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Background: Children with Down syndrome (DS) are known for their reduced balance control, and typically take longer to develop motor skills and display less coordinated movement patterns. Hopping in-place is a gross motor skill requiring whole-body vertical stiffness and horizontal movement control, particularly when attempting to modify hopping frequency. However, there is a lack of knowledge of the hopping capacity of children with DS.Research Question: The purpose of this study was to assess the ability of children with DS aged 5-11 years old to continuously hop in-place on two legs and compare their biomechanical patterns to those of typically developing (TD) children.Methods: This observational study included 14 children with DS and 16 TD children. Subjects were asked to complete 20 s trials of two-legged hopping in-place at a self-selected frequency, and four metronome guided conditions: preferred (self-selected frequency), moderate (20% increase), fast (40% increase) and slow (20% decrease). Two sample independent t-tests were conducted on whole-body vertical stiffness, horizontal center-of-mass movement, and toe displacement between hops for the self-selected hopping condition and two-way ANOVAs were used for the metronome conditions.Results and Significance: Our findings suggest that children with DS might not be able to continuously hop in-place until the age of 7 years old, and were unable to hop for as long in duration as their TD peers. Children with DS self-selected a faster hopping frequency, and demonstrated an increased medial-lateral center-of-mass movement during the stance phase of hopping, suggesting reduced balance control. Moreover, children with DS were unable to correctly modify their hopping frequency when cued by a metronome and exhibited an inability to modulate whole-body vertical stiffness and constrain horizontal or vertical movement. These results demonstrate the utility of a future hopping intervention to improve whole-body vertical stiffness and balance control in children with DS. [ABSTRACT FROM AUTHOR]

Highlights: [•] We study postural response in children using unilateral Achilles tendon vibration. [•] Both 6- and 10-year-old children show a directionally specific postural response. [•] Both 6- and 10-year-old children display an adult-like timing of postural response. [•] Only 10-year-old children show some adult-like spatial pattern in the AP direction. [ABSTRACT FROM AUTHOR]

Background: Children with Down syndrome (DS) often show underdeveloped motor ability and adaptation. Stair ascent is a common task to examine locomotor function and external ankle load is often used to perturb the stability of a system and observe the emergence of new patterns.Research Question: How do stair height and external ankle load affect locomotor adjustments in 5-to-11-year-old children with typical development (TD) and with DS during stair ascent?Methods: Fourteen children with DS and 14 age- and sex-matched children with TD participated in this study. They walked along a 5-m walkway and ascended 3-step staircases of different heights (low, moderate, and high) with or without ankle load. A 3D motion capture system was used for data collection. Dependent variables included stance time and toe-to-stair distance before stair ascent, and vertical toe clearance and horizontal toe velocity during stair ascent. Mixed ANOVAs with repeated measures were conducted for statistical analysis.Results: The DS group presented a longer stance time and a shorter toe-to-stair distance than the TD group before stair ascent. External ankle load affected, to a greater extent, the DS group than the TD group in stance time and toe-to-stair distance. During stair ascent, while the TD group generally maintained toe clearance and decreased horizontal toe velocity with the increase of stair height, the DS group decreased toe clearance and maintained horizontal toe velocity. Particularly, the DS group displayed a greater toe clearance than the TD group in the LS condition but a smaller toe clearance in the HS condition. In addition, external ankle load increased toe clearance and decreased horizontal toe velocity in both groups.Significance: Children with DS display underdeveloped locomotor adjustments during stair ascent. External ankle load appears to help the DS group regulate toe clearance and horizontal toe velocity for different stair heights. [ABSTRACT FROM AUTHOR]

Background: Increasing walking speed and including bilateral external ankle load have been shown to improve aspects of the gait pattern of children with Down syndrome (DS). However, it is unknown if speed and ankle load improves the cycle-to-cycle variability in a similar way.Research Question: How do changes of walking speed and external ankle load impact spatiotemporal variability during treadmill walking in children with and without DS?Methods: Thirteen children with DS (aged 7-10 years) and thirteen age- and sex-matched typically developing (TD) children participated in this study. Subjects completed two bouts of 60-second treadmill walking at two different speeds (slow and fast) and two load conditions (no load and ankle load equaling to 2% bodyweight at each side). Kinematic data was captured using a Vicon motion capture system. Mean and coefficient of variance of spatiotemporal gait variables were calculated and compared between children with and without DS.Results and Significance: Across all conditions, the DS group took shorter and wider steps than the TD group, but walked with a similar swing percentage, double support percentage, and foot rotation angle. Further, the DS group demonstrated greater variability of all spatiotemporal parameters, except for step width and foot rotation angle. Our results indicated that children with DS can modulate their spatiotemporal gait pattern accordingly like their TD peers when walking faster on a treadmill and/or with an external ankle load. Smaller step width variability in the DS group suggests that mediolateral stability may be prioritized during treadmill walking to safely navigate the treadmill and complete walking tasks. Similar temporal parameters but distinct spatial parameters in the DS group suggest that they may have developed similar rhythmic control but are confined by their spatial movement limitations. [ABSTRACT FROM AUTHOR]