scholarly journals Effects of External Perturbations on Anticipatory and Compensatory Postural Adjustments in Patients with Multiple Sclerosis and a Fall History

2018 ◽  
Vol 20 (4) ◽  
pp. 164-172 ◽  
Author(s):  
Shirin Tajali ◽  
Mina Rouhani ◽  
Mohammad Mehravar ◽  
Hossein Negahban ◽  
Elham Sadati ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Fall Prevention ◽  
Muscle Activity ◽  
Center Of Pressure ◽  
Trunk Muscles ◽  
Postural Adjustment ◽  
Postural Adjustments ◽  
External Perturbations ◽  
The Relationship ◽  
Adjustment Mechanisms

Abstract Background: Although previous studies have investigated postural adjustment mechanisms in patients with multiple sclerosis (MS), it seems that no study has yet investigated the relationship between anticipatory and compensatory postural adjustments (APAs and CPAs, respectively) and falls. Methods: Seventeen MS fallers, 17 MS nonfallers, and 15 controls were exposed to a series of expected and unexpected backward pull perturbations applied at the trunk level. The electrical activity of 12 leg and trunk muscles as well as center of pressure displacement were recorded. Results: The MS fallers had delayed muscle activity onsets compared with MS nonfallers and controls. In addition, a significantly lower level of muscle activity during APAs was detected in MS fallers compared with controls. Moreover, in the unexpected condition of perturbation, significantly smaller CPA was observed in MS fallers compared with controls. Both groups of patients with MS required more time to stabilize their center of pressure after both types of perturbations compared with controls. Conclusions: The inability to produce efficient APAs and CPAs during perturbations may explain the high rates of postural instability and falls in patients with MS. Findings from this study provide a background for the development of perturbation-based training programs aimed at balance improvement and fall prevention by restoring mechanisms underlying balance impairments.

Individuals With Stroke Use Asymmetrical Anticipatory Postural Adjustments When Counteracting External Perturbations

Motor Control ◽  
2019 ◽  
Vol 23 (4) ◽  
pp. 461-471
Author(s):  
Etem Curuk ◽  
Yunju Lee ◽  
Alexander S. Aruin
Keyword(s):  
Muscle Activity ◽  
Balance Control ◽  
Anticipatory Postural Adjustments ◽  
Trunk Muscles ◽  
Electromyographic Activity ◽  
Healthy Controls ◽  
Unaffected Side ◽  
Postural Adjustments ◽  
External Perturbations ◽  
Anticipatory Activation

The authors investigated anticipatory postural adjustments in persons with unilateral stroke using external perturbations. Nine individuals with stroke and five control subjects participated. The electromyographic activity of 16 leg and trunk muscles was recorded. The onsets of muscle activity during the anticipatory phase of postural control were analyzed. The individuals with stroke did not show an anticipatory activation of leg and trunk muscles on the affected side; instead, the muscle onsets were seen after the perturbation, during the balance restoration phase. However, an anticipatory activation of muscles on the unaffected side was seen in individuals with stroke, and it was observed earlier compared with healthy controls (p < .05). The individuals with stroke showed a distal to proximal order of anticipatory activation of muscles on the unaffected side. The outcome of the study provides a basis for future investigations regarding ways of improving balance control in people with stroke.

THE ROLE OF ANTICIPATORY POSTURAL ADJUSTMENTS AND COMPENSATORY CONTROL OF POSTURE IN BALANCE CONTROL OF PATIENTS WITH MULTIPLE SCLEROSIS

2015 ◽  
Vol 15 (05) ◽  
pp. 1550087 ◽  
Author(s):  
MOHAMMAD MEHRAVAR ◽  
NAVA YADOLLAH-POUR ◽  
SHIRIN TAJALI ◽  
MOHAMMAD-JAFAR SHATERZADEH-YAZDI ◽  
NASTARAN MAJDINASAB
Keyword(s):  
Multiple Sclerosis ◽  
Center Of Pressure ◽  
Balance Control ◽  
Balance Training ◽  
Trunk Muscles ◽  
Postural Perturbation ◽  
Postural Adjustments ◽  
Rehabilitation Programs ◽  
Compensatory Control ◽  
Load Release

Impaired balance is one of the most disabling multiple sclerosis (MS) symptoms. It is known that, in the presence of predictable perturbations, the central nervous system (CNS) utilizes both anticipatory (APAs) and compensatory (CPAs) postural adjustments to maintain balance. The main purpose of this study was to investigate the relationship between APAs and CPAs during self-induced postural perturbation in patients with MS. Participants performed a load release task while standing on a force platform. Electrical activity of six leg and trunk muscles, as well as displacements of the center of pressure (COP), was recorded. The results revealed significant APAs deficits in MS patients reflected in short APAs duration and reduced magnitude. The reduced APAs were not accompanied by significant compensatory muscle activity. It can be concluded that there is an impairment of feed-forward postural control in MS, and feedback-based mechanisms (CPAs) are unable to compensate for these APA deficits. These results should be considered in the rehabilitation programs for balance training of MS patients.

scholarly journals Levodopa Reduces Muscle Tone and Lower Extremity Tremor in Parkinson’s Disease

1995 ◽  
Vol 22 (4) ◽  
pp. 280-285 ◽  
Author(s):  
Anne Burleigh ◽  
Fay Horak ◽  
John Nutt ◽  
James Frank
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Lower Extremity ◽  
Muscle Activity ◽  
Center Of Pressure ◽  
Muscle Tone ◽  
High Amplitude ◽  
Trunk Muscles ◽  
Foot Pressure ◽  
Control Subjects

AbstractObjectiveWe have quantified the effects of levodopa treatment in Parkinsonian subjects during maintained stance.MethodsElectromyographic muscle activity during quiet stance was assessed in subjects with Parkinson’s disease, who exhibited a fluctuating response to levodopa, and in age-matched control subjects. Stance stability was also assessed from mean displacement and velocity of the center of pressure excursions during stance.ResultsLower extremity and trunk muscles showed high amplitude activity in all Parkinson’s subjects when “off”, and a 4–5 Hz tremor in three of these subjects. When “on”, the amplitude of muscle activity was reduced in the distal muscles more than the proximal, while tremor was suppressed in all muscles. Corresponding to the excessive muscle activity, the Parkinson’s subjects had increased velocity and variability of velocity in the anterior-posterior center of foot pressure excursions, but the mean displacement of the center of pressure excursion was not different from the controls. The velocity of center of pressure excursions in the Parkinson’s subjects “on”, approached those of the control subjects suggesting that the excessive distal muscle amplitude and tremor contributed to the high velocity of the center of pressure.ConclusionsThese findings suggest that dopaminergic systems are involved in the regulation of muscle tone during stance. Depletion of dopaminergic transmission results in increased muscle tone and tremor in the lower extremities which may contribute to changes in posture and stability.

scholarly journals A Novel Viewpoint on the Anticipatory Postural Adjustments During Gait Initiation

2021 ◽  
Vol 15 ◽  
Author(s):  
Veronica Farinelli ◽  
Francesco Bolzoni ◽  
Silvia Maria Marchese ◽  
Roberto Esposti ◽  
Paolo Cavallari
Keyword(s):  
Center Of Pressure ◽  
Force Plate ◽  
Anticipatory Postural Adjustments ◽  
The Body ◽  
Erector Spinae ◽  
Trunk Muscles ◽  
Gait Initiation ◽  
Concentrated Force ◽  
Postural Adjustments ◽  
Leg Muscles

Anticipatory postural adjustments (APAs) are the coordinated muscular activities that precede the voluntary movements to counteract the associated postural perturbations. Many studies about gait initiation call APAs those activities that precede the heel-off of the leading foot, thus taking heel-off as the onset of voluntary movement. In particular, leg muscles drive the center of pressure (CoP) both laterally, to shift the body weight over the trailing foot and backward, to create a disequilibrium torque pushing forward the center of mass (CoM). However, since subjects want to propel their body rather than lift their foot, the onset of gait should be the CoM displacement, which starts with the backward CoP shift. If so, the leg muscles driving such a shift are the prime movers. Moreover, since the disequilibrium torque is mechanically equivalent to a forward force acting at the pelvis level, APAs should be required to link the body segments to the pelvis: distributing such concentrated force throughout the body would make all segments move homogeneously. In the aim of testing this hypothesis, we analyzed gait initiation in 15 right-footed healthy subjects, searching for activities in trunk muscles that precede the onset of the backward CoP shift. Subjects stood on a force plate for about 10 s and then started walking at their natural speed. A minimum of 10 trials were collected. A force plate measured the CoP position while wireless probes recorded the electromyographic activities. Recordings ascertained that at gait onset APAs develop in trunk muscles. On the right side, Rectus Abdominis and Obliquus Abdominis were activated in 11 and 13 subjects, respectively, starting on average 33 and 54 ms before the CoP shift; Erector Spinae (ES) at L2 and T3 levels was instead inhibited (9 and 7 subjects, 104 and 120 ms). On the contralateral side, the same muscles showed excitatory APAs (abdominals in 11 and 12 subjects, 27 and 82 ms; ES in 10 and 7 subjects, 75 and 32 ms). The results of this study provide a novel framework for distinguishing postural from voluntary actions, which may be relevant for the diagnosis and rehabilitation of gait disorders.

Evidence for constancy in the modularity of trunk muscle activity preceding reaching: Implications for the role of preparatory postural activity.

2021 ◽  
Author(s):  
Alexander Stamenkovic ◽  
Lena H Ting ◽  
Paul J Stapley
Keyword(s):  
Muscle Activity ◽  
Center Of Mass ◽  
Trunk Muscle ◽  
Trunk Muscles ◽  
Equilibrium Constraints ◽  
Postural Adjustments ◽  
Postural Activity ◽  
Postural Muscle ◽  
Mass Displacement ◽  
Base Of Support

Postural muscle activity precedes voluntary movements of the upper limbs. The traditional view of this activity is that it anticipates perturbations to balance caused by the movement of a limb. However, findings from reach-based paradigms have shown that postural adjustments can initiate center of mass displacement for mobility, rather than minimize its displacement for stability. Within this context, altering reaching distance beyond the base of support would place increasing constraints on equilibrium during stance. If the underlying composition of anticipatory postural activity is linked to stability, coordination between muscles (i.e., motor modules) may evolve differently as equilibrium constraints increase. We analyzed the composition of motor modules in functional trunk muscles as participants performed multi-directional reaching movements to targets within and beyond arm's length. Bilateral trunk and reaching arm muscle activity were recorded. Despite different trunk requirements necessary for successful movement, and the changing biomechanical (i.e. postural) constraints that accompany alterations in reach distance, Non-negative Matrix Factorization identified functional motor modules derived from preparatory trunk muscle activity that shared common features. Relative similarity in modular weightings (i.e., composition) and spatial activation profiles that reflect movement goals across tasks necessitating differing levels of trunk involvement provides evidence that preparatory postural adjustments are linked to the same task priorities (i.e. movement generation rather than stability).

scholarly journals Two aspects of feedforward postural control: anticipatory postural adjustments and anticipatory synergy adjustments

2011 ◽  
Vol 105 (5) ◽  
pp. 2275-2288 ◽  
Author(s):  
Miriam Klous ◽  
Pavle Mikulic ◽  
Mark L. Latash
Keyword(s):  
Muscle Activation ◽  
Center Of Pressure ◽  
Anticipatory Postural Adjustments ◽  
Uncontrolled Manifold ◽  
Trunk Muscles ◽  
Body Sway ◽  
Postural Adjustments ◽  
Muscle Mode ◽  
Shoulder Flexion ◽  
Muscle Modes

We used the framework of the uncontrolled manifold hypothesis to explore the relations between anticipatory synergy adjustments (ASAs) and anticipatory postural adjustments (APAs) during feedforward control of vertical posture. ASAs represent a drop in the index of a multimuscle-mode synergy stabilizing the coordinate of the center of pressure in preparation to an action. ASAs reflect early changes of an index of covariation among variables reflecting muscle activation, whereas APAs reflect early changes in muscle activation levels averaged across trials. The assumed purpose of ASAs is to modify stability of performance variables, whereas the purpose of APAs is to change magnitudes of those variables. We hypothesized that ASAs would be seen before APAs and that this finding would be consistent with regard to the muscle-mode composition defined on the basis of different tasks and phases of action. Subjects performed a voluntary body sway task and a quick, bilateral shoulder flexion task under self-paced and reaction time conditions. Surface muscle activity of 12 leg and trunk muscles was analyzed to identify sets of 4 muscle modes for each task and for different phases within the shoulder flexion task. Variance components in the muscle-mode space and indexes of multimuscle-mode synergy stabilizing shift of the center of pressure were computed. ASAs were seen ∼100–150 ms prior to the task initiation, before APAs. The results were consistent with respect to different sets of muscle modes defined over the two tasks and different shoulder flexion phases. We conclude that the preparation for a self-triggered postural perturbation is associated with two types of anticipatory adjustments, ASAs and APAs. They reflect different feedforward processes within the hypothetical hierarchical control scheme, resulting in changes in patterns of covariation of elemental variables and in their patterns averaged across trials, respectively. The results show that synergies quantified using dissimilar sets of muscle modes show similar feedforward changes in preparation to action.

Cortical contributions to control of posture during unrestricted and restricted stance

2014 ◽  
Vol 111 (9) ◽  
pp. 1920-1926 ◽  
Author(s):  
Chantelle D. Murnaghan ◽  
Jordan W. Squair ◽  
Romeo Chua ◽  
J. Timothy Inglis ◽  
Mark G. Carpenter
Keyword(s):  
Muscle Activity ◽  
Critical Level ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Sensory Information ◽  
Upright Stance ◽  
Subcortical Structures ◽  
The Central Nervous System ◽  
The Relationship

There is very little consensus regarding the mechanisms underlying postural control. Whereas some theories suggest that posture is controlled at lower levels (i.e., brain stem and spinal cord), other theories have proposed that upright stance is controlled using higher centers, including the motor cortex. In the current investigation, we used corticomuscular coherence (CMC) to investigate the relationship between cortical and shank muscle activity during conditions of unrestricted and restricted postural sway. Participants were instructed to stand as still as possible in an apparatus that allowed the center of mass to move freely (“Unlocked”) or to be stabilized (“Locked”) without subject awareness. EEG (Cz) and electromyography (soleus and lateral/medial gastrocnemii) were collected and used to estimate CMC over the Unlocked and Locked periods. Confirming our previous results, increases in center of pressure (COP) displacements were observed in 9 of 12 participants in the Locked compared with Unlocked condition. Across these 9 participants, CMC was low or absent in both the Unlocked and Locked conditions. The results from the current study suggest that this increase is not associated with an increase in the relationship between cortical and shank muscle activities. Rather, it may be that increases in COP displacement with locking are mediated by subcortical structures as a means of increasing sway to provide the central nervous system with a critical level of sensory information.

scholarly journals POSTURAL ADJUSTMENTS OF ACTIVE YOUTHS IN PERTURBATION AND DUAL-TASK CONDITIONS

2019 ◽  
Vol 25 (5) ◽  
pp. 428-432
Author(s):  
Victor Spiandor Beretta ◽  
Paulo Cezar Rocha Santos ◽  
Diego Alejandro Rojas Jaimes ◽  
Mayara Borkowske Pestana ◽  
Alejandra Maria Franco Jimenez ◽  
...  
Keyword(s):  
Young Adults ◽  
Postural Control ◽  
Center Of Pressure ◽  
Cognitive Task ◽  
External Perturbation ◽  
Repeated Measurements ◽  
Level Of Evidence ◽  
Experimental Conditions ◽  
Postural Adjustments ◽  
External Perturbations

ABSTRACT Introduction Cognitive components are necessary to maintain posture during external perturbations. However, few studies have investigated postural control when external perturbations are associated with a concomitant cognitive task (DT). Objectives To analyze the behavior of reactive adjustments after perturbation with different intensities and displacements in active young adults; and to analyze the influence of DT on predictive and reactive adjustments in different perturbation conditions. Methods Twenty-eight physically active young adults stood on an item of equipment that produced displacements of the base. Four experimental conditions were introduced in a single task (ST) and DT (cognitive-report how many times a pre-established number appeared in the audio): 1 (5 cm and 10 cm/s); 2 (5 cm and 25 cm/s); 3 (12 cm and 10 cm/s) and 4 (12 cm and 25 cm/s). Three attempts were carried out for each condition (total=24). Center of pressure (CoP) parameters were analyzed considering the following windows: predictive (-250 to +50 ms), reactive 1 (+50 to +200 ms) and reactive 2 (+200 to +700 ms), in comparison to the start of the CoP activity. One-way ANOVAs were performed to analyze predictive adjustments, while two-way ANOVAs with factor for task (STxDT) and condition (1x2x3x4), with repeated measurements, were performed for the reactive adjustments. Results One-way ANOVA (predictive) indicated that the subjects had higher CoP parameters in ST vs DT. In reactive adjustments 1 and 2, ANOVA indicated greater CoP parameters in condition 2 and 4 when compared to 1 and 3, and in the ST vs DT. The subjects took longer to recover stable position in conditions 1 and 3 than in conditions 2 and 4. Conclusion Perturbation intensity has a greater influence on postural adjustments to maintain balance than on magnitude. Moreover, the association of cognitive tasks with external perturbation decreases CoP oscillation. Therefore, cognitive resources play an important role in postural control after perturbation. Level of evidence III; Study of nonconsecutive patients, with no “gold” standard applied uniformly.

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