Sit-to-Stand Movement Pattern A Kinematic Study - Physical Therapy

Sit-to-Stand Movement Pattern : A Kinematic Study
Sharon Nuzik, Robert Lamb, Ann VanSant and Susanne
Hirt
PHYS THER. 1986; 66:1708-1713.
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Sit-to-Stand Movement Pattern
A Kinematic Study
SHARON NUZIK,
ROBERT LAMB,
ANN VANSANT,
and SUSANNE HIRT
A visual model of the sit-to-stand movement pattern was developed from the film
data of 38 women and 17 men as they assumed standing from a seated position.
We used the data from these film records to identify a representative initial
starting position and displacements of body segments for each of 20 equal
intervals throughout the movement cycle. Trajectories of data points on the head,
acromion, midiliac crest, hip, and knee also were plotted. These diagrams
demonstrate the time-space relationships of various body parts during the task.
This normalized model may be used by physical therapists as a standard to
which they can compare the movement pattern of a patient.
Key Words: Biomechanics, Movement, Physical therapy.
Standing from a seated position is an activity most people
perform many times daily. Despite its frequency of occurrence
and importance to functional activities, reports in the literature
are few and do not permit clinicians to generalize their
findings easily to the observed movement characteristics of a
patient. Based on observation and clinical experience, the
physical therapist develops a concept of a normal movement
pattern, assesses the quality of the patient's movement, and
trains the patient according to the idealized model. Although
such conceptualized models approach reality, therapists disagree
about their various components (eg, initial position or
postural set, maximal joint excursion, and most efficient
pattern of movement). Quantitative data derived from a large
sample may provide a realistic model of the movement pattern,
a baseline from which further comparisons may be made.
The physical therapist then might be more certain about the
excursion of each joint, the sequence of action, and the
components of movement. A patient's movement pattern,
thus, may be compared to this norm, and treatment may be
aimed at normalizing movement with respect to this model.
Jones and associates 1-4 and Kelley et al 5 have studied selected
aspects of the sit-to-stand movement pattern in healthy
adults. Jones and associates described the trajectory of the
head in space and the effects of various postural sets on this
trajectory. Kelley et al described the kinetic characteristics of
the lower extremities of six subjects under a controlled speed
Ms. Nuzik is Supervisor, Neuroscience-Pediatrics Team, Physical Therapy
Department, Medical College of Virginia Hospitals, Virginia Commonwealth
University, Richmond, VA 23298 (USA). She was a graduate student at the
Medical College of Virginia, Virginia Commonwealth University, when this
project was undertaken.
Dr. Lamb is Associate Professor and Director of Graduate Studies, Department
of Physical Therapy, School of Allied Health Professions, Medical College
of Virginia, Virginia Commonwealth University.
Dr. VanSant is Associate Professor, Department of Physical Therapy, School
of Allied Health Professions, Medical College of Virginia, Virginia Commonwealth
University.
Ms. Hirt is Professor Emeritus, Department of Physical Therapy, School of
Allied Health Professions, Medical College of Virginia, Virginia Commonwealth
University.
This study was completed in partial fulfillment of Ms. Nuzik's master's
degree, Medical College of Virginia, Virginia Commonwealth University.
This article was submitted March 7, 1985; was with the authors for revision
30 weeks; and was accepted March 19, 1986. Potential Conflict of Interest: 4.
1708
condition. In a recent study, Wheeler et al used two groups
of female subjects to study the influences of age and chair
design in rising from a chair. 6 Electromyographic activity of
the vastus lateralis muscle and medial head of the triceps
surae muscle was recorded, as were goniometric measurements
of elbow and knee flexion and forward angle of inclination
of the trunk. In another recent report, Burdett et al
compared joint moments and range of motion of the hip,
knee, and ankle in 10 healthy male subjects and in 4 patients
with various diagnoses as they stood from two types of chairs. 7
Because information from these reports was inadequate to
develop a clinically relevant visual model of the body rising
from a seated position, we undertook a descriptive study of
this movement pattern. The model generated from this study
provides a foundation for the evaluation of patients performing
this task, determination of treatment effectiveness, and
implications for further research.
METHOD
Subjects
The protocol for this study was approved by the Committee
on Human Research, and informed consent was obtained
from the 55 healthy adults (38 women and 17 men) who
participated in the study. This group, representing a sample
of convenience, was composed of graduate and undergraduate
physical therapy students, faculty members, and clinicians at
the Medical College of Virginia, Virginia Commonwealth
University. The ages of the subjects ranged from 20 to 48
years ( = 26.4 ± 5.1 yr). We filmed these subjects in the
sagittal plane as they stood from an armless wooden chair
with a seat height of 46 cm (18.1 in).
Instrumentation
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A spring-wound 16-mm Bolex* camera equipped with a 26mm
Macro-Switar † lens was positioned 7.32 m (24.01 ft) from
* Model H-16, Rex 5, Bolex International SA, Sante-Croix, Switzerland.
† Kern and Co, Ltd, Aarau, Switzerland.
PHYSICAL THERAPY

TABLE
Mean Angular Positions Computed at Five-Percent Intervals of the Sit-to-Stand Movement Pattern (in Degrees)
Pelvis b Trunk b Neck b Frankfort b
Plane
ie
s
s
s
s
Hip a
Knee a
Ankle a
Interval
s
s
s
Movement
Pattern
(%)
11.94
-2.10
7.94
62.63
6.46
79.78
10.51
116.25
11.55
135.25
5.83
94.61
6.59
105.75
0
Start
11.78
-2.61
7.94
61.93
6.52
79.15
10.56
115.62
11.65
134.57
5.79
94.53
6.72
105.56
5
1
11.81
-3.25
8.06
60.81
6.55
77.66
10.48
114.28
11.62
133.24
5.81
94.56
6.79
105.23
10
2
11.95
-4.03
8.28
59.14
6.62
74.83
10.31
111.79
11.53
130.87
5.84
94.57
6.75
104.75
15
3
12.30
-4.80
8.65
57.09
6.80
70.39
10.14
107.53
11.40
126.94
5.89
94.68
6.63
104.10
20
4
12.82
-5.51
9.33
55.19
7.21
64.77
9.92
101.33
11.18
121.54
5.94
95.06
6.51
103.26
25
5
13.59
-5.84
10.37
53.93
7.82
58.62
9.46
93.80
10.80
115.70
5.96
96.02
6.42
102.21
30
6
14.36
-5.71
11.54
53.40
8.77
53.20
8.59
86.75
10.28
111.60
5.99
97.89
6.35
101.03
35
7
14.95
-5.27
12.47
53.47
9.90
49.52
7.95
81.65
10.28
110.88
6.20
101.08
6.26
99.93
40
8
15.09
-4.52
12.88
54.18
11.00
48.22
7.52
78.88
10.64
113.73
6.61
105.90
6.13
99.31
45
9
14.74
-3.38
12.68
55.64
11.75
49.40
7.33
77.89
11.21
119.39
7.26
112.47
5.98
99.44
50
10
13.92
-1.87
11.98
57.76
11.90
52.66
7.16
78.11
11.46
126.81
7.75
120.32
5.83
100.28
55
11
12.87
-0.13
10.99
60.36
11.53
57.55
6.90
79.13
11.41
135.35
8.35
129.07
5.79
101.68
60
12
11.79
1.49
9.86
62.98
10.60
63.44
6.53
80.62
10.97
144.33
8.94
138.21
5.78
103.44
65
13
10.95
2.73
8.91
65.27
9.22
69.72
6.12
82.30
10.04
153.19
9.15
147.20
5.79
105.30
70
14
10.39
3.36
8.28
66.94
7.61
75.90
5.84
83.95
9.25
161.49
9.01
155.75
5.63
107.19
75
15
9.91
3.55
7.79
68.08
6.06
81.33
5.61
85.41
8.24
168.60
8.08
163.11
5.31
108.87
80
16
9.56
3.59
7.45
68.88
4.95
85.65
5.45
86.59
7.54
174.32
6.86
169.06
4.94
110.21
85
17
9.43
3.71
7.22
69.54
4.25
88.86
5.30
87.53
7.01
178.68
5.78
173.46
4.67
111.12
90
18
9.31
3.78
7.15
70.09
3.88
91.00
5.18
88.17
6.77
181.56
5.17
176.22
4.51
111.59
95
19
9.28
3.67
7.21
70.06
3.65
92.49
5.13
88.58
6.74
183.40
4.98
177.86
4.45
111.74
100
20
RESEARCH
Volume 66 / Number 11, November 1986 1709
a
Values define the angular measurements between body segments as delineated by data points.
b
Angular measurements reflect the relationship of the body segment to the positive x axis.
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Fig. 1. Angles between body segments: the ankle (Angle 1), the
knee (Angle 2), and the hip (Angle 3).
the subject. An electronic digital timer visible in the photographic
field provided accurate time measurement. The camera
was operated at a film speed of 32 Frames per second.
Additional details of the filming method are described in a
previous report. 8
Procedure
Data points were established over the following body landmarks:
the fifth metatarsal head, lateral malleolus, lateral
femoral epicondyle, greater trochanter, midiliac crest, acromion
process, tragus, and the mid-Frankfort plane. (The
Frankfort plane, the center of which approximates the head's
center of gravity, is located between the tragus and the lowest
point of the orbit.) These data points defined the angles of
interest of our study (Figs. 1,2).
The data points on the fifth metatarsal head, the lateral
malleolus, and the lateral femoral epicondyle were used to
measure the angle of the ankle joint (Angle 1). The lateral
malleolus was located at the vertex of this angle. The lateral
malleolus, the lateral femoral epicondyle, and the greater
trochanter defined the knee angle (Angle 2), with the lateral
femoral epicondyle at the vertex. The hip angle (Angle 3) was
Fig. 2. Angles of inclination: the pelvis (Angle 4), the trunk (Angle
5), the neck (Angle 6), and the Frankfort plane (Angle 7).
defined by the lateral femoral epicondyle, the greater trochanter,
and the midiliac crest. The greater trochanter was the
vertex of this angle. Figure 1 identifies these angles.
The angular values we recorded reflect the relationships
among the body landmarks identified by the data points
(Table). These landmarks, however, are not always analogous
to the clinical measurements. For example, because of the
increased objectivity permitted by photographic measurement
and data reduction, the data points of the ankle angle were
not analogous to the bony landmarks used by the clinician to
obtain goniometric measurements. Our ankle values, therefore,
reflect a greater degree of plantar flexion than would be
recorded by clinical measurement.
In addition to these three lower extremity angles, we also
were interested in the movements of other body segments.
These body segments, defined by a line connecting two data
points, were 1) the pelvis, between the greater trochanter and
the midiliac crest; 2) the trunk, between the midiliac crest and
the acromion; 3) the neck, between the acromion and the
mid-Frankfort plane; and 4) the Frankfort plane, between the
mid-Frankfort plane and the tragus. The relationship of each
body segment to the horizontal plane was computed, and
1710 PHYSICAL THERAPY
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these angles are referred to in this article as the angles of
inclination (Fig. 2).
The trunk and neck angles of inclination also are relative
and should not be construed as the true reflection of trunk or
neck movement. First, the data point on the acromion is on
the appendicular skeleton. Second, no attempt was made to
assess specific spinal mobility.
The subjects were asked to assume a seated position of
readiness. Verbal commands were standardized: "I want you
to get ready to stand up. Scoot as far forward in the chair and
bring your feet as far back as you need to stand up comfortably.
Rest your hands lightly on your thighs but do not push
with them when you stand up. Do not stand up until you
hear me say, 'Stand.'" No further attempts were made to
control the subjects' postural set. After three to five trial
movements, we filmed the subjects as they stood up from a
sitting position in their usual manner and at their usual speed.
Three consecutive trials for each subject were recorded on
film.
One trial from each subject was selected for analysis. The
criteria for trial selection, in order of their importance, were
1) ability to view all data points on each frame, 2) subjective
appearance of the movement as smooth and natural, 3) feet
flat at the beginning of the movement, 4) feet symmetrical at
the beginning of the movement, and 5) a clearly defined
completion of motion. The frame preceding the first discernible
body movement was the first to be reduced. If the subject
exhibited postural sway, the end of motion was represented
by that frame in which no further forward displacement of
the pelvis occurred. Data were reduced from each frame up
to, and including, this last frame.
Data Reduction
An electronic graphics calculator ‡ was used to place the
projected film image in a two-dimensional, Cartesian-coordinate
system and to assign each data point x and y spatial
coordinates. The calculator was interfaced with a Texas Instruments
Silent 700 ASR § electronic data terminal, which
recorded x and y coordinates on digital magnetic tape cassettes.
Data from these tapes were transferred later to magnetic
disks and made accessible to a Xerox Sigma 6" computer.
A FORTRAN IV computer program was written to reduce
the data and allow for additional analyses. Computations
were made to correct for equipment error and to compensate
for the distortion inherent in the data. Angles between body
segments (Fig. 1) were calculated using the dot product
method. 9 As noted earlier, because these values reflect the
relationships among body segments, they are not always analogous
to clinical measurements. For example, in this study,
both knee and hip extension approached 180 degrees, not 0
degrees.
Numerical values for angles of inclination of the pelvis,
trunk, neck, and Frankfort plane (Fig. 2) were computed with
respect to the horizontal x axis. The positive x axis, the
reference line, was 0 degrees; the positive y axis was 90 degrees
with respect to the horizontal axis. Positive angular values
reflected angular deviations occurring in a counterclockwise
direction from the positive x axis. Negative angular values
‡ Numonics Corp, 418 Pierce St, Lansdale, PA 19446.
§ Texas Instruments, Inc, Houston, TX 77011.
1 Xerox Corp, El Segundo, CA 90265.
RESEARCH
Fig. 3. Left diagram depicts a representative movement pattern.
Data points are joined by lines to form 21 stick figures (sampling
rate), Enhanced line on the left indicates the initial position; the
enhanced line on the right indicates the final position. Right diagram
depicts trajectories of data points at the tragus, acromion, midiliac
crest, hip, and knee.
reflected angular deviations occurring in a clockwise direction
from the positive x axis (ie, below the horizontal axis).
Data Analysis
For intersubject comparison, the movement time of each
subject was divided into 5% increments. This division, which
included the initial starting position, provided for 21 points
of comparison within the movement. For each 5% interval,
the mean and standard deviation of each angle were calculated
across all subjects. The mean horizontal and vertical coordinates
of each data point were used to construct a model of
the starting position and a schematic diagram of the entire
movement cycle (Fig. 3, left diagram). Average x and y
coordinate values also were used to graph trajectories of body
landmarks during the movement cycle (Fig. 3, right diagram).
RESULTS
Movement time ranged from 1.3 to 2.5 seconds. The average
movement time was 1.8 ± 0.3 seconds.
Pattern of Movement
Figure 3 (left diagram) illustrates the data from the Table
in graphic form. The initial position of the representative
movement pattern is indicated by the enhanced line on the
left; the final position is indicated by the enhanced line on
the right. When the model stick figure leaned forward, the
trunk inclined to an angle of 80 degrees counterclockwise
Volume 66 / Number 11, November 1986 1711
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from the horizontal axis or 10 degrees to the right of the
vertical axis. The neck segment was 63 degrees from the
horizontal axis or inclined forward 27 degrees from the vertical
axis. The angle of the Frankfort plane from the horizontal
axis was negative, with the head tipped down 2 degrees. The
pelvic segment was 116 degrees from the horizontal axis or
rotated 26 degrees to the left of the vertical axis. The hip was
flexed to 135 degrees and the knee to 95 degrees. The relative
ankle measurement was 106 degrees (Table).
During the first 35% of the movement cycle, the angle of
the Frankfort plane from the horizontal axis indicated the
head was tipping downward. The angle of inclination changed
from an initial —2 degrees to a minimum of —6 degrees, at
which time 30% of the movement cycle had been completed.
Throughout the remainder of the movement cycle, the head
rotated upward from -6 to +4 degrees.
The neck, trunk, and pelvis followed similar patterns, moving
first into flexion and then into extension as the movement
cycle progressed. The neck angle inclined downward for the
first 35% of the movement cycle and then moved back toward
the vertical axis. The trunk began to move toward the vertical
axis after 45% of the movement cycle was completed. The
pelvis, initially in a position of posterior tilt with respect to
the vertical axis, rotated anteriorly from this position throughout
the first half of the movement cycle. This movement
reflected a change from 26 degrees behind the vertical axis to
12 degrees forward of the vertical axis. During the latter half
of the movement cycle, the pelvis reversed its direction,
ending in an upright position.
The hip flexed during the first 40% of the sit-to-stand
movement cycle and extended during the last 60% of the
cycle. The knee extended throughout the pattern of motion.
The ankle moved toward dorsiflexion in the first 45% of the
movement cycle. The remainder of the motion was characterized
by movement toward plantar flexion. Across all angles,
variability increased from distal to proximal and from caudal
to cephalic. The variability was smallest for each angle at the
termination of the movement cycle.
Movement Trajectories
Trajectories of various anatomical landmarks were constructed
to demonstrate the movement of these body parts in
space during the sit-to-stand task. Figure 3 (right diagram)
plots the movements of the data points on the mid-Frankfort
plane, acromion, midiliac crest, greater trochanter, and lateral
femoral epicondyle. The trajectories of the data points on the
mid-Frankfort plane and the acromion were similar, but the
excursion of the data point on the head was greater than that
of the acromion. The shapes of the trajectories of the midiliac
crest and greater trochanter also were similar. Their ascents
were more direct than those of the head or acromion, but still
curvilinear. The dip at the end of the movement of the
midiliac crest occurred as the pelvis moved from a posterior
position to an anterior position with respect to the vertical
axis. During this same time period, the greater trochanter
moved forward rather than downward.
Horizontal displacement at the knee was much greater than
vertical displacement. The knee trajectory demonstrated forward
and slightly downward displacement during earlier portions
of the movement pattern. This movement was followed
by backward and minimal upward movement as the knee
extended.
DISCUSSION
The sit-to-stand movement pattern can be divided into two
phases. The first phase, the flexion phase, occurred during the
first 35% of the movement cycle. The second phase, the
extension phase, then began at the head and knee. This change
was evidenced by a reversal of head movement and a rapid
increase in knee extension. The reversal of movement spread
from the head down the trunk to the pelvis. The reversal from
flexion to extension appeared to correspond to the lifting of
the buttocks from the chair. Because the chair was not
equipped with either a force transducer or a contact switch,
however, we were unable to document this relationship.
The body segment initiating the sit-to-stand movement
could not be identified in this study because of the distortion
inherent in the kinematic data. This problem, however,
prompted our analysis of the initial 20% of the movement
cycle to determine those angles demonstrating the greatest
displacement during that part of the cycle. The angle of the
Frankfort plane with respect to the horizontal axis (Angle 7)
demonstrated the highest frequency of maximal displacement
for 23 of the 55 subjects. When considering the hip and trunk
movements together, however, we noted that 25 subjects
exhibited maximal displacement at those angles (Angles 3
and 5) during the first 20% of the movement cycle. These
data suggest that substantial individual differences exist during
the initial phase of the movement cycle. For those individuals
who demonstrate the greatest angular displacement at the
Frankfort plane, this displacement may occur because the
head is leading the movement. Another possible explanation
is that the head displacement may be the result of movement
caudally to the head (ie, hip or trunk movement effecting
displacement at the head).
When group data are used to describe and to develop a
model of the sit-to-stand movement pattern, individual differences
are obscured. Our model, therefore, should not be
construed as directly applicable to all persons. Examination
of individual trajectories, nevertheless, allowed the grouping
of certain body parts. Although we did not analyze these
groupings further in this study, they suggest not only individual
variation but also common characteristics among individuals.
Future studies, thus, should be directed toward clarifying
these similarities and differences by considering the effects of
sex, age, and anthropometric variables on movement among
various body segments and the trajectories of body parts in
space.
Comparing data acquired in this study to those of earlier
reports is limited primarily by differences in methodology.
This study solely considered kinematic variables or time-space
relationships. No attempt was made to study the forces involved
in the sit-to-stand movement, as did Kelley et al. 5
Jones and associates 1-4 also examined the time-space characteristics
of the sit-to-stand movement, but important differences
exist between our approaches, goals, and presentation
of data. Although Jones and associates considered various
experimental conditions, they focused their attention on head
and neck movements. They reported descriptive data of other
body parts but did not document their findings with quantitative
data. The groups of subjects they used generally were
small and exclusively male, and they usually were instructed
to perform the task as quickly as possible.
1712 PHYSICAL THERAPY
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In Burdett et al's comparison of rising from two types of
chairs, mean maximal flexion values at the hip, knee, and
ankle were reported. 7 Their data points were similar to those
used in our study. They reported the mean maximal hip
flexion angle to be 116.8 degrees when using a standard chair
and not pushing up with the arms. The knee flexion value
was 91.5 degrees. Those values in our study are 110.9 and
94.5 degrees, respectively. Because of differences between our
studies in data reduction, comparisons of ankle values are not
possible.
Wheeler et al studied 10 healthy young women and 10
healthy elderly women as they stood from two types of chairs. 6
Mean knee flexion when rising from a standard chair was
reported to be 75.5 degrees for the younger group. The data
points they used were similar to those used in our study and
in the Burdett et al study. The height of the chair used in
Wheeler et al's study was only 1 cm higher than that of the
chairs used by Burdett et al or us. Other differences among
these studies, therefore, probably account for the disparities
in knee flexion values.
Mean trunk forward lean was reported by Wheeler et al as
75 degrees and was defined by the data points over the
acromion, greater trochanter, and knee. 9 To determine forward
lean in our study, we used the trunk segment as defined
by the acromion and midiliac crest and computed this segment's
angle of inclination with respect to the horizontal axis
of the body; hence, these findings cannot be compared.
Although movement of the head was not studied, Kelley et
1. Jones FP, Gray FE, Hanson JA, et al: An experimental study of the effect
of head balance on patterns of posture and movement in man. J Psychol
47:247-258, 1959
2. Jones FP: The influence of postural set on pattern of movement in man.
Int J Neurol 4:60-71, 1963
3. Jones FP, Hanson JA: Postural set and overt movement: A force platform
analysis. Percept Mot Skills 30:699-702, 1970
4. Jones FP, Hanson JA, Miller JF, et al: Quantitative analysis of abnormal
movement: The sit-to-stand pattern. Am J Phys Med 42:208-218, 1963
5. Kelley DL, Dainis A, Wood GK: Mechanics and muscular dynamics of rising
from a seated position. In Komi PV (ed): Biomechanics V-B. Baltimore,
MD, University Park Press, 1976, pp 127-133
REFERENCES
RESEARCH
al found the hip angle to be the first to demonstrate displacement.
5 In our study, the hip angle demonstrated the greatest
angular displacement in the initial 20% of the movement
cycle for a total of 21 of the 55 subjects. In 23 subjects, the
angle of the Frankfort plane with respect to the horizontal
axis had the greatest initial displacement. As discussed previously,
whether this displacement is a reflection of hip movement
remains to be demonstrated.
SUMMARY
The sit-to-stand movement, similarly to gait, is a fundamental
movement pattern of concern to physical therapists.
This study represents an initial step toward defining this
movement pattern in healthy individuals. With further refinement
of this model, physical therapists may use such
normalized data to enhance their understanding of normal
and pathological movement patterns and to set treatment
goals. Either by observing or by filming the patient's movement,
the therapist then may compare the patient's movement
sequence, postural set, movement time, and joint and bodysegment
excursions with this model.
Acknowledgment. Grateful appreciation is expressed to Anil
Chatterji, Assistant Director, Academic Computing, East
Campus, Medical College of Virginia, Virginia Commonwealth
University, whose assistance in data reduction and
computer programming was invaluable.
6. Wheeler J, Woodward C, Ucovich RL, et al: Rising from a chair: Influence
of age and chair design. Phys Ther 65:22-66, 1985
7. Burdett RG, Habasevich R, Pisciotta J, et al: Biomechanical comparison
of rising from two types of chairs. Phys Ther 65:1177-1183, 1985
8. Lamb RL, Gross LD, Meydrech EF: Electrical and mechanical correlates
of motor skill development: Triceps and anconeus as antagonists. In:
Proceedings of the Seventh International Congress of the World Confederation
for Physical Therapy. Montreal, Quebec, Canada, June 1974, pp
124-131
9. Thomas GB Jr: Calculus and Analytic Geometry. Reading, MA, Addison-
Wesley Publishing Co Inc, 1968, p 395
Volume 66 / Number 11, November 1986 1713
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Cited by
Sit-to-Stand Movement Pattern : A Kinematic Study
Sharon Nuzik, Robert Lamb, Ann VanSant and Susanne
Hirt
PHYS THER. 1986; 66:1708-1713.
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