Relationship Between Antigravity Control and Postural Control in Young Children

JEANNE S. SELLERS

The purposes of this study were 1) to determine the relationship between antigravity control (supine flexion and prone extension) and postural control (static and dynamic balance), 2) to determine the quality of antigravity and postural control, and 3) to determine whether sex and ethnic group differences correlate with differences in antigravity control and postural control in young children. I tested 107 black, Hispanic, and Caucasian children in a Head Start program, with a mean age of 61 months. The study results showed significant relationships between antigravity control and postural control. Subjects' supine flexion performance was significantly related to the quantity and quality of their static and dynamic balance performance, whereas prone extension performance was related only to the quality of dynamic balance performance. Quality scale measurements (r = .90) indicated that the children in this study had not yet developed full antigravity or postural control. The study results revealed differ­ences between sexes in the quality of static balance and prone extension performance and ethnic differences in static balance, dynamic balance, and prone extension performance.

Key Words: Child development; Pediatrics, development; Pediatrics, evaluation.

Development of skilled movement patterns requires com­plex and subtle postural adjustments and head, trunk, and limb interaction to maintain the body over its center of gravity.1 Bly noted that the development of antigravity mus­cular control is critical to normal motor development during the first year of life.2 Movement against gravity begins during the first month of life, and by 4 months of age increased flexion control balances the strong extensor muscle patterns. Adequate development of trunk flexion and extension is a prerequisite to the development of anterior and posterior pelvic tilting, lateral trunk flexion, and trunk elongation.2

These components enable the child to develop weight shifting, which in turn stimulates righting and equilibrium responses.3,4

Children with balance and coordination problems often have difficulty controlling posture in static and dynamic situations.1,5,6 Antigravity postures of prone extension and supine flexion have been used by some physical therapists to determine the integration of the tonic labyrinthine reflex, the vestibular system, and postural control.1,7-9 Studies have shown that awkward children and children with learning disabilities have considerable difficulty controlling antigravity postures of supine flexion and prone extension,1,6,10 and phys­ical therapists often use activities that aid in the development of these two antigravity postures. Most of the recent studies examining the duration, quality, and control of antigravity postures in children 4 to 8 years of age have included prone extension in their procedures.3,11-14 Only two of these studies, however, also included a supine flexion posture.1314 As noted by Bly, a paucity of research exists on the supine flexion

posture.2 No studies were found on the possible relationship between antigravity control and balance in children.

Two studies of the duration and quality of the prone extension posture showed that children under 6 years of age had less control than children 6 years of age or older.1112

Dunn found that kindergarten-aged children had difficulty assuming the prone extension posture with their legs fully extended but had little difficulty controlling supine flexion.13

The literature presents conflicting results about sex differ­ences in studies of prone extension posture. One study of 4-to 8-year-old children reported no differences in prone exten­sion duration and quality scores between the sexes,11 but another study of the same age group reported that girls had better prone extension duration scores than boys.12

Balance development has been of particular interest to researchers for many years and is often used to assess postural control.1'91516 One-foot standing, balance beam walking, sta-biliometry, and hopping have been used to assess balance. Balance improves quantitatively with age. Analysis of a wide range of balance tasks has revealed few differences in balance development between boys and girls,15,16 although girls tend to perform better than boys on specific static balance tasks.l5,17

Research on motor development by ethnic group has been inconclusive. In the United States, black and Caucasian sub­jects have been studied more than other ethnic groups.16 One study that standardized prone extension performance in pre­dominantly Hispanic or Caucasian children aged 4 to 8 years reported no ethnic differences in prone extension perform­ance.12 Capute et al made a longitudinal study of children 2 weeks to 24 months of age and reported that black children achieved motor milestones at an earlier age than Caucasian children.18 Studies cited by Haywood have shown that black children do not sustain a motoric advantage over time.16

Whether differences in control of antigravity postures and balance exist among children in various ethnic groups is unknown.

J. Sellers, EdD, is Director, Motor Development Program, and an adjunct faculty member, Department of Health and Physical Education, The University of Texas at Tyler, 3900 University Blvd, Tyler, TX 75701. Address correspond­ence to Rt 25, PO Box 980, Tyler, TX 75707 (USA).

This article was submitted October 7, 1986; was with the author for revision 14 weeks; and was accepted July 8, 1987. Potential Conflict of Interest: 4.

486 PHYSICAL THERAPY

RESEARCH The quality of movement patterns is more important to

physical therapists than the quantity of movement, and reli­able qualitative measures are needed to help physical thera­pists make objective assessments. The only movement quality rating scale available for antigravity control is a six-category scale for prone extension performance,11,12 and no movement quality scales were found for supine flexion or balance tasks.

The purposes of this study were 1) to determine the rela­tionship between antigravity control and postural control, 2) to determine the quality of antigravity control and postural control, and 3) to determine whether sex and ethnic group variables are related to differences in antigravity control and postural control in young children. Postural control is defined in this study as the ability to maintain static and dynamic balance postures. Antigravity control is the ability to maintain static prone extension and supine flexion postures. I hypoth­esized that no significant relationship would exist between balance and postural control and that no differences would exist between sex and ethnic groups on the tasks examined. The quality of antigravity and postural control was expected to be less developed in young children than in older children.

METHOD

Subjects One hundred seven children in a Head Start program (52

boys, 55 girls) participated in this study. The subjects ranged in age from 50 to 66 months ( =61 months), and the sample consisted of 79 black children (74%), 22 Hispanic children

(21%), and 6 Caucasian children (6%). The Head Start pro­gram director and school officials approved the study design.

Procedure

I divided the subjects into groups of 3 to 4 children and tested each group in a quiet area outside the classroom. A four-point quality scale was devised to determine the quality of antigravity and postural control for 1) static balance, 2) dynamic balance, 3) prone extension, and 4) supine flexion tasks. The scale was similar to one used in a previous study.19

The scale ranged from 0, indicating inability to perform the task, to 3, indicating controlled and smooth execution of the task (Appendix). Interrater reliability was determined using a videotape of two children who were not subjects in the study. Six education students in an undergraduate motor develop­ment class rated the two children's antigravity and postural control, and a Spearman rank order correlation coefficient showed high interrater reliability (r = .90).

Each subject watched the examiner (J.S.S.) demonstrate the study tasks and performed a practice trial before being tested individually on static balance, dynamic balance, prone exten­sion, and supine flexion tasks. I recorded quantitative meas­urements to the nearest second for static balance, prone extension, and supine flexion and assessed qualitative scores for each task. Static balance quality was based on the perform­ance of the better leg.

Static balance. I asked the subjects to stand on their right foot with their eyes open and arms to the side for 30 seconds.

TABLE 1 Means and Standard Deviations for Antigravity and Postural Control

Taska

SBLb

s SBRb

s SBQ

s DB

s DBQ

s PEb

s PEQ

s SFb

s SFQ

s

Sex

Boys (n = 52)

10.96 6.81

10.75 7.88

2.00 0.66

0.27 0.59

2.69 0.53

9.86 7.15

1.68 0.87

14.18 6.30

2.39 0.62

Girls (n = 55)

10.23 7.03

11.56 7.59

2.28 0.56

0.21 0.45

2.16 0.56

10.65 7.62

2.01 0.79

16.40 4.30

2.60 0.49

Black (n = 79)

11.47 5.38

12.07 8.17

2.08 0.62

0.29 0.65

2.06 0.53

9.60 7.57

1.79 0.87

18.00 5.67

2.45 0.59

Race

Hispanic (n = 22)

7.90 4.25

8.72 5.44

2.18 0.64

0.13 0.34

2.27 0.54

12.59 6.95

2.04 0.56

15.31 5.10

2.59 0.49

Caucasian (n = 6)

7.50 6.40

8.33 5.55

2.16 0.37

0.00 0.00

2.66 0.47

12.61 5.01

2.00 0.79

18.66 1.49

2.66 0.47

Age (yr)

4 (n = 35)

10.00 8.74

9.63 7.05

2.02 0.70

0.38 0.68

2.08 0.61

10.02 7.79

1.67 0.81

16.67 5.27

2.57 0.55

5 (n = 72)

10.56 8.74

11.56 7.68

2.05 0.71

0.34 0.89

2.12 0.52

9.93 7.27

1.90 0.80

14.91 5.52

2.44 0.57

Total (N = 107)

10.52 6.70

11.25 7.76

2.08 0.65

0.26 0.56

2.11 0.59

10.27 7.41

1.88 0.79

15.13 5.58

2.43 0.66

a SBL = static balance left; SBR = static balance right; SBQ = static balance quality; DB = dynamic balance; DBQ = dynamic balance quality; PE = prone extension; PEQ = prone extension quality; SF = supine flexion; SFQ = supine extension quality.

b Measured in seconds.

Volume 68 / Number 4, April 1988 487

Testing was halted and the time was recorded when the subject's nonsupport foot touched the floor or when the support foot moved. The test was then repeated for the left foot.

Dynamic balance. I used a balance beam 2.4 m long, 10 cm wide, and 10 cm from the floor for this task. I asked subjects to walk the length of the beam with alternating steps, stepping back onto the beam if one foot or both feet touched the floor. A score of 0 was assigned if the child walked the length of the beam without stepping off. One point was assigned each time one foot or both feet touched the floor.

Prone extension. I instructed subjects to lift their head, chest, arms, and legs off the floor from a prone position for 20 seconds. Subjects' arms were abducted to about 90 degrees with the forearms flexed, and the legs fully extended. Testing was stopped and the time recorded when the subject's knees, arms, or chest touched the floor.

Supine flexion. I asked subjects to flex their head, arms, and legs into a curled position from a supine position for 20 seconds. Subjects folded their arms across their chest and were not allowed to hold their legs. Testing was stopped and the time recorded when the subject's head or one foot touched the floor or the arms moved from their original position.

Data Analysis

I used Kendall's rank order correlation to determine whether significant relationships existed between antigravity control and postural control. The Mann-Whitney U test was used to determine the source of any differences.

RESULTS

Table 1 shows a descriptive analysis of the data. Kendall's rank order correlation showed significant relationships be­tween antigravity control and postural control (Tab. 2). Dy­namic balance quality was significantly related to prone ex­tension, prone extension quality, and supine flexion (p < .01). Static balance right and static balance quality were also related to supine flexion (p < .05 and p < .001). Static balance left and dynamic balance were not significantly related to antigravity control. Supine flexion quality was the only anti-gravity task that was not significantly related to postural control.

No significant differences in antigravity or postural control existed for age, but differences were found between sex and ethnic groups (Tab. 3). The Mann-Whitney U test on these data revealed the source of these differences (Tab. 4). Differ-

TABLE 2 Kendall's Rank Order Correlation Between Antigravity and Postural Control*

Antigravity Control6

SBL SBR SBQ DB DBQ

PE

.19e

Postural Control

PEQ

.15e

SF

.11c

27d

.16e

SFQ

ences in static balance quality (p < .011) and prone extension quality (p < .041) were found between boys and girls. Black and Hispanic subjects differed in static balance left (p < .03), and black and Caucasian subjects differed in dynamic balance quality (p < .037). Differences were also found between Caucasian and Hispanic subjects in prone extension (p < .045).

The mean movement quality score for subjects was between 2 and 3 on three tasks (static balance quality, = 2.08; dynamic balance quality, =2.11; supine flexion quality, = 2.43), with the score for one task (prone extension quality,

= 1.88) between 1 and 2 (Tab. 1). Twenty-three children (20%) achieved a score of 3 on the prone extension task, and 55 children (51%) scored a 3 on the supine flexion task. I recorded a score of 0 for only 6 children (6%) on the prone extension task and for no children on the supine flexion task. The mean quality static and dynamic balance score was 2 (static balance, = 2.08; dynamic balance, = 2.11). No subject received a score of 0 on either balance task.

DISCUSSION

Antigravity and Postural Control Significant relationships between antigravity control and

postural control would support Bly's hypothesis that the at-

TABLE 3 Kendall's Rank Order Correlation Between Antigravity and Postural Control, Sex, and Ethnicitya

Controlb

SBL SBQ DBQ PE PEQ

Sex

.17d

.24c

Ethnicity

.16c

.12d

.40d

TABLE 4 Mann-Whitney U-Test Results Comparing Antigravity and. Postural Control by Sex and Ethnicity

Controla

Sex SBQ

Female Male

PEQ Female Male

Ethnicity SBL

Black Hispanic

DBQ White Hispanic

PE Hispanic Black

Rank

59.15 49.41

49.76 47.90

53.76 40.77

19.00 13.27

60.14 48.46

Z

1.96

1.97

1.85

1.51

1.65

P

.01

.04

.03

.04

.04

a Only significant values are reported. b See Table 1 for abbreviation key. cp<.05. dp<.001. e p< .01 .

a Only significant values are reported. b See Table 1 for abbreviation key. c p < . 0 1 . * p < . 0 5 .

a See Table 1 for abbreviation key.

488 PHYSICAL THERAPY

RESEARCH tainment of antigravity control is essential to the normal motor development of children.2 This study showed that supine flexion was the only antigravity posture significantly related to static and dynamic balance (static balance right, static balance quality, and dynamic balance quality), whereas prone extension and prone extension quality were signifi­cantly related only to dynamic balance quality. The supine flexion and prone extension postures were related more to the quality of postural control than to the quantity of postural control. These results suggest that the prone extension posture, which has received considerable attention in the literature, may be less important to postural control than the supine flexion position, especially for development of the quality of movement.

The mean prone extension score for 4-year-old subjects in this study (10.02 seconds) was lower than the mean scores reported in another study (18.15 seconds).10 No other studies reported mean prone extension scores for 5-year-old children. The mean supine flexion scores for 4- and 5-year-old subjects in this study were lower than the mean scores reported by Lefkof.14 The 4-year-old subjects in this study had slightly higher scores on the prone extension and supine flexion tasks than the 5-year-old subjects, contrary to most studies of motor development.11,12,14-17 The cause for this discrepency is un­known; however, the 4-year-old subjects tended to try their best more consistently than the 5-year-old subjects.

The supine flexion posture was easier for the subjects to maintain than the prone extension posture. Only 2 children in this study were unable to assume the supine flexion posture; however, 20 children failed to assume the prone extension posture. Some children complained of neck discomfort after the supine flexion test. Neck discomfort has also been reported in another study.14

Subjects' static balance mean duration scores were lower in this study than in other studies. Stott and associates studied 5-year-old children and reported a combined mean static balance score for both legs to be 15.6 seconds.20 The combined mean score for this study was 10.7 seconds. Morris and associates reported a considerable increase in static balance scores in children aged 4 to 5 years.17 This study found a very small increase in static balance scores with age.

Dynamic balance was relatively stable for the subjects in this study. Eighty-four subjects (79%) walked on the balance beam without stepping off. Nineteen subjects (18%) stepped off the balance beam only once. These duration scores may be somewhat misleading, because the subjects in this study were very familiar with the balance beam. One child, who stepped off the balance beam three times, had only recently enrolled in the Head Start program and may not have been as familiar with this task as the other children.

Quality of Movement

Mean movement quality scores for the four antigravity and postural control tasks ranged from 1.88 to 2.43, indicating that these skills were not yet fully developed in my subjects (Tab. 1). This finding agrees with those of other studies.11-13

Dunn noted that kindergarten-aged children had difficulty lifting their legs with their knees extended when attempting a prone extension posture,13 and I have seen this pattern re­peated clinically. Shambes reported that 4-year-old children could not suppress extraneous muscular activity during static postural tasks when compared with 8-year-old children.9 The knees of younger children often may be flexed because they

have not learned to fully suppress the flexor component of the hamstring muscles.

Development of the quality of gross motor skills has been of recent interest to researchers,15,16 although no reliable movement quality scales have been developed. The move­ment quality scale used in this study was reliable (r = .90) and easy to use. The scale was based on clinical experience in assessing young children on the tasks used in this study. Use of such a scale allows the pediatric physical therapist to make objective qualitative measurements of antigravity and pos­tural control.

Sex and Ethnic Differences

The only sex differences this study revealed were in the quality of static balance and prone extension posture, where girls ranked slightly higher than boys. The sex difference in the prone extension posture differs from the findings of an­other study.12 Although sex differences for static balance have been reported on quantity scores,15,17 girls would also appear to be better on the quality of static balance than boys. The results of this study may have been distorted because static balance quality was based on the performance of the leg with the best quantitative score. Future researchers should measure both left and right leg static balancing.

The results of this study revealed definite differences be­tween ethnic groups on antigravity and postural control. No previous studies on antigravity control have reported ethnic data. The black and Hispanic subjects in this study differed in static balance left and prone extension tasks, and Caucasian subjects differed from Hispanic subjects in static balance quality. Examination of the mean static balance scores re­vealed that black subjects scored considerably higher than Hispanic or Caucasian subjects, whose scores were similar (Tab. 1). Caucasian subjects demonstrated a higher dynamic balance quality score than the black or Hispanic subjects, possibly because they walked on the beam without stepping off. The ethnic differences in antigravity and postural control did not indicate consistency between groups.

Study Limitations

This study used children in one Head Start program as subjects. The children were not tested to ascertain whether motor dysfunctions were present, although none of the sub­jects had obvious orthopedic or neurological problems. I assumed that the subjects were motorically healthy. Retesting of the subjects was not possible, and reliability could not be determined for the tasks measured.

The low number of Caucasian subjects in this study may have affected the study results. A significant within-group difference in dynamic balance quality existed among Cauca­sian subjects. Generalizations of this study, therefore, should be made cautiously.

Clinical Implications

Antigravity postures are an important element in the nor­mal motor development of children aged 4 to 5 years. Physical therapists should examine prone extension and supine flexion postures carefully when evaluating children and treat areas where a postural deficiency exists. Careful examination and treatment are especially critical for children with motor dys­functions. This study showed that the supine flexion and

Volume 68 / Number 4, April 1988 489

prone extension postures are significantly related to balance, especially the quality of these movement patterns.

Although several researchers have examined the develop­ment of the prone extension posture in young children, more research is needed on supine flexion development. This study presents some normative data of interest to pediatric physical therapists. Young children will have more difficulty with prone extension tasks than with supine flexion tasks, and the quality of these antigravity postures will be less developed in young children than in older children.

A scale for measuring the quality of antigravity and postural control was found to be reliable and easy to use. Physical therapists can use the quality scale with quantity measure­ments to document improvement in both the quality and quantity of a child's movements.

Implications for Further Research

More research is needed on postural control. The results of this study raise two questions: 1) Does improvement of anti-gravity postures significantly improve static and dynamic balance in healthy children and children with motor dysfunc­tion? and 2) Does the relationship between antigravity and postural control continue with increasing age? Equal numbers of Caucasian, black, and Hispanic subjects should be exam­ined to determine whether the ethnic differences in antigravity and postural control in this study are reliable.

CONCLUSIONS

A study of 107 children aged 4 and 5 years old in a Head Start program showed that antigravity control (prone exten­sion and supine flexion) was significantly related to postural control (static and dynamic balance). Supine flexion was significantly related to static and dynamic balance, whereas prone extension was significantly related to dynamic balance. Both supine flexion and prone extension were related to the quality of static and dynamic balance.

The subjects' quality of movement ranged from 1.88 to 2.43 on a four-category scale. The subjects in this study had difficulty executing prone extension with their legs fully ex­tended, and had not developed the quality of movement of older children in other studies. Dynamic balance was more developed in the subjects than static balance. Significant sex differences were found in quality of prone extension and static balance, and significant ethnic differences were found in static balance left, dynamic balance quality, and prone extension. Further research is needed on the development of antigrav­ity control, especially the supine flexion posture, in children.

REFERENCES 1. Williams HG, Fisher JM, Tritschler KA: Descriptive analysis of static pos­

tural control in 4, 6, and 8 year old normal and motorically awkward children. Am J Phys Med 62:12-26,1983

2. Bly L: The Components of Normal Movement During the First Year of Life and Abnormal Motor Development. Birmingham, AL, Pittenger and Asso­ciates Pathway Press, 1983

3. Gilfoyle EM, Grady AP, Moore JC: Children Adapt, ed 2. Thorofare, NJ, Slack Inc. 1985

4. Stockmeyer SA: A sensorimotor approach to treatment. In Pearson PH, Williams CE (eds): Physical Therapy Services in the Developmental Disa­bilities, ed 5. Springfield, IL, Charles C Thomas, Publisher, 1977, pp 186-282

5. deQuiros JB, Schrager OL: Neurophysiological Fundamentals in Learning Disabilities. Novato, CA, Academic Therapy Publications, 1979

6. Ayres AJ: Sensory Integration and Learning Disorders, ed 6. Los Angeles, CA, Western Psychological Services, 1978

7. Barnes MR, Crutchfield CA, Heriza CB: Neurophysiological Basis of Patient Treatment: Reflexes in Motor Development, ed 3. Atlanta, GA, Stokesville Publishing Co, 1982, vol 2

8. Montgomery PC: Assessment of vestibular function in children. Physical and Occupational Therapy in Pediatrics 5(2/3):33-55,1985

9. Shambes GM: Static postural control in children. Am J Phys Med 55:221-252,1976

10. Sellers JS: Incidence of Incomplete Integration of Selected Primitive Re­flexes in Children with Gross Motor Delay. Read at the Southern District Convention, American Alliance of Health, Physical Education, Recreation, and Dance, Biloxi, MS, February 1984

11. Harris NP: Duration and quality of the prone extension position in four-, six-, and eight-year-old normal children. Am J Occup Ther 35:26-30,1981

12. Gergory-Flock JL, Yerza EJ: Standardization of the prone extension pos­tural test on children ages 4 through 8. Am J Occup Ther 38:187-194, 1984

13. Dunn W: A Guide to Testing Clinical Observations in Kindergarten. Guilford, CT, American Occupational Therapy Association, Inc, 1981

14. Lefkof MB: Trunk flexion in healthy children aged 3 to 7 years. Phys Ther 66:39-44,1986

15. Williams HG: Perceptual and Motor Development. Englewood Cliffs, NJ, Prentice-Hall Inc, 1983

16. Haywood KM: Life Span Motor Development. Champaign, IL, Human Kinetics Publishers Inc, 1986

17. Morris AM, Williams JM, Atwater AE, et al: Age and sex differences in motor performance of 3 through 6 year old children. Research Quarterly for Exercise and Sport 53:214-221,1982

18. Capute AJ, Shapira BK, Palmer FB, et al: Normal gross motor development: The influences of race, sex and socioeconomic status. Dev Med Child Neurol 27:635-643,1985

19. Parmenter CL: An asymmetrical tonic neck reflex rating scale. Am J Occup Ther 37:462-465,1983

20. Stott DH, Moyes FA, Henderson SE: Test of Motor Impairment: Henderson Revision. Guelph, Ontario, Canada, Brook Educational Publishing Ltd, 1984

APPENDIX Quality Scale for Antigravity and Postural Control Tasks

Static Balance

0-Unable to lift foot from floor 1-Excessive movements of arms and trunk or holding or supporting

nonsupport foot 2-Arms and trunk used moderately to regain balance; nonsupport

leg held between 45 and 90 degrees 3-Minimal or no body movements; arms relaxed at sides

Dynamic Balance

0-Unable to walk on balance beam 1-Movements jerky; excessive arm and trunk movements to main­

tain balance 2-Moderate arm and trunk movements 3-Walks smoothly, arms and trunk relaxed, uses reciprocal gait

Prone Extension

0—Unable to lift any body segments or lifts only one body segment at a time

1 -Head, chest, and arms extended off floor; unable to lift legs off floor

2-Head, chest, and arms raised symmetrically off floor; thighs lifted, but knees bent

3-Extends body smoothly and symmetrically

Supine Flexion

0-Unable to lift any body segments off floor or lifts only one segment at a time

1-Difficulty lifting head off floor; limb movements asymmetrical 2-Maintains position with some difficulty; may roll to one or both

sides 3-Flexes body smoothly and symmetrically

490 PHYSICAL THERAPY