The Effect of Changes in the Body Configuration on Anticipatory Postural Adjustments

1. In this study, the interaction between anticipatory postural adjustments for step initiation and automatic postural responses to an external perturbation were investigated by having subjects initiate a voluntary forward step while perturbed by a backward surface translation, which caused forward sway of the body. The postural adjustments for step initiation act to move the body center of mass (COM) forward, whereas the automatic postural responses act to move the COM backward to restore stance equilibrium. Because the postural behaviors are in opposition, we asked whether a temporal hierarchy exists in which automatic postural responses are executed to restore equilibrium and followed by stereotypic postural adjustments for step initiation, or whether the interaction between these two postural behaviors is more dynamic. 2. Lower extremity electromyographs (EMGs), ground reaction forces, and kinematics were recorded from 10 subjects during three conditions: to quantify the anticipatory postural adjustments for step initiation, subjects stepped forward as soon as they felt a proprioceptive cue; to quantify the automatic postural responses to perturbation, subjects maintained stance equilibrium in response to a backward surface translation under both feet; and to quantify the interaction between the postural adjustments for the voluntary step and the automatic responses to the perturbation, subjects were exposed to a backward surface translation and instructed to step forward as soon as they felt the platform begin to move. 3. The anticipatory adjustments for step initiation included tibialis activation [stance limb = 163 +/- 28 (SE) ms; swing limb = 173 +/- 33 ms] and soleus inhibition resulting in center of foot pressure (COP) moving backward and lateral toward the swing limb to propel the COM forward over the stance limb. Subsequently, activation of the swing limb gastrocnemius resulted in heel-off. In contrast, the automatic postural adjustments for maintenance of stance equilibrium during a backward surface translation included activation of soleus and gastrocnemius (104 +/- 23 ms and 115 +/- 14 ms, respectively) resulting in a symmetrical forward displacement of the COP that moved the COM back to its original position with respect to the feet. 4. When a forward step was initiated in response to the translation, the automatic postural responses were reduced in amplitude bilaterally in soleus and in the stance limb gastrocnemius. When present the postural response occurred at the same latency when the goal was to initiate a step as when the goal was to maintain standing.(ABSTRACT TRUNCATED AT 400 WORDS)

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Anticipatory Postural Adjustments in Dart Throwing

Journal of Human Kinetics ◽

10.2478/hukin-2013-0023 ◽

2013 ◽

Vol 37 (1) ◽

pp. 39-45 ◽

Cited By ~ 3

Author(s):

Grzegorz Juras ◽

Kajetan Słomka

Keyword(s):

Repeated Measures ◽

Training Session ◽

Motor Task ◽

Anticipatory Postural Adjustments ◽

The Body ◽

Target Size ◽

Postural Adjustments ◽

Dart Throwing ◽

Task Parameters ◽

Kinetics Of

The aim of this study was to explore the effects of accuracy constraints on the characteristics of anticipatory postural adjustments (APA) in a task that involves a movement consisting of a controlled phase and a ballistic phase. It was hypothesized that APA scaling with task parameters (target size) would be preserved even when the task is performed by muscles that have no direct effects on APA. Sixteen healthy right handed subjects participated in the study. All participants had no prior experience in dart throwing. Subjects’ average age was 24.1 ± 1.9 years. A force platform and a motion capture system were used to register kinetics of the body and kinematics of the throwing arm and throwing accuracy. The experiment consisted of six series of twenty consecutive dart throws to a specified target. Target sizes (T2-T6) were set at 25%, 50%, 75%, 125% and 150% of target 1 (T1) initially set as the spread of the last 20 throws in a 50 throw training session. This allowed to distinguish six indexes of difficulty (ID’s) ranging from 2,9 to 5,9. A one-way ANOVA for repeated measures was used for statistical analysis. Results of ANOVA showed a significant effect of target size at Constant Error but no effect at APA time. There were also no significant differences between hit and miss throws. From a control perspective, it can be stated that changes in central commands did not lead to changes in APA time in the analyzed motor task.

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Anticipatory Postural Adjustments and kinematic arm features when postural stability is manipulated

PeerJ ◽

10.7717/peerj.4309 ◽

2018 ◽

Vol 6 ◽

pp. e4309 ◽

Cited By ~ 1

Author(s):

Bianca Callegari ◽

Ghislain Saunier ◽

Manuela Brito Duarte ◽

Gizele Cristina da Silva Almeida ◽

Cesar Ferreira Amorim ◽

...

Keyword(s):

Upper Limb ◽

Postural Stability ◽

Motor Planning ◽

Anticipatory Postural Adjustments ◽

The Body ◽

Postural Adjustments ◽

Pointing Task ◽

Standing Up ◽

Degree Of Stability

Beyond the classical paradigm that presents the Anticipatory Postural Adjustments (APAs) as a manner to create forces that counteract disturbances arising from the moving segment during a pointing task, there is a controversial discussion about the role APAs to facilitate the movement and perform a task accurately. In addition, arm kinematics features are classically used to infer the content of motor planning for the execution and the control of arm movements. The present study aimed to disentangle the conflicting role of APAs during an arm-pointing task in which the subjects reach a central diode that suddenly turns on, while their postural stability was manipulated. Three postures were applied: Standing (Up), Sit without feet support (SitUnsup) and Sit with feet support (SitSup). We found that challenging postural stability induced an increase of the reaction time and movement duration (observed for the SitUnsup compared to SitSUp and Up) as well as modified the upper-limb velocity profile. Indeed, a greater max velocity and a shorter deceleration time were observed under the highest stability (SitSup). Thus, these Kinematics features reflect less challenging task and simple motor plan when the body is stabilized. Concerning the APAs, we observed the presence of them independently of the postural stability. Such a result strongly suggests that APAs act to facilitate the limb movement and to counteract perturbation forces. In conclusion, the degree of stability seems particularly tuned to the motor planning of the upper-limb during a pointing task whereas the postural chain (sitting vs. standing) was also determinant for APAs.

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A Novel Viewpoint on the Anticipatory Postural Adjustments During Gait Initiation

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2021.709780 ◽

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.

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The effect of short-term changes in the body mass on anticipatory postural adjustments

Experimental Brain Research ◽

10.1007/s00221-007-0931-2 ◽

2007 ◽

Vol 181 (2) ◽

pp. 333-346 ◽

Cited By ~ 25

Author(s):

Xiaoyan Li ◽

Alexander S. Aruin

Keyword(s):

Body Mass ◽

Anticipatory Postural Adjustments ◽

The Body ◽

Short Term ◽

Postural Adjustments

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Anticipatory Postural Adjustments in the Frail Older Adults When Postural Stability is Manipulated

10.21203/rs.3.rs-107332/v1 ◽

2020 ◽

Author(s):

Bianca Callegari ◽

Alexandre Kubicki ◽

Ghislain Saunier ◽

Manuela Brito Duarte ◽

Gizele Cristina da Silva Almeida ◽

...

Keyword(s):

Older Adults ◽

Postural Stability ◽

Motor Planning ◽

Functional Independence ◽

Anticipatory Postural Adjustments ◽

The Body ◽

Upright Posture ◽

Postural Adjustments ◽

Frail Older Adults ◽

The Impact

Abstract Background: Anticipatory Postural Adjustments (APAs) are importantly affected by age and may represent restrictions for functional independence. Previous studies have already highlighted some delayed APAs during self-generated rapid arm movements in aged adults, as well as in cases of non-optimal aging, such as in frail older adults. In young (Y) adults, it was also previously demonstrated that changing the postural stability (i.e. seated vs. upright posture) affects the motor planning and APAs. Considering the clinical relevance of these balance tasks in the functional independence in frail older adults (FOA), and the lack of literature about this task, the present study aimed to investigate the impact of these different conditions of postural stability on APAs in FOA. Methods: In this paper, participants executed an arm-pointing task to reach a diode immediately after it turned on, under different conditions of stability (seated with and without feet support and in upright posture). Results: The main finding of this study is that the adopted posture and body stabilization in FOA did not reflect differences in APAs or kinematic features. In addition, they did not present an optimal APA, since postural muscles are recruited simultaneously with the deltoid. Conclusion: Thus, FOA seem to use a single non-optimal motor plan to assist the task performance and counterbalance perturbation forces, in which they present similar APAs and do not modify their kinematics features according to the body stabilization (i.e. less challenging task present greater finger velocity).

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Preparation of Anticipatory Postural Adjustments Prior to Stepping

Journal of Neurophysiology ◽

10.1152/jn.01136.2006 ◽

2007 ◽

Vol 97 (6) ◽

pp. 4368-4379 ◽

Cited By ~ 152

Author(s):

Colum D. MacKinnon ◽

Dennis Bissig ◽

Julie Chiusano ◽

Emily Miller ◽

Laura Rudnick ◽

...

Keyword(s):

Neural Control ◽

Motor Evoked Potentials ◽

Acoustic Stimulus ◽

Anticipatory Postural Adjustments ◽

The Body ◽

Electromyographic Activity ◽

Motor Sequence ◽

Subsequent Increase ◽

Postural Adjustments ◽

Step Initiation

Step initiation involves anticipatory postural adjustments (APAs) that propel the body mass forward and laterally before the first step. This study used a startle-like acoustic stimulus (SAS) and transcranial magnetic stimulation (TMS) to examine the preparation of APAs before forward stepping. After an instructed delay period, subjects initiated forward steps in reaction to a visual “go” cue. TMS or SAS was delivered before (−1,400 or −100 ms), on (0 ms), or after (+100 ms for TMS, +200 ms for SAS) the imperative “go” cue. Ground reaction forces and electromyographic activity were recorded. In control trials, the mean reaction time was 217 ± 38 ms. In contrast, the SAS evoked APAs that had an average onset of 110 ± 54 ms, whereas the incidence, magnitude, and duration of the APA increased as the stimulus timing approached the “go” cue. A facilitation of motor-evoked potentials in the initial agonist muscle was observed only when TMS was applied at +100 ms. These findings indicate that there was an initial phase of movement preparation during which the APA-stepping sequence was progressively assembled, and that this early preparation did not involve the corticomotor pathways activated by TMS. The subsequent increase in corticomotor excitability between the imperative stimulus and onset of the APA suggests that corticospinal pathways contribute to the voluntary initiation of the prepared APA-stepping sequence. These findings are consistent with a feedforward mode of neural control whereby the motor sequence, including the associated postural adjustments, is prepared before voluntary movement.

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