Relationship of Proximal and Distal Function
in Motor Development
CAROL LORIA, MS
This study questions the validity of the principle of a proximo-distal direction of
motor development and the idea that distal skill emerges out of and is dependent
upon proximal control. To determine the relationship between proximal and
distal motor function, 12 normal infants (9 girls, 3 boys), 30-weeks of age, were
recorded on videotape while reaching for a one-inch red cube contained in a
specially designed form board. Their visually guided reaching (proximal) ability
and prehensile (distal) skills were rated on nonstandardized scales. No significant linear relationship was found between proximal and distal motor behavior.
The conclusion that distal development does not necessarily follow proximal
motor development is offered. The possibility that two different motor-control
systems governing proximal and distal function is considered. Reconsideration
of the proximo-distal sequences currently used in treating motor-system dysfunction is recommended.
Key Words: Child development, Motor skills.
The treatment of motor system dysfunction is often
guided by the principle that distal motor development
depends on proximal motor development. This principle, based on early phylogenetic,1 embryologic,2 and
ontogenetic observations,3-5 was generated in the
1920s and 1930s in support of the argument that
behavior is refined from the whole rather than built
up from its parts.1 The data upon which the proximodistal principle was formulated, however, were controversial and often scant.6 Furthermore, observations
from phylogenetic and embryologic studies of lower
phyla were used to suggest the probability of a proximo-distal progression in man; yet man's increased
encephalization and greater skilled hand function
makes the validity of comparison to lower phyla
questionable.
Despite the lack of research support, this principle
has mandated a treatment sequence that has been
employed in many therapeutic procedures. For example, Ayres charts treatment sequences to suggest a
Ms. Loria was a graduate student, Sargent College of Allied
Health Professions, Division of Physical Therapy at Boston University, when this study was conducted. She is currently Education
Coordinator, Department of Physical Therapy, Kennedy Memorial
Hospital for Children, 30 Warren St, Brighton, MA 02135.
This study was supported by an Allied Health Professions Traineeship from the Public Health Service, Department of Health, Education, and Welfare.
This article was submitted August 10, 1978, and accepted August
27, 1979.
Volume 60 / Number 2, February 1980
relative emphasis and order of progression of the
treatment program for improving upper extremity
function follow the proximo-distal progression: first,
control of head and eye musculature, then control of
trunk, shoulder girdle, arm, and so on.7 The sequence
culminates with emphasis on distal motor skill. Rood,
according to Stockmeyer, uses proximo-distal sequences when facilitating responses of mobility, stability, and mobility superimposed upon stability, as
well as when promoting skill acquisition.8 Bobath
proposes control of key points according to a proximo-distal direction.9
Recently, the validity of the rationale and hence
the treatment sequences themselves has been challenged as new evidence on the neurological substrata
of movement emerges. Kuypers has advanced a concept of motor control that departs from the classical
concepts of pyramidal and extrapyramidal systems.
In their place, he postulates 1) a medial system that
exerts control over axial and proximal limb musculature and 2) a lateral system chiefly responsible for
distal limb movements.10 This theory of dual motor
control mechanisms is based on anatomical evidence
in the cat and monkey, and on functional evidence in
monkeys with lesions selectively placed in descending
motor pathways.11 Recent studies, which further confirm the concept of two kinds of motor control mediated by two distinct systems, have considered the
motor control exerted by one-half of the brain over
167
contralateral and ipsilateral extremities in monkeys
that have had commissurotomies.12,13
Does Kuypers' concept of dual mechanisms of
motor control apply to man? Evidence in split-brain
humans (who have undergone surgical disconnection
of the corpus callosum to prevent interhemispheric
spread of seizure activity) points to the likelihood of
such a duality.14 The possibility of a dual motor
control system in man raises important questions
about the proximo-distal principle. First, if there are
indeed two motor control systems with different functions, do they develop independently? If so, does their
development overlap in time or does one system
(proximal) develop first? Is development of one system (distal) dependent upon the development of the
other (proximal)?
A literature search revealed only one study that
examined this proximo-distal relationship. That study
found a lack of significant relationship between the
times of onset of goal-directed motility of the arms
and the type of grasping, suggesting that the two
functions develop differently with respect to time.10
The purpose of this study was to investigate the
relationship between proximal and distal behavior,
which should be demonstrable if the proximo-distal
principle is correct. Failure to demonstrate this relationship could have far-reaching implications for reconsideration, and perhaps replacement, of the proximo-distal sequences currently employed in the treatment of motor impairment. The assumption in the
study reported here was that the proximo-distal principle should predict a positive linear correlation between the rated quality of reaching and prehension
in 30-week-old human infants.
The second purpose was to examine the qualitative
aspects of proximal and distal motor development by
depicting the characteristics of visually guided reaching and the prehensile skill in these infants.
METHOD
The sample consisted of 12 full-term infants (9
girls, 3 boys) between the ages of 209 and 213 days,
recruited from personal acquaintances. All infants
had normal gestational periods and health records.
Pregnancy and delivery were satisfactory. All infants
were white and came from similar socioeconomic
backgrounds.
Proximal-Function Assessment Scale
For the purpose of this study, proximal function
was tested by assessing visually guided reaching ability, because this movement involves a spatial aiming
skill. To assess the infants' reaching ability, a proxi-
168
Possible Infant
Points Behavior
( )
1. Visual Orientation
Closes eyes
Looks at hand
Looks at object
2. Form of Approach
Circuitous
Moderately circuitous
Slightly circuitous
Direct
3. Number of Lateral Deviations
4 or more
3
2 or less
4. Aim of Approach
Pronated
In some aspect of forearm
rotation
Forearm rotation definitely
directed at cube
5. Vertical Approach
Slide
Loop-slide
Plane-slide
Plane-loop
Plane
6. Accuracy of Approach
Off-target; needs more than
1 adjustment
Off-target; needs only 1
adjustment
On target
7. Coarse Tremor
Moderate-severe
Mild
Absent
0
1
3
0
1
3
4
0
2
3
0
2
3
1
1
3
3
4
0
1
3
0
1
3
Subject's Total Score
Fig. 1. Proximal-Development Assessment Scale for scoring visually guided reaching in the 30-week-old infant.
mal-development assessment scale was devised (Fig.
1) that combines findings from the observational
studies of Halverson,5 the developmental norms of
Gesell and Amatruda,16 and the scale devised by
Kopp.17 This scale attempts to define the quality of
reaching for a one-inch cube by a 30-week-old infant.
Operational definitions for the seven criteria measured on the proximal-development assessment scale,
adapted from the studies just mentioned, are as follows:
1. VISUAL ORIENTATION: Visual regard upon
presentation of the cube.
Closes eyes: infant closes eyes or looks away from
the stimulus.
Looks at hand: infant's initial response is to look at
his hand.
PHYSICAL THERAPY
Looks at stimulus: infant's initial response is to look
at the cube.
2. DIRECTION OF APPROACH: Aim of the hand
along a horizontal plane.
Circuitous: the hand, in advancing, moves laterally
during the first part of the approach and medially
during the latter part, thus describing an arc.
Moderately circuitous: same as the circuitous approach except that a curvilinear figure rather than
a full arc is described.
Slightly circuitous: the forefinger fails to point definitely at the cube throughout the approach but
swings out slightly laterally during the initial phase
of the reach.
Infant
Possible
Behavior
Points
( )
1 Aim of Thumb During Approach
Down or out
Down-in
In
At
2. Final Thumb Angle
Down or out
Down-in
In
3. First Finger Position on Cube
Fingers and thumb contact—
asynchronous
Fingers and thumb contact—
synchronous
4. Accuracy of Grasp
Precarious grasp on cube;
drops or aims and misses
Precarious grasp on cube; does
not drop
Grasps top and side of cube and
maintains accuracy
5. Finger Spread on Cube
Fingers are spread apart
Fingers are not spread apart
6. Type of Grasp
Contact
Hand
Palm
Superior-palm
Inferior-forefinger
7. Number of Contacts Prior to Securing Cube
Does not secure
3 or more
2
1
8. Fine Tremor
Moderate-severe
Mild
Absent
0
1
2
4
1
2
4
1
3
0
1
3
0
3
0
0
1
2
4
Direct: the path of the forefinger approximates a
straight line.
3. NUMBER OF LATERAL DEVIATONS: The
number of changes in direction of the hand during
the approach time.
4. AIM OF APPROACH: Aim of the forearm upon
completion of the approach.
Pronated: the forearm is pronated so that the hand
is perfectly parallel to the horizontal plane and
pointed directly at or above the cube.
Some aspect of rotation: the hand is rotated slightly
and oriented toward the cube.
Forearm rotation definitely directed at the cube: the
forearm is rotated around the sagittal axis more
than 20 degrees and oriented toward the cube.
5. VERTICAL APPROACH: Profile of the infant's
route of approach when viewed laterally.
Slide: the infant slides his hand along the tabletop.
Loop-slide: a combination of the loop (the infant
first raises his hand and then directs it toward the
cube; at the end of the motion, the hand is pulled
back instead of advancing forward) and the slide.
Plane-slide: differs from loop-slide only in that in
place of the loop, the infant uses a short planing
movement (the infant raises and projects the hand
forward simultaneously so that the hand just skims
the top surface of the cube; at the end of the
approach, the hand is still moving forward as it
settles on the cube).
Plane-loop: combination of the plane and the loop
approaches.
Plane: see definition under plane-slide.
6. ACCURACY OF APPROACH: Precision of approach measured when the infant's hand is within
two inches of the recessed portion of the board.
Adjustments: changes in the infant's hand direction
when within two inches of the recess.
7. COARSE TREMOR: Involuntary muscle contractions in the arm manifested as rhythmical alternating movements.
Moderate-severe: oscillates 8 to 10 times per second.
Mild: oscillates 3 to 5 times per second.
Distal-Function Assessment Scale
0
1
2
3
Distal function was tested by evaluating prehensile
skill in grasping and retrieving the one-inch cube, as
this involves fine motor ability. The distal-development assessment scale (Fig. 2) and the operationally
0
defined
criteria (below) for assessing hand orientation
1
and grasping and releasing abilities were based on the
3
findings in studies cited for the proximal-developSubject's Total Score
ment assessment scale.
1. AIM OF THUMB DURING APPROACH: Aim
Fig. 2. Distal-Development Assessment Scale for scoring
of the thumb-forefinger angle.
quality of grasping by the 30-week-old infant.
Volume 60 / Number 2, February 1980
169
Down or out: angle faces vertically downward or
outward away from the cube.
Down-in: angle faces partly downward and partly
inward toward the cube.
In: angle faces inward toward the cube; the thumb
consistently points toward the cube.
At: angle subtends the area occupied by the cube.
2. FINAL THUMB ANGLE: The direction of the
thumb at the moment of contact with the cube.
Down or out: the thumb is pointing downward
toward the board, with very little, if any, thumb
opposition.
Down-in: the thumb is pointing toward the cube.
In: the thumb is pointing above and toward the
cube.
3. FIRST FINGER POSITION ON CUBE: Timing
of thumb and finger contact on the cube.
Asynchronous contact: two or more fingers touch
the cube and then the thumb is brought to the cube
or the thumb touches the cube and then the fingers
are brought to it.
Synchronous contact: fingers and thumb simultaneously contact the cube.
4. ACCURACY OF GRASP: Precision of hand orientation and finger fractionation as measured in
the ability to grasp the cube securely.
Precarious grasp: an undue amount of finger or
hand maneuvers to maintain the cube securely.
Secure grasp: the infant maintains the cube securely
when he is able to lift the cube out of the recess
without dropping it or appearing to be about to
drop it.
5. FINGER SPREAD: The spread of the digits after
contact with the cube.
Fingers are apart: distance between digits is greater
than ¼ inch.
Fingers are not apart: distance between digits is less
than or equal to ¼ inch.
6. TYPE OF GRASP: Relative position of palm and
digits to the cube.
Contact: infant succeeds in touching but not securing the cube.
Hand: infant brings the pronated hand down upon
the cube and presses it firmly against the heel of
the palm. All fingers appear to be of equal importance. The cube is in the middle of the palm.
Palm: infant sets the pronated hand down on the
cube and opposes the thumb and fingers to force
the cube against the palm. The cube is off-center
and toward the radial aspect of the palm.
Superior-palm: infant sets only the radial side of
the palm down on the cube; the thumb opposes the
first two fingers to press the cube against the thumb
and palm.
Inferior-forefinger: similar to the superior-palm ex-
170
cept the digits at the end of the approach point
more medialward than downward and the cube is
no longer pressed against the palm.
7. NUMBER OF CONTACTS BEFORE SECURING CUBE: Number of times the infant contacts
the cube, measured from the initial contact until
the child retrieves it out of the recessed area.
8. FINE TREMOR: Involuntary muscle contractions
in the hand manifested as rhythmical alternating
movements.
Moderate-severe: oscillates 8 to 10 times per second.
Mild: oscillates 3 to 5 times per second.
Equipment
The criteria for both scales assess the quality of
movements demonstrated when the infant reaches for
a red one-inch cube contained in the recessed area of
the Kuypers-like form board. This board is a modification of the apparatus used to minimize tactile
"cuing" and to distinguish proximal and distal function in split-brain monkeys attempting to retrieve
food pellets.13 However, compared to the original
model, the board used in this study was very simple,
in accordance with the expected achievement for the
age group under study. Specifically, the apparatus
used was a yellow board measuring 12 in. by 16 in.
by 2 in. (30.48 cm × 40.64 cm × 5.08 cm), with one
centered recess with a diameter of 3 in. (7.62 cm) and
a depth of 1 in. (2.54 cm). In addition, the board was
stabilized on adjustable legs to allow for height adjustment for each subject.
Assessment Procedure
All infants were seen at home. They were seated
on their mothers' laps and the Kuypers-like board
was placed in front of them and adjusted to waist
level. A videotape camera with a zoom lens was used
to record the infants' behavior. All infants were examined when awake, cooperative, and anticipating.
The infant was allowed a brief period to adapt to
the situation and to the examiner, after which his
attention was obtained by the mother's calling the
child's name. The mother next placed the infant's
hands on the near edge of the board and then deposited the one-inch cube into the recessed area of the
board. This procedure was followed for four trials.
Half of the subjects were videotaped with the camera
facing directly in front of them for trials 1 and 2 and
with the camera filming a lateral view during trials 3
and 4. The other half of the subjects were videotaped
from a lateral view on trials 1 and 2 and an anterior
view for trials 3 and 4. This counterbalancing was
intended to compensate for the effects of fatigue and
PHYSICAL THERAPY
practice during the procedure. A two- to three-minute
rest period was given after the first two trials and then
the infant's attention was again obtained by the
method described.
For videotape analysis, the more successful of the
two trials for each anterior view was scored. The same
criterion was used in selecting the lateral view for
scoring. Success was defined in terms of the infant's
accomplishment in securing and retrieving the cube.
The videotaped responses of three of the subjects
were previewed by two unbiased raters (one physical
therapist and one occupational therapist) to evaluate
interrater reliability. The raters were in 96 percent
agreement on the proximal-development assessment
scale and in 88 percent agreement on the distal-development asssessment scale.
RESULTS
On both the proximal-development and distal-development scales, mean scores of boys were compared
to mean scores of girls. A nondirectional t test revealed no statistically significant difference between
the two groups on either scale (on both scales, t =
2.23, df = 10, NS).18 Consequently, boys and girls
were treated as one group for all subsequent analyses.
To assess the relationship between proximal and
distal function in the 30-week-old infant, the Pearson
product-moment coefficient of correlation was used.
Analysis of the data (Table) revealed no statistically
significant correlation (r = .37) between visually
guided reaching ability and prehensile skill (if df =
10 on a one-tailed test, an r of .497 is required for p
= .05).
With the exception of two subjects, all subjects
looked at the cube when it was first presented and
throughout the majority of the test session. Most
TABLE
Individual Scores on Proximal and Distal Scales
Subject
Proximal Score
( = 17.58,
s = 3.37)
Distal Score
( = 14.75,
s = 4.12)
1
2
3
4
5
6
7
8
9
10
17
10
14
21
16
21
22
18
18
16
11
8
13
14
21
19
14
21
16
16
11
18
10
12
20
14
Volume 60 / Number 2, February 1980
infants used a slightly circuitous direction when approaching the cube and all subjects required two or
less changes in direction to reach the cube. Some
degree of forearm rotation was seen in nine infants
upon initial entry of their hand into the recessed area.
In their distal function, most infants maintained
their thumbs in abduction with lack of opposition
during the approach phase, although half of the
infants did oppose the thumb to some extent upon
initial contact with the cube. Seven subjects contacted
the cube asynchronously with regard to fingers and
thumb timing, whereas five infants did so synchronously.
Half of the infants were able to grasp the cube
securely, but the other half were not. The most common grasp, the superior-palm, was exhibited by eight
younsters. These children set only the radial side of
the palm down on the cube and used the thumb to
oppose the first two fingers, which pressed the cube
against the thumb and palm. Three infants did use
the more advanced inferior-finger grasping pattern.
Upon retrieving the cube, all infants brought it to
their mouths and explored it orally. Manual tactual
exploration was minimal.
DISCUSSION
The results of this study of 30-week-old human
infants do not support the proximo-distal hypothesis
of a relationship between reach and prehension. The
lack of a statistically and clinically significant relationship between proximal and distal motor function
suggests that proximal development is not a prerequisite for distal motor development. The theory that
distal skill emerges out of and depends on proximal
control is not confirmed by the findings of this study.
Furthermore, these findings tend to support the theory of a dual motor control mechanism in the developing human infant. The existence of two motor
systems operating during development—that is, a
proximal system controlling visually guided reaching
ability and a distal system controlling prehensile
skill—is very possible in light of this data. Kuypers'
model,10 which was formulated from animal experimentation12,13 and applied to the human adult,14 now
also appears to apply to the developing human infant.
This study, in conjunction with the findings of
research on animals and human adults cited above,
raises legitimate doubts about the rationale behind
proximo-distal treatment sequences. Clearly, the time
has come to reexamine therapeutic approaches to
motor impairment in light of the findings of these
studies. Perhaps we should no longer look at the
proximal and distal systems as one mechanism, but
rather seek new means of evaluating each function
171
separately. Treatment protocols should perhaps consider proximal and distal function individually with
regard to goals and pace of progression. For example,
in treating an individual with deficits in visually
guided reaching and prehensile skills, a therapist
would perhaps use facilitation techniques to enhance
proximal and distal control simultaneously, adhering
to the developmental sequence of each individual
system rather than emphasizing proximal improvement as a necessary prerequisite for distal recovery.
Obviously, at some point, therapy must work on the
integration of these two functions.
The dissociation of proximal and distal motor-control systems offers a possible explanation for several
clinical observations. The adult with good recovery
of hand function and little or no proximal recovery
following a cerebral vascular accident has long been
an enigma to the clinician. A similar pattern of return
has been noted in the child recovering from diffuse
head trauma and coma.
The possibility of two motor control systems with
different functions raises many further research concerns. For example, when and how do two systems
become integrated? Can and do the systems ever
operate independently? Also, can the systems be dissociated, as evidenced by damage to one, particularly
with sparing of the more sophisticated and complex
distal system?
The behaviors noted in these 30-week-old infants
confirm early developmental observations. For example, visual attention directed toward the stimulus
object for long periods is a common behavior at this
age,5 as is the predominance of oral exploration.16 In
their proximal function, those infants who were comparatively advanced used economy of space and effort. With regard to distal function, a progressive
differentiation of the thumb and index finger in grasp
and a progressive use of the digits without involvement of the palm were observed in advanced, compared to less advanced, infants. Even the most advanced infants tended to abduct their thumbs during
reach and did not use thumb rotation and opposition
until the cube was contacted. Apparently, visual guidance is not sufficient in the 30-week-old to orient the
172
thumb for grasp, and tactile input is required to call
forth the thumb action. One would expect that, later
in development, the sensory inputs become integrated
and vision alone can program the thumb position.
Acknowledgments. The author wishes to thank
Jane Coryell, PhD, and Shirley Stockmeyer for their
advice in the writing of this article.
REFERENCES
1. Coghill GE: Early development of behavior in amblystoma
and in man. Archives of Neurology and Psychiatry 2 1 : 9 8 9 1009, 1929
2. Irwin OC: Proximodistal differentiation of limbs in young
organisms. Psychol Rev 40:467-477, 1933
3. Castner BM: Development of fine prehension in infancy.
Genet Psychol Monogr 1 2 : 1 0 5 - 1 9 3 , 1932
4. Gesell A: The Mental Growth of the Pre-school Child. New
York, Macmillan Publishing Co, Inc, 1925
5. Halverson HM: Experimental study in prehension in infants
by means of systematic cinema records. Genet Psychol
Monogr 10:107-286, 1931
6. McCraw M: Grasping in infants and the proximo-distal course
of growth. Psychol Rev 4 0 : 3 0 1 - 3 0 2 , 1933
7. Ayres AJ: Ontogenetic principles in the development of arm
and hand functions. Am J Occup Ther 8:95-99, 1954
8. Stockmeyer SA: An interpretation of the approach of Rood
to the treatment of neuromuscular dysfunction. Am J Phys
Med 46(1):900-956, 1967
9. Bobath B: Facilitation of normal postural reactions and movement in the treatment of cerebral palsy. Physiotherapy 50:
2 4 6 - 2 6 2 , 1964
10. Kuypers HGJM: Organization of the motor system. Int J
Neurol 4 : 7 8 - 9 1 , 1963
11. Lawrence DG, Kuypers HGJM: Functional organization of
the motor system in the monkey: 1. The effects of bilateral
pyramidal lesions. 2. The effects of lesions of the descending
brainstem pathways. Brain 9 1 : 1 - 3 6 , 1968
12. Brinkman J, Kuypers HGJM: Cerebral control of contralateral
and ipsilateral arm, hand and finger movements in the splitbrain rhesus monkey. Brain 96:653-674, 1973
13. Brinkman J, Kuypers HGJM: Motor control in split-brain
monkeys. Brain 96:675-694, 1973
14. Gazzaniga MS: The Bisected Brain. New York, AppletonCentury-Crofts, 1970
15. Touwen BCL: Neurological Development in Infancy. London,
Spastics International Medical Publications, 1976, pp 3 8 - 4 5
16. Gesell A, Amatruda CS: Developmental Diagnosis: Normal
and Abnormal Child Development. New York, Paul B. Hober
Inc, 1947, pp 4 4 - 5 8
17. Kopp CB: Fine motor abilities in infants. Dev Med Child
Neurol 16:629-636, 1974
18. McCall RB: Fundamental Statistics for Psychology. New
York, Harcourt Brace Jovanovich, Inc, 1975, pp 119, 215,
222-223
PHYSICAL THERAPY