Abstract
OBJECTIVE:
The purpose of this study was to compare postural control in typically developing (TD) children and children with cerebral palsy (CP) during the sit-to-stand (STS) movement and to assess the relationship between static (during static standing position) and dynamic postural control (during STS movement) in both groups.
METHOD:
The center of pressure (CoP) behavior of 23 TD children and 6 children with spastic hemiplegic CP (Gross Motor Function Classification System [GMFCS] I and II) was assessed during STS movement performance and during static standing conditions with the use of a force plate. The data obtained from the force plate were used to calculate CoP variables: anteroposterior (AP) and mediolateral (ML) amplitudes of CoP displacement and the area and velocity of CoP oscillation.
RESULTS:
According to the Mann-Whitney test, children with CP exhibited higher CoP values in all of the analyzed variables during the beginning of STS movement. Pearson's correlation verified a positive correlation between the CoP variables during both static conditions and the performance of STS movement.
CONCLUSIONS:
Children with spastic hemiplegic CP present major postural oscillations during the beginning of STS movement compared with typical children. Moreover, the observed relationship between postural control in static and dynamic conditions reveals the importance of body control in the static position for the performance of functional activities that put the body in motion, such as STS movement.
hemiplegic spastic cerebral palsy; postural control; sit-to-stand movement; children; functional activity; rehabilitation
Introduction
Children with cerebral palsy (CP) exhibit neuromotor disorders11. Barela JA, Focks GMJ, Hilgeholt T, Barela AMF, Carvalho RP,
Savelsbergh GJP. Perception-action and adaptation in postural control of children and
adolescents with cerebral palsy. Res Dev Disabil. 2011;32(6):2075-83.
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2. Verschuren O, Ada L, Maltais DB, Gorter JW, Scianni A, Ketelaar M.
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33. Tammik K, Matlep M, Ereline J, Gapeyeva H, Pääsuke M. Muscle
contractile properties in children with spastic diplegia. Brain Dev.
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, among which postural control deficits have a
central role44. Woollacott MH, Shumway-Cook A. Postural dysfunction during standing
and walking in children with cerebral palsy: what are the underlying problems and
what new therapies might improve balance? Neural Plast. 2005;12(2-3):211-9,
discussion 263-72. http://dx.doi.org/10.1155/NP.2005.211.
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,
55. Carlberg EB, Hadders-Algra M. Postural dysfunction in children with
cerebral palsy: some implications for therapeutic guidance. Neural Plast.
2005;12(2-3):221-8; discussion 263-72. PMid:16097490.. The postural control deficits observed in this
population result in important limitations to daily functional activities66. Ostensjø S, Carlberg EB, Vøllestad NK. Motor impairments in young
children with cerebral palsy: relationship to gross motor function and everyday
activities. Dev Med Child Neurol. 2004;46(9):580-9.
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because postural alignment and stability are
requirements for voluntary movement77. Ju YH, You JY, Cherng RJ. Effect of task constraint on reaching
performance in children with spastic diplegic cerebral palsy. Res Dev Disabil.
2010;31(5):1076-82. http://dx.doi.org/10.1016/j.ridd.2010.04.001.
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,
88. Liao HF, Hwang AW. Relations of balance function and gross motor
ability for children with cerebral palsy. Percept Mot Skills. 2003;96(3 Pt
2):1173-84. http://dx.doi.org/10.2466/pms.2003.96.3c.1173.
PMid:12929770
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.
Although there is a wide description of postural control in CP in the literature44. Woollacott MH, Shumway-Cook A. Postural dysfunction during standing
and walking in children with cerebral palsy: what are the underlying problems and
what new therapies might improve balance? Neural Plast. 2005;12(2-3):211-9,
discussion 263-72. http://dx.doi.org/10.1155/NP.2005.211.
PMid:16097489
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,
99. Burtner PA, Woollacott MH, Qualls C. Stance balance control with
orthoses in a group of children with spastic cerebral palsy. Dev Med Child Neurol.
1999;41(11):748-57. http://dx.doi.org/10.1017/S0012162299001516.
PMid:10576639
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, most studies assessed children in static
posture1010. Donker SF, Ledebt A, Roerdink M, Savelsbergh GJP, Beek PJ. Children
with cerebral palsy exhibit greater and more regular postural sway than typically
developing children. Exp Brain Res. 2008;184(3):363-70.
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11. Ferdjallah M, Harris GF, Smith P, Wertsch JJ. Analysis of postural
control synergies during quiet standing in healthy children and children with
cerebral palsy. Clin Biomech (Bristol, Avon). 2002;17(3):203-10.
http://dx.doi.org/10.1016/S0268-0033(01)00121-8. PMid:11937258
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-
1212. Rose J, Wolff DR, Jones VK, Bloch DA, Oehlert JW, Gamble JG.
Postural balance in children with cerebral palsy. Dev Med Child Neurol.
2002;44(1):58-63. http://dx.doi.org/10.1017/S0012162201001669.
PMid:11811652
http://dx.doi.org/10.1017/S0012162201001...
and used samples formed mainly of children
with spastic diplegia CP99. Burtner PA, Woollacott MH, Qualls C. Stance balance control with
orthoses in a group of children with spastic cerebral palsy. Dev Med Child Neurol.
1999;41(11):748-57. http://dx.doi.org/10.1017/S0012162299001516.
PMid:10576639
http://dx.doi.org/10.1017/S0012162299001...
,
1111. Ferdjallah M, Harris GF, Smith P, Wertsch JJ. Analysis of postural
control synergies during quiet standing in healthy children and children with
cerebral palsy. Clin Biomech (Bristol, Avon). 2002;17(3):203-10.
http://dx.doi.org/10.1016/S0268-0033(01)00121-8. PMid:11937258
http://dx.doi.org/10.1016/S0268-0033(01)...
,
1212. Rose J, Wolff DR, Jones VK, Bloch DA, Oehlert JW, Gamble JG.
Postural balance in children with cerebral palsy. Dev Med Child Neurol.
2002;44(1):58-63. http://dx.doi.org/10.1017/S0012162201001669.
PMid:11811652
http://dx.doi.org/10.1017/S0012162201001...
. These studies assessed the importance of
postural control disorders, such as higher values of postural oscillation in CP,
modifications of the muscle recruitment order to maintain stability, and higher rates of
agonist-antagonist muscle coactivation. Few studies have assessed the postural control
of children with spastic hemiplegia CP, especially during functional activities1313. Pavão SL, Santos AN, Woollacott MH, Rocha NACF. Assessment of
postural control in children with cerebral palsy: a review. Res Dev Disabil.
2013;34(5):1367-75. http://dx.doi.org/10.1016/j.ridd.2013.01.034.
PMid:23466474
http://dx.doi.org/10.1016/j.ridd.2013.01...
. This lack of studies is more evident when
assessing postural control during a change in posture, such as sit-to-stand movement
(STS). Limitations of STS movement seriously affect an individual's daily functional
activities.
STS movement is performed numerous times in the daily routine, demanding a stable
coordination between the body segments to control the transition of the body from
sitting to a standing posture. Furthermore, it is an antigravity movement involving the
transition from a more stable position (seated) to a less stable one (standing)1414. Seven YB, Akalan NE, Yucesoy CA. Effects of back loading on the
biomechanics of sit-to-stand motion in healthy children. Hum Mov Sci.
2008;27(1):65-79. http://dx.doi.org/10.1016/j.humov.2007.11.001.
PMid:18187221
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. Therefore, it is a challenging movement with
great biomechanical demands, requiring high levels of knee and ankle extension
movements1515. Yoshioka S, Nagano A, Hay DC, Fukashiro S. Biomechanical analysis of
the relation between movement time and joint moment development during a sit-to-stand
task. Biomed Eng Online. 2009;8(1):27. http://dx.doi.org/10.1186/1475-925X-8-27.
PMid:19849859
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.
For a better understanding, STS movement is divided into phases. The division into three
phases is the most commonly used, i.e., the preparation phase, including the beginning
of anterior trunk flexion to maximum flexion, when the body starts the seat-off; the
rising phase, from the seat-off (maximum anterior flexion of the trunk) to standing
posture; and the stabilization phase, which involves maintaining the body in a
quasi-stationary position1616. Kralj A, Jaeger RJ, Munih M. Analysis of standing up and sitting
down in humans: definitions and normative data presentation. J Biomech.
1990;23(11):1123-38. http://dx.doi.org/10.1016/0021-9290(90)90005-N.
PMid:2277047
http://dx.doi.org/10.1016/0021-9290(90)9...
,
1717. Riddiford-Harland DL, Steele JR, Baur LA. Upper and lower limb
functionality: are these compromised in obese children? Int J Pediatr Obes.
2006;1(1):42-9. http://dx.doi.org/10.1080/17477160600586606.
PMid:17902214
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.
The authors observed that children with CP have altered ability to initiate the lower
limb joint movements necessary to assume the standing posture1818. Park ES, Park CI, Lee HJ, Kim DY, Lee DS, Cho SR. The
characteristics of sit-to-stand transfer in young children with spastic cerebral
palsy based on kinematic and kinetic data. Gait Posture. 2003;17(1):43-9.
http://dx.doi.org/10.1016/S0966-6362(02)00055-3. PMid:12535725
http://dx.doi.org/10.1016/S0966-6362(02)...
. These children also have higher variability in body alignment
strategies during STS movement, using greater trunk flexion in an attempt to bring their
center of pressure (CoP) closer to the support base to gain stability, which could be a
consequence of a postural control impairment1818. Park ES, Park CI, Lee HJ, Kim DY, Lee DS, Cho SR. The
characteristics of sit-to-stand transfer in young children with spastic cerebral
palsy based on kinematic and kinetic data. Gait Posture. 2003;17(1):43-9.
http://dx.doi.org/10.1016/S0966-6362(02)00055-3. PMid:12535725
http://dx.doi.org/10.1016/S0966-6362(02)...
19. Yonetsu R, Nitta O, Surya J. "Patternizing" standards of
sit-to-stand movements with support in cerebral palsy. NeuroRehabilitation.
2009;25(4):289-96. PMid:20037222.
-
2020. Santos AN, Pavão SL, Rocha NACF. Sit-to-stand movement in children
with cerebral palsy: a critical review. Res Dev Disabil. 2011;32(6):2243-52.
http://dx.doi.org/10.1016/j.ridd.2011.05.001. PMid:21624818
http://dx.doi.org/10.1016/j.ridd.2011.05...
.
Studying postural control in individuals with postural impairments caused by voluntary movement55. Carlberg EB, Hadders-Algra M. Postural dysfunction in children with cerebral palsy: some implications for therapeutic guidance. Neural Plast. 2005;12(2-3):221-8; discussion 263-72. PMid:16097490. allows for conditions to be reproduced that are closer to those experienced by the children in their daily routine and, thus, better understanding the postural control impairments associated with CP. Therefore, this study aimed to compare the postural control of typically developing children with that of children with spastic hemiplegia CP during each one of the three phases of STS movement. In addition, this study assessed the relationship between static (during standing posture) and dynamic postural control (during STS movement) in the assessed groups.
Children with CP exhibit increased postural oscillation when performing STS movement,
reflecting difficulty in assuming the standing position. In addition, taking into
account the importance of postural control while in the standing position to perform
motor tasks and to perform functional activities in the daily routine88. Liao HF, Hwang AW. Relations of balance function and gross motor
ability for children with cerebral palsy. Percept Mot Skills. 2003;96(3 Pt
2):1173-84. http://dx.doi.org/10.2466/pms.2003.96.3c.1173.
PMid:12929770
http://dx.doi.org/10.2466/pms.2003.96.3c...
,
1212. Rose J, Wolff DR, Jones VK, Bloch DA, Oehlert JW, Gamble JG.
Postural balance in children with cerebral palsy. Dev Med Child Neurol.
2002;44(1):58-63. http://dx.doi.org/10.1017/S0012162201001669.
PMid:11811652
http://dx.doi.org/10.1017/S0012162201001...
, one expects the postural control in the
static standing condition to be directly related to the postural control during STS
movement in both of the assessed groups. These expectations emphasize the importance of
static control in the performance of daily functional activities, such as the STS
movement.
Method
Participants
Children were recruited from rehabilitation and childcare-specialized centers. The children were included in the study after their guardians signed the Informed Consent form. This study was approved by the Ethics Committee on Human Research of the Universidade Federal de São Carlos (UFSCar), São Carlos, SP, Brazil (Opinion No 363/2010).
Two groups were assessed. The control group consisted of 23 typically developing children between the ages of 5 to 12 years (mean=8.3±2.15). Patients with orthopedic disorders of the lower limbs or neurological, cardiovascular or systemic disorders that could limit the participants' level of physical activity were excluded from the study.
The experimental group consisted of 6 children with CP, all with spastic hemiplegia, Gross Motor Function Classification System (GMFCS) level I and aged between 5 and 12 years (mean=8.2±2.5). The inclusion criteria for the experimental group were: (a) the ability to follow simple verbal commands, assessed by the child's ability to follow the instructions to get up from a chair when asked; (b) the ability to independently assume the standing position; (c) 0 (no increase in muscle tone) or 1 score (slight increase in muscle tone) on a muscle tone classification, according to the modified Ashworth scale; (d) participation in a twice a week physical therapy program for at least 6 months. The exclusion criteria were: (a) orthopedic surgery of the lower limbs in the last year (b) the use of botulinum toxin in the last 6 months; (c) presence of shortening or deformities of the ankle, knee and/or hip joints that prevented the children from keeping their feet on the ground, hindered them from maintaining the standing position, or made it impossible for them to independently perform an STS movement; and (d) difficulty maintaining an upright position without support for more than 30 seconds.
Procedures
Inclusion and exclusion criteria were first assessed. Then, the accepted children were seated in an adjustable (i.e. height and inclination) chair without back support; hips, knees, and ankles were at 90°, and the feet were on a BERTC System 400 (EMG System do Brasil(r)) force platform, with an acquisition frequency of 100 Hz. Once seated, they were instructed to assume an upright position, without support of the upper limbs and at a self-selected speed. At the beginning of the activity, the feet were aligned with the hips, and the hands were placed on the thighs. A circle was drawn in the center of the platform, wherein the feet were placed before each attempt, which ensured the consistency of the initial positioning of the children's feet. After this initial positioning, the children were free to make the necessary adjustments to perform the task.
After STS movement assessment, the children were assessed in an upright posture to assess the correlation between static and dynamic postural control. They stood on the platform for 30 seconds, feet aligned with the hips, upper limbs along the sides of the body and staring at a fixed point 1 meter away at the height of their eyes. Five attempts were performed: two as familiarization and warmup, followed by three valid attempts for assessment, with a 2-minute rest between each attempt.
Data analysis
Data obtained from the force platform were processed and filtered using a digital
Butterworth fourth-order low-pass filter with a 5 Hz cut-off frequency2121. Pavão SL, Santos AN, de Oliveira AB, Rocha NACF. Functionality level
and its relation to postural control during sitting-to-stand movement in children
with cerebral palsy. Res Dev Disabil. 2014;35(2):506-11.
http://dx.doi.org/10.1016/j.ridd.2013.11.028. PMid:24374603
http://dx.doi.org/10.1016/j.ridd.2013.11...
using Matlab software (Mathworks Inc.,
Natick, MA, USA). Data normalization was performed using the children's
body weight values.
The criteria for STS movement division into phases were established according to
Kralj et al.1616. Kralj A, Jaeger RJ, Munih M. Analysis of standing up and sitting
down in humans: definitions and normative data presentation. J Biomech.
1990;23(11):1123-38. http://dx.doi.org/10.1016/0021-9290(90)90005-N.
PMid:2277047
http://dx.doi.org/10.1016/0021-9290(90)9...
. For the preparation phase
(F1), the beginning was determined by a decrease in vertical force greater than 2.5%
relative to the weight of the feet on the platform, and the end was determined by the
vertical peak force. For the rising phase (F2), measurement began with the vertical
peak force on the platform and ended when the vertical force matched the body weight.
The beginning of the stabilization phase (F3) was determined by the point at which
the vertical force reached the body weight, and the end was determined by a vertical
force oscillation of approximately 2.5% of the body weight. Details of the division
of STS movement into phases are presented in Figure
1.
Schematic representation of the division process of the three different phases of the sit-to-stand movement. Preparation phase (T1-T2); rising phase (T2-T3); and stabilization phase (T3-T4). BW, body weight; MGRF (maximum ground reaction force); OS(overshoot); IC (incline); WFL (weight of feet/legs at rest); T1 (start of movement); T2 (seat-off); T3 (extension of body); T4 (end of movement). Source: Kralj et al.16.
For each of 3 phases, the variables related to the CoP were calculated: i.e., the
anteroposterior CoP displacement amplitude (Amp AP1, Amp AP2 and Amp AP3), the
mediolateral CoP displacement amplitude (Amp ML1, Amp ML2 and Amp ML3), the CoP
oscillation area (Area 1, Area 2 and Area 3) and the mean CoP oscillation velocity
(Vel1, Vel2 e Vel3). The variables were calculated according to Duarte and
Freitas2222. Duarte M, Freitas SMSF. Revision of posturography based on force
plate for balance evaluation. Rev Bras Fisioter. 2010;14(3):183-92.
http://dx.doi.org/10.1590/S1413-35552010000300003. PMid:20730361
http://dx.doi.org/10.1590/S1413-35552010...
. The variables calculated for STS
movement were also used during the standing position (i.e. Amp AP, Amp ML, Area and
Vel).
Statistical analyses of the values obtained both during STS movement and while in the standing position were based on the mean value of the three attempts performed by the children for each of the variables analyzed.
Statistical analysis
Ryan-Jones' normality test (p<0.01) was used and revealed a lack of normality for all data analyzed.
Therefore, Mann-Whitney's non-parametric test was used to compare Amp AP, Amp ML, Area and Vel variables between groups when performing STS movement. Spearman's correlation was used to assess the relationship between CoP behavior during STS movement and while in the standing position. This method was applied in each group to assess the relationships between the evaluated variables while in the standing position and during STS movement (in each of the three phases).
A significance level of 5% was adopted, and software SPSS 17 for Windows (SPSS Inc. Chicago, IL, USA) was used for the analysis.
Results
Postural control in STS movement
Significant differences in postural control were observed during STS movement between typically developing children and children with CP in the first phase (preparation phase) for the variables Amp AP (U=19.0; p=0.005), Amp ML (U=11.0; p=0.001), Area (U=12.0; p=0.001) and Vel (U=16.0; p=0.003). Children with CP exhibited higher values for these variables compared with typically developing children. The other phases of STS movement did not show significant differences between groups for the variables analyzed. A large size effect (0.92) was found, and the statistical power was 60%. The plots of these results are shown in Figure 2.
Comparison of postural control during the sit-to-stand movement between the groups of children with typical development (Control Group) and cerebral palsy (CP Group) in each of the three phases of movement. A: Antero/Posterior Amplitude of CoP displacement (AP Amp); B: Medial/Lateral Amplitude of CoP displacement (ML Amp); C: Area of CoP oscillation; D: Mean Velocity of CoP oscillation (Vel).
Relationship between Static (during the Static Standing Position) and Dynamic (STS Movement) Postural Control
Typically developing children exhibited no correlations between postural control during STS movement and while in the standing position for all of the variables analyzed in all phases of STS movement (Table 1). However, children with CP exhibited moderate to strong correlations between the variables for both the standing position and STS movement in the second and third phases of STS movement (Table 2).
Discussion
This study revealed differences in the postural control of typically developing and CP
children during the preparatory phase of STS movement. Children with CP exhibit higher
CoP AP, ML, Area and Vel values in the first phase of movement1616. Kralj A, Jaeger RJ, Munih M. Analysis of standing up and sitting
down in humans: definitions and normative data presentation. J Biomech.
1990;23(11):1123-38. http://dx.doi.org/10.1016/0021-9290(90)90005-N.
PMid:2277047
http://dx.doi.org/10.1016/0021-9290(90)9...
. During this phase, the body should make adjustments in the trunk
region, initially performing flexion, with anterior displacement of the center of
mass1919. Yonetsu R, Nitta O, Surya J. "Patternizing" standards of
sit-to-stand movements with support in cerebral palsy. NeuroRehabilitation.
2009;25(4):289-96. PMid:20037222., to then overcome gravity, lifting from
the chair and assuming a standing position. This study also showed a correlation between
static (i.e. during standing posture) and dynamic (i.e. during STS movement) postural
control in the CP group.
Previous studies showed that children with CP exhibited higher values of hip flexion and
anterior pelvic tilt in the beginning of STS movement when compared with typically
developing children1818. Park ES, Park CI, Lee HJ, Kim DY, Lee DS, Cho SR. The
characteristics of sit-to-stand transfer in young children with spastic cerebral
palsy based on kinematic and kinetic data. Gait Posture. 2003;17(1):43-9.
http://dx.doi.org/10.1016/S0966-6362(02)00055-3. PMid:12535725
http://dx.doi.org/10.1016/S0966-6362(02)...
,
2323. Santos AN, Pavão SL, Santiago PR, Salvini TF, Rocha NA. Sit-to-stand
movement in children with hemiplegic cerebral palsy: relationship with knee extensor
torque and social participation. Res Dev Disabil. 2013;34(6):2023-32.
http://dx.doi.org/10.1016/j.ridd.2013.03.021. PMid:23584182
http://dx.doi.org/10.1016/j.ridd.2013.03...
. The strategy of flexing the trunk moves the
center of mass to the support base1919. Yonetsu R, Nitta O, Surya J. "Patternizing" standards of
sit-to-stand movements with support in cerebral palsy. NeuroRehabilitation.
2009;25(4):289-96. PMid:20037222., thus
reducing postural imbalance; this movement could possibly be considered an adaptive
action to compensate for postural control deficits2424. Schultz AB, Alexander NB, Ashton-Miller JA. Biomechanical analyses
of rising from a chair. J Biomech. 1992;25(12):1383-91.
http://dx.doi.org/10.1016/0021-9290(92)90052-3. PMid:1491016
http://dx.doi.org/10.1016/0021-9290(92)9...
. Furthermore, the head movements that follow this increased trunk flexion
may stimulate vestibular receptors2525. Horak F, Shupert C. The role of the vestibular system in postural
control. In: Herdman S, editor. Vestibular rehabilitation. New York: FA Davis; 1994.
p. 22-46., thus
providing greater stability and control of body positioning in space. Therefore, the
higher CoP oscillation in the first phase of the movement could be a compensatory
adjustment used by children with CP to succeed in the task of lifting up from the
chair.
In a previous study by the same research group, using a similar sample to that of the
present study, Santos et al.2323. Santos AN, Pavão SL, Santiago PR, Salvini TF, Rocha NA. Sit-to-stand
movement in children with hemiplegic cerebral palsy: relationship with knee extensor
torque and social participation. Res Dev Disabil. 2013;34(6):2023-32.
http://dx.doi.org/10.1016/j.ridd.2013.03.021. PMid:23584182
http://dx.doi.org/10.1016/j.ridd.2013.03...
observed that
children with CP exhibited increased ankle excursion in the frontal and transverse
planes during STS movement when compared with typically developing children. This
increased excursion might explain the increase in AP and ML CoP displacements and
determines a larger CoP oscillation area during STS movement. Studies with healthy
participants show that higher values of subtalar pronation are related to increased AP
and ML CoP displacements2626. Cobb SC, Tis LL, Johnson BF, Higbie EJ. The effect of forefoot varus
on postural stability. J Orthop Sports Phys Ther. 2004;34(2):79-85.
http://dx.doi.org/10.2519/jospt.2004.34.2.79. PMid:15043000
http://dx.doi.org/10.2519/jospt.2004.34....
. Due to the neuromotor
changes children with CP display, they exhibit biomechanical misalignment of the lower
limbs, with higher values of internal rotation of the tibia and femur and subtalar
pronation when compared with typically developing children2323. Santos AN, Pavão SL, Santiago PR, Salvini TF, Rocha NA. Sit-to-stand
movement in children with hemiplegic cerebral palsy: relationship with knee extensor
torque and social participation. Res Dev Disabil. 2013;34(6):2023-32.
http://dx.doi.org/10.1016/j.ridd.2013.03.021. PMid:23584182
http://dx.doi.org/10.1016/j.ridd.2013.03...
. Therefore, children with CP, due to their biomechanical and
neuromuscular limitations, increase their ankle excursion in the act of getting up2323. Santos AN, Pavão SL, Santiago PR, Salvini TF, Rocha NA. Sit-to-stand
movement in children with hemiplegic cerebral palsy: relationship with knee extensor
torque and social participation. Res Dev Disabil. 2013;34(6):2023-32.
http://dx.doi.org/10.1016/j.ridd.2013.03.021. PMid:23584182
http://dx.doi.org/10.1016/j.ridd.2013.03...
, possibly leading to larger AP and ML
displacements, as observed in the present study. In addition, the increased ankle
excursion could be interpreted as a strategy to increase the arrival of proprioceptive
afferents to the central nervous system2727. Patla A, Frank J, Winter D. Assessment of balance control in the
elderly: major issues. Physiother Can. 1990;42(2):89-97.
http://dx.doi.org/10.3138/ptc.42.2.089.
http://dx.doi.org/10.3138/ptc.42.2.089...
, thus
facilitating the maintenance of stability to perform a function.
These results may bring new prospects for rehabilitation for these children, demonstrating the importance of the ankle joint in the execution of STS movement. Based on these results, one could also make inferences regarding the need to work on functional activities during therapy to improve ankle stability and proprioception and, thus, to improve the performance of daily tasks, such as STS movement.
The CP children of this study also exhibited increased CoP oscillation velocity in the
first phase of STS movement compared with typically developing children. CoP oscillation
velocity is one of the main predictors of body stability, with higher values being
related to greater difficulty in controlling body positioning in space2828. Sobera M, Siedlecka B, Syczewska M. Posture control development in
children aged 2-7 years old, based on the changes of repeatability of the stability
indices. Neurosci Lett. 2011;491(1):13-7.
http://dx.doi.org/10.1016/j.neulet.2010.12.061. PMid:21215293
http://dx.doi.org/10.1016/j.neulet.2010....
. Therefore, the increase in oscillation velocity
observed in CP children indicates their difficulty in controlling body segments when
perfoming the STS movement.
It is noteworthy that the high biomechanical demand of STS movement1414. Seven YB, Akalan NE, Yucesoy CA. Effects of back loading on the
biomechanics of sit-to-stand motion in healthy children. Hum Mov Sci.
2008;27(1):65-79. http://dx.doi.org/10.1016/j.humov.2007.11.001.
PMid:18187221
http://dx.doi.org/10.1016/j.humov.2007.1...
,
1515. Yoshioka S, Nagano A, Hay DC, Fukashiro S. Biomechanical analysis of
the relation between movement time and joint moment development during a sit-to-stand
task. Biomed Eng Online. 2009;8(1):27. http://dx.doi.org/10.1186/1475-925X-8-27.
PMid:19849859
http://dx.doi.org/10.1186/1475-925X-8-27...
could impose restrictions on children with CP
during its execution. However, even with a greater postural instability to begin the
movement, the children with CP assessed in this study were able to successfully perform
the movement, possibly because of their mild motor impairment.
All of the CoP differences noted between typically developing children and CP children in the first phase of STS movement indicated that the beginning of this movement could be a critical moment for children with CP. Thus, rehabilitation programs should focus on and exhaustively train the start of the getting up action to improve children's ability to anteriorly displace their center of gravity and to assume an upright position.
There were no significant differences between groups in the other phases, namely the
rising phase (F2) and the stabilization phase (F3). These phases involve gravity-defying
body movement (F2) and movement deceleration (F3). Therefore, they demand muscle
strength and concentric-eccentric muscle control of the lower limbs, respectively, for
proper interarticular coordination and for remaining in a standing position without the
risk of falling. Although children with spastic hemiplegia exhibit knee-extension
strength deficits2323. Santos AN, Pavão SL, Santiago PR, Salvini TF, Rocha NA. Sit-to-stand
movement in children with hemiplegic cerebral palsy: relationship with knee extensor
torque and social participation. Res Dev Disabil. 2013;34(6):2023-32.
http://dx.doi.org/10.1016/j.ridd.2013.03.021. PMid:23584182
http://dx.doi.org/10.1016/j.ridd.2013.03...
, which could compromise the
rising phase, it was assumed that interlimb compensation occurred during the movement.
In this compensation, the healthy limb acts as a support limb, providing stability and
compensating the plegic limb deficits2929. Sadeghi H, Allard P, Prince F, Labelle H. Symmetry and limb
dominance in able-bodied gait: a review. Gait Posture. 2000;12(1):34-45.
http://dx.doi.org/10.1016/S0966-6362(00)00070-9. PMid:10996295
http://dx.doi.org/10.1016/S0966-6362(00)...
,
3030. Gabbard C, Hart S. A question of foot dominance. J Gen Psychol.
1996;123(4):289-96. http://dx.doi.org/10.1080/00221309.1996.9921281.
PMid:9042740
http://dx.doi.org/10.1080/00221309.1996....
during the last two phases of STS movement.
However, the present study did not assess postural control in specific platforms for
each lower limb.
In typically developing children, unlike CP children, there was no correlation between postural control during the standing position and STS movement. A possible explanation for the lack of correlation in this group could be the less varying behavior of the postural oscillation when compared with the CP group.
There was a correlation between static and dynamic postural control in the CP group. In
the CP children, the higher values of Amp AP, Amp ML and CoP oscillation Area and Vel
during the standing position were related to the higher values of the same variables for
STS movement (i.e., the rising and stabilization phases). This correlation was noted
only in the last two phases of the movement. These phases represent when the support
base, initially formed by the surface of the feet and the gluteal region, is then formed
only by the individual's feet. This change may determine greater postural instability,
and, thus, a more varying oscillatory behavior. In the last two phases of STS movement,
the support base is similar to the base during the standing position. Therefore, one
could consider the existence of common components of posture and movement of the lower
limbs actively controlling these body segments, thus avoiding falls. In addition, the
neuromotor deficits observed in CP99. Burtner PA, Woollacott MH, Qualls C. Stance balance control with
orthoses in a group of children with spastic cerebral palsy. Dev Med Child Neurol.
1999;41(11):748-57. http://dx.doi.org/10.1017/S0012162299001516.
PMid:10576639
http://dx.doi.org/10.1017/S0012162299001...
,
3131. Burtner PA, Qualls C, Woollacott MH. Muscle activation
characteristics of stance balance control in children with spastic cerebral palsy.
Gait Posture. 1998;8(3):163-74. http://dx.doi.org/10.1016/S0966-6362(98)00032-0.
PMid:10200406
http://dx.doi.org/10.1016/S0966-6362(98)...
can compromise muscle recruitment
patterns3232. Nashner LM, Shumway-Cook A, Marin O. Stance posture control in
select groups of children with cerebral palsy: deficits in sensory organization and
muscular coordination. Exp Brain Res. 1983;49(3):393-409.
http://dx.doi.org/10.1007/BF00238781. PMid:6641837
http://dx.doi.org/10.1007/BF00238781...
, resulting in postural control
deficits during STS movement - especially in the final phase, which involves movement
deceleration control when the individual changes from a dynamic movement to a
semi-static position.
Therefore, according to the results observed, the postural oscillation of children during the standing position is related to their performance in dynamic tasks, such as STS movement. This relationship demonstrates the importance of static posture control for children with CP for performing functional tasks.
Extrapolating the conclusions of this study to rehabilitation, the authors believe the results of this study provide relevant information for clinical practice: namely, children with CP require interventions that include functional activities focused on performing the STS movement. Greater attention should be paid to the preparation phase of this movement because the main differences in postural control compared to typically developing children were observed in this phase. In addition, the correlation identified between static and dynamic postural control allows one to infer that the use of dynamic activities, such as STS, may facilitate patients' stability in the maintenance of static postures. Additionally, the training of static posture maintenance can assist in the performance of the movement of getting up.
The limitations of the study were the use of only one force platform to assess the lower limbs and the low statistical power of the tests applied. We believe that in further studies with larger samples, differences in other phases of STS movement may be identified. Furthermore, only children with mild motor dysfunction were assessed. Studies using two force platforms should be conducted to assess the relationship between postural behavior in static postures and dynamic activities in populations with greater neuromotor impairment.
Conclusion
The children with CP assessed in this study exhibited increased CoP oscillation at the beginning of STS movement compared with typically developing children, which indicates greater difficulty of initiating the movement for children with CP. Moreover, in children with CP, increased CoP oscillation in static posture is related to increased oscillation during dynamic activities, as observed in the last two phases of STS movement. These results reveal the importance of controlling the body in the static posture to perform functional activities that put the body in motion.
Acknowledgements
The Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil, for financial support (processes 2010/12594-4 and 2010/15010-3).
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29Sadeghi H, Allard P, Prince F, Labelle H. Symmetry and limb dominance in able-bodied gait: a review. Gait Posture. 2000;12(1):34-45. http://dx.doi.org/10.1016/S0966-6362(00)00070-9. PMid:10996295
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30Gabbard C, Hart S. A question of foot dominance. J Gen Psychol. 1996;123(4):289-96. http://dx.doi.org/10.1080/00221309.1996.9921281. PMid:9042740
» http://dx.doi.org/10.1080/00221309.1996.9921281 -
31Burtner PA, Qualls C, Woollacott MH. Muscle activation characteristics of stance balance control in children with spastic cerebral palsy. Gait Posture. 1998;8(3):163-74. http://dx.doi.org/10.1016/S0966-6362(98)00032-0. PMid:10200406
» http://dx.doi.org/10.1016/S0966-6362(98)00032-0 -
32Nashner LM, Shumway-Cook A, Marin O. Stance posture control in select groups of children with cerebral palsy: deficits in sensory organization and muscular coordination. Exp Brain Res. 1983;49(3):393-409. http://dx.doi.org/10.1007/BF00238781. PMid:6641837
» http://dx.doi.org/10.1007/BF00238781
Publication Dates
-
Publication in this collection
03 Feb 2015 -
Date of issue
Jan-Feb 2015
History
-
Received
30 Jan 2014 -
Reviewed
15 Apr 2014 -
Accepted
07 July 2014