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Previous research has argued that consecutive interpreters constitute laminated speakers in the sense that they engage with different kinds of footing at once, representing another's point of view through their words in another language. These multiple roles also play out in their gesturing, as they sometimes indicate deictically who is the source of the ideas and stances they are expressing (the principal). Simultaneous interpreters, though, often work in an interpreting booth; they are often not seen by the audience, yet many of them gesture, sometimes frequently. How are simultaneous interpreters using gesture in relation to stance-taking and footing? We consider the case of simultaneous interpreters rendering popular science lectures between (both to and from) Russian (their L1) and either English or German (their L2). Though only hearing the audio of the lectures, the interpreters produced many gestures, which were analyzed for their function. Some representational and deictic gestures appeared to clearly involve the interpreter as the principal (writing numbers with one's finger to help remember them or pointing to two places on the desk to keep track of two different quantities mentioned). Other representational and deictic gestures are ambiguous as to whether they are enacting what the interpreter may have imagined what the lecturer did or whether they arose out of the interpreter's own thinking for speaking (e.g., tracing the form of a bird being mentioned or pointing to an empty space when the lecturer was referring to a graph). Pragmatic gestures, showing one's stance toward the topic of the talk, were the most ambiguous as to the footing, reflecting how the interpreter may be engaged in fictive interaction with their imagined audience. Self-adapters, however, more clearly involve the interpreter as the principal, as such actions are known to support cognitive focussing and self-soothing. In sum, we see varying degrees of clarity as to whose stance and principal footing simultaneous interpreters are expressing bodily as laminated speakers. The variable ambiguity can be attributed to the nature of gesture as a semiotic system, the functions of which are more often dependent on co-occurring speech than vice versa. [ABSTRACT FROM AUTHOR]

Although research into multimodal stance-taking has gained momentum over the past years, the multimodal construction of so-called stacked stances has not yet received systematic attention in the literature. Mocking enactments are a prime example of such complex social actions as they are layered both interactionally and stance-related, and they rely significantly on the use of bodily visual resources, depicting rather than describing events and stances. Using Du Bois’ Stance Triangle as a framework, this study investigates mocking enactments as a case study to unravel the multimodal aspects of layered stance expressions. Drawing on three data sets—music instruction in Dutch, German, and English, spontaneous face-to-face interactions among friends in Dutch, and narrations on past events in Flemish Sign Language (VGT)—this study provides a qualitative exploration of mocking enactments across different communicative settings, languages, and modalities. The study achieves three main objectives: (1) illuminating how enactments are used for mocking, (2) identifying the layers of stance-taking at play, and (3) examining the multimodal construction of mocking enactments. Our analysis reveals various different uses of enactments for mocking. Aside from enacting the target of the mockery, participants can include other characters and viewpoints, highlighting the breadth of the phenomenon under scrutiny. Second, we uncover the layered construction of stance on all axes of the Stance Triangle (evaluation, positioning, and alignment). Third, we find that mocking enactments are embedded in highly evaluative contexts, indexed by the use of bodily visual resources. Interestingly, not all mocking enactments include a multimodally exaggerated depiction, but instead, some merely allude to an absurd hypothetical scenario. Our findings contribute to the growing body of literature on multimodal stance-taking, by showing how a nuanced interpretation of the Stance Triangle can offer a useful framework for analyzing layered stance acts. [ABSTRACT FROM AUTHOR]

Previous research has argued that consecutive interpreters constitute laminated speakers in the sense that they engage with different kinds of footing at once, representing another’s point of view through their words in another language. These multiple roles also play out in their gesturing, as they sometimes indicate deictically who is the source of the ideas and stances they are expressing (the principal). Simultaneous interpreters, though, often work in an interpreting booth; they are often not seen by the audience, yet many of them gesture, sometimes frequently. How are simultaneous interpreters using gesture in relation to stance-taking and footing? We consider the case of simultaneous interpreters rendering popular science lectures between (both to and from) Russian (their L1) and either English or German (their L2). Though only hearing the audio of the lectures, the interpreters produced many gestures, which were analyzed for their function. Some representational and deictic gestures appeared to clearly involve the interpreter as the principal (writing numbers with one’s finger to help remember them or pointing to two places on the desk to keep track of two different quantities mentioned). Other representational and deictic gestures are ambiguous as to whether they are enacting what the interpreter may have imagined what the lecturer did or whether they arose out of the interpreter’s own thinking for speaking (e.g., tracing the form of a bird being mentioned or pointing to an empty space when the lecturer was referring to a graph). Pragmatic gestures, showing one’s stance toward the topic of the talk, were the most ambiguous as to the footing, reflecting how the interpreter may be engaged in fictive interaction with their imagined audience. Self-adapters, however, more clearly involve the interpreter as the principal, as such actions are known to support cognitive focussing and self-soothing. In sum, we see varying degrees of clarity as to whose stance and principal footing simultaneous interpreters are expressing bodily as laminated speakers. The variable ambiguity can be attributed to the nature of gesture as a semiotic system, the functions of which are more often dependent on co-occurring speech than vice versa.

Although research into multimodal stance-taking has gained momentum over the past years, the multimodal construction of so-called stacked stances has not yet received systematic attention in the literature. Mocking enactments are a prime example of such complex social actions as they are layered both interactionally and stance-related, and they rely significantly on the use of bodily visual resources, depicting rather than describing events and stances. Using Du Bois’ Stance Triangle as a framework, this study investigates mocking enactments as a case study to unravel the multimodal aspects of layered stance expressions. Drawing on three data sets—music instruction in Dutch, German, and English, spontaneous face-to-face interactions among friends in Dutch, and narrations on past events in Flemish Sign Language (VGT)—this study provides a qualitative exploration of mocking enactments across different communicative settings, languages, and modalities. The study achieves three main objectives: (1) illuminating how enactments are used for mocking, (2) identifying the layers of stance-taking at play, and (3) examining the multimodal construction of mocking enactments. Our analysis reveals various different uses of enactments for mocking. Aside from enacting the target of the mockery, participants can include other characters and viewpoints, highlighting the breadth of the phenomenon under scrutiny. Second, we uncover the layered construction of stance on all axes of the Stance Triangle (evaluation, positioning, and alignment). Third, we find that mocking enactments are embedded in highly evaluative contexts, indexed by the use of bodily visual resources. Interestingly, not all mocking enactments include a multimodally exaggerated depiction, but instead, some merely allude to an absurd hypothetical scenario. Our findings contribute to the growing body of literature on multimodal stance-taking, by showing how a nuanced interpretation of the Stance Triangle can offer a useful framework for analyzing layered stance acts.

Although researchers of language and communication have become increasingly interested in both embodiment and conflict in recent years, little is known about how elementary students use embodied actions modeled by their teachers as they engage in peer conflicts. This paper addresses such questions, focusing on the “quiet coyote” gesture and the “open hand prone” gesture, two emblems commonly used as classroom management strategies in elementary grades. Building on work in language socialization, gesture studies, and other areas of discourse analysis, I propose what I call a gestural socialization perspective for analyzing the nuanced ways the US second-grade children in this study use and socialize one another to use these gestures, as well as other semiotic resources, to handle peer disputes. An ethnographically informed, multimodal discourse analysis centering on a multiracial group of girls reveals how students' gesture practices draw on their teacher's gestural socialization practices while also diverging from them, especially with regard to gestural form, stance object, intended recipient, and accompanying metapragmatic commentary. These aspects of the participants' appropriations of the “open hand prone” and “quiet coyote” emblems, together with their use of gestural innovations, metagestures, and other semiotic resources, allow them to take more oppositional stances than those made relevant by the teacher's practices. Through these multimodal stances, students take a hands-on approach to starting, continuing, and closing peer disputes on their own terms. Overall, the study highlights how participants' handling of disputes often subverted a local emphasis on conflict avoidance, efficiency, and appropriateness and the developmentalist, neoliberal, and standard language ideologies underpinning these norms. The paper closes with a discussion of implications for research and pedagogy, emphasizing the importance of closely attending to the multimodal, interactionally emergent, and culturally situated nature of conflicts among children and people of all ages.

Research article conclusions form an important sub-genre in the academic community. This study aims to compare the use of stance markers in English and Chinese research article conclusions and investigate how stance markers may vary in soft and hard sciences. Based on Hyland's stance model, an analysis of stance markers over 20 years was made in two corpora, which were compiled with 180 research article conclusions in each language from four disciplines. It was found that English writers and soft science writers tended to make statements more tentatively by hedges and craft their persona more explicitly through self-mentions. However, Chinese writers and hard science writers made their claims with more certainty by boosters and showed their affective attitude more frequently through attitude markers. The results reveal how writers from different cultural backgrounds construct their stances and also unveil the disciplinary differences involved in stance-taking. It is hoped that this corpus study will inspire future research on stance-taking in the conclusion section and also help cultivate writers' genre awareness. [ABSTRACT FROM AUTHOR]

Stance-taking, the public act of positioning oneself toward objects, people or states of affairs, has been studied in many fields of research. Recently, its multimodal realization in interaction has received increasing attention. The current contribution aims to take stock of research on multimodal stance-taking so far, and to present possible avenues for future research. We systematically gathered and appraised 76 articles that investigate the involvement of bodily-visual resources in stance-taking in interaction. The critical appraisal focused on two dimensions of the stance act: form-function relations constituting it, and its dynamic organization in interaction. Regarding form-function relations, we found systematic involvement of specific bodily-visual resources in different stance acts, as well as patterns of multimodal intensification and mitigation of stances. As for its dynamic organization, the review discusses how stance-taking is organized temporally throughout an interaction, with all participants involved carefully negotiating and adapting their stances to one another. Finally, attention is paid to the broader context of stance-taking, including its role in different social and societal contexts. Based on this review, we were able to identify several gaps in the literature, and avenues for future research. We argue that much potential for broadening the scope of research lies in increasing the methodological diversity in approaching multimodal stance-taking, as well as in cross-linguistic studies and varying settings and participant constellations. In conclusion, research into multimodal stance-taking is vibrant, with ample opportunities for future work. This review can be considered as a call to action to move beyond the premise that stance-taking is multimodal, and further investigate this intriguing and fundamental human capacity.

Deterioration in movement and posture often occurs with aging. Yet there may be approaches to movement training that can maintain posture and movement coordination patterns as we age. The Alexander Technique is a non-exercise-based approach that aims to improve everyday movement and posture by increasing awareness and modulating whole-body postural muscle activity. This study assessed whether nineteen 55–72-year-old Alexander Technique teachers showed different posture and movement coordination patterns than twenty age-matched controls during a standing and walking protocol using 3D inertial sensors. During upright stance, Alexander Technique teachers showed lower centroidal sway frequency at the ankle (p = .04) and lower normalized jerk at the sternum (p = .05) than controls. During gait, Alexander Technique teachers had more symmetrical gait cycles (p = .04), more symmetrical arm swing velocity (p = .01), greater arm swing velocity (p < .01), greater arm swing range of motion (p = .02), and lower range of acceleration of the torso in the frontal plane (p = .03) than controls. Smoother control of upright posture, more stable torso motion, and less restrained arm mobility suggest that Alexander Technique training may counter movement degradation that is found with aging. Results highlight the important balance between mobility and stability within the torso and limbs.

Different measurements of body oscillations in the time or frequency domain are being employed as markers of gait and balance abnormalities. This study investigates basic relationships within and between geometric and spectral measures in a population of young adult subjects. Twenty healthy subjects stood with parallel feet on a force platform with and without a foam pad. Adaptation effects to prolonged stance were assessed by comparing the first and last of a series of eight successive trials. Centre of Foot Pressure (CoP) excursions were recorded with Eyes Closed (EC) and Open (EO) for 90s. Geometric measures (Sway Area, Path Length), standard deviation (SD) of the excursions, and spectral measure (mean power Spectrum Level and Median Frequency), along the medio-lateral (ML) and antero-posterior (AP) direction were computed. Sway Area was more strongly associated than Path Length with CoP SD and, consequently, with mean Spectrum Level for both ML and AP, and both visual and surface conditions. The squared-SD directly specified the mean power Spectrum Level of CoP excursions (ML and AP) in all conditions. Median Frequency was hardly related to Spectrum Level. Adaptation had a confounding effect, whereby equal values of Sway Area, Path Length, and Spectrum Level corresponded to different Median Frequency values. Mean Spectrum Level and SDs of the time series of CoP ML and AP excursions convey the same meaning and bear an acceptable correspondence with Sway Area values. Shifts in Median Frequency values represent important indications of neuromuscular control of stance and of the effects of vision, support conditions, and adaptation. The Romberg Quotient EC/EO for a given variable is contingent on the compliance of the base of support and adaptation, and different between Sway Area and Path Length, but similar between Sway Area and Spectrum Level (AP and ML). These measures must be taken with caution in clinical studies, and considered together in order to get a reliable indication of overall body sway, of modifications by sensory and standing condition, and of changes with ageing, medical conditions and rehabilitation treatment. However, distinct measures shed light on the discrete mechanisms and complex processes underpinning the maintenance of stance. [ABSTRACT FROM AUTHOR]

Different measurements of body oscillations in the time or frequency domain are being employed as markers of gait and balance abnormalities. This study investigates basic relationships within and between geometric and spectral measures in a population of young adult subjects. Twenty healthy subjects stood with parallel feet on a force platform with and without a foam pad. Adaptation effects to prolonged stance were assessed by comparing the first and last of a series of eight successive trials. Centre of Foot Pressure (CoP) excursions were recorded with Eyes Closed (EC) and Open (EO) for 90s. Geometric measures (Sway Area, Path Length), standard deviation (SD) of the excursions, and spectral measure (mean power Spectrum Level and Median Frequency), along the medio-lateral (ML) and antero-posterior (AP) direction were computed. Sway Area was more strongly associated than Path Length with CoP SD and, consequently, with mean Spectrum Level for both ML and AP, and both visual and surface conditions. The squared-SD directly specified the mean power Spectrum Level of CoP excursions (ML and AP) in all conditions. Median Frequency was hardly related to Spectrum Level. Adaptation had a confounding effect, whereby equal values of Sway Area, Path Length, and Spectrum Level corresponded to different Median Frequency values. Mean Spectrum Level and SDs of the time series of CoP ML and AP excursions convey the same meaning and bear an acceptable correspondence with Sway Area values. Shifts in Median Frequency values represent important indications of neuromuscular control of stance and of the effects of vision, support conditions, and adaptation. The Romberg Quotient EC/EO for a given variable is contingent on the compliance of the base of support and adaptation, and different between Sway Area and Path Length, but similar between Sway Area and Spectrum Level (AP and ML). These measures must be taken with caution in clinical studies, and considered together in order to get a reliable indication of overall body sway, of modifications by sensory and standing condition, and of changes with ageing, medical conditions and rehabilitation treatment. However, distinct measures shed light on the discrete mechanisms and complex processes underpinning the maintenance of stance.

The dynamics of the human body can be described by the accelerations and masses of the different body parts (e.g., legs, arm, trunk). These body parts can exhibit specific coordination patterns with each other. In human walking, we found that the swing leg cooperates with the upper body and the stance leg in different ways (e.g., in-phase and out-of-phase in vertical and horizontal directions, respectively). Such patterns of self-assistance found in human locomotion could be of advantage in robotics design, in the design of any assistive device for patients with movement impairments. It can also shed light on several unexplained infrastructural features of the CNS motor control. Self-assistance means that distributed parts of the body contribute to an overlay of functions that are required to solve the underlying motor task. To draw advantage of self-assisting effects, precise and balanced spatiotemporal patterns of muscle activation are necessary. We show that the necessary neural connectivity infrastructure to achieve such muscle control exists in abundance in the spinocerebellar circuitry. We discuss how these connectivity patterns of the spinal interneurons appear to be present already perinatally but also likely are learned. We also discuss the importance of these insights into whole body locomotion for the successful design of future assistive devices and the sense of control that they could ideally confer to the user. [ABSTRACT FROM AUTHOR]

The dynamics of the human body can be described by the accelerations and masses of the different body parts (e.g., legs, arm, trunk). These body parts can exhibit specific coordination patterns with each other. In human walking, we found that the swing leg cooperates with the upper body and the stance leg in different ways (e.g., in-phase and out-of-phase in vertical and horizontal directions, respectively). Such patterns of self-assistance found in human locomotion could be of advantage in robotics design, in the design of any assistive device for patients with movement impairments. It can also shed light on several unexplained infrastructural features of the CNS motor control. Self-assistance means that distributed parts of the body contribute to an overlay of functions that are required to solve the underlying motor task. To draw advantage of self-assisting effects, precise and balanced spatiotemporal patterns of muscle activation are necessary. We show that the necessary neural connectivity infrastructure to achieve such muscle control exists in abundance in the spinocerebellar circuitry. We discuss how these connectivity patterns of the spinal interneurons appear to be present already perinatally but also likely are learned. We also discuss the importance of these insights into whole body locomotion for the successful design of future assistive devices and the sense of control that they could ideally confer to the user.

Background: Several investigations have addressed the process of balance adaptation to external perturbations. The adaptation during unperturbed stance has received little attention. Further, whether the current sensory conditions affect the adaptation rate has not been established. We have addressed the role of vision and haptic feedback on adaptation while standing on foam. Methods: In 22 young subjects, the analysis of geometric (path length and sway area) and spectral variables (median frequency and mean level of both total spectrum and selected frequency windows) of the oscillation of the centre of feet pressure (CoP) identified the effects of vision, light-touch (LT) or both in the anteroposterior (AP) and mediolateral (ML) direction over 8 consecutive 90 s standing trials. Results: Adaptation was obvious without vision (eyes closed; EC) and tenuous with vision (eyes open; EO). With trial repetition, path length and median frequency diminished with EC (p < 0.001) while sway area and mean level of the spectrum increased (p < 0.001). The low- and high-frequency range of the spectrum increased and decreased in AP and ML directions, respectively. Touch compared to no-touch enhanced the rate of increase of the low-frequency power (p < 0.05). Spectral differences in distinct sensory conditions persisted after adaptation. Conclusion: Balance adaptation occurs during standing on foam. Adaptation leads to a progressive increase in the amplitude of the lowest frequencies of the spectrum and a concurrent decrease in the high-frequency range. Within this common behaviour, touch adds to its stabilising action a modest effect on the adaptation rate. Stabilisation is improved by favouring slow oscillations at the expense of sway minimisation. These findings are preliminary to investigations of balance problems in persons with sensory deficits, ageing, and peripheral or central nervous lesion. [ABSTRACT FROM AUTHOR]

BackgroundSeveral investigations have addressed the process of balance adaptation to external perturbations. The adaptation during unperturbed stance has received little attention. Further, whether the current sensory conditions affect the adaptation rate has not been established. We have addressed the role of vision and haptic feedback on adaptation while standing on foam.MethodsIn 22 young subjects, the analysis of geometric (path length and sway area) and spectral variables (median frequency and mean level of both total spectrum and selected frequency windows) of the oscillation of the centre of feet pressure (CoP) identified the effects of vision, light-touch (LT) or both in the anteroposterior (AP) and mediolateral (ML) direction over 8 consecutive 90 s standing trials.ResultsAdaptation was obvious without vision (eyes closed; EC) and tenuous with vision (eyes open; EO). With trial repetition, path length and median frequency diminished with EC (p < 0.001) while sway area and mean level of the spectrum increased (p < 0.001). The low- and high-frequency range of the spectrum increased and decreased in AP and ML directions, respectively. Touch compared to no-touch enhanced the rate of increase of the low-frequency power (p < 0.05). Spectral differences in distinct sensory conditions persisted after adaptation.ConclusionBalance adaptation occurs during standing on foam. Adaptation leads to a progressive increase in the amplitude of the lowest frequencies of the spectrum and a concurrent decrease in the high-frequency range. Within this common behaviour, touch adds to its stabilising action a modest effect on the adaptation rate. Stabilisation is improved by favouring slow oscillations at the expense of sway minimisation. These findings are preliminary to investigations of balance problems in persons with sensory deficits, ageing, and peripheral or central nervous lesion.

We addressed postural instability during stance with eyes closed (EC) on a compliant surface in healthy young people. Spectral analysis of the centre of foot pressure oscillations was used to identify the effects of haptic information (light-touch, EC-LT), or vision (eyes open, EO), or both (EO-LT). Spectral median frequency was strongly reduced by EO and EO-LT, while spectral amplitude was reduced by all "stabilising" sensory conditions. Reduction in spectrum level by EO mainly appeared in the high-frequency range. Reduction by LT was much larger than that induced by the vision in the low-frequency range, less so in the high-frequency range. Touch and vision together produced a fall in spectral amplitude across all windows, more so in anteroposterior (AP) direction. Lowermost frequencies contributed poorly to geometric measures (sway path and area) for all sensory conditions. The same subjects participated in control experiments on a solid base of support. Median frequency and amplitude of the spectrum and geometric measures were largely smaller when standing on solid than on foam base but poorly affected by the sensory conditions. Frequency analysis but not geometric measures allowed to disclose unique tuning of the postural control mode by haptic and visual information. During standing on foam, the vision did not reduce low-frequency oscillations, while touch diminished the entire spectrum, except for the medium-high frequencies, as if sway reduction by touch would rely on rapid balance corrections. The combination of frequency analysis with sensory conditions is a promising approach to explore altered postural mechanisms and prospective interventions in subjects with central or peripheral nervous system disorders. [ABSTRACT FROM AUTHOR]

We addressed postural instability during stance with eyes closed (EC) on a compliant surface in healthy young people. Spectral analysis of the centre of foot pressure oscillations was used to identify the effects of haptic information (light-touch, EC-LT), or vision (eyes open, EO), or both (EO-LT). Spectral median frequency was strongly reduced by EO and EO-LT, while spectral amplitude was reduced by all “stabilising” sensory conditions. Reduction in spectrum level by EO mainly appeared in the high-frequency range. Reduction by LT was much larger than that induced by the vision in the low-frequency range, less so in the high-frequency range. Touch and vision together produced a fall in spectral amplitude across all windows, more so in anteroposterior (AP) direction. Lowermost frequencies contributed poorly to geometric measures (sway path and area) for all sensory conditions. The same subjects participated in control experiments on a solid base of support. Median frequency and amplitude of the spectrum and geometric measures were largely smaller when standing on solid than on foam base but poorly affected by the sensory conditions. Frequency analysis but not geometric measures allowed to disclose unique tuning of the postural control mode by haptic and visual information. During standing on foam, the vision did not reduce low-frequency oscillations, while touch diminished the entire spectrum, except for the medium-high frequencies, as if sway reduction by touch would rely on rapid balance corrections. The combination of frequency analysis with sensory conditions is a promising approach to explore altered postural mechanisms and prospective interventions in subjects with central or peripheral nervous system disorders.

Lower limb exoskeletons require the correct support magnitude and timing to achieve user assistance. This study evaluated whether the sign of the angular velocity of lower limb segments can be used to determine the timing of the stance and the swing phase during walking. We assumed that stance phase is characterized by a positive, swing phase by a negative angular velocity. Thus, the transitions can be used to also identify heel-strike and toe-off. Thirteen subjects without gait impairments walked on a treadmill at speeds between 0.5 and 2.1 m/s on level ground and inclinations between −10 and +10°. Kinematic and kinetic data was measured simultaneously from an optical motion capture system, force plates, and five inertial measurement units (IMUs). These recordings were used to compute the angular velocities of four lower limb segments: two biological (thigh, shank) and two virtual that were geometrical projections of the biological segments (virtual leg, virtual extended leg). We analyzed the reliability (two sign changes of the angular velocity per stride) and the accuracy (offset in timing between sign change and ground reaction force based timing) of the virtual and biological segments for detecting the gait phases stance and swing. The motion capture data revealed that virtual limb segments seem superior to the biological limb segments in the reliability of stance and swing detection. However, increased signal noise when using the IMUs required additional rule sets for reliable stance and swing detection. With IMUs, the biological shank segment had the least variability in accuracy. The IMU-based heel-strike events of the shank and both virtual segment were slightly early (3.3–4.8% of the gait cycle) compared to the ground reaction force-based timing. Toe-off event timing showed more variability (9.0% too early to 7.3% too late) between the segments and changed with walking speed. The results show that the detection of the heel-strike, and thus stance phase, based on IMU angular velocity is possible for different segments when additional rule sets are included. Further work is required to improve the timing accuracy for the toe-off detection (swing).

Lower limb exoskeletons require the correct support magnitude and timing to achieve user assistance. This study evaluated whether the sign of the angular velocity of lower limb segments can be used to determine the timing of the stance and the swing phase during walking. We assumed that stance phase is characterized by a positive, swing phase by a negative angular velocity. Thus, the transitions can be used to also identify heel-strike and toe-off. Thirteen subjects without gait impairments walked on a treadmill at speeds between 0.5 and 2.1 m/s on level ground and inclinations between −10 and +10°. Kinematic and kinetic data was measured simultaneously from an optical motion capture system, force plates, and five inertial measurement units (IMUs). These recordings were used to compute the angular velocities of four lower limb segments: two biological (thigh, shank) and two virtual that were geometrical projections of the biological segments (virtual leg, virtual extended leg). We analyzed the reliability (two sign changes of the angular velocity per stride) and the accuracy (offset in timing between sign change and ground reaction force based timing) of the virtual and biological segments for detecting the gait phases stance and swing. The motion capture data revealed that virtual limb segments seem superior to the biological limb segments in the reliability of stance and swing detection. However, increased signal noise when using the IMUs required additional rule sets for reliable stance and swing detection. With IMUs, the biological shank segment had the least variability in accuracy. The IMU-based heel-strike events of the shank and both virtual segment were slightly early (3.3–4.8% of the gait cycle) compared to the ground reaction force-based timing. Toe-off event timing showed more variability (9.0% too early to 7.3% too late) between the segments and changed with walking speed. The results show that the detection of the heel-strike, and thus stance phase, based on IMU angular velocity is possible for different segments when additional rule sets are included. Further work is required to improve the timing accuracy for the toe-off detection (swing). [ABSTRACT FROM AUTHOR]

Balance control is fundamental for most daily motor activities, and its impairment is associated with an increased risk of falling. Growing evidence suggests the human cortex is essentially contributing to the control of standing balance. However, the exact mechanisms remain unclear and need further investigation. In a previous study we introduced a new protocol to identify electrocortical activity associated with performance of different continuous balance tasks with the eyes opened. The aim of this study was to extend our previous results by investigating the individual alpha peak frequency (iAPF), a neurophysiological marker of thalamo-cortical information transmission, which remained unconsidered so far in balance research. Thirty-seven subjects completed nine balance tasks varying in surface stability and base of support. Electroencephalography (EEG) was recorded from 32 scalp locations throughout balancing with the eyes closed to ensure reliable identification of the iAPF. Balance performance was quantified as the sum of anterior-posterior and medio-lateral movements of the supporting platform. The iAPF, as well as power in the theta, lower alpha and upper alpha frequency bands were determined for each balance task after applying an ICA-based artifact rejection procedure. Higher demands on balance control were associated with a global increase in iAPF and a decrease in lower alpha power. These results may indicate increased thalamo-cortical information transfer and general cortical activation, respectively. In addition, a significant increase in upper alpha activity was observed in the fronto-central region whereas it decreased in the centro-parietal region. Furthermore, midline theta increased with higher task demands probably indicating activation of error detection/processing mechanisms. IAPF as well as theta and alpha power were correlated with platform movements. The results provide new insights into spectral and spatial characteristics of cortical oscillations subserving balance control. This information may be particularly useful in a clinical context as it could be used to reveal cortical contributions to balance dysfunction in specific populations such as Parkinson’s or vestibular loss. However, this should be addressed in future studies.

Balance control is fundamental for most daily motor activities, and its impairment is associated with an increased risk of falling. Growing evidence suggests the human cortex is essentially contributing to the control of standing balance. However, the exact mechanisms remain unclear and need further investigation. In a previous study, we introduced a new protocol to identify electrocortical activity associated with performance of different continuous balance tasks with the eyes opened. The aim of this study was to extend our previous results by investigating the individual alpha peak frequency (iAPF), a neurophysiological marker of thalamo-cortical information transmission, which remained unconsidered so far in balance research. Thirty-seven subjects completed nine balance tasks varying in surface stability and base of support. Electroencephalography (EEG) was recorded from 32 scalp locations throughout balancing with the eyes closed to ensure reliable identification of the iAPF. Balance performance was quantified as the sum of anterior-posterior and medio-lateral movements of the supporting platform. The iAPF, as well as power in the theta, lower alpha and upper alpha frequency bands were determined for each balance task after applying an ICA-based artifact rejection procedure. Higher demands on balance control were associated with a global increase in iAPF and a decrease in lower alpha power. These results may indicate increased thalamo-cortical information transfer and general cortical activation, respectively. In addition, a significant increase in upper alpha activity was observed in the fronto-central region whereas it decreased in the centro-parietal region. Furthermore, midline theta increased with higher task demands probably indicating activation of error detection/processing mechanisms. IAPF as well as theta and alpha power were correlated with platform movements. The results provide new insights into spectral and spatial characteristics of cortical oscillations subserving balance control. This information may be particularly useful in a clinical context as it could be used to reveal cortical contributions to balance dysfunction in specific populations such as Parkinson's or vestibular loss. However, this should be addressed in future studies. [ABSTRACT FROM AUTHOR]

Background: Subjective postural imbalance is a key symptom in the somatoform phobic postural vertigo (PPV). It has been assumed that more attentional control of body posture and/or co-contraction of leg muscles during standing is used to minimize the physiological body sway in PPV. Here we analyze nonlinear variability of body sway in patients with PPV in order to disclose changes in postural control strategy associated with PPV.Methods: Twenty patients with PPV and 20 age-matched healthy controls were recorded on a stabilometer platform with eyes open, eyes closed and while standing on a foam rubber with eyes closed. Spatio-temporal changes of the center of pressure (CoP) displacement were analyzed to assess the structure of postural variability by computing the scaling exponent α and the sample entropy (SEn) of the time series.Results: With eyes open on firm ground α and SEn of CoP displacement were significantly lower in patients (p < 0.001). For more difficult conditions (eyes closed, standing on a foam rubber) postural variability in PPV assimilated to that of healthy controls.Conclusions: Postural control in PPV patients differs from controls under normal stance condition. It is characterized by a reduced scaling behavior and higher regularity. These changes in the structure of postural variability might suggest an inappropriate attentional involvement with stabilizing strategies, which are used by healthy subjects only for more demanding balance tasks.

This review describes the effect of unilateral peripheral vestibular deficit (UPVD) on balance control as observed in stance and gait tests. Normally, a UPVD is defined based on vestibular ocular reflex (VOR) function. Therefore, we compare recovery observed in balance control over time with similar patterns of recovery or lack thereof in VOR function. Three types of UPVD are considered; acute vestibular neuritis, vestibular loss prior to and after cerebellar pontine angle tumor (CPAT) surgery during which a vestibular neurectomy was performed, and vestibular loss following neurectomy to eliminate disabling Ménière’s disease.To measure balance control, body-worn gyroscopes, mounted near the body’s centre of mass, were used for stance and gait tests. Measurement variables were the pitch (anterior-posterior) and roll (lateral) sway angles and angular velocities of the lower trunk-pelvis. All three groups showed balance deficits during stance tasks on foam, especially with eyes closed when stable control is highly dependent on vestibular inputs. Deficits in balance control during gait were present but were more profound for complex gait tasks such as tandem gait. Differences emerged between the groups concerning the severity of the deficit and its recovery. Generally, the effects of acute neuritis were more severe but recovered rapidly, deficits due to vestibular neurectomy were less severe but longer lasting. These results paralleled deficits in VOR function and raise questions about two modes of neural plasticity occurring in the vestibular system following vestibular loss: one mode being the limited central compensation for the loss, and the second mode being some restoration of peripheral vestibular function. Future work will need to correlate deficits in balance control during stance and gait more exactly with VOR deficits and carefully consider the differences between insufficient central compensation compared to inadequate peripheral restoration of function.

Background: Subjective postural imbalance is a key symptom in the somatoform phobic postural vertigo (PPV). It has been assumed that more attentional control of body posture and / or co-contraction of leg muscles during standing is used to minimize the physiological body sway in PPV. Here we analyze nonlinear variability of body sway in patients with PPV in order to disclose changes in postural control strategy associated with PPV. Methods: Twenty patients with PPV and 20 age-matched healthy subjects (HS) were recorded on a stabilometer platform with eyes open (EO), eyes closed (EC), and while standing on a foam rubber with eyes closed (ECF). Spatio-temporal changes of the center of pressure (CoP) displacement were analyzed to assess the structure of postural variability by computing the scaling exponent α and the sample entropy (SEn) of the time series. Results:With EO on firm ground α and SEn of CoP displacement were significantly lower in patients (p <0.001). For more difficult conditions (EC, ECF) postural variability in PPV assimilated to that of HS. Conclusion: Postural control in PPV patients differs from HS under normal stance condition. It is characterized by a reduced scaling behavior and higher regularity. These changes in the structure of postural variability might suggest an inappropriate attentional involvement with stabilizing strategies, which are used by HS only for more demanding balance tasks. [ABSTRACT FROM AUTHOR]

This review describes the effect of unilateral peripheral vestibular deficit (UPVD) on balance control for stance and gait tests. Because a UPVD is normally defined based on vestibular ocular reflex (VOR) tests, we compared recovery observed in balance control with patterns of recovery in VOR function. Two general types of UPVD are considered; acute vestibular neuritis (AVN) and vestibular neurectomy. The latter was subdivided into vestibular loss after cerebellar pontine angle tumor surgery during which a vestibular neurectomy was performed, and vestibular loss following neurectomy to eliminate disabling Ménière's disease. To measure balance control, body-worn gyroscopes, mounted near the body's center of mass (CoM), were used. Measurement variables were the pitch (anterior-posterior) and roll (lateral) sway angles and angular velocities of the lower trunk/pelvis. Both patient groups showed balance deficits during stance tasks on foam, especially with eyes closed when stable balance control is normally highly dependent on vestibular inputs. Deficits during gait were also present and were more profound for complex gait tasks such as tandem gait than simple gait tasks. Major differences emerged between the groups concerning the severity of the deficit and its recovery. Generally, the effects of acute neuritis on balance control were more severe but recovered rapidly. Deficits due to vestibular neurectomy were less severe, but longer lasting. These results mostly paralleled recovery of deficits in VOR function. However, questions need to be raised about the effect on balance control of the two modes of neural plasticity occurring in the vestibular system following vestibular loss due to neuritis: one mode being the limited central compensation for the loss, and the second mode being some restoration of peripheral vestibular function. Future work will need to correlate deficits in balance control during stance and gait more exactly with VOR deficits and carefully consider the differences between insufficient central compensation compared to inadequate peripheral restoration of function. [ABSTRACT FROM AUTHOR]