Effects of frequency on single leg hopping in typically developing preadolescents

Hopping is considered a mass-spring model movement in which the leg supports the center of mass. There is a preferred hopping frequency and hopping outside of that frequency is more difficult and requires more energy. Leg stiffness has been shown to be an important factor when hopping at different frequencies in young adult populations. The purpose of this study was to observe how a still-developing preadolescent population would modify leg stiffness while hopping at different frequencies and if they have similar motor control strategies compared to young adults. The subjects hopped on their dominant leg to the beat of a metronome at one of four frequency conditions based on their calculated preferred frequency, MP (preferred frequency), MM (20% increase), MF (40% increase), and MS (20% decrease). It was found that this population could change their hopping frequency and they achieved this by manipulating their leg stiffness. At the higher frequency conditions there was less movement of the toe and the center of mass in both the vertical and horizontal directions, including decreased hopping height, decreased COM displacement and COM range of motion. Preadolescents demonstrated an adult-like ability to increase leg stiffness and modulate movement of the toe and the COM while adapting to a range of hopping frequencies. This ability could translate into other mass-spring model movements such as running and jumping

Children Display Adult-Like Kinetic Pattern in the Time Domain but not in the Frequency Domain While Walking with Ankle Load

While external load is added during locomotion, humans increase the activation of extensors during stance and suppress the initiation of flexors during swing. External load at the ankles, rather than on the waist or thigh, elicits higher activities from ankle extensors, and increases stride length and decreases cadence in adults. Spatiotemporal and kinematic patterns become adult-like in children aged 5-8 years. However, little is known if children show adult like kinetic patterns while walking with external load This study aimed to investigate differences in kinetic patterns between children and adults while walking with external ankle load using both time and frequency domain analyses

Walking pattern in children with and without Down syndrome via a Force-Driven Harmonic Oscillator Model

Children with Down syndrome (DS) display poorer kinematic and kinetic patterns of walking than typically developing ( TD) children. However, little is known on neuromuscular control in children with DS during locomotion. A force driven harmonic oscillator (FDHO) model sheds light on general muscular activation with respect to the gravitational load of the thigh-shank-foot system. The K/G ratio derived from this model represents a scaling between the elastic restoring torque from muscles and soft tissues and the gravitational torque from the weight of the leg during walking. The K/G ratio has shown different muscular function in infant walkers and children with cerebral palsy. This study aimed to compare the K/G ratio between children with and without DS during walking

Effect of whole-body vibration on center-of-mass movement during standing in children and young adults

Whole body vibration (WBV) can affect postural control and muscular activation. The purpose of this study was to investigate the center-of-mass (COM) movement of children and young adults before, during, immediately after, and 5min after 40-s WBV in quiet standing. Fourteen young adults (mean age 24.5 years) and fourteen children (mean age 8.1 years) participated in the study. A full-body 35-marker set was placed on the participants and used to calculate COM. Forty-second standing trials were collected before, during, immediately after, and 5min after WBV with an frequency of 28Hz and an amplitude of \u3c1mm. Two visual conditions were provided: eyes-open (EO) and eyes-closed (EC). COM variables included time-domain measures (average velocity, range, sway area and fractal dimension), frequency-domain measures (total power and median frequency), and detrended fluctuation analysis (DFA) scaling exponent in both anterior-posterior (AP) and medial-lateral (ML) directions. Results show that during WBV both children and adults increased average velocity and median frequency, but decreased range and the DFA scaling exponent. Immediately after WBV both groups increased the range, but showed pre-vibration values for most of the COM variables. Comparing to adults, children displayed a higher COM velocity, range, fractal dimension, and total power, but a lower DFA scaling exponent at all phases. The results suggest that both children and adults can quickly adapt their postural control system to WBV and maintain balance during and after vibration. Children display some adult-like postural control during and after WBV; however, their postural development continues into adolescence

Variability of spatiotemporal gait parameters in children with and without Down syndrome during treadmill walking

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

Improvement in overground walking after treadmill-based gait training in a child with agenesis of the corpus callosum

Background: Agenesis of the corpus callosum (ACC) is a rare congenital brain defect that produces a wide variety of cognitive and motor impairments. Literature regarding the response of pediatric populations with ACC to physical rehabilitation is scarce. Treadmill-based gait training (TT) has been shown to improve walking ability in some pediatric populations but has not been investigated in children with ACC. Objective: The purpose of this study was to investigate the effect of a novel treadmill intervention paradigm on the gait parameters of a child with ACC. Design: A single-participant design with 2 phases was used. Methods: The settings were the participant\u27s home and the laboratory. The participant was a 13-year-old girl who had ACC and cortical visual impairment and who ambulated independently using a reverse walker for household and short community distances. A home-based TT intervention (2 phases of 3 months of training over 6 months) was implemented, and a laboratory-based gait analysis was conducted at 4 time points: baseline, after each of the 2 training phases, and 3 months after the cessation of training. The intervention consisted of weekly bouts of TT. Phase I incorporated forward, backward, and incline walking for 15 minutes each; in phase II, this protocol was continued, but short-burst interval training for 10 minutes was added. Data collected at each laboratory visit included spatiotemporal parameters and kinematics (joint angles) during overground and treadmill walking. Results: After both phases of training, increased step length, decreased step width, and foot progression angle and decreased variability of most spatiotemporal parameters were observed for the participant. Further, after phase II, increased peak extension at the hip, knee, and ankle, decreased crouched gait, and improved minimum foot clearance during overground walking were observed. Most gait improvements were retained for 3 months after the cessation of the intervention. Limitations: The small sample size of this study and wide variety of presentations within individuals with ACC limit the generalizability of our findings. Conclusions: TT may be a safe and effective treatment paradigm for children with ACC. Future research should investigate the effect of intervention dosage on gait improvements and generalization in individuals with ACC

Replication of Zahradnik et al (2020)

Replication of the study titled "Associated ACL risk factors differences during an unanticipated volleyball blocking movement" as part of the large replication project in the Sports Science Replication Centr

Walking Dynamics in Preadolescents with and without Down Syndrome

Background. A force-driven harmonic oscillator (FDHO) model reveals the elastic property of general muscular activity during walking. Objective. This study aimed to investigate whether children with Down syndrome (DS) have a lower K/G ratio, a primary variable derived from the FDHO model, compared with children with typical development during overground and treadmill walking and whether children with DS can adapt the K/G ratio to walking speeds, external ankle load, and a treadmill setting. Design. A cross-sectional study design was used that included 26 children with and without DS, aged 7 to 10 years, for overground walking and 20 of them for treadmill walking in a laboratory setting. Methods. During overground walking, participants walked at 2 speeds: normal and fastest speed. During treadmill walking, participants walked at 75% and 100% of their preferred overground speed. Two load conditions were manipulated for both overground and treadmill walking: no load and an ankle load that was equal to 2% of body mass on each side. Results. Children with DS showed a K/G ratio similar to that of their healthy peers and increased this ratio with walking speed regardless of ankle load during overground walking. Children with DS produced a lower K/G ratio at the fast speed of treadmill walking without ankle load, but ankle load helped them produce a K/G ratio similar to that of their healthy peers. Limitations. The FDHO model cannot specify what muscles are used or how muscles are coordinated for a given motor task. Conclusions. Children with DS show elastic property of general muscular activity similar to their healthy peers during overground walking. External ankle load helps children with DS increase general muscular activity and match their healthy peers while walking fast on a treadmill