Differences in Postural Oscillation during Quiet Stance Alone and Quiet Stance Following Sit-To-Stand Movement in Children with Cerebral Palsy

Special Article – Cerebral Palsy

Phys Med Rehabil Int. 2017; 4(3): 1121.

Differences in Postural Oscillation during Quiet Stance Alone and Quiet Stance Following Sit-To-Stand Movement in Children with Cerebral Palsy

Pavão SL*, de Oliveira Sato T and Rocha NACF

Department of Physiotherapy, Neuropediatrics Section, Federal University of São Carlos, Rod. Washington Luis, km 235, 13565-905, São Carlos-SP, Brazil

*Corresponding author: Sílvia Leticia Pavão, Department of Physiotherapy, Neuropediatrics Section, Federal University of São Carlos, Rod. Washington Luis, km 235, 13565-905, São Carlos-SP, Brazil

Received: August 23, 2017; Accepted: September 18, 2017; Published: September 25, 2017


We evaluated differences in CoP trajectories during quiet stance alone (QSA) and quiet stance following sit to stand (STS) (QSFS) in typical children (TD) and children with cerebral palsy (CP). Forth two TD, 23 spastic CP were evaluated. The assessment during QSA occurred with the maintenance on a force plate during 30 seconds. For evaluation in QSFS children were instructed to rising from a bench and maintain stance for 30. We observed higher oscillation (AP and ML Amplitude of CoP displacement, Velocity and Area of CoP oscillation) in QSFS than in QSA. All the variables, except AP Amp, presented higher values for the CP group compared with TD. With exception of the variable AP Amp, all the other ones presented interaction between condition and group. CP group present higher CoP oscillation than TD, these values were higher in QSFS.

Keywords: Children; Cerebral palsy; Sit-to-stance movement; Postural control; Dynamical activity


Many of the activities performed by children in daily routine demand the maintenance of quiet stance in order to reach adaptive success [1]. Some examples include: the waiting time in lines, activities involving washing hands and brushing teeth, as well as social activities performed during stance [2]. The maintenance of standing posture involves the ability to keep the center of pressure (CoP) within the limits of the support base and suitable alignment between body segments [3-5] to keep balance and avoid falls [6,7].

A literature review reveals a large amount of studies addressing postural control during quiet stance in children with cerebral palsy (CP) [8-13]. According to these studies children with mild motor impairments present reduced\automaticity in postural sway [12] and less adaptive patterns of postural control regulation in this posture [3,8] than typical children. Nashner et al. [5] report an inverted pattern of muscle activation in lower limbs (distal to proximal) to keep balance during quiet stance. In addition, the crouch posture often observed in these children contributes to the greater postural sway that they present.

However, the experimental design of the existing studies is not able to reproduce functional experienced circumstances in daily life. In most of the studies children were instructed to keep standing posture as static as possible by a limited period of time [13], and in some cases they had to perform a concurrent cognitive task [12,14,15] or sensory manipulations [8,11] were required while remaining static.

Nevertheless, daily routine tasks involving upright stance maintenance commonly occur following functional movements, such as postural transitions or body displacements. Sit-to-stand (STS) movement is an example of a task that commonly precedes stance maintenance. The sequence of muscle activation and the positioning of the center of mass (CoM) occurring during the body movement of rising from a chair modifies postural demands to keep stability [4,7]. STS movement requires specific postural adjustments, such as, muscle co-activation in lower limbs to decelerate CoM movement [16,17], interjoint coordination in ankle, knee and hip joints to keep body alignment and a stable base of support [18]. These adjustments are believed to influence balance in the following quiet stance maintenance.

In fact, when considering a sequence of motor tasks, the preceding task exerts biomechanical influences on the following, since muscle and joint receptors, as well as other sensory system organs, catch the information coming from the movement in order to guide and correct the performed action [19]. In addition, the body movement changes the alignment between the segments creating specific demands for postural control system [5]. In this context, the task preceding upright stance maintenance seems to challenge postural control in a different way than the upright stance maintenance alone [20].

Studies have addressed postural control in CP children during dynamical circumstances such as, STS movement [16,21,22], gait [23,24], gait initiation [6] and gait initiation following STS movement [25]. These studies report a greater postural sway observed in CP children, as well as a greater ankle excursion in frontal and transverse planes during the movement [26], possibly due to the lack of coordination of ankle muscles activation reported in CP [27].

Nevertheless, none of the above studies have addressed postural control during quiet stance preceded by some of these functional body movements that are so common in daily living. This lack of studies is even more significant when considering the population of children with CP. Addressing this gap would allow us to understand how body movement and alignment might influence balance maintenance, guiding rehabilitation professionals in the selection of the more challenging activities to improve balance and stability.

Thus, the aim of our study was to evaluate differences in patterns of postural oscillation during quiet stance alone and quiet stance following STS movement. For this purpose we evaluated children with cerebral palsy and children with typical development.

We believe that postural demands in upright stance position following STS movement are greater than the ones of keeping stance alone. In this context we expected to find greater postural oscillation in the former conditions than in the later one. Moreover, despite children with mild CP were able to perform STS movement independently and to keep stance following this postural transition we believe that in stance maintenance following STS movement children with CP will present greater postural oscillations compared with children with typical development.



We evaluated three groups of participants. The typicallydeveloping group (TD) included 42 healthy children, 19 male and 23 female, with ages from 5 to 15 years (mean±SD; Age: 10±2.9 years; Height: 143±19.1cm; Weight: 41.5±17.2Kg). Participants with current lower limb injuries, or who had any cardiovascular, pulmonary, neurological, or systemic conditions that limited physical activity were excluded from the study.

The other group included 23 children with spastic CP , 15 male and 8 female, with ages from 5 to 15 years (mean ± SD; Age: 9.8±3.3 years; Height: 129.7±33.4cm; Weight: 31.3±12.4Kg). The participants were classified by Gross Motor Function Classification System (GMFCS) as level I (15 children) or level II (8 children). For statistical analyses the CP group was divided according to the level of GMFCS.

The inclusion criteria for the CP group were as follows: (a) ability to follow simple commands; (b) ability to come to a standing position independently. Exclusion criteria were: (a) loss of passive joint mobility in trunk or lower limbs, which may indicate presence of deformities and contractures; (b) orthopedic surgery and/ or botulinum toxin injection in the previous 12 and 6 months, respectively; (c) any muscle tone impairment other than spasticity, such as ataxia, dystonia, and/or hypotonia.

The local Ethics Committee for Human Research approved the study, which is in agreement with the Declaration of Helsinki and the resolution 196/96 from National Health Council. Children were admitted in the study following informed written parental consent. Children were recruited in rehabilitation centers specialized in child care and in regular schools.


The anthropometric data of all the children were previously collected.

For the assessment of postural control during quiet stance alone, children were asked to assume upright standing posture standing on a force platform (Bertec400) with their feet parallel to and aligned with the side of their feet and to remain standing for 30 seconds. Following this preceding time, we initiated our data collection instructing them to remain on the force plate as quietly as possible for 30 seconds while looking ahead at a fixed point located one meter away [28]. Each child performed a total of three trials.

For postural control testing during quiet stance following STS movement children were initially seated in a bench without trunk or upper limbs support. Their hips, knees and ankles were flexed at 90° and their feet were positioned on a force plate, at an acquisition rate of 100Hz. The participants were tested in barefoot. After a verbal command, the children were asked to assume upright standing position in a self-selected speed, keeping their arms folded across the chest when they stood (to prevent them from using their upper limbs to push up of the bench). Immediately after standing up, they were instructed to remain in static stand up for 30 seconds. The task was performed for a total of three times.

A circle was drawn at the center of the platform to orient feet placement before each trial in both conditions, which provided consistency of the initial position across trials. There was no discrepancy of the support base adopted by the children among the performed conditions. Children did not perform training tasks in none of the conditions.

For analysis of body oscillations, in both conditions, we used the mean of the three performed trials.

Data analysis

Data from the force platform were processed and filtered (4th order Butterworth filter, with a low pass frequency of 5Hz) on Matlab (Mathworks Inc., Natick, MA, USA); outcome measures were computed on the same software. Data were normalized by the participants’ body weight.

STS movement can be divided into three different phases [16,22]. The criteria for STS movement division into phases were: 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; rising phase (F2), measurement began with the vertical peak force on the platform and ended when the vertical force matched the body weight; 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 [29]. The phase division of STS movement is shown in Figure 1.