction velocity, or muscle strength
per cross-sectional area. “Physical performance”
is the ability
to integrate these physiological
systems into coordinated, efficient movements to achieve optimum physical function. For
example, lower extremity strength is a measure of physical
performance,
whereas the ability to walk upstairs represents
physical functional performance. “Psychosocial
factors’ ’ such
as confidence, motivation, perceived ability, depressive symptomology, and social role also influence physical function.
“Physical function, ’ ’ then, is the integration of physiological
capacity and physical performance capability mediated by psychosocial factors. In this study, maximal physical performance
measures were made under standard laboratory conditions at
maximal effort. We measured strength as isokinetic torque, cardiovascular fitness as Vo,max, and neurological function as step
reaction time and balance time.
To measure physical functional performance, we developed
Arch
Phys
Med
Rehabil
Vol 77, December
1996
1244
CONTINUOUS-SCALE
PHYSICAL
an instrument based on ordinary activities of daily life, tested
at maximal effort, relying on the patient’s judgment to remain
within the bounds of safety and comfort. This new measure,
called “continuous
scaled physical functional performance”
(CS-PFP), utilizes a continuous scale to quantify physical functional performance of the whole body as well as across several
physical domains. Physical functional performance was measured under standard conditions in a homelike setting using
tasks similar to those required in independent living. We assessed the reliability and validity of the CS-PFP.
We hypothesized that persons living independently
in the
community would have higher physical performance (strength,
aerobic capacity, shorter reaction time) than those living in a
long-term care facility. Of the latter, we hypothesized that those
who expressed some dependency in physical tasks would have
lower physical performance than those who did not. We further
hypothesized that these differences in maximal physical performance (strength, aerobic capacity, reaction time) would be associated with physical functional performance (CS-PFP).
METHODS
CS-PFP Instrument
Development
Fifteen everyday tasks were chosen to represent activities
essential to independent living. Common activities were chosen
to minimize the effects of learning or strategizing between tests.
Each task was simplified to reflect one primary physical domain,
minimizing
reliance on other domains to accomplish the task.
Participants performed real, not simulated, tasks, eg, transferring laundry from an actual washer and dryer. Seven of the 15
final tasks were pilot-tested using 29 participants from each of
the 3 living status groups in the study.7 The 1.5 tasks tested
ranged from those requiring little strength or endurance to those
demanding greater stamina. They were ordered for performance
from easiest (personal) to moderate (household) to most difficult
(mobility) (fig 2). Participants were asked to pace themselves
to complete as many tasks as possible. Tasks were quantified
by weight carried and/or time to complete the task, or distance.
The instruction for each task was to perform it safely but to
work at maximal perceived level, reaching as high as possible,
carrying maximal weight, and working as quickly as possible.
The average time required to complete the test is 60 minutes
(for community dwellers [CD], approximately
45min; for residents of a long-term care facility living independently
[LTC/I],
approximately
60min; and for residents of a long-term care
facility who were defined as dependent [LTUD], approximately
75min). The rate of perceived exertion using the Borg scale (6
Physiological
Capacity
Performance
Psychosocial Factors
Fig 1. Venn diagram
illustrating
nents of physical
function.
Arch
Phys Med
Rehabil
Vol77,
the
relationships
December
1996
among
the
compo-
FUNCTION
PERFORMANCE,
Fig 2. Distribution
distance)
Cress
of CS-PFP measures
by physical
domain.
(0,
no measure;
I,
weight;
q,
to 20) and heart rate were also recorded after completion of
each task.*
Nine judges (1 geriatrician, 1 physiatrist, 2 biomechanists, 1
physical therapist, 1 occupational
therapist, 1 physiologist,
1
retirement home administrator/physical
therapist, and 1 biomechanist/physical
therapist) categorized the tasks into five
physical domains (fig 2) using a modified Delphi procedure.’
The judges regarded weight-carried
data as providing information about skeletal muscle strength. Time to complete the task
was regarded primarily as a reflection of balance and coordination, although in some tasks time was deemed to be a measure of
strength. The judges considered distance measured as providing
information about flexibility and endurance. Also, the CS-PFP
presents a number of tasks to be performed serially because
this closely mimics the real demands of everyday physical functions, eg, go shopping, take the bus, cook, wash dishes, etc.
The cumulative time of the timed tasks was regarded as one
measure of endurance.
The CS-PFP tests were administered in a facility with a neighborhood setting. The facility contains a kitchen, dining room,
bedroom, grocery store, and bus platform. Distances and procedures were constant from test to test. Participant instructions
and measurement protocols were standardized.
The following is a brief description of the tasks. (A detailed
description of the tasks and procedure dialog is available from
the first author.) The distribution
of these measures across the
physical domains is shown in figure 2. A subscale score is
determined for each domain and these scores are averaged to
determine the total score. Tasks that are quantified using both
weight and time include: (1) carrying a pan of water a distance
of 1 meter; (2) carrying and then pouring from a jug of water
into a cup; (3) carrying sandbags in a luggage carry-on bag
from a park bench, up a 3-stair public transportation platform
and returning to the bench; and (4) distributing groceries into
one or two paper bags covered with plastic bags and carrying
the groceries a distance of 70 meters, including
ascent and
descent of the public transportation platform and negotiating a
closed door. Tasks that are quantified by time alone include:
(1) transferring 7.7kg of laundry and sandbags from the washer
to a dryer and then to a basket which is then set on the counter;
(2) donning and removing a jacket and a seat-belt; (3) sweeping
a set amount of kitty litter into a dustpan from a prescribed
area; (4) vacuuming a set amount of oats from a prescribed area
of carpet; (5) making a double bed with fitted sheet, comforter,
and pillows; (6) climbing a set of stairs; and (7) getting into
and out of a bathtub. Tasks that are quantified by distance
include: (1) walking as far as possible in 6 minutes; and (2)
CONTINUOUS-SCALE
PHYSICAL
placing and removing a sponge from the highest adjustment of
a sliding shelf. Only one task is quantified with weight alone:
pulling on a spring scale to simulate the opening of a fire door.
Tasks were selected so that the lowest two levels of difficulty
were judged by the panel to reflect all physical domains. This
was done to gain the most information
on individuals who may
not have had the stamina to complete all tasks. In addition,
tasks were selected so that several tasks contributed to any
particular domain score. For example, putting on a jacket, putting on a seat belt, and reaching onto a high shelf all represent
upper body flexibility. Tasks reflective of upper body strength
and balance and coordination included all three levels of difficulty. Tasks requiring lower body strength were moderate or
difficult.
Time as a measure of strength. While time to complete a
task was usually used as a measure of balance and coordination,
in several tasks it is a measure of strength (fig 2). Strength
is dependent on the integration of muscular and neurological
systems. Isokinetic performance used to measure strength is the
optimal integration of the neuromuscular properties (physiological capacity) to generate force (physical performance). The potential for strength training to improve physical performance in
older adults is dependent on the inverse relationship
between
strength (kg) and fatigue (set). The logarithmic
relationship
between maximum strength and muscular endurance at submaximal tasks was first described by Simonson and later clarified.‘O~ll Consider a person who can lift a maximum of 20kg
isotonically and hold it for 1 second. After a progressive resistance exercise program, that person can lift 40kg for 1 second
and sustain a 20.kg force for 60sec. This principle also helps
to clarify the relationship between strength and time. A weaker
person is incapable of sustaining the contraction that allows
performance
in the most efficient manner. Accommodation
strategies that will take longer are used to accomplish the task.
For example, in the floor sweeping task, a person with weak
back muscles will stand upright, using arm motion to gather
me kitty litter into a pile, minimizing the time required to stoop
and sweep it into the dustpan. A person with stronger back
muscles will accomplish the task in a shorter time by stooping
from the beginning and sweeping directly into the dustpan.
For the CS-PFP, tasks requiring lower back and trunk strength
were classified in the lower body strength domain. For example,
transferring laundry, floor sweeping, vacuuming, and making a
bed require sustained contraction of the hip extensors throughout the duration of the task.
Time as a measure of balance and coordination. For most
tasks, the time required also reflected the subject’s level of
balance and coordination.
For example, once a weight (bag,
pan, or basket) is lifted, the time it takes to accomplish the task
is dependent on balance and coordination. Physical performance
measures of the neuromuscular
system (time on the wide balance beam; step reaction time) were significantly
associated
with time to complete tasks of the CS-PFP.
Scales and Measurement Issues
Combining measures derived from rating scales or questionnaires is usually easy when the same rating scale is used for
each item measured. However, when measures are made using
performance parameters such as time or weight, as in this study,
the task of combining them into a single scale is not as simple.
The most common approach to this problem is to transform the
measures of a scale into a standard score. This indicates how
far above or below a norm group mean an individual measure
is, using standard deviation units. The standard deviation units
are then summed to form a scale. Some measures of performance, such as the Jebsen-Taylor
Hand Function Test” and
FUNCTION
PERFORMANCE,
1245
Cress
almost all achievement and intelligence tests, use this solution.13
Normative scoring, however, is particularly troublesome when
it is applied to direct measures of functional performance. An
extremely high or low individual score can skew the entire scale
it belongs to, and if a person is unable to perform a task there
is no clear way of computing a scale score.
To counter these problems for the CS-PFP, all measures of
time, weight, and distance were transformed to standard scores
with the mean of all persons tested set at 0, using the descriptive
statistical procedure of the Statistical Package for Social Sciences (SPSS). This procedure standardized varying units (kg,
cm, set) and directions of measurement (lower time scores but
higher weight scores generally indicate higher function). Stan
dard scores were converted into a scale of 0 to 12, with the
lowest 10% being scored as 1 and the highest 10% scored as
12. Scores between the 10th and 90th percentile were grouped
in S-percentile increments that were assigned the numbers 2
through 11. Zero was used for persons unable or refusing to
perform a task. The total CS-PFP score is the sum of all standard
scores, scaled 0 to 12. The sensitivity of the scales to an exercise
intervention is currently being assessed, and is not reported on
here.
Weighting of the domains. In the CS-PFP, domain scores
are obtained by summing the scaled scores for the tasks of each
domain (fig 2). The CS-PFP-total is the average of the 5 domain
scores. By leaving the domains equally weighted we avoid imposing a bias of importance on any particular physical domain.
For a person with Parkinson’s disease, the most important domain may be balance and coordination,
whereas for a person
with generalized weakness, the strength domains may be more
important. An equal weighting system allows this testing procedure to be easily interpreted across clinical circumstances.
Study Participants
Men and women 70 years of age or older and in relatively
good health were recruited from the greater Seattle area. Respondents were screened to exclude persons with unstable cardiovascular or metabolic disease, recent unhealed fractures, disorders with a highly variable course (eg, multiple sclerosis), a
pacemaker, a life expectancy of less than 1 year, excessive
alcohol intake (more than 2 drinks a day), inability to speak
English, inability to follow directions, or inability to keep appointments. Ability to keep a rather complicated appointment
schedule in 5 different testing sites in a timely manner and
properly dressed was accepted as sufficient evidence of adequate cognitive function to participate in the study. The final
sample included 148 participants (26 men; 122 women) from
3 living-status categories: 78 community dwellers, persons living in single-family
dwellings, apartments, or condominiums
(CD group); 31 residents of a long-term care facility who said
they were living independently,
eg, without assistance (LTC/I
group); and 39 residents of a long-term care facility who had
a score of <65 on the physical function scale of the Health
Survey SF-36 and were defined as dependent (LTUD group).
The study was approved by the university’s and hospital’s Human Subjects Review committees.
Maximal Physical Performance Measures
Maximal. oxygen consumption. Maximal
oxygen consumption (Vo,max) was elicited using a ramp testing protocol
on a Medgraphics CPX electronically braked cycle ergometer.a
Watts were increased at a fixed rate per minute (8 to 16 watts)
to complete the test in 8 to 12min. Expired air was analyzed
using Medgraphics zirconia fuel cell O2 and infrared CO* analyzers.” Gas how was measured using a pneumatach and a waveform analyzer. Data were averaged over an g-breath period, and
the final report was for every 30 seconds.
Arch
Phys Med
Rehabil
Vol 77, December
1996
1246
CONTINUOUS-SCALE
Table
1: Age, Selected
Age (vr)
i/o, max (mL/ka/min)
Biceps peak isometric
90" (Nm)
Knee extension
isokinetic
work 60"/sec
Shoulder
flexion (")
Hip flexion t")
Wide balance beam (set)
Step reaction time (msec)
(Nm)
_.. _-.-.
SIP total
SIP physical
dimension
SF36aeneral
health
SF36 physical function
SF36 mental health
*Significant
PHYSICAL
Maximal
Physical
Performance,
PERFORMANCE,
and Self-Perceived
Cress
Function
Measures
Long-Term Care
Dependent
(X + SD), n = 39
Long-Term Care
Independent
(X i SD), n = 31
Community
DbVl?ller5
IX + SD), n = 4.9
84.65
12.54
15.59
56.47
143.57
72.05
22.7
1196
13.9
15.15
50.80
49.73
74.31
80.51
18.68
21.29
72.64
144.70
66.59
8.01
1100
4.29
4.37
52.87
85.48
74.75
72.29
21.93
27.89
101.35
150.78
67.19
6.33
899
1.54
2.17
61.68
89.72
70.11
k
2
i
i
2
k
IL
2
2
?
2
2
5
6.17
4.48
5.96
15.10
21.31
11.5
16.8
220
10.2
12.0
11.3
18.12
14.4
+
+
k
t
I
t
+
t
t
f
t
t
t
6.09
5.16
9.93
17.60
15.01
9.9
2.94
288
4.2
5.6
13.4
9.5
13.6
i
t
i
i
I
!I
2
i
2
t
k
?
+
5.17
7.12
14.23
38.36
16.10
12.1
1.90
149
5.4
5.2
12.4
7.2
11.4
All (X + SD),
n = 118
77.19
18.41
21.66
76.87
146.42
68.75
12.20
1050
7.28
7.47
55.31
74.15
73.02
+
+
f
k
i
2
2
k
f
e
i
i
t
7.81
7.1
11.7
32.3
18.0
11.4
12.2
250
8.6
10.1
13.2
22.3
13.3
FVFhe
23.25"
,25.52*
‘12.04"
26.29"
1.78
2.54
28.12"
21.53*
16.75"
13.66*
7.9"
109"
1.24
p < .OOOl.
A physician continuously
monitored the 12-lead Quinton
Q650b electrocardiogram
(ECG) throughout the test, and heart
rates were recorded every 30 seconds. Criteria for test termination included subject fatigue, signs and symptoms of exercise
intolerance, ECG changes, and abnormal blood pressure or respiratory response. The test was stopped if the subject showed
signs of cardiovascular incompetence in accordance with American College of Sports Medicine guidelinesI
Strength.
Biceps bracchi isometric strength at 90” elbow
flexion and isokinetic knee flexion and extension strength were
assessed using a LID0 dynamometer.c Grip strength was assessed on both left and right sides and was reported as the sum
of the best of 3 trials on both hands. Good reliability has been
previously shown with this age group on LID0 equipmentI
Range of motion. Range of motion was determined for hip
and shoulder flexion using a goniometer. The standard Thomas
technique was used for hip flexion.16 For shoulder flexion the
subject stood with the heels placed 8.9cm from the wall and
the back against the wall. The hand was rotated 90” in pronation
and the arm lifted, supported by the examiner, until the subject’s
back ribs started to pull away from the wall. The goniometer
distal arm was in correct alignment over the lateral epicondyle,
and the goniometer’s proximal arm was aligned with the midline
of the thorax.r7
Gait, balance, and reaction time. Time to walk 9m on a
17-cm-wide balance beam was recorded as a measure of balance.18 Self-selected walking speed was determined over a 40m distance with a 3-m runway and ending strip. To test the
ability of the nervous system to respond quickly in shifting the
body weight, a device to measure simple step reaction time was
built by Diversified Productsd to our specification expressly for
this study. The subject stood with weight equally distributed
and the right foot on the start pad. The subject was visually
cued with an amber “caution”
light (randomized in duration
from 1 to 4sec) followed by a green “go” light. At the green
light the subject stepped forward with the right foot onto the
stop pad. Simple reaction time was measured as the total time
from the green light signal to the step onto the stop pad. Movement time was measured from the lifting of the foot from the
start pad to the placement on the stop pad. Reaction time is
the difference between the total or step reaction time and the
movement time.
Self-Perceived
Function
Psychosocial factors were measured as self-defined health
status using the Sickness Impact Profile (SIP),19 self-perceived
function using the Health Survey (SF36),” and Instrumental
Activities of Daily Living (IADL).*r Both questionnaires were
Arch
FUNCTION
Phys Med
Rehabil
Vol77,
December
1996
administered before CS-PFP testing. These health status questionnaires are valid and reliable instruments.19~20
Validity
Construct validity. We reasoned that living status is a reflection of a person’s physical performance capacity (strength,
aerobic capacity, and reaction time). We hypothesized that in
our population
samples, the community dwellers as a group
would show greater physical performance capacity and therefore reflect greater physical functional performance than the
LTC facility residents. Among the LTC residents we expected
the independent participants (LTCYI) to show greater physical
performance
and physical functional performance than those
needing assistance (LTC/D). We performed analysis of variance
(ANOVA)
to determine the mean differences among the groups
in physical performance measures (strength, aerobic, reaction
time), physical functional performance (CS-PFP total) and the
physical functional domains (Upper body strength, Lower body
strength, Upper body flexibility, Balance and coordination, Endurance), and psychosocial factors that included self-report assessment of function and health status (SIP, SF-36, IADL).
We reasoned that persons who perceived themselves as having
higher function would score higher on the CS-PFP than those
who perceived lower function. We compared these measures
by calculating
bivariate correlations
between total CS-PFP
scores and subscale scores on the SIP and SF36. The CS-PFP
is a performance-based
measure of physical function that we
hypothesized
would not correlate with scales of emotion or
mental health.
Reliability
and Internal Consistency
To assess both test-retest and inter-rater reliability, two different raters rated each subject on two different days. A repeatedmeasures ANOVA was used to a analyze for mean differences
between raters. Pearson product moment correlations were calculated for all scores using the SPSS Correlation procedure.
Internal consistency for four of the CS-PFP subscales (Upper
Body Strength, Lower Body Strength, Balance and Coordination, and Endurance) was measured by Cronbach’s (Y, calculated
using the SPSS Reliability
procedure. A Cronbach’s a! of 0.6
or greater is considered an index that the items in the scale are
measuring the same attribute.22
RESULTS
Maximal
Physical Performance
Measures
Significant differences were found on all physical performance capacity measures among the three groups of residents.
CONTINUOUS-SCALE
Table
CS-PFP-TOT
CS-PFP-UBS
CS-PFP-LBS
CS-PFP-UBF
CS-PFP-B&C
CS-PFP-END
Biceps
strength
(Nm)
Knee
extensor
strength
(Nm)
Shoulder
flexion (7
Step-reaction
time (set)
i/o, max 1L/
min)
Hip flexion (“)
2: Correlation
Coefficients
PHYSICAL
Between
CS-PFP
Scores
CS-PFP-UBS
CS-PFP-LBS
CS-PFP-UBF
CS-PFP-B&C
CS-PFP-END
.93*
1 .oo
.98*
.94*
1 .oo
.91”
.79*
.83*
1 .oo
.93”
.76*
.89”
.82*
1.oo
.96*
.84*
.91*
.86”
.91*
1 .oo
Biceps
Strength
(Nm)
.55*
.63*
.57*
.52*
.40*
.49*
Cress
Phvsical
1247
Performance
Caoacitv
Shoulder
Flexion
(“1
stepReaction
Time kc)
i/o, max
.68X
.71*
.69*
.62*
.53*
.63*
23”
.23*
.I9
.26*
.28*
.30*
-.65*
-.62*
-.65*
-.58*
-.57*
-.63*
.65*
.66”
-.64*
.59*
.51*
.65”
-.I9
-.05
-.I6
-.I3
-.21*
.81*
.03”
-.422”
.58*
.I4
.I4
-.49*
.82*
.I0
1.oo
-.I8
.I9
.05
-.44x
.06
1.00
.07
1 .oo
Knee
Exrensor
Strength
(Nm)
1.oo
1.oo
CS-PFP upper
CS-PFP balance
24
s
Maximal
1 .oo
Self-Perceived
Function
As expected, there were significant differences between the
groups in physical but not nonphysical domains and in health
status. IADL scores did not differ among the groups, and a
clear ceiling effect is shown for the LTC/I and community
dweller groups (fig 3). Table 1 presents selected scales of selfdefined health status from the SIP and of self-perceived function
from the SF36 for the three subject groups. There were significant differences among the three groups on the SIP and SF36
d
and Selected
I .oo
Selected physical characteristics and physical performance capacity measures of participants in the three living status groups
are shown in table 1. The three groups were significantly different in all areas shown except shoulder and hip flexion. Differences in strength, vo,max, and balance measures remained significant after correcting for age. All physical domains of the
CS-PFP were significantly associated with the 5 physical performance capacity measures (table 2). Except for lower body flexibility, the strongest correlation in all other domains was with
the physical characteristic that was intuitively reasonable, eg,
CS-PFP upper body strength score is highly correlated with
biceps strength (Y = .93).
g
PERFORMANCE,
CS-PFP-TOT
Abbreviations:
CS-PFP-TOT,
CS-PFP total score; CS-PFP-UBS,
PFP-UBF, CS-PFP upper body flexibility
score; CS-PFP-B&C.
*Significant
correlation
< .05.
2
FUNCTION
23.5
23
22.5
22
21.5
LTClD
N=39
LTCll
N=31
CD
N=78
Fig 3. Mean IADL scores for community
dwellers
(CD); residents
of congregate
care facilities,
dependent
(LTC/D);
and residents
of congregate
care facilities,
independent
(LTC/I).
(Urnin)
Hip
flexion
(“I
body strength
score; CS-PFP-LBS,
CS-PFP lower body strength
score;
and coordination
score; CS-PFP-END,
CS-PFP endurance
score.
CS-
physical scales but not on the SF36 mental health scale. Bivariate correlations on all groups between CS-PFP scores and SIP
and SF36 scores are shown in table 3. Although CS-PFP scores
were significantly correlated with physical function and overall
health status using the SIP and SF36, they were not related to
mental and emotional scales of these scales.
Reliability
and Internal Consistency
Inter-rater reliability correlation coefficients for
total and individual
domains ranged from .92 to
significant rater differences on the CS-PFP total or
cal domains. Test-retest correlations ranged from
(table 4). Cronbach’s (Y ranged from .74 to .97 for
total and individual domains indicate good internal
(table 4).
the CS-PFP
.98 with no
the 5 physi.85 to .97
the CS-PFP
consistency
CS-PFP Validity
The CS-PFP was capable of distinguishing
physical functional performance among the three groups, whereas IADL did
not. The dependent group of participants living in LTC facilities
did not differ significantly
from the independent residents of
LTC facilities or the community dwellers on the IADL scale
(fig 3). In contrast, all three groups differed significantly in total
CS-PFP scores (fig 4A) (F = 24.09, p < .OOOl), as well as in
individual CS-PFP physical domain subscores (fig 4B) (F = 73
to 119, p < .OOOl). In each physical domain and the CS-PFP
total, CD participants scored higher than LTC/I participants,
who scored higher than LTUD participants. The overall effort,
as measured by the rate of perceived exertions (RPE) scale, was
significantly
(F = 12.18; p = .OOOl) less in the community
dwellers (RPE = 10.8 2 1.7) than in the LTC groups (RPE:
LTC/l = 11.5 + 1.8; LTC/D = 12.48 5 1.4).
DISCUSSION
The CS-PFP is a unique, valid, and reliable comprehensive
test of physical functional performance. Evaluations are administered under standard conditions and quantification is based on
continuous scaling. It is useful for measuring higher levels of
function without evidence of ceiling effects, as well as accommodating persons who cannot perform individual tasks. Physical functional performance is reported as a total score and in
Arch
Phys Med
Rehabil
Vol77,
December
1996
1248
CONTINUOUS-SCALE
Table
SF36 TOT
CS-PFP-TOT
CS-PFP-UBS
CS-PFP-LBS
CS-PFP-UBF
CS-PFP-B&C
CS-PFP-END
SF36 GH
.75”
.67X
.70*
.72*
.68*
.77*
3: Correlation
SF36 MH
-.30*
p.30”
-.26*
-.27*
-.25*
-.37*
Coefficients
SF36 PF
.75*
.67
.70*
.72*
.68*
.77*
-.I5
-.I2
p.14
-.21*
-.I8
-.I1
PHYSICAL
Between
SF36 RP
FUNCTION
CS-PFP
SF36 VIT
-.08
-.06
-.07
-.08
-.I0
-.06
.4a*
.42
.42*
.49*
.43
.51*
PERFORMANCE,
Scores
SIP TOT
-.58*
-.51*
-.53*
-.63*
-.57*
-.59*
and Health
SIP AM
-62”
-.53*
-.5r3*
-.63*
-.60*
-.64*
Cress
Status
Measures
SIP MOB
-.52*
-.45*
-.48”
-.54*
-.49*
-.52*
SIP PD
SIP BMC
-.63*
-.55*
-.59*
-.66*
-.61*
-.64”
-.54*
-.47*
-.50*
p.58”
-.54*
-.54*
SIP REC
-.51*
-.43*
-.48*
-.50*
-.49*
-52”
SIP MOOD
-.I5
-.I1
-.06
-.I9
-.08
-.19*
On the CS-PFP a higher score represents
higher function.
On the SIP a lower score represents
better perceived
health.
Abbreviations:
CS-PFP-TOT,
CS-PFP total score; CS-PFP-UBS,
CS-PFP upper body strength
score; CS-PFP-LBS,
CS-PFP lower body strength
score; CSPFP-UBF, CS-PFP upper body flexibility
score; CS-PFP-B&C,
CS-PFP balance and coordination
score; CS-PFP-END,
CS-PFP endurance
score; SF36, Short
Form 36 Health Survey:
TOT, total; GH, general health; MH, mental health; PF, physical
function;
RP, role physical;
VIT, vitality;
SIP, Sickness
Impact
Profile Health Status: AM, ambulation;
MOB, mobility;
PD, physical
dimension;
BMC, body care and movement;
REC, recreation;
MOOD, mood.
* Correlations
significant
p < .Ol.
several physical domains that include upper and lower body
strength, endurance, balance, and flexibility.
Levels of Function
The CS-PFP fills the need for measurement of physical function in people living independently. Although the evaluation is
applicable to adults with a broad range of functional levels, it
is not intended for people who require assistance with ADL
tasks or for those with cognitive impairments. Assessment tools
(eg, Functional Independence Measure [FIM]) that quantify the
level of assistancea person requires provide crucial information
for discharge planning or for assessingprogress of inpatients.
Measures of physical function that target ADL limitations requiring assistancedo not lend themselves to timing-based evaluation. For example, if a person requires some assistancedressing, such as getting the arm into the sleeve, the time to complete
the task may be more dependent on timing of the assistance
given or on cueing than on physical function. For the same
reason, the CS-PFP is not intended to measure function in individuals with cognitive impairments or who may require multiple
cues to complete a task. Although the CS-PFP is intended for
measurement of higher levels of function, the scaling is designed to accommodate people who cannot perform an individual task, minimizing a measurement floor effect. The minimum
CS-PFP-total score was 1.3 out of 12, and no one received a
score of 0 on any of the domains.
Several aspects of the testing process contribute to minimizing a ceiling effect: instruction to work at maximal effort, performance of several tasks serially, evaluation of several physical
domains, and continuous scaling. People are asked to work at
their functional capacity as quickly as they can or carrying the
maximum amount of weight within the limits of comfort and
safety. They are required to judge their ability and rest if they
need to in order to complete all tasks. People who are stronger
can carry more weight, work faster, and cover more distance.
Using continuous scales of time, weight, and distance, as well
as providing additional weight for carrying tasks, challenges
stronger participants, reducing the possibility of reaching a cap
on the highest score attained. Of the possible total scale of 12,
the maximum score achieved was 10.6, and no one scored 12
on any domain. Assessing total body physical functional performance may also help to minimize the ceiling effect. By taking
Table
4: Reliability
Physical
Upper body
Upper body
Lower body
Balance and
Endurance
CS-PFP total
and Internal
Domain
strength
flexibility
strength
coordination
*All
correlations
Arch
Phys Med
Correlation
of the CS-PFP
Test-Retest*
Cronbach-a*
.92
.97
.98
.99
.95
.98
significant
Rehabil
Consistency
Inter-rater*
.95
.85
.94
.96
.93
.97
p < .Ol.
Vol77,
December
1996
.87
.74
.83
.91
.86
.97
several physical systems (cardiorespiratory, neuromuscular)
into account, the test assessesthe integration of total body physical functional performance, rather than relying on only one
or two nerformance scores (eg.
~ -. tandem walk, sit-to-stand) to
represent overall physical function.
A
LTC/D
N=39
upper
I3
bodv
stre&th
LTC/I
N=31
upper
body
flexibility
CD
N=78
balance endurance
lower
body
&
strength coordination
Fig 4. (A) Mean CS-PFP total scores for community
dwellers
(CD); residents of congregate
care facilities,
dependent
(LTC/D); and residents
of
congregate
care facilities,
independent
(LTC/I).
Significant
differences
were found between
groups within each domain (F = 24.09). (B) Mean
CS-PFP domain scores for community
dwellers
(CD, N = 78 101); residents of congregate
care facilities,
dependent
(LTC/D, N = 39 [WI; and
residents
of congregate
care facilities,
independent
fLTC/I, N = 31 [@I.
Significant
differences
were found between
groups within each domain
(F = 73 to 119).
CONTINUOUS-SCALE
PHYSICAL
The ideal subject sample for testing this instrument would
include some people with high muscular strength and low cardiovascular endurance, and visa versa; however, in untrained
people, physical characteristics generally decline in concert with
age. We are currently testing the training response of the individual domains to different physical interventions.
Continuous Scaling
By using a continuous scale for the CS-PFP we can examine
relationships between CS-PFP scores and measures of physical
performance capacity. Our data show a high degree of correlation between CS-PFP physical domain scores and related physical performance capacity measures (table 2). Each task was
simplified to reduce the influence of more than one domain.
For instance, when putting on a jacket the subject is asked to pull
it together but not zip it up, in order to minimize interference
of sight, dexterity, and abdominal girth. Selecting tasks and
administering
them to reflect the dominant physical trait involved in performance contributes to the significant correlation
between the physical performance and physical functional performance measures (table 2) and the high degree of internal
consistency within the domains (table 4).
FUNCTION
PERFORMANCE,
1249
Cress
domain contributes to an individuals
CS-PFP total score can
provide insight into intervention strategies.
Although we hypothesized a physical domain for lower body
flexibility, our final set of tasks did not include any tasks for
which hip flexibility
was the primary physical characteristic
required for performance. We initially expected that getting in
and out of a bathtub would be dependent primarily on lower
body flexibility. However, this task is primarily a reflection of
the balance between leg strength and hip flexibility, and therefore it did not correlate primarily with degrees of hip flexion.
This was the only task not performed by all of the participants.
Those participants who could not perform it (n = 12; 9%) had
significantly less hip flexion and knee extension strength than
the other participants. Ten (83%) of the 12 participants who
could not perform the bath tub task had musculoskeletal
limitations (arthritis, low back pain, or a pulled muscle). Only one
stated that fear of falling was a consideration for not performing
the task. All other tasks were completed by all participants.
Other tasks requiring hip flexibility and less reliant on strength,
such as picking up scarves or closing a Velcro strap around a
shoe being worn by the subject, might have provided more
insight into lower body flexibility as a physical domain of function.
Standard Conditions
It is recognized in the laboratory sciences that testing under
standard conditions minimizes variance and enhances the ability
to detect significant differences. However, many functional assessment tools lack adequate sensitivity to detect differences
that may in part be due to ordinal rather than interval scaling
but may also result from the variable conditions under which
tests are administered.
Physical Domains
The development of tests to assess function (eg, IADL, ADL)
has emphasized quick administration
(< 10min) in a physician’s
office (nonstandard conditions) using a test that does not require
specific training to administer.23 Yet a need for more accurate
and comprehensive tests has grown with the increased scope of
disability and number of patients with disabilities. Many measures of function include domains other than the physical, eg,
social, cognitive, and communicative
domains (SF36, FIM),
which are important aspects of overall function. However, we
suggest that upper and lower body physical function and all
other physical domains cannot be adequately assessed in 10min.
They demand an in-depth assessment that carefully segregates
the various domains of physical function. The need for a physiological approach to functional tests is eloquently argued by
Fried et al.’ Serial presentation of the tasks provides greater
insight into physical function than do short tests because it
simulates normal conditions. To function comfortably
in the
continuum of life, a person must be able to complete many
tasks, such as personal care, shopping, cooking, and cleaning,
with energy and time remaining for recreation.
The data yielded by a comprehensive physical function test
have critical and wide-ranging
implications
for the care of the
patient. Such data are needed to determine home care or chore
worker needs, types of physical intervention, eligibility
for financial assistance, and the safety of home placement. Maximal
physical
performance
(strength,
Vo,max,
etc) contribute
uniquely to physical domains. Isometric arm strength explains
40% (Y = .63) of the CS-PFP-upper
body strength domain,
whereas it explains 30% (Y = 55) of overall physical functional
performance (table 2). Maximal leg strength and Vo2max, on
the other hand, both explained similar amounts of the variance
(42% and 46%, respectively) for the CS-PFP-total. How each
Living Status
We have established that the CS-PFP has the precision to
detect differences in physical function among three groups of
participants, demonstrating the instrument’s construct validity.
The maximum IADL score of 24 was attained by all CD and
LTC/I residents, and those participants who were residents of
a congregate care facility and dependent (LTC/D) indicated
some IADL functional deficits (mean score 22.5) but there
were no significant differences among the groups. Direct observation of physical functional performance using the CS-PFP
total score indicates that our participants represent three distinct
groups physically: community dwellers (CD) have the highest
functional level, LTC/I residents retain 80% of the function of
the CD, and LTC/D residents have 45% of the function of the
CD (fig 4A). Participants’ ages ranged from the youngest in the
CD group to the oldest in the LTC/D group (table 1). Age is
associated with many aspects of health that may also affect
function, eg, multiple illnesses, loss of lean muscle mass, loss
of strength, depression. Significant differences remain among
the three groups, on both CS-PFP total scores (fig 4A) and
scores within the physical domains (fig 4B) after correcting for
age. This is strong evidence that physical function is a more
important determinant of living status than age. In other words,
just because a person is older does not mean that he or she will
be physically dependent, but rather that strength, endurance,
balance and coordination,
and flexibility
are better predictors
of living status than age. In addition, the community dwellers
worked at a significantly
higher level of physical functional
performance with significantly
less effort (RPE = 10.8), between very light and fairly light. As all of the participants functioned within their prescribed social roles, they were nondisabled according to the Nagi model of disability.”
For diagnostic
and intervention purposes, however, physical changes need to
be recognized at the impairment level before they begin to affect
social roles, ie, become disabilities. The CS-PFP may be useful
for the individual who is completing an inpatient rehabilitation
program and is soon to be discharged to home. In such a case,
the CS-PFP may be able to predict success in the home environment and indicate areas where assistance or home modification
may be required.
Arch
Phys Med
Rehabil
Vol77,
December
1996
1250
CONTINUOUS-SCALE
Self-Perceived
PHYSICAL
Function
CS-PFP total scores correlated significantly with scales of
self-defined health status, the SIP and self-perceived physical
function, the SF36 (table 3). This indicates that the CS-PFP
is tapping some of the same characteristics as the other two
assessments.Equally important is the evidence that the CS-PFP
discriminates the physical aspects of function from other aspects
such as emotion or mental health (SIP mood and SF36 mental
health Y = -.15; p = 0.1). These findings support other work
that has found that physical disability does not necessarily relate
to social disability.25
CONCLUSION
The CS-PFF is a unique, valid, and reliable test of physical
functional performance. For persons without cognitive impairment the CS-PFP offers a continuously
scaled instrument that
measures whole-body
physical functional performance, comprising 5 physical domains that reflect upper and lower body
strength, upper body flexibility, balance and coordination,
and
endurance. Three groups of seniors were not significantly different in dependence on the IADL scale; however, they did differ
significantly
in CS-PFP total scores, CS-PFP domain scores,
maximal physical performance, and health status scores, indicating construct validity. Each physical domain of the CS-PFP was
significantly correlated with the physical performance measure
it reflects, further demonstrating
construct validity. Measures
of self-perceived physical function were significantly correlated
with CS-PFP scores, and measures of nonphysical domains were
not. The CS-PFP does not show a floor effect for older adults
without ADL deficiencies or a ceiling effect in highly active
community dwellers. Possible applications include research into
physical functional performance,
intervention
strategies, and
program outcomes, as well as use in occupational and physical
therapy evaluations.
Acknowledgment:
The authors express appreciation to Roberta
Wilkes for her editorial assistance in preparation of this manuscript,
Barbara Inglin and Chris Mogadam for collection of the data, Dr. Robert
Schoene for the use of the Pulmonary Exercise Laboratory at Harborview Medical Center, and Northwest Hospital for the use of its Easy
Street Environments@, a rehabilitation facility designed and built by
Guynes Design Inc., Phoenix, AZ, for testing.
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Suppliers
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