Introduction: It is crucial to comprehend the interplay between the center of mass (CoM) and base of support (BoS) in elderly individuals\' body movements, as it could have implications for fall prevention. Methods: The purpose of this study is to characterize age-related differences using the instantaneous location of the CoM and CoM velocity vector in relation to the dynamically changing BoS during walking. Thirty subjects participated in the experiments. Derivation formulas of feasible stability region and age-related statistical analyses were proposed. Results: The stability margin and distance to centroid for elderly group were found to be significantly different from the young group (p < 0.05). At heel strike, while the CoMv distance was similar for age-based groups (p > 0.05), older individuals demonstrated a greater CoMv distance to the border than the younger at right limb, which suggesting age-related differences in momentum control. In addition, Bland-Altman analysis indicated that the validity was substantial, making it feasible to capture stride-to-stride variability. Discussion: The CoM trajectories and feasible stability region could provide a better understanding of human momentum control, underlying mechanisms of body instability and gait imbalance.

UNASSIGNED: It is known that even under static conditions a backpack wearer will need to make some adjustments to maintain postural stability. There is a paucity of research exploring the impact of altering the position of the feet with imposed loads of variable distance from the posterior midline.
UNASSIGNED: Therefore, the aim of this study was to determine if changes in the horizontal position of a fixed load when wearing a backpack affect specific variables derived from foot tracings of males and females standing with their self-selected natural feet position.
UNASSIGNED: 150 healthy volunteer participants were instructed to adopt a natural stance across four conditions: Backpack with no weight, backpack with a weight (5% of body mass) placed at 0 cm, 20 cm, and 40 cm distance from the posterior body. Foot tracings were made for each condition. Base of Support (BoS), Feet Width (FW), and Feet Opening Angle (FOA) were calculated.
UNASSIGNED: The BoS significantly decreased in loaded conditions (0 cm, 20 cm and 40 cm) compared to unloaded. This was supported by FW and FOA significant findings that once the load was imposed the response was to approximate the feet and reduce \'toeout\'.
UNASSIGNED: This reaction of people to reduce their BoS in response to added backpack load appears counter intuitive and raises the question of whether this is maladaptive. Clarification by further investigation will inform backpack wearers to counter this instinctive response to load and increase postural stability.

BACKGROUND: Challenges to postural stability emerge in the transition from locomotion to a standing posture as during gait termination, often accompanied by another task (e.g., opening a door), which may complicate control. However, less is known about postural control during terminating gait while engaged in a secondary manual task.
OBJECTIVE: What are the changes in postural control when terminating gait with and without a prehension task?
METHODS: In a cross-sectional design, 15 healthy young adults (M=8, F=7; 27±2 years; 69±13 kg; 171±8 cm) underwent both a single task gait termination (GTO) and dual task (gait termination plus reaching; GTR). Postural Time-to-Contact (TtC) was measured using Center of Pressure (CoP) and the sternum position in anterior-posterior (AP) and medial-lateral (ML) directions over two different phases: preparatory phase and stabilization phase. Five successful trials were recorded to obtain a mean TtC. For statistical analysis of TtC, a two-tailed paired t-test was used (p =.05) as normality was satisfied.
RESULTS: For the preparatory phase, there were no differences for the CoP, but TtC of the sternum position in AP was shorter in GTR than GTO (p =.001). Meanwhile, for the stabilization phase, TtCs of both the CoP and sternum position were longer in GTR in both AP and ML directions (p\'s <.001).
CONCLUSIONS: We suggest that for the preparatory phase, the shorter TtC of the sternum position with intact TtC of the CoP in GTR indicates that healthy young individuals are flexible, in that they smoothly integrate CoP control with the upper body demands required to also perform the prehension task. Meanwhile, for the stabilization phase, the longer TtC in dual termination and prehension task indicates that the perturbation imposed by the prehension movement did not result in reduced stabilization when returning to an upright posture.

Older adults, as well as those with certain neurological disorders, may compensate for poor neural control of postural stability by widening their base of foot support while walking. However, the extent to which this wide-based gait improves postural stability or affects postural control strategies has not been explored. People with idiopathic Parkinson\'s disease (iPD, n = 72), frontal gait disorders (FGD, n = 16), and healthy older adults (n = 32) performed walking trials at their preferred speed over an 8-m-long, instrumented walkway. People with iPD were tested in their OFF medication state. Analyses of covariance were performed to determine the associations between stride width and measures of lateral stability control. People with FGD exhibited a wide-based gait compared to both healthy older adults and iPD. An increased stride width was associated with an increase in lateral margin of stability in FGD. Unlike healthy older adults or iPD, people with FGD did not externally rotate their feet (toe-out angle) or shift their center of pressure laterally to aid lateral dynamic stability during walking but slowed their gait instead to increase stability. By adopting a slow, wide-based gait, people with FGD take advantage of the passive, pendular mechanics of walking.

UNASSIGNED: Systematically review literature addressing the effects of changes in base of support (BoS) configuration and characteristics of support surface (SS) on postural control of children with cerebral palsy (CP).
UNASSIGNED: We conducted a tailored electronic database search in PubMed/Web of Science/SCOPUS/Embase.
UNASSIGNED: We identified 15 studies meeting inclusion criteria.
UNASSIGNED: The extant literature suggests that when children with CP experience changes in BoS and SS, they engage in fewer adaptive postural control responses than typically developing children. Documented response patterns of children with CP in the literature might guide the selection and development of rehabilitation strategies to appropriately facilitate or challenge postural control in children with CP.

Photogrammetry is often used to evaluate standing static postural alignment. Patients are often instructed to self-select a natural feet position but it\'s unclear whether this position can be consistently replicated across repeated assessments.
To determine whether people can replicate a self-selected natural feet position in upright standing across three sessions on different days.
Between days test-retest reliability.
University laboratory.
Three variables - Base of Support (BoS), Foot Width (FW), Feet Opening Angle (FOA) - were measured from foot tracings of 150 participants (18-30 years) using established procedures. BoS data were assessed for systematic bias (Analysis of Variance), and absolute (Coefficient of Variation - CV%) and relative (Intraclass Correlation Coefficient - ICC) reliability.
There was systematic bias in the BoS data across the three testing sessions. The CV% for the BoS data was 15.2%. The ICC (95% CI) for the BoS data was 0.84 (0.79-0.87). There were moderate-large correlations between the BoS and both FOA and FW respectively within each session.
If clinicians want to allow patients to use their self-selected natural feet position for repeated photogrammetric assessment of their static postural alignment it would be better to standardise the position of the feet, for example, by creating a tracing of a patient\'s self-selected natural feet position.

Children\'s ability to maintain balance requires effective integration of multisensory and biomechanical information. The current project examined the interaction between such sensory inputs, manipulating visual input (presence vs. absence), haptic (somatosensory) input (presence vs. absence of contact with a stable or unstable finger support surface), and biomechanical (sensorimotor) input (varying stance widths). Analyses of mean velocity of the center of pressure and the percentage stability gain highlighted the role of varying multisensory inputs in postural control. Developmentally, older children (6-11 years) showed a multisensory integration advantage compared with their younger counterparts (3-5.9 years), with the impact of varying sensory inputs more closely akin to that seen in adults. Subsequent analyses of the impact of anthropometric individual difference parameters (e.g., height, leg length, weight, areas of base of support) revealed a shifting pattern across development. For younger children, these parameters were positively related to postural stability across experimental conditions (i.e., increasing body size was related to increasing postural control). This pattern transitioned for older children, who showed a nonsignificant relation between body size and balance. Interestingly, because adults show a negative relation between anthropometric factors and stability (i.e., increasing body size is related to decreasing postural control), this shift for the older children can be seen as a developmental transition from child-like to adult-like balance control.

Stepping strategies following external perturbations from different directions is investigated in this work. We analysed the effect of the perturbation angle as well as the level of awareness of individuals and characterised steps out of the sagittal plane between Loaded Side Steps (LSS), Unloaded Medial Steps (UMS) and Unloaded Crossover Steps (UCS). A novel experimental paradigm involving perturbations in different directions was performed on a group of 21 young adults (10 females, 11 males, 20-38 years). Participants underwent 30 randomised perturbations along 5 different angles with different levels of awareness of the upcoming perturbations (with and without wearing a sensory impairment device) for a total of 1260 recorded trials. Results showed that logistic models based on the minimal values of the Margin of Stability (MoS) or on the minimal values of the Time to boundary (Ttb) performed the best in the sagittal plane. However, their accuracy stayed above 79% regardless of the perturbation angle or level of awareness. Regarding the effect of the experimental condition, evidences of different balance recovery behaviours due to the variation of perturbation angles were exposed, but no significant effect of the level of awareness was observed. Finally, we proposed the Distance to Foot boundary (DtFb) as a relevant quantity to characterise the stepping strategies in response to perturbations out of the sagittal plane.

The analysis of the stability of human gait may be effectively performed when estimates of the base of support are available. The base of support area is defined by the relative position of the feet when they are in contact with the ground and it is closely related to additional parameters such as step length and stride width. These parameters may be determined in the laboratory using either a stereophotogrammetric system or an instrumented mat. Unfortunately, their estimation in the real world is still an unaccomplished goal. This study aims at proposing a novel, compact wearable system, including a magneto-inertial measurement unit and two time-of-flight proximity sensors, suitable for the estimation of the base of support parameters. The wearable system was tested and validated on thirteen healthy adults walking at three self-selected speeds (slow, comfortable, and fast). Results were compared with the concurrent stereophotogrammetric data, used as the gold standard. The root mean square errors for the step length, stride width and base of support area varied from slow to high speed between 10-46 mm, 14-18 mm, and 39-52 cm2, respectively. The mean overlap of the base of support area as obtained with the wearable system and with the stereophotogrammetric system ranged between 70% and 89%. Thus, this study suggested that the proposed wearable solution is a valid tool for the estimation of the base of support parameters out of the laboratory.

Freezing of gait (FOG) is a sudden episodic inability to produce effective stepping despite the intention to walk. It typically occurs during gait initiation (GI) or modulation and may lead to falls. We studied the anticipatory postural adjustments (imbalance, unloading, and stepping phase) at GI in 23 patients with Parkinson\'s disease (PD) and FOG (PDF), 20 patients with PD and no previous history of FOG (PDNF), and 23 healthy controls (HCs). Patients performed the task when off dopaminergic medications. The center of pressure (CoP) displacement and velocity during imbalance showed significant impairment in both PDNF and PDF, more prominent in the latter patients. Several measurements were specifically impaired in PDF patients, especially the CoP displacement along the anteroposterior axis during unloading. The pattern of segmental center of mass (SCoM) movements did not show differences between groups. The standing postural profile preceding GI did not correlate with outcome measurements. We have shown impaired motor programming at GI in Parkinsonian patients. The more prominent deterioration of unloading in PDF patients might suggest impaired processing and integration of somatosensory information subserving GI. The unaltered temporal movement sequencing of SCoM might indicate some compensatory cerebellar mechanisms triggering time-locked models of body mechanics in PD.