Multi-segmental postural control patterns in down syndrome

Analysis of the centre of pressure in bipedal stance among individuals with and without intellectual disabilities, individuals with Down syndrome and dancers with Down syndrome

BACKGROUND

Individuals with intellectual disabilities (IDs) often present deficiencies in motor, balance and postural control. On the other hand, the practice of physical activity and dance usually reduces these deficiencies. Therefore, in this study, we aimed to compare the control of the centre of pressure (COP) in people with Down syndrome (DS) or other causes of ID in relation to people without disabilities and to observe the influence of vision and the practice of dance.

METHODS

This cross-sectional study analyses the COP in a static standing position with open and closed eyes in four study groups. A total of 273 people were recruited (80 adults without ID, 46 adults with DS, 120 adults with other causes of ID and 27 dancers with DS).

RESULTS

A greater area of oscillation and path of the COP was observed in the participants with ID compared with the participants without ID, especially in the sway area of the COP. The oscillation speed of the COP was also higher. When analysing the displacement of the COP, anteroposterior and mediolateral components, there were also differences, except when comparing the group of dancers with DS with respect to the group without ID. The visual condition only influenced the group of participants without disabilities.

CONCLUSIONS

The results of our study show that there is a less efficient static postural control in people with ID, as greater displacements were observed in the COP of the participants with ID. The differences in some specific variables that analyse the displacement of the COP were smaller when comparing the group of dancers with DS and the individuals without ID.

Age and Visual Contribution Effects on Postural Control Assessed by Principal Component Analysis of Kinematic Marker Data

Postural control, the ability to control the body's position in space, is considered a critical aspect of health outcomes. This current study aimed to investigate the effects of age and visual contribution on postural control. To this end, principal component analysis (PCA) was applied to extract movement components/synergies (i.e., principal movements, PMs) from kinematic marker data of bipedal balancing on stable and unstable surfaces with eyes closed and open, pooled from 17 older adults (67.8 ± 6.6 years) and 17 young adults (26.6 ± 3.3 years), one PCA-analysis for each surface condition. Then, three PCA-based variables were computed for each PM: the relative explained variance of PM-position (PP_rVAR) and of PM-acceleration (PA_rVAR) for measuring the composition of postural movements and of postural accelerations, respectively, and the root mean square of PM-acceleration (PA_RMS) for measuring the magnitude of neuromuscular control. The results show the age and visual contribution effects observed in PM₁, resembling the anteroposterior ankle sway in both surface conditions. Specifically, only the greater PA₁_rVAR and PA₁_RMS are observed in older adults (p ≤ 0.004) and in closed-eye conditions (p < 0.001), reflecting their greater need for neuromuscular control of PM₁ than in young adults and in open-eye conditions.

Kinematic patterns during walking in children: Application of principal component analysis

The relative displacements of body segments during walking can be reduced to a small number of multi-joint kinematic patterns, pm_k, through Principal Component Analysis (PCA). These patterns were extracted from two groups of children (n = 8, aged 6-9 years, 4 males, and n = 8, aged 10-13 years, 4 males) and 7 adults (21-29 years, 1 male), walking on a treadmill at various velocities, normalized to body stature (adimensional Froude number, Fr). The three-dimensional coordinates of body markers were captured by an optoelectronic system. Five components (pm₁ to pm₅) explained 99.1% of the original dataset variance. The relationship between the variance explained ("size") of each pm_k and the Fr velocity varied across movement components and age groups. Only pm₁ and pm₂, which described kinematic patterns in the sagittal plane, showed significant differences (at p < 0.05) across pairs of age groups. The time course of the size of all the five components matched various mechanical events of the step cycle at the level of both body system and lower limb joints. Such movement components appeared clinically interpretable and lend themselves as potential markers of neural development of walking.