Regulation Of Dynamic Balance Research Articles

Manual stabilization reveals a transient role for balance control during locomotor adaptation.

A fundamental feature of human locomotor control is the need to adapt walking patterns in response to changes in the environment. For example, when people walk on a split-belt treadmill, which has belts that move at different speeds, they adapt to the asymmetric speed constraints by reducing spatiotemporal asymmetry. Here, we aim to understand the role of balance control as a potential factor driving this adaptation process. We recruited 24 healthy, young adults to adapt to walking on a split-belt treadmill while either holding on to a handrail or walking with free arm swing. We measured whole body angular momentum and step length asymmetry as measures of dynamic balance and spatiotemporal asymmetry, respectively. To understand how changes in intersegmental coordination influenced whole body angular momentum, we also measured segmental angular momenta and the coefficient of cancellation. When participants were initially exposed to the asymmetry in belt speeds, we observed an increase in whole body angular momentum that was due to both an increase in the momentum of individual segments and a reduction in the coefficient of cancellation. Holding on to a handrail reduced the perturbation to asymmetry during the early phase of adaptation and resulted in a smaller aftereffect during early postadaptation. In addition, the stabilization provided by holding on to a handrail led to reductions in the coupling between angular momentum and asymmetry. These results suggest that regulation of dynamic balance is most important during the initial, transient phase of adaptation to walking on a split-belt treadmill.NEW & NOTEWORTHY We investigated the role of dynamic balance during adaptation to a split-belt treadmill by measuring whole body angular momentum with or without holding on to a handrail. The initial step length asymmetry and associations between balance and asymmetry reduced when holding on to a handrail during early adaptation. These findings indicate that dynamic balance mostly contributes to the initial phase of adaptation when people are exposed to an asymmetric walking constraint.

Relating Underlying Performance Objectives of Overground Walking to Observable Walking Mechanics using Predictive Musculoskeletal Simulations.

There exists motor redundancy during human gait that allows individuals to perform the same task in different observable ways (i.e., with varied styles). However, how differences in observable walking mechanics depend on unique and underlying biomechanical objectives is unclear. As an example, these objectives could include metabolic energy consumption, sum of muscle activations, limb mechanical loading, balance and combinations thereof. In this study, we develop predictive neuromuscular simulations to investigate the relationships between these biomechanical objectives and observable mechanics during level walking. We simulated 3D normal walking of five healthy subjects, while optimizing each of the aforementioned objectives-resulting in 25 forward dynamics simulations for analysis. We compared the resulting joint kinematics and moments of different simulations. One of main findings suggests that decreased hip abduction angle is tightly related to when the regulation of dynamic balance (computed as whole-body angular momentum) is included in a movement cost function. We also find that increased joint moments are related to including metabolic cost (i.e., objectives associated with improving the energy economy of movement). Further, the timing of joint kinematics is adjusted for different performance objectives. These findings could guide the development of rehabilitation training and assistive devices that target specific individuals, tasks, and specific styles of movement.

Time evolution of frontal plane dynamic balance during locomotor transitions of altered anticipation and complexity

BackgroundLocomotor transitions between different ambulatory tasks are essential activities of daily life. During these transitions, biomechanics are affected by various factors such as anticipation, movement direction, and task complexity. These factors are thought to influence the neuromotor regulation of dynamic balance, which can be quantified using whole-body angular momentum (H). However, the specific effects of these factors on balance during transitions are not well understood. The ability to regulate dynamic balance in the presence of these contextual factors is especially important in the frontal plane, as it is usually challenging to maintain walking balance in the frontal plane for individuals with neuromuscular impairments. The purpose of this study was to apportion their effects on the time evolution of frontal plane dynamic balance during locomotor transitions of healthy, unimpaired individuals.MethodsFive healthy young subjects performed 10 separate types of transitions with discrete combinations of factors including complexity (straight walking, cuts, combined cut/stair ascent), cut style (crossover, sidestep), and anticipation (anticipated and unanticipated). A three-way analysis of variance (ANOVA) was used to compare the maxima, minima, and average rates of change of frontal-plane H among all transitions.ResultsBefore transition, within anticipated state peak value of H increased 307% in crossover style relative to sidestep style (p < 0.0001). During Transition Phase, within unanticipated state the magnitudes of average rate of change and peak value increased 70 and 46% in sidestep style compared to crossover style (p < 0.0001 and p = 0.0003). Within sidestep style, they increased in unanticipated state relative to anticipated state. Later in Correction Phase, within both anticipation states peak value of H increased 41 and 75% in cut/stairs transitions relative to cuts (p = 0.010 and p < 0.0001). For cut/stairs transitions, peak value of H increased 45% in unanticipated state compared to anticipated state (p = 0.0001).ConclusionsThese results underlined the detrimental effects of unanticipated state and task complexity on dynamic balance during walking transitions. These findings imply increased demand of neuromuscular system and functional deficits of individuals with neuromuscular disorders during these tasks. In addition, cutting style influenced frontal plane dynamic balance before transition and in response to unanticipated direction change. Collectively, these results may help identify impaired balance control of fall-prone individuals and inform interventions targeting specific destabilizing scenarios.

Avaliação da regulação sensorial do equilíbrio corporal e risco de queda de mulheres adultas e idosas fisicamente ativas

OBJECTIVE: To examine the sensory performance of static and dynamic balance regulation and the risk of falling in physically active adult and elderly women.METHOD: This is a non-probabilistic and intentional cross-sectional study. Thirty four women (51.90±15.84 years) enrolled in a gym attended. The population evaluated was stratified in age groups: 20-59 years (n=18) and 60 69 years (n=16). The gait was evaluated by the Time Up and Go (TUGs), Time Up and Go manual (TUGm), and Time Up and Go cognitive (TUGc), the balance by the Dynamic Gait Index (DGI) and Body Balance Test (TEC). RESULTS: Student’s t-test showed significant differences between age groups for comorbidities: hearing, vision, vertigo, labyrinthitis (p≤0.05). Comparatively, adult women showed better performance indices than older women in physical tests. According to the standards of the tests, there was no risk of falling for any group. However, regardless of age, a detailed examination of the TEC test showed a deficit in the sensory regulation of the visual, vestibular and somatosensory systems of the static and dynamic balance of fallers and non fallers (p≤0.05). The logistic regression analysis indicated the interoceptive regulation of the dynamic balance as a predictor of fall (p≤0.05). CONCLUSION: Deficits in the vestibular and somatosensory systems gradually potentiate the risk of falls in adult and elderly women, even if they remain physically active.

The Contribution of Upper Body Movements to Dynamic Balance Regulation during Challenged Locomotion.

Recent studies suggest that in addition to movements between ankle and hip joints, movements of the upper body, in particular of the arms, also significantly contribute to postural control. In line with these suggestions, we analyzed regulatory movements of upper and lower body joints supporting dynamic balance regulation during challenged locomotion. The participants walked over three beams of varying width and under three different verbally conveyed restrictions of arm posture, to control the potential influence of arm movements on the performance: The participants walked (1) with their arms stretched out perpendicularly in the frontal plane, (2) spontaneously, i.e., without restrictions to the arm movements, and (3) with their hands on their thighs. After applying an inverse-dynamics analysis to the measured joint kinematics, we investigated the contribution of upper and lower body joints to balance regulation in terms of torque amplitude and variation. On the condition with the hands on the thighs, the contribution of the upper body remains significantly lower than the contribution of the lower body irrespective of beam widths. For spontaneous arm movements and for outstretched arms we find that the upper body (including the arms) contributes to the balancing to a similar extent as the lower body. Moreover, when the task becomes more difficult, i.e., for narrower beam widths, the contribution of the upper body increases, while the contribution of the lower body remains nearly constant. These findings lend further support to the hypothetical existence of an “upper body strategy” complementing the ankle and hip strategies especially during challenging dynamic balance tasks.

Balance recovery reactions in individuals with recurrent nonspecific low back pain: Effect of attention

People who suffer from Low Back Pain (LBP) demonstrate impaired postural control. Deficits in sensory-motor systems have been proposed to be related to these changes. Considering higher cognitive process contribution to postural control, the aim of this study was to investigate the effects of cognitive load on balance control of patients with LBP. Twenty subjects with recurrent non-specific LBP and 20 healthy controls participated. They stood on a moveable platform with each foot placed on a separate force plate. They were asked to maintain their balance (a) while expecting translations of the support surface at two sizes of perturbation (b) with and without performing a cognitive (auditory Stroop) task. The outcomes included reaction time (RT), latency, initial velocity and amplitude of center of pressure response for balance, and RT for cognitive performance. Compared to the healthy group, LBP group demonstrated delayed RT and latency, and reduced initial velocity (P<0.05). Moreover, they had slower Stroop RT (F=70.88, P<0.001). Concurrent performance of tasks resulted in increased Stroop RT (F=3.42, P=0.03) and adaptation in initial velocity (F=6.70, P=0.01). At the smaller size of perturbation, cognitive load increased velocity in LBP group but decreased this variable in the healthy group. When the cognitive load was added at the larger size of perturbation, velocity of response decreased in LBP group (P<0.05). These findings imply altered cognitive regulation of dynamic balance in patients with LBP and suggest that the adopted strategy might alter depending upon the characteristics of the postural challenge.

Association between omentin-1, bone metabolism markers, and cytokines of the RANKL/RANK/OPG system in girls with anorexia nervosa.

Omentin-1, secreted by visceral adipose tissue, has been indicated in the regulation of bone metabolism in girls with anorexia nervosa (AN). The aim of the study was to evaluate the relationship between omentin-1 and bone metabolism in girls with AN as well as the potential involvement of OPG and RANKL in this relationship. Serum omentin-1, OC, CTx, OPG, and sRANKL were determined by ELISA in 49 girls with AN and in 30 healthy controls, aged 13 to 17 years. Girls with AN exhibited significant reduction in body weight, BMI, and Cole index as well as a significant increase in serum omentin-1 levels, compared to healthy participants. These changes were associated with a significant decrease in serum OC and CTx levels and a significant increase in OPG and sRANKL while the OC/CTx and OPG/sRANKL ratios were significantly decreased. BMI and the Cole index correlated negatively and significantly with omentin-1 levels, positively with CTx levels and the OC/CTx ratio in the control group (C), girls with AN, and all study participants (C + AN). Girls with AN showed a significant negative correlation between BMI, the Cole index, and OPG levels. The combined group (C + AN) showed a significant positive correlation between BMI, the Cole index, and the OPG/sRANKL ratio. Omentin-1 levels correlated negatively and significantly with OC and CTx levels as well as with the OC/CTx and OPG/sRANKL ratios in the C, AN, and C + AN groups. The relationship between omentin-1, bone markers, and the OC/CTx and OPG/sRANKL ratios observed in girls with AN indicates the involvement of this adipokine in the regulation of dynamic balance between bone formation and resorption processes. Omentin-1 might exert a negative effect on bone remodelling in girls with AN by inhibiting both bone formation and resorption. The OPG/sRANKL system plays an important role in the latter.

Role of visual input in the control of dynamic balance: variability and instability of gait in treadmill walking while blindfolded

While vision obviously plays an essential role in orienting and obstacle avoidance, its role in the regulation of dynamic balance is not yet fully understood. The objective of this study was to assess dynamic stability while blindfolded, under optimal conditions that minimized the fear of falling. The hypothesis was that visual deprivation could be compensated for by using other sensory strategies to stabilize gait. One hundred healthy adults (aged 20-69 years) participated in the study. They were previously accustomed to blindfolded treadmill walking wearing a safety harness. Their preferred walking speeds (PWS) were assessed with eyes open (PWSEO) and with eyes closed (blindfolded, PWSEC). Three five-minute tests were performed: (A) normal walking at PWSEO, (B) blindfolded walking at PWSEC, and (C) normal walking at PWSEC. Trunk acceleration was measured with a lightweight inertial sensor. Dynamic stability was assessed by using (1) acceleration root mean square (RMS), which estimates the variability of the signal, and hence, the smoothness of the trunk movement and (2) local dynamic stability (LDS), which reflects the efficiency of the motor control to stabilize the trunk. Although walking at PWSEC with eyes open (comparing conditions A and C) had a slight impact on gait stability (relative difference: RMS +4 %, LDS -5 %), no destabilizing effect of visual deprivation (B vs. C, RMS -4 %, LDS -1 %) was observed. Therefore, it is concluded that when reassuring conditions are offered to individuals while walking, they are able to adopt alternative sensory strategies to control dynamic equilibrium without the help of vision.

Study on Real-Time Regulation of Water Resources Yellow River Basin

This paper puts forward and studies the concept, features as well as regulation process of real-time dispatch of basin water resources. The real-time regulation of basin water resources features temporal regulation system of multiple time-step nesting, dynamic balance regulation system of self-adapting demand-supply, dynamic information-based feedback regulation system, and three-element regulation system in combination of reservoir dispatch, river reach water distribution and flow forecast control. With example of lower Yellow River reaches below Xiaolangdi, a real-time regulation model of water resources in river basin with multiple time-step nesting and scrolling-amendment has been developed. The developed model has been put into actual practice and resulted in the safety of water supply and avoid of dry-up in consecutive low flow yeas of Yellow River Basin.

Anticipatory postural adjustments in the back and leg lift.

This study examined anticipatory postural adjustments in a dynamic multi-joint action in which a relatively fast voluntary movement is being executed while balance is maintained in the field of gravity. In a bi-manual whole body lifting task, the pickup of the load induces a forward shift in the position of the center of mass, challenging the dynamic balance regulation while simultaneously impeding the ongoing extension movement. We investigated whether anticipatory postural adjustments are an addition to a voluntary motor command or an inherent component of this command. Using a global mechanical analysis of the movement, we found that anticipatory postural adjustments are present in bimanual lifting, both in back lifting and leg lifting, and that lifting technique had a significant influence on the pattern of the adjustments. If the mass of the object was reduced unexpectedly, balance was disturbed in 92% of the mass-reduced trials. These findings suggest that the anticipatory postural adjustments to be performed are specified in advance such that the expected changes in the mechanical interaction with the environment are taken into account. The observations lend support to the hypothesis that the control of the observed anticipatory postural adjustments is an integral part of the control of the lifting movement itself. Consequently, the strict dichotomy in the control of posture and movement is being questioned.