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Journal of Pediatric Rehabilitation Medicine: An Interdisciplinary Approach 10 (2017) 47–59 47
DOI 10.3233/PRM-170410
IOS Press
Unimanual versus bimanual therapy in
children with unilateral cerebral palsy: Same,
same, but different
Brian Hoarea,b,∗and Susan Greavesa,c
aDepartment of Paediatrics, Monash University, Clayton, Victoria, Australia
bCPtherapy, Australian Catholic University, Victoria, Australia
cOccupational Therapy Department, The Royal Children’s Hospital, Victoria, Australia
Accepted 28 November 2016
Abstract.
BACKGROUND: There is high-level evidence supporting constraint-induced movement therapy (CIMT) and bimanual therapy
for children with unilateral cerebral palsy. Evidence-based intervention includes time-limited, goal-directed, skills-based, inten-
sive blocks of practice based on motor learning theory.
AIM AND METHODS: Using supporting literature and clinical insight, we provide a theoretical rationale to highlight previ-
ously unreported differences between CIMT and bimanual therapy.
DISCUSSION: The current emphasis on total dosage of practice for achieving positive outcomes fails to recognise the influence
of other critical concepts within motor learning. Limitations exist in the application of motor learning principles using CIMT due
to its unimanual nature. CIMT is effective for development of unimanual actions brought about by implicit learning, however it
is difficult to target explicit learning that is required for learning how to use two hands together. Using bimanual therapy, object
properties can be adapted to trigger goal-related perceptual and cognitive processes required for children to learn to recognise
when two hands are required for task completion.
CONCLUSION: CIMT and bimanual should be viewed as complementary. CIMT could be used to target unimanual actions.
Once these actions are established, bimanual therapy could be used for children to learn how to use these actions for bimanual
skill development.
Keywords: Cerebral palsy, constraint-induced movement therapy, bimanual therapy, motor learning theory
Abbreviations
AHA Assisting Hand Assessment
CIMT Constraint-induced movement therapy
CNS Central nervous system
CP Cerebral palsy
RDBM Role differentiated bimanual
manipulation
uCP Unilateral cerebral palsy
∗Corresponding author: Brian Hoare, Paediatric Rehabilitation
Department, Monash Children’s Hospital, 246 Clayton Road, Clay-
ton, Vic 3168, Australia. Tel.: +61 3 9594 4620; Fax: +61 3 9594
6136; E-mail: brianhoare@cpteaching.com.
1. Introduction
Cerebral palsy (CP) is a permanent disorder that
occurs as a result of a disturbance in the developing
brain [1]. It is the most common form of physical dis-
ability with a prevalence of 2.1 per 1000 live births [2].
Children with unilateral CP (uCP), who often demon-
strate an early hand preference or hand disregard, ac-
count for 38.8% of children with CP [3]. Although the
upper limb impairments associated with uCP predom-
inantly affect one hand/arm, the resultant functional
outcome is a deficit in the ability to use two hands
together. This is problematic as most daily activities
such as dressing, eating and playing involve the coordi-
1874-5393/17/$35.00 c
2017 – IOS Press and the authors. All rights reserved
48 B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP
nated use of both hands. Without early, effective ther-
apy, children with uCP often avoid and do not learn to
use their more impaired upper limb,leading to aberrant
changes in neurological development, increasing phys-
ical impairment, reduced function, reduced indepen-
dence and restrictions in leisure activities [4–7]. Medi-
cal specialists are now encouraged to refer for therapy
intervention immediately once an infant is considered
at risk of CP [3] and there is currently a strong research
focus on the early identification of CP and the devel-
opment of very early intervention models to capitalise
on critical periods of brain development [8–11].
Upper limb activity-level interventions for children
with uCP are now supported by the strongest evidence
for any intervention in children with CP [12]. As Elias-
son [13] states, the initial excitement about improv-
ing hand function by training is probably over. Re-
search demonstrates that well-defined, intensive train-
ing models are more effective than usual care [14]. To
improve bimanual performance, therapists can select
from a range of evidence-based models of constraint-
induced movement therapy (CIMT), bimanual ther-
apy, or a combined models known as hybrid ther-
apy [15]. All evidence-based models of intervention
involve time-limited, goal-directed, skills-based, in-
tensive blocks of practice [12,14,16]. The focus is
on encouraging repetitive, self-initiated movement of
the more impaired limb for performance of moder-
ately challenging activities to harness neural activity-
dependent processes and to improve function [11].
CP is a heterogeneous condition. While the main ef-
fects and between group differences across studies of
upper limb intervention demonstrate statistically sig-
nificant changes on a range of outcomes, not all chil-
dren with uCP achieve clinically important change.
Studies of CIMT demonstrate there is wide inter-
individual variability, indicated by the large standard
deviations and broad confidence intervals. Where in-
dividual responses to CIMT have been reported, 18
to 65% of children do not demonstrate change on the
Assisting Hand Assessment (AHA) greater than the
smallest detectable difference of 5 AHA units [16].
While more limited data exists for individual responses
following bimanual therapy, similar variability in re-
sponse has been demonstrated [17–19]. There is no
“one size fits all” or superior approach for the treat-
ment of the upper limb in children with uCP [14]. Both
unimanual and bimanual therapies can be effective if
provided to the right child, at the right time. The ex-
citement in upper limb intervention research now lies
in the exploration of primary predictors for positive
change following CIMT, bimanual or hybrid therapy.
It is also in refining and identifying the essential in-
gredients of evidence-based upper limb therapy. It is
widely accepted that a therapeutic dosage greater than
usual care needs to be achieved in order to improve
upper limb outcomes, but is upper limb therapy simply
all about the dosage? Are CIMT and bimanual therapy
essentially the same? While considering current con-
cepts for learning motor skills, along with the devel-
opment of bimanual skills, this paper aims to explore
these questions and to providea theoretical rationale to
highlight the differences between CIMT and bimanual
therapy.
2. Learning motor skills
In the not so distant past, dominant theories guid-
ing upper limb intervention for children with uCP
were based on a hierarchical model of the central ner-
vous system (CNS) that was proposed over a century
ago [20]. Hierarchical theory viewed movement as a
combination of sequences of reflexes. Sensory stimuli
elicit specific and stereotypical motor patterns. Ther-
apy approaches aimed to modify sensory input, in-
hibit primitive reflexes and modify or inhibit abnor-
mal movement patterns [21]. Experimental research
has since irrefutably disproven the hierarchical model
of the CNS and therefore, the basis upon which these
therapeutic approaches were developed [22–24]. A
modern view of motor systems organization demon-
strates heterarchical organization of the CNS where
higher centers interact with the lower centers but do
not control them [25]. The CNS is seen as one part
of task performance. It interacts with multiple per-
sonal and environmental systems to achieve a goal.
Bernstein’s [24] contemporary model of motor learn-
ing views movement emerging from three general sys-
tems: the person, the task, and the environment. Prac-
tice and experience alter the development of move-
ment patterns through interaction with the environment
and the demands of the task [26]. The focus of con-
temporary upper limb intervention is not on inhibition
of primitive reflexes or normalization of movement,
but on maximizing the efficiency of the damaged CNS
in response to the environment and demands of the
task leading to relatively permanent changes in the ca-
pability for movement and task performance. Appli-
cation of motor learning theory is the one consistent
feature across all evidence-based, upper limb activity-
level models of therapy, including CIMT and biman-
B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP 49
ual therapy [14]. Motor learning theory however is not
one theory, but several interpretations and concepts re-
lated to how motor skills are acquired [26]. Applica-
tion of motor learning principles including the type of
task, the type and amount of practice and the type of
feedback are therefore open to interpretation. Imple-
mentation varies broadly across intervention protocols.
Our understanding of how humans learn and general-
ize motor skills has mostly developed from experimen-
tal research involving typically developing adults and
children. We currently know very little about how chil-
dren with CP learn goal-oriented tasks [27]. While it
is acknowledged that children with uCP require longer
than typically developing children to improve perfor-
mance [27], the amount of practice or dosage is only
one part of the motorlearning concept. Howwe as ther-
apists, or mediators between the child and the task, ma-
nipulate the activity and the environment through tech-
niques such as modeling task performance and varia-
tion in the type of task and the type of feedback will
also greatly influence a child’s learning and general-
ization of bimanual skills. In order to explore and un-
derstand this, we believe it is important to first recog-
nize how infants and children, with and without uCP,
develop and learn bimanual skills especially those re-
quiring complex patterns of differentiated hand use.
3. Development of bimanual skills in typically
developing children
Humans are essentially bimanual beings; from the
earliest midline clasping of fingers at 3 months to the
performance of complicated bimanual sequences of ac-
tions that are coordinated both temporally and spa-
tially, such as tying shoelaces. Like the development
of all motor skills, bimanual skills emerge gradually
with their maturation working in parallel to the de-
velopment of postural, sensory, perceptual and cog-
nitive skills as well as unilateral hand skill develop-
ment [28,29]. While the development of unimanual ac-
tions such as reaching, grasping and releasing are im-
portant for the development of bimanual hand skills in
this paper we will focus on the development of biman-
ual skills.
3.1. Early bimanual responses (0 to 6 months)
Even from early infancy humans move both arms. At
first, an infant’s upperlimb responses are asymmetrical
and predominantly involve involuntary general move-
ments or are influenced by infant reflexes. From ap-
proximately 3 months of age, when the infant’s postu-
ral skill development allows the adoption of a midline
head position, arm movements begin to develop sym-
metrical patterns; for example when both hands pull at
their clothes, during early bimanual holding of a toy,
or early midline fingering of the hands (hand inter-
play) [28]. When toys are presented either in midline
or to the side, unilateral movements towards toys are
replaced by bilateral hand reaching so that by 4 to 41/2
months this is the most common response to toys pre-
sented anywhere [29]. However, it is the development
of midline orientation that drives the development of
bimanual coordination [29].
3.2. Development of bimanual coordination
(6–12 months)
Once visually guided reaching and grasping become
well established (between 5 to 6 months), there is a lin-
ear decrease in bimanual reach and it becomes depen-
dent on the property of the objects as well as postu-
ral development and control [30]. However, while ac-
quisition of an object becomes unimanual, manipula-
tion of the object remains bimanual. Additionally, the
development of postural skills such as learning to sit,
allows for considerable transformation in how objects
are manipulated in the second half of the first year of
life [29]. At 5 to 7 months, object manipulation usually
involves one object at a time and is mainly devoted to
unimanual mouthing, banging and shaking. Between 7
to 9 months infants develop the capacity to handle two
objects at a time as well as objects with two or more
parts. It is between 9 to 12 months that acquisition of
objects returns from a unimanual to a bimanual ap-
proach [31]. Early manipulative movements when the
two hands are used at the same time are relatively sym-
metrical in nature such as when banging two objects
together, inserting one object into another, or pulling
two parts of an object apart. From 7 months of age, a
new type of asymmetrical manipulation starts to occur.
3.3. Role differentiated bimanual manipulations
Role differentiated bimanual manipulation (RDBM)
refers to manual actions in which two hands perform
different but complementary movements on one or
more objects [32,33]. RDBM’s differ from uniman-
ual manipulation as they involve coordinated senso-
rimotor control between the two hands, which likely
requires the collaboration of the two hemispheres
50 B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP
through the corpus callosum [34,35]. This reflects
an important shift in the organization of motor con-
trol [36] that may have consequences for cognitive
functioning [37,38]. Thus, this shift in an infant’s man-
ual skill from unimanual actions with objects (e.g.
grasping, banging, shaking) to bimanual manipulation
in a role-differentiated manner is seen as a major mile-
stone [33,37].
Early RDBM actions consist of one hand holding
an object while one or two fingers of the other hand
manipulate it (fingering, poking). This is followed by
manipulation where the palm or whole hand explores
the toy (stroking). Object removal (pulls) occurs first
at 7 months, but becomes more frequent by 11 months;
while object insertion is first seen at 9 months, but is
more frequently seen at 13 months. Other RDBM’s
such as spins and pushes also represent more diffi-
cult RDBM’s [31], and even later skills are actions
such as unscrewing and unzipping [32]. Early or sim-
ple RDBM’s such as fingering or stroking a toy are
highly influenced by the affordances of the particular
toy, and are likely to be accidental [32]. More diffi-
cult RDBM’s such as pulling, inserting, spinning and
pushing are more consistently seen at 11 to 13 months,
and involve greater control organization. It is hypoth-
esized that these more controlled RDBM’s might re-
quire an understanding of the relationship within and
among objects and also necessitate an amount of plan-
ning in order for the action to occur [32,33].
As RDBM’s develop during the first two years
of life, they move from non-differentiated bimanual
movements, where both hands play active manipulat-
ing roles, through partially differentiated movements
where there is alternation between the roles of the two
hands, to complex patterns of completely differenti-
ated hand use [38,39]. Differentiation refers to dis-
tinct role division between the two hands [31]. One
reason that infants move through this sequence may
be that it requires the ability to pay attention to both
hands at the same time, which requires more exten-
sive interhemispheric coordination [29,31]. Initially in-
fants may use their two hands in succession until they
can coordinate them in a new non-mirror, simultaneous
synergies. That is, sequential movements of the two
hands come before simultaneous asymmetric move-
ments. Using both hands to acquire objects also facil-
itates the development of non-differentiated bimanual
manipulation, which in turn facilitates the development
of partially and fully differentiated RDBM’s [31].
In terms of frequency, at 7 months of age RDBM’s
comprise less than 10% of an infant’s manual reper-
toires with toys, with unimanual play dominating
at more than 50%, and non-differentiated bimanual
movements (NDBM) accounting for 40% of manual
play. By 13 months, there is a decline in uniman-
ual (mostly) and NDBM play and increase in RDBM
play [34]. At 19 months, RDBM’s represent 25% of
manual repertoire in infants, and 50% at the age of
3 years [40]. Finally, hand preference for RDBM’s
also emerge as this skill develops in typically devel-
oping children. Before 12 months, infants may use ei-
ther hand as the stabilizing hand, while the other hand
acts in a manipulating role. However from this age on-
ward, as infants begin to discern the affordances of ob-
jects, they begin to adjust their manual ability so that
they grasp objects with their non-preferred hand so the
preferred hand can manipulate it [33]. In typically de-
veloping children, while the preferred hand eventually
becomes more skilled their non-preferred hand is also
proficient [41].
This pattern of developing a hand role preference, as
well as proficiency and skill in both hands when com-
pleting RDBM’s and other bimanual actions is not ob-
served in young children with uCP. In this instance, the
different roles of the two hands during bimanual ma-
nipulative play are much more evident.
3.4. Hand role differentiation and functional hand
use in children with uCP
The pioneering work by Lena Krumlinde-Sundholm
in the development of the Assisting Hand Assessment
(AHA) [42] has significantly influenced understanding
of bimanual performance, hand role differentiation and
functional hand use in children with uCP. The AHA bi-
manual performance construct recognises that all hu-
mans have a dominant hand and a non-dominant hand
or hand role differentiation [43]. The two hands do
not perform the same role. The dominant hand is used
for high precision tasks such as writing and tool han-
dling whereas the non-dominant hand plays a more
supportive, assisting role [43]. This differentiation is
greatly exaggerated following congenital unimanual
upper limb impairment, with the more impaired up-
per limb adopting the role of a helping or assisting
hand, regardless of expected or perceived hand dom-
inance. The concept of hand role differentiation may
become distorted in upper limb rehabilitation programs
where successful outcomes are often measured by the
capacity to use the more impaired upper limb in uni-
manual, dominant hand activities. Outside this con-
trolled environment however, a child would most of-
B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP 51
ten choose their less impaired, dominant hand to per-
form a unimanual task. This would be quicker, re-
quire no increase in effort and would lead to imme-
diate success. Krumlinde-Sundholm [43] defines func-
tional hand use as when the hand/arm is used in a man-
ner that makes activity performance successful, effec-
tive and done with minimal effort [43]. Task perfor-
mance, and what is functional for children with uCP,
is therefore unique to each child and what object is
to be handled. For some children with lower ability,
grasping objects directly from the table with their as-
sisting hand will not be functional i.e. successful, ef-
fective and done with minimal effort. Instead, learn-
ing to first grasp the object using the dominant hand
and thereafter grasping from the dominant hand us-
ing the assisting hand will be successful, effective and
done with minimal effort or functional. Consistent with
gross motor development [44], preliminary longitudi-
nal data demonstrates bimanual abilities in children
with uCP do not develop at the same rate or reach the
same ability limit [45]. There are limits to how well a
child is able to use their more impaired hand in uni-
manual and bimanual tasks, most likely based on their
brain pathology [46–48]. The extent to which interven-
tion may influence these limits remains unknown [49],
however this data provides insight into the possible
reasons for the broad variability in response to upper
limb intervention [16,47]. Clinical experience, along
with data from studies of upper limb intervention, sup-
ports a realistic view that whatever the intervention
model, and whatever the dosage, some children with
uCP do not demonstrate clinically important change
following upper limb intervention. Conversely, some
children demonstrate enormous gains and perhaps the
rate of improvement and bimanual ability limit is per-
manently altered following intervention. Knowledge of
hand role differentiation and functional hand use [43]
have significantly influenced our understanding of the
development of bimanual performance in children with
uCP. It is this knowledge that helps to highlight the fun-
damental differences between CIMT and bimanual in-
tervention and may help explain some of the observed
differences following intervention.
4. Constraint-induced movement therapy
First described by Edward Taub in 1993 [50], the
original, or signature, model of CIMT has been sig-
nificantly adapted for use in children with CP [15].
To distinguish CIMT from other models of upper limb
intervention, expert consensus proposed two key in-
gredients that define CIMT: (1) restraint of the well-
functioning upper limb (irrespective of device/type)
and (2) intensive structured training (irrespective of
type) [15]. The fundamental principle of CIMT is in-
tensive practice of the more impaired limb [50]. This
aims to reverse or prevent the very early behavioural
adaptation that takes place in children with uCP who
demonstrate a strong early hand preference or limb dis-
regard, known as developmental disregard [51]. The
intensive spontaneous use of the more impaired limb
also aims to drive neuroplasticity, mitigate secondary
musculoskeletal impairment and improve function. It
is now recommended that developmentally appropriate
models of CIMT are implemented when asymmetric
hand use is first observed, commonly at three to five
months of age [52].
CIMT involvesplacing a constraint on a child’s less-
impaired upper limb (e.g. cast, mitt, sling) to facili-
tate spontaneous and repetitive use the more impaired
limb in a range of unimanual activities, specifically tar-
geted to the child’s individual ability and developmen-
tal level. This can take place in the child’s daily envi-
ronment (home, day care, school etc.) or therapy cen-
ters during frequent, long duration treatment sessions
for 2 to 3 weeks [53,54] or in a more distributed fashion
with less frequent, shorter sessions across a longer pe-
riod of 6 to 10 weeks [17,55]. The constraint replaces
the need for repetitive physical and/or verbal prompts
to use the more impaired limb. The skill of the thera-
pist and/or caregiver is to maintain the child’s interest
and motivation, grade the level of task difficulty and to
provide as many opportunities as possible for intensive
practice of unimanual goal-related actions e.g. reach,
grasp, hold, release.
As much as possible, CIMT should be a hands-off
approach to allow a child to learn using intrinsic feed-
back or information provided by sensory systems dur-
ing repetitive movements [56]. During CIMT, uniman-
ual actions are performed over and over again and ul-
timately; improvements are achieved by doing it repet-
itively or by implicit learning. Implicit learning is the
ability to acquire a new skill without a corresponding
increase in knowledge about the skill [57]. It is how
infants acquire new skills [57]. It generally occurs in
the absence of the cognitive phase of learning [58], re-
quires minimal attention and is not dependent on work-
ing memory [57]. Implicit learning is therefore rela-
tively independent of age and IQ [57]. When consid-
ering this, it becomes evident why massed practice or
dosage is the fundamental ingredient of CIMT. Uni-
52 B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP
manual actions are learned by doing it repetitively or
by implicit learning. It also provides possible support
for clinical experience where CIMT has been found
to be a relatively easy intervention to implement, es-
pecially in infants and children with more impaired
cognitive function [17,59]. The cognitive demands for
children during CIMT remain relatively low due to the
nature of tasks that can be practiced.
While it is acknowledged that motor learning con-
cepts can be applied using CIMT, it is obvious that
limitations exist due to the fact that only one hand is
being used. Typically, the type of tasks practiced in a
CIMT program are discrete, meaning there is a recog-
nisable beginning and end (e.g. picking up a ball to
place in a tower). More complex serial tasks, or dis-
crete tasks that are strung together (e.g. threading, con-
struction, dressing) are very difficult, or impossible to
practice as these most often require two hands to per-
form. Children are therefore unable to practice and
learn the relationships between critical phases of se-
rial tasks [60]. Furthermore, in the absence of a con-
straint device, these unimanual tasks would typically
be performed using the dominant hand as it would be
functional or successful, effective and done with min-
imal effort [43]. Using CIMT, children practice domi-
nant hand actions with their assisting or non-dominant
hand. It is not possible for them to practice and learn
how to use their more impaired hand for assisting hand
actions.
Performing bimanual tasks, especially those requir-
ing complimentary actions, requires procedural knowl-
edge i.e. knowing how to do something. To learn
skilled tasks children need to build up a set of per-
formance rules that guides motor performance or
skills [57]. This is known as explicit learning.Ex-
plicit learning is correlated with age and IQ [57]. It
requires a high level of inter-related cognitive pro-
cesses including attentional control, information pro-
cessing, cognitive flexibility and goal setting to pro-
duce an appropriate (motor) action [61]. Skilled task
performance also requires working memory, the pro-
cess of retaining information in conscious awareness
in order to manipulate it and to use it to guide be-
havior [62]. Deficits in executive function and work-
ing memory may manifest as an inability to focus and
attend to tasks, perseveration, increased errors without
subsequent self-correction, and taking longer to com-
plete tasks [63] and are known to be impaired in chil-
dren with uCP [63]. We propose that the difficulties
children with uCP experience when faced with per-
forming skilled bimanual tasks are often associated
with not knowing what to do rather than not being
able to perform the required motor actions [64,65]. The
two however,are not mutually exclusive. Children with
uCP require motor actions for task performance; how-
ever,once a child possesses basic actions such as reach,
grasp, hold, release they need to learn how to use these
actions during bimanual task performance, especially
those that require differentiated hand use [66]. In line
with the motor learning principle of you learn what
you practice, we propose that learning bimanual skills
is best achieved through practice of bimanual tasks.
Further, we postulate that deficits in cognitive function
are a contributing factor for why some children with
uCP make clinically significant improvements in uni-
manual actions following CIMT (i.e. learn to grasp,
hold, release), but these gains do not necessarily gen-
eralize to similar improvements in bimanual skill per-
formance [17]. A hypothesis perhaps supported by the
evolution of hybrid models of upper limb intervention
where bimanual therapy is added to varying degrees to
CIMT [10,53,67,68]. Once a child improves uniman-
ual actions through CIMT they need to learn the cogni-
tive and perceptual strategies to guide performance of
bimanual skills. Further research is required to under-
stand the impact of cognitive impairment on bimanual
skill performance [65].
5. Bimanual therapy
5.1. The bimanual therapy concept
Occupational therapists have traditionally used bi-
manual therapy for children with uCP [69], however
no documented model of bimanual training existed
until Charles and Gordon [70] published a protocol
for Hand-Arm Bimanual Intensive Training (HABIT)
in 2006. Consistent with our previously documented
theoretical concepts for bimanual occupational ther-
apy [71], we define bimanual therapy as a process of
learning bimanual hand skills through the repetitive
use of carefully chosen, goal related, two-handed ac-
tivities that provoke specific bimanual actions and be-
haviors. It extends beyond the goal of shaping uniman-
ual actions, and we propose bimanual therapy is not all
about the dosage [71]. This is supported by outcomes
in young children with uCP, aged 18 months to 6 years
of age, where 98.5 hours of mCIMT was not found to
be superior to 31.6 hours of bimanual therapy [17]. Bi-
manual therapy is strongly grounded in concepts from
cognitive-motor based theory and aims to provide the
B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP 53
ABC
Fig. 1. Presentation of the same object provoking different behaviors.
opportunity for children with uCP to practice and learn
bimanual skills and strategies that are targeted to their
individual ability level [71–74]. While repetitive prac-
tice of bimanual tasks facilitates opportunity for im-
plicit learning, we propose bimanual therapy also tar-
gets explicit learning or procedural knowledge through
a mediated learning experience [74].
Skilled bimanual performance involves perceptual
and cognitive processes whereby information from the
environment and the task is analysed before a move-
ment response is executed [23]. Greaves et al. [75]uses
action-perception theory to illustrate the important in-
teraction between an infant, the object and the task
for bimanual skill development. By seeing, touching
and manipulating objects, infants learn about the ob-
ject’s physical properties [75]. In a reciprocal and dy-
namic relationship perception helps guide action, and
action in turn allows for more precise perception for
future actions. We propose that action-perception the-
ory can be used to further illustrate important differ-
ences between CIMT and bimanual therapy. For ex-
ample, Figure 1 illustrates how the same object can
be presented in specific ways to provoke different uni-
manual and bimanual actions and behaviours. Percep-
tually, the single object in Fig. 1(A) provokes reach
with the dominant hand alone. Adding an additional
object, and/or altering the orientation of the same ob-
jects (Figs 1(B) and (C)), would typically provoke a bi-
manual response. For children with uCP however, who
lack prior experience or internal representations for
bimanual actions, a unimanual response would most
likely be used in all three examples. Using therapeu-
tic strategies such as modelling, adaptation of the en-
vironment, intentionally filtering and focussing stim-
uli and repetitive practice of carefully chosen uniman-
ual and bimanual tasks, clinical experience, along with
emerging evidence [76], suggests it is possible for chil-
dren with uCP to develop the perceptual and cognitive
skills required to independently plan appropriate uni-
manual or bimanual responses prior to executing a mo-
tor action. Bimanual therapy is therefore much more
than simply playing with two-handed toys. It requires
extremely careful consideration of toy properties that
trigger the goal-related perceptual and cognitive pro-
cesses required for children to learn to recognise when
two hands are required to complete a task. It is the ob-
ject and the task requirements that facilitate this learn-
ing. Through repetitive practice of motivating and tar-
geted activities, improved perception helps guide mo-
tor actions, and action in turn allows for more precise
perception for future actions [75]. We propose it is dif-
ficult for children to learn the perceptual and cognitive
skills required for bimanual responses when a restraint
is placed on the dominant hand and only unimanual
tasks can be practiced.
Evidence demonstrates the importance of using
moderately challenging, goal-directed activities to
drive motor cortex plasticity [77]. If a child is pro-
vided with a task that is challenging (i.e. possible at
the child’s upper limit of capabilities or zone of proxi-
mal development) and motivating, it is more likely that
motor skill acquisition will be improved [78,79]. Rep-
etition of previously acquired motor movements does
not result in significant synapse addition or map ex-
pansion in motor cortex in animal models [80]. There-
fore, how a therapist selects a task and adapts model-
ing, practice and feedback can improve or potentially
interfere with the perceptual and cognitive processes
that promote learning and generalization of bimanual
skills. While we acknowledge the importance of rep-
etition of practice for both CIMT and bimanual ther-
apy, we propose that grouping two fundamentally dif-
ferent interventions to explore the impact of dosage
fails to acknowledge the influence of other critical con-
cepts within motor learning theory. We propose that
how much is essential for implicit learning but how
well is even more essential for explicit learning and bi-
manual therapy.
5.2. Bimanual therapy concepts for children older
than 18 months
Consistent with models of cognitive-motor based
theory [73,74,81], bimanual therapy for children with
54 B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP
uCP should be a mediated learning experience where
children are encouraged to learn to think and think to
learn [74]. The role of the therapist is to carefully se-
lect goal-related, motivating, moderately challenging
activities/toys and to regulate the type, intensity, fre-
quency and sequence of both practice and feedback.
Knowledge of the Assisting Hand Assessment hierar-
chy can assist in guiding graded skill progression [71].
The atmosphere in a therapy session needs to be one of
acceptance and support forrisk-taking focussing on the
development of resilience or mastery motivation [82].
Working in partnership with the parents, the environ-
ment should also facilitate an understanding of bound-
aries for acceptable behaviour to establish patterns of
sustained attention and on-task behaviour [71]. Mod-
elling task performance or action observation is criti-
cal for children with uCP with limited past experiences
and impaired anticipatory planning [66]. Observation
of task performance activates the mirror neuron sys-
tem [83] and is also a prerequisite for understanding
the task requirements [84]. Evidence suggests both ef-
fectual and ineffectual strategy usage should be mod-
elled [85]. In the early stages of learning closed tasks
with lower demands should be considered before pro-
gressing to open tasks with higher demands [56]. Mo-
tor learning is inferred when a child accurately and
consistently performs motor skill in different settings
across various points in time [86]. Random practice is
therefore critical to promote generalisation of skills. It
is important to ask questions, not tell the answers when
providing verbal prompts. Although typically develop-
ing children benefit more from higher feedback fre-
quency than adults [27,87], too much feedback can im-
pact on learning. By learning problem solving strate-
gies such as Meichenbaum’s goal, plan, do, check [73]
it is possible that children with uCP can learn to in-
dependently plan and regulate unimanual and biman-
ual behaviors. Active problem solving assists them to
extract explanatory rules in order to bridge and gener-
alize beyond the immediate skill teaching to other sit-
uations [88]. Over time, perceptual and cognitive de-
velopment occurs through the gradual internalization
of concepts and relationships [78]. In summary, we
propose bimanual therapy should focus on cognitive
and perceptual development to enable a child to ac-
tively problem solve and learn to plan appropriate re-
sponses based on the objects that are to be handled.
This requires a high degree of cognitive load [89]es-
pecially for children with known deficits in working
memory [63]. As a result, we hypothesize that a thresh-
old exists for the dose response of bimanual therapy
due to the cognitive demands placed on children par-
ticipating in models using cognitive-motor based the-
ory.
5.3. Bimanual therapy concepts for infants
While the concepts remain the same, many of the
cognitive strategies we propose for bimanual therapy
in children older than 18 months are not possible to
implement in infants who learn skills and make devel-
opmental gains using implicit learning. As a result, we
propose that important differences and developmental
restrictions exist when implementing bimanual therapy
for infants less than 18 months. To date, no study has
examined outcomes of bimanual therapy in young in-
fants therefore effectiveness remains unknown in this
population.
The first consideration for implementation of bi-
manual therapy in infants is knowledge of develop-
ment. Understanding early motor development, in par-
ticular bimanual development, is essential in order to
determine what actions are possible and when they
should be provoked [75]. Additionally, therapists re-
quire knowledge about the effect of postural, sensory,
perceptual and in particular cognitive influences on the
acquisition of motor skills. Newly developed assess-
ments such as the Hand Assessment for Infants [90]
and the Mini-Assisting Hand Assessment [91]may
assist in targeting specific goal-directed, developmen-
tally appropriate bimanual skills.
In the very early stages of learning bimanual actions
young infants and especially those with greater mo-
tor impairment, are likely to require increased phys-
ical prompting to facilitate a desired motor response
and to achieve success. For example, bringing the more
impaired upper limb forward to join the less impaired
hand to achieve simultaneous actions such as biman-
ual holding or to encourage sequential bimanual ac-
tions such transferring toys from hand to hand. It is
critical to ensure this physical assistance is only used
to show how [9] and removed as soon as possible to
allow a child to learn using intrinsic feedback or in-
formation provided by sensory systems during repet-
itive movements [56]. It is the spontaneous initiation
of movement that drives development of motor control
and neuroplasticity [11].
Imitation or observational learning and repeated task
exposure are effective ways to promote task knowledge
and skill acquisition in infants [92,93]. At 6 months
infants can imitate simple actions. By 10 months they
can perform target actions more quickly after observa-
B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP 55
tions however, if the task is not part of their current
motor repertoire, it is not until 12 months that benefits
can be seen from demonstration [94,95].
While the developmental process of perception-
action matching is influenced by constraints in the
motor system [30], toy affordances help provoke spe-
cific bimanual play and behaviours, even in early in-
fancy [32,33]. How infants perceive an object directly
influences how they act on it [96]. For example, the
size of a toy, interesting parts to hold and explore, or
the where the object is located will provoke a variety
of responses [97]. Equally, set up of the infant’s phys-
ical environment is especially important as it provides
for increased motor opportunities. Positioning an in-
fant’s cot may encourage awareness of the more af-
fected side; or when infants are lying in supine or in
a bouncer, toys may be hung from baby gyms only on
the more affected side to encourage spontaneous initia-
tion of upper limb actions. As soon as able, exploratory
play should be encouraged in an upright, stable seated
position, as this has shown to be advantageous for mo-
tor, cognitive and perceptual development [98].
When infants are presented with multiple objects
one at a time, they must learn how to manipulate and
manage the objects so that the first object is available
for later interaction [99,100]. This concept is known
as storage and is a further example of utilising cog-
nition and perception to provoke bimanual hand use.
Storage places a cognitive demand on the infant for
the toy to be mentally represented for later retrieval or
use and can be observed in infants from 6 to 8 months
when presented with two objects. From 9 to 11 months
strategies used to handle three or more objects can be
observed and increasingly complex strategies continue
to develop throughout infancy [99]. For infants with
uCP, providing opportunities to learn how to manage
object storage, such as transferring one of the objects
to their affected hand, is an important strategy for them
to learn. Storage allows for the practice of simulta-
neous usage of both hands, comparison between ob-
jects, and the examination of the effect of one object on
another [99]. By storing objects more effectively, the
properties of the objects can be explored, relationships
between objects examined, and planning of actions on
objects can be more successful [99,100].
While easy role differentiated bimanual manipula-
tion’s (RDBMs) commencing around 7 months are
thought to be accidental or occur by chance, from
12 months the deliberate planning of holding a toy with
one hand so that the second hand can perform a ma-
nipulation is seen more consistently [31,32]. This con-
cept is known as planfulness and evidence from typi-
cally developing infants suggests that from 12 months
infants with uCP may be capable of learning the strat-
egy of using the more impaired hand as the hold-
ing/stabilising hand so that their less impaired hand can
act on the object [31].
Tool use is an important skill that involves means-
end reasoning [101]. It requires the integration of per-
ceptual, cognitive and motor skills. How infants learn
to use a tool is considered to be a continuous and grad-
ual process of discovery and exploration [102]. It is
thought to arise from early attempts to relate objects to
others, and discovery of the affordances that may ex-
ist between objects. Infants need to detect these affor-
dances and establish these relationships through man-
ual action. While young infants can handle objects as
tools, early handling is likely to be exploratory. It is
not until 14 months of age that an element of anticipa-
tory planning is consistent when using tools with self-
directed goals [103]. Knowledge of the development
of tool use in typically developing infants is a useful
guide for the introduction of specific activities into up-
per limb intervention programs for young children with
uCP. For example, tasks such as replacing the lid on the
correct end of a marker during a drawing task could be
introduced at around 14 months.
6. Conclusion
In this paper, we combine clear theoretical ratio-
nale and clinical insight to propose previously unre-
ported differences between CIMT and bimanual ther-
apy. While intensity or dosage of practice is acknowl-
edged as fundamental to both models of interven-
tion, we propose that an emphasis on dosage alone
fails to address the influence of other critical concepts
within the motor learning concept. This includes mod-
elling, the type of task, type of practice and type of
feedback. We provide a rationale that limitations ex-
ist in the application of motor learning principles us-
ing CIMT due to the unimanual nature of the inter-
vention. CIMT is effective for development of uniman-
ual actions brought about by implicit learning, how-
ever it is not possible to target the cognitive and per-
ceptual skills or explicit learning required for using
two hands together. Using cognitive-motor and action-
perception based strategies in bimanual therapy allows
object properties to be used to trigger the goal-related
perceptual and cognitive processes required for chil-
dren to learn to recognise when two hands are required
56 B. Hoare and S. Greaves / Unimanual versus bimanual therapy in children with uCP
to complete a task. We propose that CIMT and biman-
ual should be viewed as complementary. CIMT could
be used to target unimanual actions. Once these ac-
tions are established, bimanual therapy could be used
for children to learn how to use these actions for bi-
manual skill development and learning how to perform
daily activities with two hands.
Conflict of interest
Both authors are involved in the teaching of the
Hand Assessment for Infants, mini-Assisting Hand As-
sessment and Assisting Hand Assessment certification
courses.
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