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Background: While mini-trampolines have been used among a variety of groups including children as an intervention tool, the motor behavior children adopt while hopping on this soft, elastic surface is unknown. Identifying coordinative structures and their stability for hopping on a mini-trampoline is imperative for recommending future interventions and determining appropriateness to populations with motor dysfunctions.Research Question: Do children demonstrate similar biomechanical and coordination patterns as adults while hopping on a mini-trampoline?Methods: Fifteen adults aged 18-35 years and 14 children aged 7-12 years completed bouts of continuous two-legged hopping in-place on a stiff surface for 10 s at a time and on a mini-trampoline for 30 s at a time. 3-D motion capture tracked whole-body movement. We evaluated whole-body vertical stiffness as a ratio of peak vertical force and peak vertical displacement, as well as spatiotemporal parameters of hopping. Coordinative structures were evaluated as continuous relative phase angles of the foot, shank, thigh, and pelvis segments.Results and Significance: Adults did not modify whole-body vertical stiffness on a mini-trampoline, while children increased whole-body vertical stiffness to compensate for the reduced surface stiffness. Both groups conserved the coordinative structure for hopping on a mini-trampoline by modulating hopping cycle timing. Moreover, children hopped with an adult-like coordinative structure, but required greater shank-thigh and thigh-pelvis out-of-phase motion. However, the consistency of their coordination was diminished compared to adults. Children aged 7-12 years old have formed a stable coordinative structure for spring-mass center-of-mass dynamics that is preserved on this soft, elastic surface. However, children might be developing control strategies for preferred whole-body vertical stiffness, particularly when required to dampen peak vertical forces. These results highlight the importance of evaluating the emerging motor behavior to manipulated environmental constraints, particularly when considering the utility and appropriateness of mini-trampoline interventions for children with motor dysfunctions. [ABSTRACT FROM AUTHOR]

Background: Backward walking and fast walking have distinctive gait patterns in adults; however, there is minimal literature describing these gait modifications in typically developing children. Additionally, most of previous research focused on overground backward walking, but not on a treadmill.Research Question: How do typically developing children adapt their gait patterns, including spatiotemporal parameters, joint kinematics, and muscle activation, to changes in direction and speed during treadmill walking?Methods: We recruited 19 children (10 M/9 F) aged 6-12 years. Treadmill conditions included forward and backward walking at three speeds: slow (75 % of normal speed), normal speed, and fast (125 % of normal speed). Subjects completed a 2-minute trial under each condition. Spatiotemporal, kinematic, kinetic and electromyography data were collected and analyzed. Correlations between forward and time-reversed backward walking were calculated for joint angles and vertical ground reaction force.Results: During backward walking, children (a) decreased step lengths and increased step widths and foot clearance, (b) decreased peak hip and knee flexion and increased peak ankle dorsiflexion, and (c) increased muscle activity at the vastus lateralis, rectus femoris, and tibialis anterior. At faster speeds, children increased step lengths and inconsistently increased overall muscle activity. Both the hip and knee showed high correlation between forward and time-reversed backward walking, while correlation at the ankle was low.Significance: Overall, children adapt their gait to changes in direction and speed of treadmill walking in similar ways to adults. However, notable differences emerged in that children limited their ankle range of motion. Our results suggest that, while many aspects of gait are mature enough by this age to adapt to backward walking on a treadmill, neuromuscular control at the ankle may still be lacking in children while walking backward on a treadmill. [ABSTRACT FROM AUTHOR]

Background: The Wartenberg pendulum test is a common clinical test that is used to measure stiffness about the knee in persons with and without disabilities such as cerebral palsy and Down syndrome (DS). Adults and adolescents with DS show fewer number of swing cycles and a lower relaxation index than healthy controls. However, it is not clear if children with DS show a similar trend compared to typically developing (TD) children.Research Question: Was the knee joint kinematics different between children with and without DS during the pendulum test?Methods: Thirteen children with DS and 13 TD children participated in this study. There were two load conditions: no load (NL) and with ankle load (AL) equal to 2 % of the subject's body weight. Five trials of a pendulum test were collected for each condition.Results: The DS group showed a smaller first flexion excursion, a lower relaxation index, lower mean and peak velocities and accelerations during the first and second flexion and extension, and greater variability of acceleration during the first flexion than the TD group across both load conditions. This suggests that the DS group may have greater stiffness of the knee than the TD group to compensate for joint instability.Significance: The pendulum test appears to be a valid test to evaluate the passive stiffness of the knee in children with DS. The lower relaxation index in children with DS suggests that larger bursts of quadriceps may be activated during a pendulum test, particularly in the first flexion excursion, to assure the knee joint stability. [ABSTRACT FROM AUTHOR]

Background: The timed up-and-go (TUG) test consists of multiple functional activities of daily living performed in a sequence, with the goal to complete the test as quickly as possible. Considering children with Down syndrome (DS) have been shown to take longer to complete the TUG test, it is imperative to identify which tasks are problematic for this population in order to individualize physical interventions.Research Question: Is the biomechanical pattern of each functional task during the TUG test different between children with DS and typically developing (TD) children?Methods: Thirteen children with DS and thirteen TD children aged 5-11 years old completed the TUG test. Kinematic data was captured using a Vicon motion capture system. We visually coded the TUG test into five phases: sit-to-stand, walk-out, turn-around, walk-in, and stand-to-sit. We focused on the center-of-mass (COM) movement in the sit-to-stand phase, spatiotemporal parameters in the walk-out phase, and intersegmental coordination in the turn-around phase.Results and Significance: Children with DS took longer to complete the entire test, as well as each of the five phases. During the sit-to-stand phase, children with DS produced smaller peak vertical COM velocity, medial-lateral COM excursion, and peak knee and hip extension velocity compared to TD peers. Children with DS walked at a slower velocity during the walk-out phase. Both groups demonstrated a similar intersegmental coordination pattern between the head, thorax, and pelvis during the turn-around phase although children with DS had slower average and peak angular velocity at the head, thorax, and pelvis. Our results suggest that children with DS were less able to anticipate transitioning between motor tasks and took longer to initiate motor tasks. Our TUG analysis provides the detailed insights to help evaluate individual motor tasks as well as the transition from one task to another for clinical populations. [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]