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1.
Neurocirugía (Soc. Luso-Esp. Neurocir.) ; 34(1): 1-11, ene.-feb. 2023. tab
Artigo em Espanhol | IBECS | ID: ibc-214408

RESUMO

La literatura que explica los mecanismos neurológicos que subyacen al desarrollo o a la compensación de la escoliosis idiopática es limitada. El objetivo del presente artículo es describir e integrar los mecanismos y las vías nerviosas por medio de las cuales se compensa y/o se desarrolla la escoliosis idiopática. Se realizó una revisión sistemática narrativa en diferentes bases de datos sobre los estudios publicados entre el 1 de enero 1967 y el 1 de abril de 2021, empleando los siguientes términos: «scoliosis», «vision», «ocular», «vestibule», «labyrinth», «posture», «balance», «eye movements», «cerebellum», «proprioception» y «physiological adaptation». En la búsqueda se identificaron 1.112 referencias, de las cuales al final se incluyeron 50: 46 estudios clínicos observacionales analítico-descriptivos (entre cohortes, reporte y serie de casos) y 4 estudios experimentales. En la respuesta neurológica a la escoliosis idiopática, la integración sensitivo-cortical de las aferencias visual-oculomotor-vestibular-propioceptiva permite realizar modificaciones a nivel postural con el fin de lograr una compensación inicial sobre el balance sagital y el centro de masa; sin embargo, con el tiempo dicho mecanismo de compensación puede agotarse y causar progresión de la deformidad inicial. (AU)


The literature that explains the neurological mechanisms underlying the development or compensation of idiopathic scoliosis is limited. The objective of the article is to describe and integrate the mechanisms and nerve pathways through which idiopathic scoliosis is compensated and/or developed. A narrative systematic review in different databases of the studies published between January 1, 1967 and April 1, 2021 was performed, using the following terms: «scoliosis», «vision», «eye», «vestibule», «labyrinth», «posture», «balance», «eye movements», «cerebellum», «proprioception», and «physiological adaptation». In the search, 1112 references were identified, of which 50 were finally included: 46 observational analytical clinical studies-descriptive (between cohorts, report and series of cases) and 4 experimental studies. In the neurological response to idiopathic scoliosis, the sensory-cortical integration of the afferences in the visual-oculomotor-vestibular-proprioceptive systems, allows modifications at the postural level in order to achieve an initial compensation on the sagittal balance and the centre of body mass; however, over time these compensation mechanisms may be exhausted causing progression of the initial deformity. (AU)


Assuntos
Humanos , Escoliose/etiologia , Escoliose/fisiopatologia , Vestíbulo do Labirinto/fisiopatologia , Vias Neurais , Postura/fisiologia , Propriocepção/fisiologia , Progressão da Doença
2.
Sci Rep ; 13(1): 522, 2023 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-36627328

RESUMO

Efficient postural control results from an effective interplay between sensory feedbacks integration and muscle modulation and can be affected by ageing and neuromuscular injuries. With this study, we investigated the effect of whole-body vibratory stimulation on postural control strategies employed to maintain an upright posture. We explored both physiological and posturography metrics, through corticomuscular and intramuscular coherence, and muscle networks analyses. The stimulation disrupts balance in the short term, but leads to a greater contribution of cortical activity, necessary to modulate muscle activation via the formation of (new) synergies. We also observed a reconfiguration of muscle recruitment patterns that returned to pre-stimulation levels after few minutes, accompanied by a slight improvement of balance in the anterior-posterior direction. Our results suggest that, in the context of postural control, appropriate mechanical stimulation is capable of triggering a recalibration of the sensorimotor set and might offer new perspectives for motor re-education.


Assuntos
Postura , Vibração , Postura/fisiologia , Equilíbrio Postural/fisiologia , Músculos , Retroalimentação Sensorial , Músculo Esquelético/fisiologia
3.
Sensors (Basel) ; 23(2)2023 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-36679516

RESUMO

In recent years, employment in sedentary occupations has continuously risen. Office workers are more prone to prolonged static sitting, spending 65-80% of work hours sitting, increasing risks for multiple health problems, including cardiovascular diseases and musculoskeletal disorders. These adverse health effects lead to decreased productivity, increased absenteeism and health care costs. However, lack of regulation targeting these issues has oftentimes left them unattended. This article proposes a smart chair system, with posture and electrocardiography (ECG) monitoring modules, using an "invisible" sensing approach, to optimize working conditions, without hindering everyday tasks. For posture classification, machine learning models were trained and tested with datasets composed by center of mass coordinates in the seat plane, computed from the weight measured by load cells fixed under the seat. Models were trained and evaluated in the classification of five and seven sitting positions, achieving high accuracy results for all five-class models (>97.4%), and good results for some seven-class models, particularly the best performing k-NN model (87.5%). For ECG monitoring, signals were acquired at the armrests covered with conductive nappa, connected to a single-lead sensor. Following signal filtering and segmentation, several outlier detection methods were applied to remove extremely noisy segments with mislabeled R-peaks, but only DBSCAN showed satisfactory results for the ECG segmentation performance (88.21%) and accuracy (90.50%).


Assuntos
Doenças Musculoesqueléticas , Postura , Humanos , Postura/fisiologia , Ocupações , Postura Sentada , Eletrocardiografia
4.
Sensors (Basel) ; 23(2)2023 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-36679781

RESUMO

The alteration of the hydrostatic pressure gradient in the human body has been associated with changes in human physiology, including abnormal blood flow, syncope, and visual impairment. The focus of this study was to evaluate changes in the resonant frequency of a wearable electromagnetic resonant skin patch sensor during simulated physiological changes observed in aerospace applications. Simulated microgravity was induced in eight healthy human participants (n = 8), and the implementation of lower body negative pressure (LBNP) countermeasures was induced in four healthy human participants (n = 4). The average shift in resonant frequency was -13.76 ± 6.49 MHz for simulated microgravity with a shift in intracranial pressure (ICP) of 9.53 ± 1.32 mmHg, and a shift of 8.80 ± 5.2097 MHz for LBNP with a shift in ICP of approximately -5.83 ± 2.76 mmHg. The constructed regression model to explain the variance in shifts in ICP using the shifts in resonant frequency (R2 = 0.97) resulted in a root mean square error of 1.24. This work demonstrates a strong correlation between sensor signal response and shifts in ICP. Furthermore, this study establishes a foundation for future work integrating wearable sensors with alert systems and countermeasure recommendations for pilots and astronauts.


Assuntos
Voo Espacial , Dispositivos Eletrônicos Vestíveis , Ausência de Peso , Humanos , Voo Espacial/métodos , Postura/fisiologia , Pressão Negativa da Região Corporal Inferior
5.
J Appl Biomech ; 39(1): 54-61, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36649715

RESUMO

Left-right differential erector spinae (ES) muscle strengthening is required to correct ES muscle imbalances. The objective was to test the effect of 6 body positions on the differential activation of the ES muscles. In 14 able-bodied young women, using a surface electromyography system, the bilateral ES muscles activity at the third lumbar (ESL3) and the 10th (EST10) and 6th (EST6) thoracic vertebral levels was measured with the contralateral arm and leg lifted in the prone and quadruped conditions and with a single arm lifted in the quadruped position. Results showed that the activity of the ESL3 was symmetrical (P > .05) and significantly smaller than that of the thoracic ES muscles in all body positions (P < .01). The EST10 and EST6 were differentially activated in all tests (P < .001). Besides, the differential activation was higher in the contralateral-arm and -leg lift in the quadruped position than in the other positions. In conclusion, contralateral-arm and -leg lift and single-arm lift in the quadruped and prone positions are capable of differentially activating the ES muscles on one side more than the other side. Further studies are recommended to examine the effectiveness of these exercises on the correction of ES muscle imbalances in clinical populations.


Assuntos
Exercício Físico , Postura , Humanos , Feminino , Postura/fisiologia , Eletromiografia/métodos , Terapia por Exercício , Músculos/fisiologia , Músculo Esquelético/fisiologia
6.
BMC Musculoskelet Disord ; 24(1): 61, 2023 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-36690958

RESUMO

BACKGROUND: Frequent smartphone use in a pathological way forces the user to adopt a compromised posture. This gradually results in changes to both the postural and musculoskeletal systems. This study's objectives were evaluation of head posture, muscle endurance, neck range of motion (ROM) and joint position sense in two separate smartphone user groups, one 'Addicted', the other 'Non-Addicted'. METHODS: A sample of convenience (n = 60) was recruited from medical students (age 24.57 ± 4.38, 53.3% male) with a history of smartphones use > 2 h/day for 1-year. Based on the cut-off values of the smartphone addiction scale-short version (SAS-SV), participants were entered into each group (cut-off for male ≥ 31, female ≥ 33). Neck muscle endurance time, joint position error and cervical ROM, along with forward head posture parameters of craniovertebral angle (CVA), shoulder angle (SA), sagittal head angle (SHA) and forward head distance (FHD)) were evaluated. A Mann-Whitney test and Spearman correlation coefficient were used to determine the difference between groups and the correlations between variables. RESULTS: The difference between 'Addicted' and 'Non-Addicted' groups was confirmed by the values for SAS-SV scores (25.23 ± 5.5 versus 43.9 ± 6.61) (p < 0.001). There were statistically significant differences between groups for the CVA and FHD parameters (p < 0.001). Further, the neck extensor muscle endurance (97 ± 3.79 versus 74.86 ± 2.23 s), was significantly different between groups (p = 0.010) but not after Bonferroni correction. There was no notable difference in the neck flexor muscle endurance, joint position error, SA, and SHA parameters between groups (p > 0.05). CONCLUSIONS: There is a positive correlation between smartphone addiction and both decreased extensor muscle endurance and changes in neck postural alignment.


Assuntos
Transtorno de Adição à Internet , Cervicalgia , Humanos , Masculino , Feminino , Postura/fisiologia , Músculos do Pescoço/fisiologia , Amplitude de Movimento Articular , Propriocepção/fisiologia , Smartphone
7.
PeerJ ; 11: e14631, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36650837

RESUMO

The ability to actively track posture using visual targets as indicators is important for improving impairments in whole-body coordination, and accurate visual feedback on tasks is considered effective in promoting sensory-motor integration and behavioral success. In the present study, we examined inter- and intramuscular modulation between the two lower limbs in response to visual perturbation. Sixteen healthy young subjects (age: 21.3 ± 0.7 years) were asked to move their weight back and forth while tracking a visual target displayed on a monitor in front of them for 30 s. Three types of target movements were examined: a sinusoidal wave (i.e., a predictable pattern), more complex patterns (random), and no movement (stationary). Electromyography (EMG) was used to assess intra- and intermuscular coherence modulation of the plantar flexor muscles (right and left soleus and right and left medial gastrocnemius). The ability to adjust posture to follow the target signal was assessed using a stabilometer. Inter- and intramuscular coherence increased during the visual perturbation task compared to the stationary task. In addition, left-right differences in lower limb modulation were observed during the visual perturbation task. Furthermore, interlimb coherence was related to the motor accuracy of tracking. The muscles of both lower limbs cooperated in response to visual perturbation, suggesting that these muscles control visually induced anteroposterior postural sway. Since such visual perturbations promote coordination between both lower extremities, this relationship may indicate the potential for rehabilitation training to help individuals acquire and improve the motor functions necessary to efficiently and stably perform activities of daily living.


Assuntos
Atividades Cotidianas , Movimento , Humanos , Adulto Jovem , Extremidade Inferior , Movimento/fisiologia , Músculo Esquelético/fisiologia , Postura/fisiologia
8.
Am J Physiol Heart Circ Physiol ; 324(1): H122-H125, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36525481

RESUMO

Sedentary behavior has been identified as an independent predictor of future cardiovascular disease risk and all-cause mortality. To explain this association, a growing body of literature has sought to investigate the physiological underpinnings of this association with the goal of developing a biologically plausible model. In time, this biologically plausible model can be tested, and effective, translatable public health guidelines can be developed. However, to ensure that evidence across studies can be effectively synthesized, it is necessary to ensure their congruency and comparability. Although there are several key factors that should be considered and controlled across prolonged sitting studies, one pertinent issue is that of participant posture. There is currently a discourse within the literature regarding the posture that cardiovascular assessments are performed in and rest periods between posture transitions and subsequent measures. This perspectives piece makes the case for standardizing approaches across the research area and offers practical recommendations for future work.


Assuntos
Doenças Cardiovasculares , Comportamento Sedentário , Humanos , Doenças Cardiovasculares/diagnóstico , Postura/fisiologia , Postura Sentada , Fatores de Tempo
9.
Clin Biomech (Bristol, Avon) ; 101: 105868, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36580828

RESUMO

BACKGROUND: We examined the association of sagittal spinal alignment in the standing position with the masses and amounts of intramuscular non-contractile tissue of multiple trunk and lower extremity muscles, such as the hip joint muscles, measured using an ultrasound imaging device in patients with Parkinson's disease (PD). METHODS: The participants were 10 patients with PD. Sagittal spinal alignment (thoracic kyphosis, lumbar lordosis, and sacral anterior inclination angles) in the standing position was measured using a Spinal Mouse. Muscle thicknesses and echo intensities of the trunk and lower extremity muscles, including the hip joint muscles, were also measured in the prone or supine position using an ultrasound imaging device. FINDINGS: Partial correlation analysis with body height and weight as control variables showed that a low lumbar lordosis angle in the standing position was significantly associated with low thicknesses of the trunk extensor muscles (lumbar erector spinae and multifidus). Partial correlation analysis also revealed that a high sacral anterior inclination angle in the standing position was significantly associated with low lumbar multifidus muscle thickness. However, the thicknesses and echo intensities of the trunk flexor and hip joint muscles were not significantly related to thoracic kyphosis, lumbar lordosis, or sacral anterior inclination angles. INTERPRETATION: The results of this study suggested the association between a low lumbar lordosis angle in the standing position and low lumbar erector spinae and multifidus muscle thicknesses and between a high sacral anterior inclination angle in the standing position and low lumbar multifidus muscle thickness in patients with PD.


Assuntos
Cifose , Lordose , Doença de Parkinson , Animais , Camundongos , Lordose/diagnóstico por imagem , Posição Ortostática , Doença de Parkinson/diagnóstico por imagem , Postura/fisiologia , Cifose/diagnóstico por imagem , Músculos Paraespinais , Extremidade Inferior/diagnóstico por imagem , Vértebras Lombares/diagnóstico por imagem
10.
Neuroscience ; 510: 32-48, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36535577

RESUMO

Noisy galvanic vestibular stimulation has been shown to improve vestibular perception in healthy subjects. Here, we sought to obtain similar results using more natural stimuli consisting of small-amplitude motion perturbations of the whole body. Thirty participants were asked to report the perceived direction of antero-posterior sinusoidal motion on a MOOG platform. We compared the baseline perceptual thresholds with those obtained by applying small, stochastic perturbations at different power levels along the antero-posterior axis, symmetrically distributed around a zero-mean. At the population level, we found that the thresholds for all but the highest level of noise were significantly lower than the baseline threshold. At the individual level, the threshold was lower with at least one noise level than the threshold without noise in 87% of participants. Thus, small, stochastic oscillations of the whole body can increase the probability of recognizing the direction of motion from low, normally subthreshold vestibular signals, possibly due to stochastic resonance mechanisms. We suggest that, just as the external noise of the present experiments, also the spontaneous random oscillations of the head and body associated with standing posture are beneficial by enhancing vestibular thresholds with a mechanism similar to stochastic resonance.


Assuntos
Percepção de Movimento , Vestíbulo do Labirinto , Humanos , Equilíbrio Postural/fisiologia , Vestíbulo do Labirinto/fisiologia , Percepção de Movimento/fisiologia , Ruído , Postura/fisiologia
11.
Exp Brain Res ; 241(1): 289-299, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36502432

RESUMO

When humans are exposed to a predictable external perturbation, they usually generate anticipatory postural adjustments (APAs), which reduce the effect of potential body disturbance. However, when an external perturbation comes from behind and as such unpredicted, no APAs are generated, which challenges postural control. The aim of this study was to examine whether humans exposed to unpredictable perturbations could generate APAs using an auditory cue. Ten young adults were exposed to external perturbations hitting their shoulders from behind with or without an auditory cue prior to the physical impact. Electromyography (EMG) activities of eight trunk and leg muscles and center-of-pressure (COP) displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Outcome measures included the latencies and integrals of muscle activities, COP displacements, and indices of co-contraction and reciprocal activation of muscles. The results showed that young adults were able to rely on an auditory cue to generate APAs prior to external perturbations coming from behind, and they demonstrated stronger APAs with training. Moreover, they utilized co-contraction of ventral and dorsal muscles as their APA response. The outcome provides a foundation for future studies aiming at using auditory cues to facilitate the generation of APAs and improve postural control in people with impaired balance while exposed to perturbations.


Assuntos
Sinais (Psicologia) , Contração Muscular , Adulto Jovem , Humanos , Estudos de Viabilidade , Contração Muscular/fisiologia , Postura/fisiologia , Músculo Esquelético/fisiologia , Eletromiografia/métodos , Equilíbrio Postural/fisiologia
12.
J Neuroeng Rehabil ; 19(1): 139, 2022 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-36510259

RESUMO

BACKGROUND: Restoring or improving seated stability after spinal cord injury (SCI) can improve the ability to perform activities of daily living by providing a dynamic, yet stable, base for upper extremity motion. Seated stability can be obtained with activation of the otherwise paralyzed trunk and hip musculature with neural stimulation, which has been shown to extend upper limb reach and improve seated posture. METHODS: We implemented a proportional, integral, derivative (PID) controller to maintain upright seated posture by simultaneously modulating both forward flexion and lateral bending with functional neuromuscular stimulation. The controller was tested with a functional reaching task meant to require trunk movements and impart internal perturbations through rapid changes in inertia due to acquiring, moving, and replacing objects with one upper extremity. Five subjects with SCI at various injury levels who had received implanted stimulators targeting their trunk and hip muscles participated in the study. Each subject was asked to move a weighted jar radially from a center home station to one of three target stations. The task was performed with the controller active, inactive, or with a constant low level of neural stimulation. Trunk pitch (flexion) and roll (lateral bending) angles were measured with motion capture and plotted against each other to generate elliptical movement profiles for each task and condition. Postural sway was quantified by calculating the ellipse area. Additionally, the mean effective reach (distance between the shoulder and wrist) and the time required to return to an upright posture was determined during reaching movements. RESULTS: Postural sway was reduced by the controller in two of the subjects, and mean effective reach was increased in three subjects and decreased for one. Analysis of the major direction of motion showed return to upright movements were quickened by 0.17 to 0.32 s. A 15 to 25% improvement over low/no stimulation was observed for four subjects. CONCLUSION: These results suggest that feedback control of neural stimulation is a viable way to maintain upright seated posture by facilitating trunk movements necessary to complete reaching tasks in individuals with SCI. Replication of these findings on a larger number of subjects would be necessary for generalization to the various segments of the SCI population.


Assuntos
Atividades Cotidianas , Traumatismos da Medula Espinal , Humanos , Estudos de Viabilidade , Postura/fisiologia , Modalidades de Fisioterapia
13.
Medicina (Kaunas) ; 58(12)2022 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-36556992

RESUMO

Dizziness or vertigo can be caused by dysfunction of the vestibular or non-vestibular systems. The diagnosis, treatment, and mechanism of dizziness or vertigo caused by vestibular dysfunction have been described in detail. However, dizziness by the non-vestibular system, especially cervicogenic dizziness, is not well known. This paper explained the cervicogenic dizziness caused by abnormal sensory input with references to several studies. Among head and neck muscles, suboccipital muscles act as stabilizers and controllers of the head. Structural and functional changes of the suboccipital muscles can induce dizziness. Especially, myodural bridges and activation of trigger point stimulated by abnormal head posture may be associated with cervicogenic dizziness.


Assuntos
Tontura , Músculos do Pescoço , Humanos , Tontura/etiologia , Tontura/diagnóstico , Vertigem/complicações , Postura/fisiologia
14.
Physiol Rep ; 10(24): e15525, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36541216

RESUMO

Sheep are popular large animals in which to model human disorders and to study physiological processes such as cerebrospinal fluid dynamics. However, little is known about vascular compensatory mechanisms affecting cerebrospinal fluid pressures during acute postural changes in sheep. Six female white Alpine sheep were anesthetized to investigate the interactions of the vascular and cerebrospinal fluid system by acquiring measurements of intracranial pressure and central and jugular venous pressure during passive postural changes induced by a tilt table. The cross-sectional area of the common jugular vein and venous blood flow velocity was recorded. Anesthetized sheep showed bi-phasic effects of postural changes on intracranial pressure during tilting. A marked collapse of the jugular vein was observed during head-over-body tilting; this is in accordance with findings in humans. Active regulatory effects of the arterial system on maintaining cerebral perfusion pressure were observed independent of tilting direction. Conclusion: Anesthetized sheep show venous dynamics in response to posture-induced changes in intracranial pressure that are comparable with those in humans.


Assuntos
Postura , Veias , Humanos , Feminino , Animais , Ovinos , Postura/fisiologia , Pressão Intracraniana/fisiologia , Veias Jugulares/fisiologia , Pressão Arterial , Pressão Venosa , Líquido Cefalorraquidiano , Circulação Cerebrovascular
15.
Sensors (Basel) ; 22(24)2022 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-36559987

RESUMO

Personal protective equipment (PPE) is an essential key factor in standardizing safety within the workplace. Harsh working environments with long working hours can cause stress on the human body that may lead to musculoskeletal disorder (MSD). MSD refers to injuries that impact the muscles, nerves, joints, and many other human body areas. Most work-related MSD results from hazardous manual tasks involving repetitive, sustained force, or repetitive movements in awkward postures. This paper presents collaborative research from the School of Electrical Engineering and School of Allied Health at Curtin University. The main objective was to develop a framework for posture correction exercises for workers in hostile environments, utilizing inertial measurement units (IMU). The developed system uses IMUs to record the head, back, and pelvis movements of a healthy participant without MSD and determine the range of motion of each joint. A simulation was developed to analyze the participant's posture to determine whether the posture present would pose an increased risk of MSD with limits to a range of movement set based on the literature. When compared to measurements made by a goniometer, the body movement recorded 94% accuracy and the wrist movement recorded 96% accuracy.


Assuntos
Doenças Musculoesqueléticas , Postura , Humanos , Fenômenos Biomecânicos , Postura/fisiologia , Movimento/fisiologia , Fenômenos Mecânicos , Algoritmos
16.
Sensors (Basel) ; 22(23)2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36502048

RESUMO

(1) Background: Cycling is characterized by a sustained sitting posture on the bicycle, where physiologic spinal curvatures are modified from standing to cycling. Therefore, the main objective was to evaluate and compare the morphology of the spine and the core muscle activity in standing posture and cycling at low intensity. (2) Methods: Twelve competitive cyclists participated in the study. Spinal morphology was evaluated using an infrared-camera system. Muscle activation was recorded using a surface electromyography device. (3) Conclusions: The lumbar spine changes its morphology from lordosis in standing to kyphosis (lumbar flexion) when pedaling on the bicycle. The sacral tilt significantly increases its anterior tilt when cycling compared to when standing. The spinal morphology and sacral tilt are dynamic depending on the pedal's position during the pedal stroke quadrants. The infraspinatus, latissimus dorsi, external oblique, and pectoralis major showed significantly higher activation pedaling than when standing, although with very low values.


Assuntos
Cifose , Lordose , Humanos , Coluna Vertebral/fisiologia , Postura/fisiologia , Vértebras Lombares , Músculos
17.
PLoS Comput Biol ; 18(11): e1010035, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36374914

RESUMO

To successfully traverse their environment, humans often perform maneuvers to achieve desired task goals while simultaneously maintaining balance. Humans accomplish these tasks primarily by modulating their foot placements. As humans are more unstable laterally, we must better understand how humans modulate lateral foot placement. We previously developed a theoretical framework and corresponding computational models to describe how humans regulate lateral stepping during straight-ahead continuous walking. We identified goal functions for step width and lateral body position that define the walking task and determine the set of all possible task solutions as Goal Equivalent Manifolds (GEMs). Here, we used this framework to determine if humans can regulate lateral stepping during non-steady-state lateral maneuvers by minimizing errors consistent with these goal functions. Twenty young healthy adults each performed four lateral lane-change maneuvers in a virtual reality environment. Extending our general lateral stepping regulation framework, we first re-examined the requirements of such transient walking tasks. Doing so yielded new theoretical predictions regarding how steps during any such maneuver should be regulated to minimize error costs, consistent with the goals required at each step and with how these costs are adapted at each step during the maneuver. Humans performed the experimental lateral maneuvers in a manner consistent with our theoretical predictions. Furthermore, their stepping behavior was well modeled by allowing the parameters of our previous lateral stepping models to adapt from step to step. To our knowledge, our results are the first to demonstrate humans might use evolving cost landscapes in real time to perform such an adaptive motor task and, furthermore, that such adaptation can occur quickly-over only one step. Thus, the predictive capabilities of our general stepping regulation framework extend to a much greater range of walking tasks beyond just normal, straight-ahead walking.


Assuntos
, Caminhada , Adulto , Humanos , Caminhada/fisiologia , Pé/fisiologia , Postura/fisiologia , Adaptação Fisiológica , Extremidade Inferior , Marcha/fisiologia , Equilíbrio Postural/fisiologia , Fenômenos Biomecânicos
18.
Sci Rep ; 12(1): 19484, 2022 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-36376467

RESUMO

Forward head posture (FHP) is a serious problem causing head and neck disability, but the characteristics of muscle activity during long-term postural maintenance are unclear. This study aimed to investigate a comparison of electromyography (EMG) activation properties and subjective fatigue between young adults with and without habitual FHP. In this study, we examined the changes in the spatial and temporal distribution patterns of muscle activity using high-density surface EMG (HD-SEMG) in addition to mean frequency, a conventional measure of muscle fatigue. Nineteen male participants were included in the study (FHP group (n = 9; age = 22.3 ± 1.5 years) and normal group (n = 10; age = 22.5 ± 1.4 years)). Participants held three head positions (e.g., forward, backward, and neutral positions) for a total of 30 min each, and the EMG activity of the trapezius pars descendens muscle during posture maintenance was measured by HD-SEMG. The root mean square (RMS), the modified entropy, and the correlation coefficient were calculated. Additionally, the visual analogue scale (VAS) was evaluated to assess subjective fatigue. The RMS, VAS, modified entropy, and correlation coefficients were significantly higher in the FHP group than in the normal group (p < 0.001). With increasing postural maintenance time, the modified entropy and correlation coefficient values significantly decreased, and the mean frequency and VAS values significantly increased (p < 0.001). Furthermore, the forward position had significantly higher RMS, correlation coefficient, modified entropy, and VAS values than in the neutral position (p < 0.001). The HD-SEMG potential distribution patterns in the FHP group showed less heterogeneity and greater muscle activity in the entire muscle and subjective fatigue than those in the normal group. Excess muscle activity even in the neutral/comfortable position in the FHP group could potentially be a mechanism of neuromuscular conditions in this population.


Assuntos
Músculos Superficiais do Dorso , Humanos , Adulto Jovem , Masculino , Adulto , Músculos Superficiais do Dorso/fisiologia , Postura/fisiologia , Eletromiografia , Fadiga Muscular/fisiologia , Cabeça/fisiologia , Músculo Esquelético/fisiologia
19.
Sensors (Basel) ; 22(21)2022 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-36365931

RESUMO

Few standards and guidelines to prevent health problems have been associated with tablet use. We estimated the effects of posture and tablet tilt angle on muscle activity and posture in healthy young adults. Seventeen healthy young adults (age: 20.5 ± 3 years) performed a cognitive task using a tablet in two posture (sitting and standing) and tablet tilt angle (0 degrees and 45 deg) conditions. Segment and joint kinematics were evaluated using 16 inertial measurement unit sensors. Neck, trunk, and upper limb electromyography (EMG) activities were monitored using 12 EMG sensors. Perceived discomfort, kinematics, and EMG activities were compared between conditions using the Friedman test. The perceived discomfort in the standing-0 deg condition was significantly higher than in the remaining three conditions. Standing posture and tablet inclination significantly reduced the sagittal segment and joint angles of the spine, compared with sitting and flat tablet conditions. Similarly, standing posture and tablet inclination significantly reduced EMG activities of the dorsal neck, upper, and lower trunk muscles, while increasing EMG activity of shoulder flexors. Standing posture and tablet inclination reduced the sagittal flexion angle, and dorsal neck, upper, and lower trunk muscle activities, while potentially increasing the muscle activity of arm flexors.


Assuntos
Postura Sentada , Posição Ortostática , Adulto Jovem , Humanos , Adolescente , Adulto , Postura/fisiologia , Fenômenos Biomecânicos , Eletromiografia , Músculo Esquelético
20.
PLoS One ; 17(11): e0276240, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36327229

RESUMO

BACKGROUND: Connective tissue links the skeletal muscles, creating a body-wide network of continuity. A recent in-vivo experiment demonstrated that passive elongation of the calf caused a caudal displacement of the semimembranosus muscle, indicating force transmission across the dorsal knee joint. However, it remains unclear as to whether this observation is dependent on the joint angle. If force would not be transmitted at flexed knees, this would reduce the number of postures and movements where force transmission is of relevance. Our trial, therefore, aims to investigate the influence of passive calf stretching with the knee in extended and flexed position on dorsal thigh soft tissue displacement. METHODS: Participants are positioned prone on an isokinetic dynamometer. The device performs three repetitions of moving the ankle passively (5°/s) between plantar flexion and maximum dorsiflexion. With a washout-period of 24 hours, this procedure is performed twice in randomised order, once with the knee extended (0°) and once with the knee flexed (60°). Two high-resolution ultrasound devices will be used to visualize the soft tissue of the calf and dorsal thigh during the manoeuvre. Maximal horizontal displacement of the soft tissue [mm] during ankle movement will be quantified as a surrogate of force transmission, using a frame-by-frame cross-correlation analysis of the obtained US videos. DISCUSSION: Understanding myofascial force transmission under in-vivo conditions is a pre-requisite for the development of exercise interventions specifically targeting the fascial connective tissue. Our study may thus provide health and fitness professional with the anatomical and functional basis for program design. TRIAL REGISTRATION: The study is registered at the German Clinical Trials Register (TRN: DRKS00024420), registered 8 Februar 2021, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00024420.


Assuntos
Articulação do Tornozelo , Tornozelo , Humanos , Tornozelo/fisiologia , Articulação do Tornozelo/fisiologia , Joelho/fisiologia , Articulação do Joelho/fisiologia , Músculo Esquelético/fisiologia , Postura/fisiologia , Amplitude de Movimento Articular/fisiologia , Ensaios Clínicos Controlados Aleatórios como Assunto
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