Early Intensive Postural and Movement Training
Advances Head Control in Very Young Infants
Hui-Min Lee and James Cole Galloway
PHYS THER. 2012; 92:935-947.
Originally published online March 30, 2012
doi: 10.2522/ptj.20110196
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Research Report
Early Intensive Postural and
Movement Training Advances Head
Control in Very Young Infants
Hui-Min Lee, James Cole Galloway
Background. Daily experiences are thought to play an important role in motor
development during infancy. There are limited studies on the effect of postural and
movement experiences on head control.
Objective. The purpose of this study was to quantify the effects of postural and
movement experiences on head control through a comprehensive set of measurements beginning when infants were 1 month old.
Design. This was a prospective, longitudinal, 2-cohort study.
Methods. Twenty-two full-term infants who were healthy were randomly
assigned to either a training group or a control group. Infants were observed every
other week from 1 to 4 months of age. Head control was assessed using a standardized developmental assessment tool, the Test of Infant Motor Performance (TIMP), as
well as behavioral coding and kinematics of infants’ head postures and movements in
a supported sitting position. Caregivers performed at least 20 minutes of daily
postural and movement activities (training group), or social interaction (control
group) for 4 weeks.
Results. The training group had higher TIMP scores on head control–related items
during the training period and after training stopped compared with the control
group. Starting from the during training phase, the training group infants had their
heads in a vertical and midline position longer compared with the control group
infants. After training stopped, the training group infants actively moved their heads
forward more often and for larger distances.
H-M. Lee, PT, PhD, was a graduate
student in the Department of
Physical Therapy, University of
Delaware, Newark, Delaware, at
the time this study was conducted. Address all correspondence to Dr Lee at: noralee0724@
yahoo.com.
J.C. Galloway, PT, PhD, Infant
Motor Behavior Laboratory, and
Biomechanics and Movement Sciences Graduate Program, Departments of Physical Therapy and
Psychology, Center for Biomedical
Engineering Research, University
of Delaware.
[Lee H-M, Galloway JC. Early
intensive postural and movement
training advances head control in
very young infants. Phys Ther.
2012;92:935–947.]
© 2012 American Physical Therapy
Association
Published Ahead of Print:
March 30, 2012
Accepted: March 23, 2012
Submitted: June 13, 2011
Limitations. The experiences outside daily training were not monitored, and the
results may be specific to the experimental setup for infants with typical
development.
Conclusions. Young infants are able to take advantage of postural and movement
experiences to rapidly advance their head control as early as 4 to 6 weeks of postnatal
life. Infant positioning, caregiver handling, and caregiver-infant interactions were
likely contributing factors. This database of comprehensive measures may be useful
in future trials focused on head control in infants with special needs.
Post a Rapid Response to
this article at:
ptjournal.apta.org
July 2012
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Physical Therapy f
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Early Intensive Postural and Movement Training in Very Young Infants
T
he development of head control begins during the prenatal
period. Head movement is one
of the first fetal movements observed
as early as 7 to 8 weeks of postmenstrual age, with increasing movement varieties seen by the 11th
week.1 Infants display dramatic
changes in their head control during
the first months of their postnatal
life. Not surprisingly, head control is
critical for a range of early behaviors,
including those involving vision, oromotor skills, and the trunk and arms.
For example, a dynamically stable
head may provide less mechanical
perturbation to the trunk and arms
and may support the function of
vision.2 Less perturbation and
improved use of vision, in turn, may
allow for better body control, which,
in turn, assists infants in learning
more complex behaviors.
Conventional wisdom, based on
studies that typically involve infants
raised in Western cultures, holds that
a newborn’s neck muscles are rela-
tively weak and poorly controlled.
Thus, newborns often are provided
external support when they are held.
By 3 months old of age, infants typically maintain their heads in an
upright, midline position when held
upright. Clinically, this upright, midline position has been considered an
important basic level of head control,3,4 which continues to increase
throughout the first year and
beyond.5–9
The above description of the “natural” timing of the emergence of head
control should not be taken as universal and immutable. Cross-cultural
studies on the handling of young
infants by non-Western cultures suggest that the above descriptions
strongly reflect culture norms. One
implication of these studies is that
early head control is influenced by
the degree to which infants are provided with postural and movement
opportunities (reviewed in Adolph
et al10). As outlined below, systemic
investigations of the effect of early
The Bottom Line
What do we already know about this topic?
For infants with typical development, movement experiences play an
important role in motor development. For example, infants provided with
additional advanced postural or movement experiences reach earlier than
infants provided with additional social experiences.
experiences on head control, however, are rare. The general purpose
of the current study was to address
the need for a longitudinal investigation of the effect of postural and
movement experiences on head control during early infancy.
Head control is the first major motor
milestone on most assessments of
early skills.11–14 Head control impairments often are cited as an early risk
factor for future developmental
delays.15 For example, head control
on the Test of Infant Motor Performance (TIMP) in the first months of
life is a factor in predicting which
children will be diagnosed with
cerebral palsy by 2 years of age.16
In several studies, infants born prematurely or developing cerebral
palsy at a later age displayed poorer
head control compared with
infants with typical development.17–22 Delayed head control
greatly influences many aspects of
a child’s life.23–25
Despite the importance of head control in early intervention,4 comprehensive studies are limited and are
typically cross-sectional investigations of infants at term age.17–22,26
The assessment of head control usually was conducted as a part of
larger, more general neuromotor or
neurobehavioral evaluation.11,13,14
Therefore, results often were composed of general posture control or
What new information does this study offer?
This study provides the first longitudinal quantification of the effect of
postural and movement experiences on the development of head control.
Very young infants with typical development who were provided with
additional experiences rapidly displayed advanced head control.
If you’re a caregiver, what might these findings mean
for you?
The daily experiences that families provide to their infants during play or
therapy may influence the emergence of even the earliest skills such as
head control. Daily play involving a range of positions and movements
may influence the motor development of infants with special needs.
936
f
Physical Therapy
Available With
This Article at
ptjournal.apta.org
• eAppendix: Training Activities for
the Training Group (20 Minutes
Total per Day)
• eTable: Summary of the Effects
of Postural and Movement
Training on Head Control
• Demonstration Video of Infants
in the Control Group and the
Training Group During Chair Play
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Early Intensive Postural and Movement Training in Very Young Infants
posture response scores, with few
specifics on head control. Furthermore, results on specific head control impairments were not always
consistent, such as in the case of
impairments in pull-to-sit and sitting
tasks.17–22,26
The above review points out that
most studies on very young infants
determined the presence or absence
of milestones, which do not provide
information on the process by which
these infants develop impaired head
control or what factors lead to
impaired head control. Without a
detailed understanding of these factors, there is little evidence from
which to build early interventions.
This is the current situation with
respect to treating infants with head
control impairments. The current
study addressed the need for a more
comprehensive and longitudinal
investigation on the development of
head control from 1 to 4 months of
age with multilevel measures. As a
first step, this study focused on building a normative database using
infants with typical development.
If very young infants were receptive
to additional postural and movement
experiences, this receptiveness
would provide support for the study
of the effects of these experiences as
“training” for infants with poor head
control. In general, daily experience
is critical for the emergence of basic
motor skills in early childhood.7,27,28
Studies of infants who were developing typically have shown the effects
of postural and movement experiences on a range of behaviors,
including stepping, kicking, reaching, sitting, crawling, and postural
muscle responses.27,29 –37 These studies demonstrated positive effects of
training after as well as before a
behavior initially emerged.
Training after a behavior is displayed
can advance the quality of the practiced behavior.33,35,36 Although less
July 2012
studied, training before the onset of
a behavior can advance the emergence and the quality of the practiced behavior.27,31,32,37 For example,
infants had earlier onset of crawling
after receiving 3 weeks of training.31
Six-week-old infants who received 7
weeks of sitting training displayed
longer upright sitting duration immediately posttraining.37 We know of
no empirical investigation of the
training effects on head control in
typical development.
In pediatric intervention, postural
and movement training are generally
well-accepted strategies for promoting behaviors for young infants.38,39
Few studies, however, have focused
on the effect of specific training for
head control in young infants, and
none were comprehensive and longitudinal. As mentioned previously,
cross-culture research on motor
development supports the use of
physical activities and active handling as a potentially effective intervention for head control impairments.40 – 44 These studies suggest
that child-rearing practices through
daily formal training (eg, training to
sit or walk) or informal handling (eg,
how infants are carried) affect the
onset ages of many motor milestones, including the development
of head control. The specific purpose of the current study, therefore,
was to test the hypothesis that daily
postural and movement experiences
would significantly influence the
development of early head control.
Results from this study of infants
with typical development could be
useful for future intervention studies
of infants at risk for long-term impairments in head control.
Method
Participants
Twenty-four full-term infants with no
known sensory or motor impairments were recruited after their parents signed informed parental consent forms approved by the
University of Delaware Human Subjects Review Board. Due to scheduling conflicts, 2 infants did not continue the study. Twenty-two infants
were randomly assigned to either a
training group (n⫽11, 6 male and 5
female) or a control group (n⫽11, 8
male and 3 female). Two infants
were Asian, 2 were African American, and the remaining infants were
Caucasian.
Procedures
Infants were seen for testing every
other week for 3 months, from 1 to 4
months of age. There was no significant difference in averaged age at
each testing session between groups
(P⫽.67–.95). There were a total of 9
testing sessions, including 2 home
testing sessions and 7 laboratory testing sessions (see Table for the summary of procedures).
Home Testing Sessions
One experimenter visited infants at
their home when they were 1 and
1.5 months old. During the home
sessions, a standardized developmental test (ie, TIMP) was conducted. When infants were 2 to 4
months old, the TIMP was conducted in the laboratory (see “Laboratory Testing Sessions” section for
details), and there were no more
home testing sessions.
The TIMP is a sensitive, predictive,
and valid tool for detecting the
changes and differences in motor
performance in young infants.45,46 In
previous studies, the TIMP discriminated among infants with different
degrees of risk for poor motor
impairments at the time of initial
testing,46 – 48 as well as predicted
future motor impairments.16,49 –53
The TIMP scores also were sensitive
to detect changes in development in
infants with typical development
over a 2-week period.48 In our study,
we used specific TIMP items related
to head control to quantify the development of head control in full-term
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Early Intensive Postural and Movement Training in Very Young Infants
Table.
Summary of Study Proceduresa
Variable
Results
Age of infants (mo)
1
Average age in each group (wk)
Study week
2
CG: 4.57
TG: 4.48
1
1
CG: 8.78
TG: 8.69
3
3
5
2.5
...
CG: 10.71
TG: 10.70
7
4
CG: 16.73
TG: 16.69
...
13
Visit number
Home 1
Laboratory 1
Home 2
Laboratory 2
Laboratory 3
Laboratory 4
...
Laboratory 7
Location
Home
Laboratory
Home
Laboratory
Laboratory
Laboratory
...
Laboratory
Weeks of training
0 (pretraining)
0 (pretraining)
(training was
introduced right
after this visit)
2
2
4
Posttraining
K
B
K
B
K
B
...
K
B
TIMP
TIMP
...
TIMP
Measures
Chair play
Developmental test
a
1.5
CG: 4.47
TG: 4.46
K
B
TIMP
TIMP
Posttraining
CG⫽control group, TG⫽training group, K⫽kinematics, B⫽behavioral coding of head postures and movements, TIMP⫽Test of Infant Motor Performance.
infants who were healthy (see the
“Behavioral Coding” section for
details). Most of these items have
been shown to be key characteristics
for identifying differences between
children with and without cerebral
palsy.16
During the second home testing session, caregivers were asked to demonstrate training activities introduced at the end of the first
laboratory testing session. The
experimenter checked for proper
training and answered trainingrelated questions.
Laboratory Testing Sessions
Caregivers brought their infants to
the Infant Motor Behavior Laboratory, Department of Physical Therapy, University of Delaware, every 2
weeks while the infants were 1 to 4
months of age. There were 2 com-
ponents: chair play and the TIMP.
When infants were 1 and 1.5 months
old, only the chair play was performed in the laboratory. Starting
from the session at 2 months of age,
the TIMP was added to laboratory
procedures.
Chair play. Motion capture procedures (see “Kinematic Data Acquisition” section for details) were conducted during the chair play. Infants
were seated in a customized infant
chair reclined 30 degrees (Fig. 1)
with their trunk secured with a wide
cloth band. Two synchronized video
cameras recorded right front and
bird’s-eye views of the infants for
behavioral coding. Three experimental conditions were conducted:
no-toy arm-free (NTAF), no-toy armheld (NTAH), and toy (TOY). The
NTAF and TOY conditions were
used to test for differences in head
control with and without a midline
toy present. The NTAF and NTAH
conditions were used to test for differences in head control during free
and restricted arm movements.
Experimental conditions were randomly ordered across infants and
sessions.
Figure 1.
The setting of chair play. The picture shows the TOY condition.
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Early Intensive Postural and Movement Training in Very Young Infants
There were six 15-second trials for
each condition. For each trial, the
experimenter held the infant’s head
in a neutral (midline and upright)
position before the start of a trial and
then gently released the head right
after a trial start. The starting position of infants’ arms was not
restricted for the NTAF and TOY
conditions.
TIMP. The TIMP was conducted
and videotaped to quantify the general motor development with specific focus on the development of
head control.
Kinematic Data Acquisition
A 6-camera (120-Hz) Vicon motion
capture system (Pulnix TM6701-120
Progressive, Vicon Motion Systems
Inc, Los Angeles, California) was
used to obtain 3-dimensional (3D)
position-time data of the infants’
head movements. The cameras were
arranged in a circular fashion, with 2
cameras on each side and 2 in the
front and in the back of the infant.
Infants were seated within a calibrated volume of 160 cm ⫻ 160
cm ⫻ 200 cm. The average range of
calibration residuals was no larger
than 0.35 mm for the given calibrated volume. Arrays of three 8-mmdiameter, retroreflective, nonlinear
markers were placed on the center
of the forehead. Two single markers
were placed on the toy in line. The
array positions were kept the same
between a static trial that defined the
reference position of the arrays and
the movement trials. The static trial
data were collected with the head
and trunk maintained in a neutral
(upright and midline) position.
Training Group
Infants in the training group
received postural and movement
activities provided by their caregivers for 20 minutes daily for 4 weeks
starting when they were 1 month of
age. The specific training activities
were selected based on our previous
July 2012
studies27,32,54 using various types of
training for young infants, including
both postural training, requiring
increased use of neck, shoulder
girdle, and trunk muscles, and movement training, requiring increased
use of arm movements for reaching
(see eAppendix, available at
ptjournal.apta.org, for detailed information on training activities). In our
previous studies, infants received the
2 types of training separately, either
postural or movement training, and
began at an older age (8 weeks of age
or older). To provide infants with
additional upright experience, caregivers were instructed to carry their
infant for an additional 20 minutes
daily with a front carrier (BabyBjörn,
Bredaryd, Sweden) provided to families of the training group infants.
Control Group
To control for the increased social
interaction that infants in the training group experienced during training, infants in the control group
received structured, face-to-face
communication with their caregivers
for 20 minutes daily for 4 weeks.
Caregivers were asked to place their
infants in a supine position and interact with their infants visually and verbally without physically contacting
their infant or presenting toys.
Daily activity journals were provided
to caregivers in both groups to track
the amount of activities performed
each day. The percentage of training
completed for the daily 20-minute
activities was similar between
groups (training group: X⫽103.2 %,
SD⫽43.1%;
control
group:
X⫽102.1%, SD⫽10.3%; z⫽⫺0.413,
P⫽.68). On average, the use of the
front carrier was completed for more
than 85% of the required time in the
training group.
Data Analysis
Kinematics. Standard kinematic
analysis was conducted for head
movements during chair play. A stan-
dard low-pass, recursive filter (Butterworth filter) with a cutoff frequency of 4 Hz reduced highfrequency noise. The position of the
head in 3D space was computed by
the singular value decomposition
method.55 A loss of no more than 10
frames consecutively was interpolated using cubic spline interpolation. A customized MATLAB program (The Mathworks Inc, Natick,
Massachusetts) was used to calculate
the head kinematics. Variables of
head kinematics were analyzed
based on the data concatenated
across trials in each condition.
The kinematic dependent variables
were: (1) maximum lateral displacement (in millimeters), defined
as the maximum displacement from
the midline along the x axis; (2)
maximum anterior-posterior displacement (in millimeters), defined
as the maximum displacement along
the y axis; (3) speed of head movement (in millimeters per second),
defined as the average 3D speed of
head movement; and (4) variability
of head 3D speed, defined as the
coefficient of variation of head 3D
speed.
Behavioral coding. Videotapes
were coded for head postures and
movements during chair play and
the TIMP. The following behavioral
coding dependent variables for head
control behaviors were chosen
based on observations from a pilot
study showing that infants frequently display these behaviors
when seated in the infant chair: (1)
percentage of time in lean, defined
as amount of time infants laterally tilt
their heads from the midline more
than 15 degrees; (2) percentage of
time upright, defined as amount of
time infants keep their heads in an
upright, midline position and faced
forward; (3) percentage of time in
turn, defined as amount of time
infants turn their heads to the right
or left over 15 degrees from the mid-
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Early Intensive Postural and Movement Training in Very Young Infants
Total Scores of the TIMP
Group
CG
150
*
TG
*
*
125
Raw Score
line with their head in an upright,
midline position; (4) percentage of
time in pop-up, defined as amount of
time infants move their head forward
and away from the back of the infant
chair with their head in an upright,
midline position; and (5) percentage
of time with other postures and
movements, defined as amount of
time infants show head postures and
movements other than lean, upright,
turn, or pop-up. Each variable was
coded frame by frame (1 frame⫽1/
120 second) and normalized with
respect to time for group
comparisons.
100
75
50
The total score of the TIMP was the
summed score of all of the 42 items
of the TIMP. The summed score of
the head control–related items was
separated out from the total score to
quantify head control from 1 to 4
months of age. Selected head control
items reflected the infants’ ability to
hold their head in midline or an
upright position without additional
visual or auditory stimulation in different body orientations (ie, supine,
prone, and sitting). The following 10
items were selected: item 1 (head in
midline in supine); items 15, 16, 17,
and 18 (head control: supported sitting, posterior neck muscle, anterior
neck muscle, lower from sitting);
item 21 (head in midline without
visual simulation [supine]); item 32
(pull to sit); item 36 (head lift in
prone position); and items 41 and 42
(lateral head turning to the right and
left).
Reliability of behavioral coding.
The primary experimenter (H-M.L.)
was not blinded to group assignment. To promote coding score
reliability, 2 blinded coders were
first trained to code with interrater
reliability of greater than 90% for
variables measuring head postures
and movements using 2 randomly
selected infants in each group. Two
random sessions were selected for
testing the reliability of head pos940
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Physical Therapy
Baseline
After Training After Training
Phase 1
Phase 2
During
Training
Phase
Figure 2.
The box plots for the total scores of the Test of Infant Motor Performance (TIMP)
between the control group (CG) and the training group (TG) in each phase. The median
for each group is represented by the single line in the box. The boxes represent the
distribution of data from the 2 middle quartiles. The error bars represent the maximum
and minimum values and the top and bottom quartiles of data distribution. Asterisk
signifies a group difference (P⬍.05) based on the Mann-Whitney U test.
tures and movements coding. Following training, each coder was
assigned half of the infants to code
for head postures and movements.
The infants each coder received
were randomly selected from the 2
groups. Head control–related items
in the TIMP were scored by a third
coder for all infants. The interrater
reliability of TIMP items then was
tested with the scoring of 2 randomly selected infants coded by a
fourth
coder.
The
reliability
([amount of agreement/(amount of
agreement ⫹ amount of disagreement)] ⫻ 100) for the coding of head
postures and movements was
greater than 90%: upright (⬎90%),
lean (⬎91%), turn (⬎91%), and
pop-up (⬎95%). Interrater reliability,
calculated as intraclass correlation
coefficient between 2 coders for the
head control–related items in the
TIMP, was .943.
Statistical Analysis
The focus of the current study was to
determine the training effects on the
development of head control by testing for differences between infants
in the training and control groups.
Preliminary analysis did not show
consistent patterns of significant differences among the 3 experimental
conditions across the 7 experimental
sessions. That is, certain conditions
were significantly different for certain ages, but there was no clear pattern of results across conditions and
sessions. Thus, these 3 conditions
were combined for the final analysis.
The 7 experimental sessions were
combined into 3 phases for the final
analysis based on when sessions
occurred relative to the training period: the baseline phase (1-month-old
session), the during training phase
(1.5- and 2-month-old sessions when
the training was being performed),
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Early Intensive Postural and Movement Training in Very Young Infants
As the data did not follow a normal
distribution and the nonkinematic
data were rank orders or proportions, a nonparametric analysis
(Mann-Whitney U test) was used to
analyze all of the variables for group
differences in each phase. The MannWhitney U test was conducted using
SPSS software (SPSS Inc, Chicago,
Illinois) with Pⱕ.05. The effect size
(r) was calculated using the equation: Z/(N)1/2, in which Z is the z
score and N is the total number of
participants.56
Results
Total Scores of the TIMP
Results of total scores of the TIMP
showed that the training group had
higher scores in the during training
phase (z⫽⫺3.309, P⫽.001, r⫽⫺.71)
and the after training phases (phase
1: z⫽⫺3.514, P⫽.000, r⫽⫺.75;
phase 2: z⫽⫺1.977, P⫽.048,
r⫽⫺.42) compared with the control
group (Fig. 2).
TIMP Scores of Head Control–
Related Items
Results of the TIMP scores of head
control–related items showed that
the training group had higher scores
during the training period and after
training stopped compared with the
control group. Figure 3 shows that
training group infants had higher
scores on head control–related items
in the TIMP compared with control
July 2012
TIMP Scores of Head Control–Related Items
Group
50
CG
TG
*
*
40
Raw Score
and the after training phase. The
after training phase was split into 2
phases—after training phase 1 (2.5and 3-month-old sessions), and after
training phase 2 (3.5- and 4-monthold sessions)—to match the length
of the during training phase. We
combined data from 2 sessions into
phases to decrease the number of
comparisons and ease interpretation
in this initial study of head control.
Data from each of the 2 sessions per
phase were averaged. Future studies
may build on our results to use noncombined data.
*
30
20
10
Baseline
During
Training
After Training After Training
Phase 1
Phase 2
Phase
Figure 3.
The box plots for the summed scores of head control–related items in the Test of Infant
Motor Performance (TIMP) in each phase between the control group (CG) and the
training group (TG). Asterisk signifies a group difference (P⬍.05) based on the MannWhitney U test.
group infants in all phases (during
training phase: z⫽⫺3.715, P⫽.000,
r⫽⫺.79; after training phase 1:
z⫽⫺3.909, P⫽.000, r⫽⫺.83; after
training phase 2: z⫽⫺3.367,
P⫽.001, r⫽⫺.72), except for the
1-month-old baseline session.
In the during training phase (age
1.5–2 months), the training group
infants had significantly higher
scores on all 10 individual head
control–related items except item 1
(z⫽⫺3.447 to ⫺2.009, P⫽.001 to
.045, r⫽⫺.73 to ⫺.42) compared
with control group infants. In after
training phase 1 (age 2.5–3 months),
the training group had significantly
higher scores in 6 of the 10 items
(items 15–18, 32, and 42: z⫽⫺3.811
to ⫺2.591, P⫽.000 to .010, r⫽⫺0.81
to ⫺.55). In after training phase 2
(age 3.5– 4 months), the training
group had significantly higher scores
in 5 of the 10 items (items 15, 18, 32,
36, and 41: z⫽⫺3.330 to ⫺2.186,
P⫽.001 to .029, r⫽⫺.71 to ⫺.47).
Behavior Coding of Head
Postures and Movements
Results of behavior coding of head
postures and movements showed
that starting from the training phase,
training group infants had their
heads in a vertical and midline position longer compared with control
group infants. Training group infants
continued to display advanced head
control in the phases after training
stopped. The percentage of the
types of head postures and movements infants displayed when they
were seated in the infant chair is
shown in Figure 4A–D.
In the baseline phase (age 1 month,
Fig. 4A), 3 main behaviors characterized both training and control group
infants’ head postures and movements in our infant chair: lean,
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Early Intensive Postural and Movement Training in Very Young Infants
A Percentage of Types of Head Postures and Movements
B Percentage of Types of Head Postures and Movements
in the During Training Phase
100
100
90
90
80
80
70
70
Percentage
Percentage
in the Baseline Phase
60
50
40
30
50
30
20
10
Group
0
TG
C Percentage of Types of Head Postures and Movements
*
40
10
CG
CG
Group
TG
D Percentage of Types of Head Postures and Movements
After Training Phase 1
After Training Phase 2
100
100
*
90
90
80
80
70
70
Percentage
Percentage
Lean
Upright
Pop-up
Turn
Others
60
20
0
*
60
50
40
30
20
60
50
40
30
*
20
*
10
10
0
CG
Group
TG
0
*
CG
Group
TG
Figure 4.
The percentage of types of head postures and movements between the control group (CG) and the training group (TG) in the
baseline phase (A), the during training phase (B), and after training phases 1 (C) and 2 (D) when infants were seated in an infant
chair. Asterisk signifies a group difference (P⬍.05) based on the Mann-Whitney U test.
upright, and turn. Infants in both
groups spent most of the time
(approximately 50%) leaning their
head in various directions. The percentage of time infants kept their
heads in upright and turn was the
second and third highest, respectively. There was no significant
group difference in any of the coded
head postures and movements during the baseline phase.
In the during training phase (age
1.5–2 months, Fig. 4B), infants in
both groups spent the majority of
the time keeping their heads in
upright, lean, and turn, in the order
of the highest to lowest percentages,
respectively. The training group
infants demonstrated less lean
(z⫽⫺3.016, P⫽.03, r⫽⫺.64) and
more upright (z⫽⫺2.043, P⫽.041,
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Physical Therapy
r⫽⫺.44) behaviors compared with
the control group infants. There
were no significant differences
between groups for turn and pop-up
behaviors during the training phase.
In after training phase 1 (age 2.5–3
months, Fig. 4C), infants in both
groups spent the majority of the time
with their heads upright, but the
order of the percentage of time in
the other head postures and movements varied between groups. The
training group infants demonstrated
less lean (z⫽⫺2.017, P⫽.044,
r⫽⫺.43) and more pop-up (z⫽⫺
2.753, P⫽ .006, r⫽⫺.59) of their
heads in the chair compared with
the control group infants. There was
no significant difference in upright
and turn behaviors between groups
during after training phase 1.
In after training phase 2 (age 3.5– 4
months, Fig. 4D), infants in both
groups demonstrated upright, popup, and turn as the main behaviors
characterizing their head postures
and movements in an infant chair.
The training group infants had more
pop-up
(z⫽⫺3.354,
P⫽.001,
r⫽⫺.72) and less turn (z⫽⫺3.243,
P⫽.001, r⫽⫺.69) of their heads in
the chair compared with the control
group infants. (See a demonstration
video of infants in the control group
and the training group during chair
play, available at ptjournal.apta.org.)
There was no significant difference
in lean and upright behaviors
between groups during after training
phase 2.
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Early Intensive Postural and Movement Training in Very Young Infants
B Maximum Head Displacement Along
A Maximum Head Displacement Along
the y Axis
the x Axis
Group
250
300
CG
TG
*
Displacement (mm)
Displacement (mm)
200
150
100
*
*
After
Training
Phase 1
After
Training
Phase 2
250
200
150
50
100
Baseline
0
Baseline
During
Training
After
Training
Phase 1
After
Training
Phase 2
During
Training
Phase
Phase
C Average Speed of Head Movements
100
*
Speed (mm/s)
80
*
60
40
20
0
Baseline
During
Training
After
Training
Phase 1
After
Training
Phase 2
Phase
Figure 5.
The box plots for head kinematics between the control group (CG) and the training (TG) in each phase: the maximum head
displacement along the x axis (A), the maximum head displacement along the y axis (B), and the average speed of head movements
(C). Asterisk signifies a group difference (P⬍.05) based on the Mann-Whitney U test.
Head Kinematics
Results showed measurable quantitative differences in head control ability between the training and control
groups, especially during the phases
after the training stopped. Head
kinematics with significant differences between groups are shown in
Figure 5A–C.
July 2012
In the baseline phase (age 1 month),
the training group infants had
smaller maximum head displacement along the x axis (z⫽⫺2.084,
P⫽.037, r⫽⫺.44, Fig. 5A) and
slower average speed of head movements (z⫽⫺2.097, P⫽.036, r⫽⫺.45,
Fig. 5C) compared with the control
group infants.
In the during training phase (age
1.5–2 months), there was no significant difference in any of the measured head kinematics between
groups. In after training phase 1 (age
2.5–3 months), the training group
infants had larger maximum head
displacement along the y axis
(z⫽⫺2.121,
P⫽.034,
r⫽⫺.45,
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Early Intensive Postural and Movement Training in Very Young Infants
Fig. 5B) compared with the control
group infants. In after training phase
2 (age 3.5– 4 months), the training
group infants had larger maximum
head displacement along the y axis
(z⫽⫺2.626,
P⫽.009,
r⫽⫺.56,
Fig. 5B) and faster average speed of
head
movements
(z⫽⫺3.668,
P⫽.000, r⫽⫺.78, Fig. 5C) compared
with the control group infants.
There was no significant difference
between groups in the coefficient of
variation of head movement speed in
all phases.
Discussion
trol. Two major findings from the
during training phase are: (1) the
speed with which training experiences led to advances in head control and (2) the rapid changes across
multiple measures.
First, changes in head control began
within weeks of providing infants
with additional postural and movement experiences. Our data showed
that within the first 2 weeks of daily
training, the training group infants
displayed significant differences
from the control group infants. Specifically, the training group infants
had higher scores for all head
control–related items except item 1,
which is an easy item on which most
infants in both groups achieved the
highest score during the baseline
phase.48 Second, training effects
were not only rapid but also were
seen across multiple measures. Specifically, training altered both the
quality and the quantity of infants’
performance on the TIMP, as well as
how they used their head during
seated play (Fig. 4C and D). Taken
together, the training group infants
scored higher on head control items
in prone, supine, and sitting positions and during activities that
required active participation.
Training Advances Head Control
in Infants Developing Typically
Results from the multiple measures
suggest that enhanced postural and
movement experiences (ie, training)
advanced the development of head
control. The training group infants
showed more advanced head control
compared with the control group
infants during the 4-week training
period, as well as months after training. Moreover, advances displayed
by training group infants showed an
interesting additive pattern with
advanced behavioral measures in the
during
training
phase,
then
advanced behavioral and spatial
kinematics (ie, maximum displacement) in after training phase 1, followed by advances in behavioral,
spatial, and temporal kinematics (eg,
average speed) in after training
phase 2. Findings from total TIMP
scores indicated that the training
group infants were more advanced
in their general motor development
compared with the control group
infants. A summary of the results of
training effects on head control is
provided in the eTable (available at
ptjournal.apta.org). The results of
each phase are further discussed in
the following sections.
These changes, combined with the
cross-cultural research on caregiver
handling,10,40 – 44 strongly suggest
that a young infant’s head and neck
are neither as muscularly weak nor
as poorly controlled as traditionally
thought. Moreover, young infants
are able to take advantage of postural
and movement experiences to
advance their head control as early
as 4 to 6 weeks of postnatal life, if
not much earlier. The clinical implications will be discussed in a later
section.
Training Effects in the During
Training Phase
Training had an immediate and significant effect on infants’ head con-
Training Effects in After Training
Phases 1 and 2
In the weeks and months after training stopped, the training group
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infants continued to show greater
head control and more advanced
head behaviors. Interestingly, these
training effects differed from those
noted during the training period.
The after training phase results suggest that training has a lasting, positive effect on the development of
head control. First, the training
group infants not only achieved a
basic level of head control but also
were able to perform basic behaviors
for longer durations or with larger
degrees of movement than the control group infants. For example, in
after training phase 2, the training
group infants had higher scores in 5
of the 10 head control–related items.
These particular items are of interest,
as a Rasch analysis suggested they
were more difficult items to perform.48 Second, the training group
infants continued the advanced head
control from the during training
phase and displayed advanced movement strategies while engaging in
activities in the infant chair in the
weeks and months after training
stopped. For example, in after training phase 1, for the first time, the
training group infants moved their
heads off the back of the chair (eg,
pop-up) longer than the control
group infants (Fig. 4C). Interestingly,
in after training phase 2, although
the training group infants had more
time in pop-up behavior, the control
group infants continued to spend
more time in turn behavior (Fig. 4D).
Pop-up behavior may be an especially interesting measure to follow
in future studies, given that it clearly
shows purposeful intent and
requires significant effort. It is important to note, however, that pop-up
behavior may require supported sitting in a reclined seat.
Lastly, kinematic and behavioral
results during the after training
phases suggest that the training
group infants continued to gain
strength and advanced control compared with the control group infants
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Early Intensive Postural and Movement Training in Very Young Infants
in the months after training. For
instance, the training group infants
not only held their heads off the back
of the chair for longer durations but
also moved with greater excursions
(Fig. 5B) and moved their heads
faster than the control group infants
(Fig. 5C). During the baseline phase,
when infants’ head control was generally poor, the faster speed of head
movements likely resulted from
insufficient control to counteract
gravity or a lack of motivation to
maintain an upright position. In after
training phase 2, head control in
both groups was beyond the basic
level such that the training group
infants were likely purposefully producing faster movement speeds
through greater muscle activation
levels, for example.57
How Early Postural and
Movement Experiences
Advanced Head Control
Results from the current study provide empirical evidence that the
emergence of head control can be
advanced through early intensive
postural and movement training. In
addition, these results join those of
other studies to strongly suggest that
postnatal experience is an important
factor in typical development of
head control.30,35 To better understand how our training had rapid and
significant effects during the training
period and continued effects months
after training, 3 training components—positioning, handling, and
infant-caregiver interaction—are discussed next.
Infant positioning. In the during
training phase, the training group
infants received positioning experiences that were advanced for infants
during the first months of their life.
Typically, in Western cultures,
young infants spend much of their
waking hours in a supine position.58,59 More than 30% of 4-montholds never experienced a prone position while awake, and 75% spent less
July 2012
than 20 minutes daily in a prone
position.60 Based on the training
activities in the current study, the
training group infants spent an additional 6 minutes in a prone position
and 12 minutes in an upright position, which are body positions typical of older, more mobile infants.
Prone and upright positions would
be expected to increase the muscle
performance and coordination of an
infant’s neck, shoulders, and upper
trunk; provide a new view of the
environment; and provide novel vestibular stimulation, all of which have
been associated with increased alertness and motor development.61– 68
Caregiver handling. In addition
to the positions that infants were
placed in for play activities, the activities themselves altered the typical
manner in which caregivers handled
their infants. As stated previously, in
Western cultures, caregivers tend to
hold young infants carefully, supporting their heads for at least the
first months of their life (reviewed in
Adolph et al10). In the current study,
caregivers of the training group
infants were instructed to perform
activities that facilitated head control
and were encouraged to handle their
infants daily with less passive support of the head and in a much more
active manner overall. The gains in
head control in the current study fit
with the cross-cultural research
showing active handling advances
head control.
Infant-caregiver
interaction.
Lastly, the training may have influenced infant-caregiver interaction
beyond physical handling. During
daily training time, caregivers of the
training group infants likely encouraged their infants to actively control
their head appropriately. As infants
developed better head control ability, their caregivers likely continued
to offer additional opportunities to
facilitate advanced head control
even outside of the prescribed “train-
ing time.” Future studies can now
build on these foundation data to
develop valid and reliable methods
to track the type and duration of
infant-caregiver interaction both during and after the daily training
period.
Clinical Implications
One major principle of early intervention is to provide activities to
advance behaviors in infants and
children at risk for a developmental
delay before the delay is directly
observed. Several recent reviews,
including a meta-analysis, however,
have not found strong effects of traditional early intervention strategies
on motor development during
infancy, preschool age, or school
age.69 Authors highlighted the need
for comprehensive, sensitive measures to quantify both the short-term
training period and longer-term
follow-up period for intervention
programs for functional abilities.38,70
As discussed above, we know of no
longitudinal study with sensitive
measurements on the effectiveness
of interventions focused on head
control. The dependent variables
and training program from the current study were specifically chosen
to provide a framework for future
trials with pediatric populations at
risk for lifelong motor impairments.
The head control measures in the
current study are appropriate for longitudinally tracking the development
and effectiveness of intervention for
head control ability during early
infancy. These measures are multilevel, which provides a comprehensive view of infants’ performance of
head control, and can be conducted
on infants as young as 1 month old.
Results from the current study suggest these measures successfully
detected the training effects on head
control from general behavioral
changes to specific kinematic
differences.
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Early Intensive Postural and Movement Training in Very Young Infants
Limitations
Given that this is the first comprehensive, longitudinal study of the
training effect on the emergence of
head control, there are several limitations that need to be considered
when generalizing these results and
planning for future studies. First, the
experiences outside the daily training sessions were not monitored.
Caregivers likely altered the infants’
daily experiences outside of the formal training time, which would be
expected to influence head control.
Such procedural validity will be
important in future studies interested in actual intervention dosage.
Second, only head behaviors were
assessed. The development of head
control involves not only the head,
but also the limbs and trunk, as well
as sensory-perceptual and cognitive
development. It will be necessary to
investigate the range of related systems to fully understand the development of head control.
Third, data were analyzed and
reported as group effects. Individual
infants likely responded to the training differently. Identifying subgroups and individual patterns
would assist the detection of infants
with head control impairments who
often form subgroups based on the
distribution and degree of motor
involvement. Fourth, our primary
analysis focused on between-group
studies. Secondary analysis of withingroup comparisons is equally important. Fifth, the results are specific to
the experimental setup. Typical
head control emerges within multiple, dynamic environments. Investigations that include different physical and social contexts, including a
range of cultures, are necessary to
fully understand head control. Sixth,
this study focused on infants with
typical development as a first step. In
terms of clinical implications, the
key effects of training will not be
known until after studying infants
with special needs. Future studies
946
f
Physical Therapy
can build on these findings but will
need to tailor the methods and
hypotheses to the patient population, age, and level of experience of
the cohort of these clinical trials.
Both authors provided concept/idea/research design, writing, and project management. Dr Lee provided data collection and
analysis. Dr Galloway provided fund procurement, facilities/equipment, institutional
liaisons, and consultation (including review
of the manuscript before submission). The
authors thank all of the infants and their
parents for their effort and enthusiasm for
participation. They also thank many undergraduate assistants for their help with data
collection and processing.
Preliminary data from this study were presented at PT 2009: Annual Conference and
Exposition of the American Physical Therapy
Association; June 10 –13, 2009; Baltimore,
Maryland. Parts of the manuscript were presented at the XVIIth Biennial International
Conference on Infant Studies; March 10 –14,
2010; Baltimore, Maryland; and the North
American Society for the Psychology of Sport
and Physical Activity (NASPSPA) Annual
Conference; June 10 –14, 2010; Tucson,
Arizona.
DOI: 10.2522/ptj.20110196
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Volume 92 Number 7
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Physical Therapy f
947
Early Intensive Postural and Movement Training
Advances Head Control in Very Young Infants
Hui-Min Lee and James Cole Galloway
PHYS THER. 2012; 92:935-947.
Originally published online March 30, 2012
doi: 10.2522/ptj.20110196
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