Body coordination during sit-to-stand in blind and sighted female children

Abstract

Detecting coordination pattern and coordination variability help us to find how joints organize collaboratively to perform sit-to-stand (STS) under restricted visual input. This experiment aimed to compare the coordination of the trunk, hip, knee, and ankle and its variability between individuals with long- and short-term restricted visual input during STS. Forty-five female children participated in this study, including fifteen congenitally blind (CB) children and 30 healthy children. The healthy children were divided randomly into two groups: one group in which the participants were instructed to keep their eyes open (EO) and another to keep their eyes closed (EC) for 20 min before the test. In the standing phase, CB children had a decreased ankle-knee vector angle on the nondominant (ND) side compared to that of healthy children. In the sagittal plane, a small coefficient-of-correspondences (CoC) was observed at seat-off (hip-trunk CoC on the dominant (D) side and ankle-hip CoC on the ND side) and in the preparation phase (ankle-hip CoC on the ND side and bilateral hip CoC). In the frontal plane (at the end: ankle-knee, in the standing phase: bilateral hip) a high CoC was observed (in the standing phase: knee-trunk CoC on the D side). The EC group had smaller CoCs at initiation event (knee-trunk and bilateral knee CoCs on both sides), the end event (ankle-knee and ankle-hip CoCs on the ND side), and in the standing phase (bilateral hip CoC) in the frontal plane than the other groups. The findings reveal that vector and CoC variables are altered because of long- and short-term restricted visual data and should be a focus in rehabilitation programs.

Introduction

Coordination refers to the organization across multiple segments during movement. Evaluating coordination allows us to understand how various joints work together harmoniously and simultaneously maintain a balance to complete a functional activity. Some factors have led to poor coordination patterns, including aging (which has influence on the hip and ankle) (Hafer and Boyer, 2018), chronic ankle instability (in the hip and ankle in the sagittal and frontal planes) (Yen et al., 2017), neurological involvements (such as hemiparetic stroke (Lessard et al., 2017)) and orthopedic involvements (hip osteoarthritis) (Wallard et al., 2018). The coefficient-of-correspondence (CoC), measuring coordination variability, is reduced in all these conditions. Reducing coordination variability has been suggested as a strategy to avoid movement errors when the balance is challenged (Yen et al., 2017). To maintain postural balance, it is necessary to integrate information from the visual, vestibular, and somatosensory systems (Sousa et al., 2012, Wikstrom et al., 2017). The data provided by the visual system play a paramount role in regulating postural orientation (Horak, 2006), while the somatosensory system prepares location and movement data about the body.

It was observed in animal experiments that the early sensory deprivation induces functional higher compensation (Völgyi et al., 1993). In blind, it has been indicated that it would have a cross-modal manner to engaged the pieces of the visual cortex with other sensory conditions and the visual cortex could be recruited to a role in somatosensory processing (Cohen et al., 1997). This idea suggests that the short (i.e., eyes closed (EC) group) and long-term (i.e., congenitally blind (CB) children) restricted visual data could lead to different adaptations and also changes in the coordination.

This experiment aimed to determine if the consolidation process occurs during rod intercept, or if it occurred only during long-term restricted visual input. The consolidation process for a new motor memory may take several hours (McGaugh, 2000) or, under certain conditions, minutes (IYa, 1998). This study tries to find more information about the process of dark adaptation for the visual system is adjusting to whole darkness or less levels of illumination. The time of rod intercept is less than or equal to 20 min, usually 8.2 min (Jackson and Edwards, 2008) and 12.5 min (Holfort et al., 2010), in young and older people, respectively.

Sit-to-stand (STS) is a challenging functional task that needs the coordination of all body segments (Manckoundia et al., 2006) and the uninterrupted management of different sensory data; thus, STS performance is an indicator of mobility level (Souza et al., 2011). So, the function of the postural control system prevents falling and keeps postural stability during STS. Therefore, STS has been used to evaluate biomechanical variables in visual impairment ones (Aylar et al., 2019).

Abnormal ankle (Aylar et al., 2016), knee, and hip (Aylar et al., 2018) kinematics have been observed in CB children when performing STS. When examining body movements of blind, it may be vital to consider not only the lower extremity joints but also the trunk. Specifically, it may be important to examine how blind individuals “coordinate” their lower and trunk segments during functional tasks.

In addition, a previous study (Aylar et al., 2019) showed that the center-of-mass (COM) displacement of the nondominant (ND) foot segment and COM displacement of the dominant (D) leg segment were altered in blind individuals compared to healthy individuals. Therefore, the COM displacement of the foot and leg segments could affect the vector-angle components, and CB subjects showed less coordination variability than the other subjects. When sensorimotor control impairments are combined with long-term visual constraints, such as that in CB individuals, perhaps the memory of them could also provoke altered coordination of the lower extremity and trunk, and CB individuals can present lower CoCs than healthy individuals. However, few studies have explored this topic.

The measure of vector angle and CoC of human bodies under restricted visual data during a highly challengeable task such as STS, needing complex and huge movement constraints, can show a critical step toward comprehending visual rehabilitative programs and interventions to improve physical functioning. Here, we aimed to analyze the coordination of the ankle, knee, hip, and trunk during STS (on both the D and ND sides) among CB, EC, and eyes open (EO) individuals. In addition, we hypothesized that the EC group would show a larger CoC of the ankle and hip than the CB group would.