Anticipatory and compensatory postural adjustments in individuals with multiple sclerosis in response to external perturbations

Deficit in balance control is a common and often an initial disabling symptom of multiple sclerosis (MS). The aim of the study was to investigate the organization of anticipatory and compensatory postural adjustments in individuals with MS dealing with external perturbations. Ten individuals with MS and ten age-and-gender matched healthy controls were exposed to external perturbations applied at the shoulder level. The perturbations were either predictable or unpredictable as subjects stood with eyes open or closed. Electrical activity of six leg and trunk muscles as well as displacements of the center of pressure (COP) were recorded and quantified within the time intervals typical of anticipatory (APAs) and compensatory (CPAs) postural adjustments. Individuals with MS demonstrated delayed anticipatory onsets of muscle activity and smaller anticipatory COP displacements as compared to healthy control subjects. The deficiency of the APAs was associated with increased displacements of the COP during the balance restoration phase. The results demonstrate the underlying impairment in anticipatory postural control of individuals with MS. The study outcome provides a background for development of rehabilitation strategies focused on balance restoration in people with MS.

Timely identification of palliative patients and anticipatory care planning by GPs: practical application of tools and a training programme

Background

Palliative care is mainly restricted to terminal care. General practitioners (GPs) are not trained to early identify palliative patients with cancer, COPD or heart failure. With the help of the RADboud indicators for PAlliative Care needs (RADPAC), we trained GPs to identify patients’ needs and to make a proactive care plan. They were also able to join two role-plays where they discussed the patient’s future, and consulted a palliative care consultant to fine-tune the care plan. We evaluated the programme with the GPs and consultants and noted its impact on their daily practice.

Methods

Two years after they had participated in the programme, we held semi-structured interviews with the GPs and a focus group interview with the consultants and performed a thematic content analysis.

Results

Six consultants and nine GPs participated in the programme. Most GPs and consultants mentioned positive changes in the thinking or acting of GPs regarding early palliative care. A number continued to use the tool to identify patients; most of the others noted they had internalised the indicators. Although half of them still considered discussing end-of-life aspects difficult, particularly in patients with organ failure, the others were more easily able to discuss the future with their palliative patients.

Conclusion

Although most GPs and consultants were positive about the training programme and applying it in daily practice, we conclude that in future programmes, more attention needs to paid to timely identification of palliative patients with COPD or CHF and how to discuss the future with them.

Older adults utilize less efficient postural control when performing pushing task

The ability to maintain balance deteriorates with increasing age. The aim was to investigate the role of age in generation of anticipatory (APA) and compensatory (CPA) postural adjustments during pushing an object. Older (68.8 ± 1.0 years) and young adults (30.1 ± 1.4 years) participated in the experiment involving pushing an object (a pendulum attached to the ceiling) using both hands. Electrical activity of six leg and trunk muscles and displacements of the center of pressure (COP) were recorded and analyzed during the APA and CPA phases. The onset time, integrals of muscle activity, and COP displacements were determined. In addition, the indexes of co-activation and reciprocal activation of muscles for the shank, thigh, and trunk segments were calculated. Older adults, compared to young adults, showed less efficient postural control seen as delayed anticipatory muscle onset times and delayed COP displacements. Moreover, older adults used co-activation of muscles during the CPA phase while younger subjects utilized reciprocal activation of muscles. The observed diminished efficiency of postural control during both anticipatory and compensatory postural adjustments observed in older adults might predispose them to falls while performing tasks involving pushing. The outcome provides a background for future studies focused on the optimization of the daily activities of older adults.

Anticipatory and compensatory postural adjustments in conditions of body asymmetry induced by holding an object

The effect of body asymmetry on anticipatory and compensatory postural adjustments was studied. Ten healthy subjects stood on the force platform and held an object in one hand which induced body asymmetry. Subjects were exposed to external perturbations applied to their shoulders while standing with either normal or narrow base of support. Bilateral electromyographic activity (EMG) of dorsal and ventral trunk and leg muscles and center-of-pressure displacements were recorded. Data was analyzed within the intervals typical for anticipatory (APA) and compensatory postural adjustments. Integrals of EMG activity and co-contraction and reciprocal activation of muscles were calculated and analyzed. Reciprocal activation of muscles on the target side and co-contraction of muscles on the contralateral side were seen when standing in asymmetrical stance and being subjected to external perturbations. Decreased magnitudes of co-contraction and reciprocal activation of muscles were seen in the APA phase while standing asymmetrically with narrow base of support. The findings highlight the importance of investigating the role of body asymmetry in maintaining control of vertical posture. The outcome of the study provides a foundation for future studies focusing on improvement in postural control in individuals with body asymmetry due to unilateral weakness.

Characteristic muscle activity patterns during gait initiation in the healthy younger and older adults

It is thought that gait initiation (GI) might be an optimal task for identifying postural control deficiencies. Thus, the aim of this study was to clarify the strategies adopted by older subjects during this task. 16 healthy younger and 15 healthy older adults participated in the study. Subjects were instructed to begin forward stepping with their dominant limb in response to an auditory stimulus. The mean muscle activity, co-contraction index, and intra-subject coefficients of variation (intra-subject CVs) of dominant limb muscles in different phases of GI were measured. The level of association between the co-contraction index and intra-subject CV of muscles was also explored. This study showed that in the anticipatory phase, the younger group had larger amplitudes and more intra-subject CVs than older the group, particularly for the tibialis anterior muscle. However, the co-contraction index was greater in older subjects relative to younger subjects. During the weight transition phase, tibialis anterior, semitendinosus and vastus lateralis muscles of older adults had a lower amplitude as compared to younger adults. However, during the locomotor phase, the activity of tibialis anterior was greater in comparison to younger adults. Also, during this phase, similar to the anticipatory phase, the co-contraction index between tibialis anterior and gastrocnemius muscles was greater in older subjects relative to younger subjects. Additionally, the larger co-contraction index of some muscles was associated with smaller intra-subject CV. These findings suggest that muscle behaviors are altered with aging and older adults employ different strategies in the different phases of GI as compared to younger adults.

Role of point of application of perturbation in control of vertical posture

The role of point of application of perturbation in the anticipatory (APAs) and compensatory (CPAs) postural control was studied. Twelve healthy participants stood on a sliding board (that was either locked and as such motionless or unlocked and as such free to move in the anterior-posterior direction). The body perturbations were applied either to the shoulders (by a pendulum impact) or the feet (by the movement of the sliding board). Electromyographic activity (EMG) of the trunk and lower extremity muscles was recorded. Latencies, integrals of EMG and muscle co-contraction (C) and reciprocal (R) activation indices were calculated and analyzed within the intervals typical for the APAs and CPAs. Higher EMG integrals were seen in the APAs phase when perturbation was applied to the shoulders. Reciprocal activation of muscles was seen in the APAs phase in the shoulders perturbation condition, while co-contraction was seen in the feet perturbation condition. Co-contraction was observed within the CPA phase in both experimental conditions. Higher C values were found in the feet perturbation condition in the CPA phase. The results suggest that different motor control strategies are employed by the central nervous system when encounter perturbations of similar magnitude but applied to different parts of the body. The outcome highlights the importance of investigation of the role of the point of application of the perturbation.

Asymmetries in reactive and anticipatory balance control are of similar magnitude in Parkinson's disease patients

Many Parkinson's disease (PD) patients show asymmetries in balance control during quiet stance and in response to perturbations (i.e., reactive balance control) in the sagittal plane. In addition, PD patients show a reduced ability to anticipate to self-induced disturbances, but it is not clear whether these anticipatory responses can be asymmetric too. Furthermore, it is not known how reactive balance control and anticipatory balance control are related in PD patients. Therefore, we investigated whether reactive and anticipatory balance control are asymmetric to the same extent in PD patients. 14 PD patients and 10 controls participated. Reactive balance control (RBC) was investigated by applying external platform and force perturbations and relating the response of the left and right ankle torque to the body sway angle at the excited frequencies. Anticipatory postural adjustments (APAs) were investigated by determining the increase in the left and right ankle torque just before the subjects released a force exerted with the hands against a force sensor. The symmetry ratio between the contribution of the left and right ankle was used to express the asymmetry in reactive and anticipatory balance control; the correlation between the two ratio's was investigated with Spearman's rank correlation coefficients. PD patients were more asymmetric in anticipatory (p=0.026) and reactive balance control (p=0.004) compared to controls and the symmetry ratios were significantly related (ρ=0.74; p=0.003) in PD patients. These findings suggest that asymmetric reactive balance control during bipedal stance may share a common pathophysiology with asymmetries in the anticipation of voluntary perturbations during, for instance, gait initiation.

Standing on a sliding board affects generation of anticipatory and compensatory postural adjustments

Postural control is compromised in the presence of body instability. We studied anticipatory and compensatory postural adjustments people use to maintain balance while standing on an unstable surface and performing voluntary arm movements. Nine healthy participants stood on a sliding board (that was either locked and as such motionless or unlocked and as such free to move in the anterior-posterior direction) and performed fast bilateral arms flexion. Arm acceleration, bilateral electromyographic activity (EMG) of the trunk and lower extremity muscles and center of pressure (COP) displacements were recorded and analyzed within the intervals typical for the anticipatory (APAs) and compensatory (CPAs) postural adjustments. Peaks of acceleration of the arm movements were not different between the locked and unlocked conditions. Larger EMG integrals were seen in the muscles of the lower extremity in both APAs and CPAs when standing on the unlocked sliding board. No significant difference was observed in the trunk muscles. Larger maximum COP displacement was seen when participants stood on the locked board. The results demonstrated that when standing on a free to move sliding board and performing bilateral arm flexion, the central nervous system (CNS) does not slow down the arm movements; instead it modifies activation of the lower extremity muscles. The observed differences in APAs and CPAs between the locked and unlocked conditions suggest that the CNS employs similar strategy while controlling the focal part of the task and adjusts the activity of muscles that are close to the source of instability to control postural task.

An altered spatiotemporal gait adjustment during a virtual obstacle crossing task in patients with diabetic peripheral neuropathy

This study investigates spatiotemporal gait adjustments that occur while stepping over virtual obstacles during treadmill walking in people with/without diabetic peripheral neuropathy (DPN). Eleven adults with Type 2 diabetes mellitus, ten DPN, and 11 age-matched healthy adults (HTY) participated in this study. They stepped over forthcoming virtual obstacles during treadmill walking. Outcomes such as success rate, spatiotemporal gait characteristics during obstacle crossing, and correlations between these variables were evaluated. The results partially supported our hypotheses that when comparing with HTY and DM, people with DPN adopted a crossing strategy which decreased obstacle crossing success rate and maximal toe elevation, and increased stride time and stance time during virtual obstacle crossing. This might be due to the compromised somatosensory functions of their lower extremity which may increase the risk of falling. This study also found an inter-leg relationship which may be applied to future stepping or obstacle crossing training that incorporates both legs as a means for improving outcomes of the trailing leg during daily obstacle negotiation.

Predictive cues and spatial attentional bias for alcohol: Manipulations of cue-outcome mapping

Previous studies suggest that cues predicting the outcome of attentional shifts provide a measure of anticipatory alcohol-related attentional bias that is correlated with risky drinking and has high reliability. However, this is complicated by potential contributions of visual features of cues to reliability, unrelated to their predictive value. Further, little is known of the sensitivity of the bias to variations in cue-outcome mapping manipulations, limiting our theoretical and methodological knowledge: Does the bias robustly follow varying cue-outcome mappings, or are there automatic cue-related associative processes involved? The current studies aimed to address these issues. Participants performed variations of the cued Visual Probe Task (cVPT) in which cues were non-predictive; in which there were multiple cue pairs, used simultaneously and serially; and in which the cue-outcome mapping was reversed. The major findings were, first, that previously found reliability cannot be attributed to aspects of the cues not related to outcome-prediction; second, that reliability of the bias does not survive deviations from a simple, consistent cue-outcome mapping; third, that all predictive versions of the task showed a bias towards alcohol; fourth, that the bias did not simply follow awareness of the cue-outcome mapping; and finally, that only in the case of simultaneous multiple cue pairs, an association with risky drinking was replicated. The results provide support for the reliability of the anticipatory attentional bias for alcohol, suggest that relatively persistent associative processes underlie the bias in the alcohol context, and provide a foundation for future work using the cVPT.

Neck muscle activity in skydivers during parachute opening shock

This observational study investigated skydiver neck muscle activity during parachute opening shock (POS), as epidemiological data recently suggested neck pain in skydivers to be related to POS. Twenty experienced skydivers performed two terminal velocity skydives each. Surface electromyography quantified muscle activity bilaterally from the anterior neck, the upper and lower posterior neck, and the upper shoulders; and two triaxial accelerometers sampled deceleration. Muscle activity was normalized as the percentage of reference maximum voluntary electrical activity (% MVE); and temporal muscle activity onset was related to POS onset. Our results showed that neck muscle activity during POS reached mean magnitudes of 53-104% MVE, often exceeding reference activity in the lower posterior neck and upper shoulders. All investigated muscle areas' mean temporal onsets occurred <50 ms after POS onset (9-34 ms latencies), which is consistent with anticipatory motor control. The high muscle activity observed supports that the neck is under substantial strain during POS, while temporal muscle activation suggests anticipatory motor control to be a strategy used by skydivers to protect the cervical spine from POS. This study's findings contribute to understanding the high rates of POS-related neck pain, and further support the need for evaluation of neck pain preventative strategies.

Anticipatory and compensatory postural adjustments in people with low back pain: a protocol for a systematic review and meta-analysis

BACKGROUND

Anticipatory (APAs) and compensatory (CPAs) postural adjustments are organised by the central nervous system (CNS) and serve to control postural perturbations. Ineffective APAs and CPAs have been hypothesised to contribute to the persistence of symptoms and disability in people with low back pain (LBP). Despite two decades of research, there is no systematic review investigating APAs and CPAs in people with LBP. Thus, the aim of the current review is to determine if APA and CPA onset or amplitude, as measured by electromyography (EMG), centre of pressure (COP), and kinematics, are altered in people with LBP.

METHODS/DESIGN

A systematic review and meta-analysis will be conducted. Searches will be conducted in electronic databases for full-text articles published before January 2016 using pre-defined search strategies that utilise combinations of keywords and medical subject heading terms. Two independent reviewers will screen potentially relevant articles for inclusion, extract data, and assess risk of bias for individual studies. Any disagreements will be resolved by a third reviewer. Studies comparing APA onset and amplitude and CPA onset and amplitude measured by EMG, COP, or kinematics between people with LBP and healthy individuals will be included if all aspects of the eligibility criteria are met. Data will be synthesised if studies are homogeneous; otherwise, results will be reviewed narratively.

DISCUSSION

To our knowledge, this is the first systematic review to examine APAs and CPAs, as measured by EMG, COP, and kinematics in people with LBP. The findings of this review may aid in the identification of factors that play a role in the persistence of symptoms and disability and aid in the development of interventions to treat symptoms.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016032815.

Efficacy of augmented visual environments for reducing sickness in autonomous vehicles

The risk of motion sickness is considerably higher in autonomous vehicles than it is in human-operated vehicles. Their introduction will therefore require systems that mitigate motion sickness. We investigated whether this can be achieved by augmenting the vehicle interior with additional visualizations. Participants were immersed in motion simulations on a moving-base driving simulator, where they were backward-facing passengers of an autonomous vehicle. Using a Head-Mounted Display, they were presented either with a regular view from inside the vehicle, or with augmented views that offered additional cues on the vehicle's present motion or motion 500ms into the future, displayed on the vehicle's interior panels. In contrast to the hypotheses and other recent studies, no difference was found between conditions. The absence of differences between conditions suggests a ceiling effect: providing a regular view may limit motion sickness, but presentation of additional visual information beyond this does not further reduce sickness.

Age-related differences in postural adjustments during limb movement and motor imagery in young and older adults

Recent research has shown that systematic postural adjustments occur during periods of manual motor imagery (MI), but the timing (anticipatory or reactive) and directionality (against or in the direction of arm extension) of these postural motions relative to individual manual actions or imagery are not well understood. This study analyzed the anteroposterior hip and head motion of healthy young and older participants, while they imagined bilateral arm raises under self-initiated or environmentally triggered performance conditions. When MI was self-initiated, both age groups showed significant forward postural motion during the second prior to MI initiation. When MI (or physical arm movement) was environmentally triggered, however, older people did not show anticipatory forward postural motion, but did show compensatory backward head motion. These results suggest that manual MI is indeed accompanied by anticipatory postural motion, but this anticipation is attenuated in older people when they do not have control over the timing of manual movement onset.

Redefining medicine from an anticipatory perspective

The meaning of the concept of anticipation escapes the majority of those concerned with change, in particular those who study health. To characterize only genetic disorders, such as conditions with progressively earlier symptoms and higher intensity of disease from generation to generation, in terms of anticipatory expression is rather limited and limiting. Practitioners of medical care could benefit from understanding anticipation as definitory of the living. This view explains why diminished anticipatory expression, in all forms of the living, results in conditions calling for medical attention. So far, medicine has opted for a deterministic-reductionist perspective that reduces the living to a machine. Medical care, stuck in the grey zone between success and failure, should overcome its reactive obsession. From an almost exclusively mechanistic activity, it should evolve into a holistic proactive practice of well-being that reflects awareness of anticipation.

Age-related asymmetry in anticipatory postural movements during unilateral arm movement and imagery

Reaching movements of the arms are accompanied by anticipatory (APM) and compensatory postural motion (CPM) that counteract the resulting perturbations to body stability. Recent research has shown that these postural actions are also observable in the context of imagined arm movements. As motor imagery (MI) shares many neurophysiological and behavioral characteristics with physical movements, and MI training can affect subsequent performance, MI tasks provide a good setting for studying the anticipatory aspects of postural control. This study investigated APMs and CPMs of the head and hip of healthy young and older adults in the temporal vicinity of physical and imagined forward raises of the dominant and non-dominant arm. When MI of the dominant arm was self-initiated, both age groups showed APM in the anteroposterior plane. When the self-initiated MI was of the non-dominant arm, only the older group showed anteroposterior APM. The older group did not show APM when an expected arm movement (or MI) was made to an external signal. This suggests an age-related deficit in coordinating postural preparation with external events. Only the older group showed mediolateral APM, and only for dominant arm MI, indicating sensitivity to potential perturbation to the weaker, non-dominant side of the body. Overall, the older group showed more anticipatory postural motion at the head. Systematic APM for manual MI suggests that MI training may be an effective intervention for anticipatory postural control. An integrated model of postural support for executed and imagined limb movements is suggested.

Non-pharmacological treatments for anticipatory nausea and vomiting during chemotherapy: a systematic review and meta-analysis of the Clinical Practice Guidelines for Antiemesis 2023

BACKGROUND

Anticipatory chemotherapy-induced nausea and vomiting (CINV) is a conditioned response influenced by the severity and duration of previous emetic responses to chemotherapy. We aimed to evaluate the efficacy of non-pharmacologic interventions for anticipatory CINV among patients with cancer.

METHODS

We conducted a systematic search in databases, including PubMed, the Cochrane Library, CINAHL, and Ichushi-Web, from January 1, 1990, to December 31, 2020. Randomized controlled trials, non-randomized designs, observational studies, or case-control studies that utilized non-pharmacological therapies were included. The primary outcomes were anticipatory CINV, with an additional investigation into adverse events and the costs of therapies. The risk-of-bias for each study was assessed using the Cochrane risk-of-bias tool, and meta-analysis was performed using Revman 5.4 software.

RESULTS

Of the 107 studies identified, six met the inclusion criteria. Three types of non-pharmacological treatments were identified: systematic desensitization (n = 2), hypnotherapy (n = 2), and yoga therapy (n = 2). Among them, systematic desensitization significantly improved anticipatory CINV as compared to that in the control group (nausea: risk ratio [RR] = 0.60, 95% confidence interval [CI] = 0.49-0.72, p < 0.00001; vomiting: RR = 0.54, 95% CI = 0.32-0.91, p = 0.02). However, heterogeneity in outcome measures precluded meta-analysis for hypnotherapy and yoga. Additionally, most selected studies had a high or unclear risk of bias, and adverse events were not consistently reported.

CONCLUSIONS

Our findings suggest that systematic desensitization may effectively reduce anticipatory CINV. However, further research is warranted before implementation in clinical settings.

Role of angular position of the seat in control of posture in response to external perturbation

Ability of the human body to regain balance after being externally perturbed is important in the maintenance of vertical posture. The goal of this study was to investigate trunk and leg muscle response to external perturbation while sitting on a stool with varying seat inclinations. Ten healthy subjects were required to receive a perturbation applied to the upper body while sitting on an adjustable stool with 0°, 10° forward or 10° backward inclination of the seat and without footrest and leg support. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory (APA) and compensatory (CPA) phases of postural control. APAs and CPAs were generated in response to an external perturbation. Delays in the onset of anticipatory muscle activity were seen when seated on the inclined seat compared to sitting on the horizontal seat (p < 0.05). To maintain balance after a perturbation, participants activated the trunk and thigh muscles, the activity of which was modulated to a greater degree than that of leg muscles. Moreover, they utilized co-contraction of muscles as the main mechanism of balance control in sitting. Furthermore, there was no effect of a seat inclination on COP displacements. The outcome provides a background for future investigations of the effect of seat inclination on control of balance in sitting.