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Leg and trunk muscle coordination and postural sway during increasingly difficult standing balance tasks in young adults and older adults

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... [14] In environments that demand greater balance, such as irregular surfaces, individuals tend to rely excessively on co-contractions or heightened contractions of TM and leg muscles for postural control. [15][16][17][18] Greater activation of TM has been linked to impaired postural control during unstable balancing tasks. [18,19] Moreover, as SC presents a greater challenge compared to simple walking, older adults need to exert increased attention and balance during SC. ...
... [15][16][17][18] Greater activation of TM has been linked to impaired postural control during unstable balancing tasks. [18,19] Moreover, as SC presents a greater challenge compared to simple walking, older adults need to exert increased attention and balance during SC. [20,21] Therefore, evaluating TM activation during SC is crucial for assessing the SC performance and balance capacity needed by older adults during SC. ...
... [19,46] Specifically, reduced activation of TMs and decreased involvement of adjacent lower joints during challenging postural control tasks indicated an improvement in balance. [15][16][17][18][19] In this study, both groups showed reduced activation of all TMs, including RA, EO, TrA-IO, and ES during SC in both groups, consistent with the study by Nagai et al demonstrating that balance training effectively diminishes excessive activity of muscles for postural control among older adults. [16] Furthermore, the improved postural adjustments through training mitigated unnecessary activation patterns mobilized to sustain balance, as reported by previous studies involving individuals with stroke, anterior cruciate ligament rupture, and young adults. ...
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Background Stair-climbing (SC) is an essential daily life skill, and stair-climbing exercise (SCE) serves as a valuable method for promoting physical activity in older adults. This study aimed to compare the impact of SCEs with heel contact (HC) and heel off (HO) during SC on functional mobility and trunk muscle (TM) activation amplitudes in community-dwelling older adults. Methods In the pilot randomized controlled trial, participants were randomly allocated to either the HC group (n = 17; mean age 75.9 ± 6.3 years) or the HO group (n = 17; mean age 76.5 ± 4.6 years). The HC participants performed SCE with the heel of the ankle in contact with the ground, while the HO participants performed SCE with the heel of the ankle off the ground during SC. Both groups participated in progressive SCE for one hour per day, three days per week, over four consecutive weeks (totaling 12 sessions) at the community center. We measured timed stair-climbing (TSC), timed up and go (TUG), and electromyography (EMG) amplitudes of the TMs including rectus abdominis (RA), external oblique (EO), transverse abdominus and internal oblique abdominals (TrA-IO), and erector spinae (ES) during SC before and after the intervention. Results Both groups showed a significant improvement in TSC and TUG after the intervention ( P < .01, respectively), with no significant difference between the groups. There was no significant difference in the EMG activity of the TMs between the groups after the intervention. The amplitude of TMs significantly decreased after the intervention in both groups ( P < .01, respectively). Conclusion Both SCE methods could improve balance and SC ability in older adults while reducing the recruitment of TMs during SC. Both SCE strategies are effective in improving functional mobility and promoting appropriate posture control during SC in older adults.
... Taken together, the results of the present study and of Dohm-Acker et al. (2008) suggest that thigh muscle activity seems to increase until a certain level of BTD is reached and then plateaus. Further, it might be speculated that an additional increase in trunk muscle activity could have been found with increasing BTD due to changes in the postural strategy (i.e., from ankle to hip strategy) as reported by Donath et al. (2016). This assumption becomes even more apparent when looking at lower limb muscle coactivation data. ...
... In the present study, we investigated how an increase in BTD affects the coactivation of the muscles surrounding ankle and knee joints in healthy adolescents. In our study CAI values obtained for the ankle joint muscles were higher than those reported for young adults in double leg stance on unstable ground by Donath et al. (2016). These differences suggest that ankle muscle activation in adolescents and young adults is not comparable. ...
... These differences suggest that ankle muscle activation in adolescents and young adults is not comparable. Additionally, the CAI for muscles encompassing the knee joint showed similar values to those of young adults (Donath et al., 2016). The significant increases observed in the CAI for TA-GM and VM-BF with increasing BTD suggest that higher postural demands result in joint stiffening. ...
Thesis
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Background and objectives: The intricate interdependencies between the musculoskeletal and neural systems build the foundation for postural control in humans, which is a prerequisite for successful performance of daily and sports-specific activities. Balance training (BT) is a well-established training method to improve postural control and its components (i.e., static/dynamic steady-state, reactive, proactive balance). The effects of BT have been studied in adult and youth populations, but were systematically and comprehensively assessed only in young and old adults. Additionally, when taking a closer look at established recommendations for BT modalities (e.g., training period, frequency, volume), standardized means to assess and control the progressive increase in exercise intensity are missing. Considering that postural control is primarily neuronally driven, intensity is not easy to quantify. In this context, a measure of balance task difficulty (BTD) appears to be an auspicious alternative as a training modality to monitor BT and control training progression. However, it remains unclear how a systematic increase in BTD affects balance performance and neurophysiological outcomes. Therefore, the primary objectives of the present thesis were to systematically and comprehensively assess the effects of BT on balance performance in healthy youth and establish dose-response relationships for an adolescent population. Additionally, this thesis aimed to investigate the effects of a graded increase in BTD on balance performance (i.e., postural sway) and neurophysiological outcomes (i.e, leg muscle activity, leg muscle coactivation, cortical activity) in adolescents. Methods: Initially, a systematic review and meta-analysis on the effects of BT on balance performance in youth was conducted per the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement guidelines. Following this complementary analysis, thirteen healthy adolescents (3 female/ 10 male) aged 16-17 years were enrolled for two cross-sectional studies. The participants executed bipedal balance tasks on a multidirectional balance board that allowed six gradually increasing levels of BTD by narrowing the balance boards’ base of support. During task performance, two pressure sensitive mats fixed on the balance board recorded postural sway. Leg muscle activity and leg muscle coactivation were assessed via electromyography while electroencephalography was used to monitor cortical activity. Results: Findings from the systematic review and meta-analysis indicated moderate-to-large effects of BT on static and dynamic balance performance in youth (static: weighted mean standardized mean differences [SMDwm] = 0.71; dynamic: SMDwm = 1.03). In adolescents, training-induced effects were moderate and large for static (SMDwm = 0.61) and dynamic (SMDwm = 0.86) balance performance, respectively. Independently (i.e. modality-specific) calculated dose-response relationships identified a training period of 12 weeks, a frequency of two training sessions per week, a total of 24-36 sessions, a duration of 4-15 minutes, and a total duration of 31-60 minutes as the training modalities with the largest effect on overall balance performance in adolescents. However, the implemented meta-regression indicated that none of these training modalities (R² = 0%) could predict the observed performance-increasing effects of BT. Results from the first cross-sectional study revealed that a gradually increasing level of BTD caused increases in postural sway (p < 0.001; d = 6.36), higher leg muscle activity (p < 0.001; 2.19 < d < 4.88), and higher leg muscle coactivation (p < 0.001; 1.32 < d < 1.41). Increases in postural sway and leg muscle activity were mainly observed during low and high levels of task difficulty during continuous performance of the respective balance task. Results from the second cross-sectional study indicated frequency-specific increases/decreases in cortical activity of different brain areas (p < 0.005; 0.92 < d < 1.80) as a function of BTD. Higher cortical activity within the theta frequency band in the frontal and central right brain areas was observed with increasing postural demands. Concomitantly, activity in the alpha-2 frequency band was attenuated in parietal brain areas. Conclusion: BT is an effective method to increase static and dynamic balance performance and, thus, improve postural control in healthy youth populations. However, none of the reported training modalities (i.e., training period, frequency, volume) could explain the effects on balance performance. Furthermore, a gradually increasing level of task difficulty resulted in increases in postural sway, leg muscle activity, and coactivation. Frequency and brain area-specific increases/decreases in cortical activity emphasize the involvement of frontoparietal brain areas in regulatory processes of postural control dependent on BTD. Overall, it appears that increasing BTD can be easily accomplished by narrowing the base of support. Since valid methods to assess and quantify BT intensity do not exist, increasing BTD appears to be a very useful candidate to implement and monitor progression in BT programs in healthy adolescents.
... The RMS angular velocity, with its positive correlation (coef = 0.3182, p = 0.004), indicated that faster and more varied movements at the lower back are generally associated with an increased risk of poor balance. According to Donath et al. (2016) [34], older adults with high RMS angular velocities during balance tasks exhibited reduced postural stability. Although their study primarily focused on static balance tasks and used surface electromyography to measure muscle activity rather than kinematics directly, it reinforced the idea that high RMS angular velocity measures might be associated with deficiencies in the ability to maintain balance. ...
... The RMS angular velocity, with its positive correlation (coef = 0.3182, p = 0.004), indicated that faster and more varied movements at the lower back are generally associated with an increased risk of poor balance. According to Donath et al. (2016) [34], older adults with high RMS angular velocities during balance tasks exhibited reduced postural stability. Although their study primarily focused on static balance tasks and used surface electromyography to measure muscle activity rather than kinematics directly, it reinforced the idea that high RMS angular velocity measures might be associated with deficiencies in the ability to maintain balance. ...
Article
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Falls among the elderly have been a significant public health challenge, with severe consequences for individuals and healthcare systems. Traditional balance assessment methods often lack ecological validity, necessitating more comprehensive and adaptable evaluation techniques. This research explores the use of inertial measurement units to assess postural balance in relation to the Berg Balance Scale outcomes. We recruited 14 participants from diverse age groups and health backgrounds, who performed 14 simulated tasks while wearing inertial measurement units on the head, torso, and lower back. Our study introduced a novel metric, i.e., the volume that envelops the 3-dimensional accelerations, calculated as the convex hull space, and used this metric along with others defined in previous studies. Through logistic regression, we demonstrated significant associations between various movement characteristics and the instances of balance loss. In particular, greater movement volume at the lower back (p = 0.021) was associated with better balance, while root-mean-square lower back angular velocity (p = 0.004) correlated with poorer balance. This study revealed that sensor location and task type (static vs. dynamic) significantly influenced the coefficients of the logistic regression model, highlighting the complex nature of balance assessment. These findings underscore the potential of IMUs in providing detailed objective balance assessments in the elderly by identifying specific movement patterns associated with balance impairment across various contexts. This knowledge can guide the development of targeted interventions and strategies for fall prevention, potentially improving the quality of life for older adults.
... One way to understand the utilization of motor and sensory systems in maintaining posture and orientation is to vary environmental and task-related conditions during upright stance. Common steady-state standing balance tasks, such as quiet stance, would be useful for assessing postural control but may not be sufficiently challenging for the postural control system to infer balance abilities (Clifford & Holder-Powell, 2010;Donath, Kurz, Roth, Zahner, & Faude, 2016;Shumway-Cook & Woollacott, 2017). As Riccio (1993) noted, the functional topology for postural control differs across postural tasks, for which postural orientation and stability have functional consequences. ...
... The only other exception was between the TS and SS postural tasks for the Range ML measure. Similarly, participants swayed more on the deformable surface than on the rigid surface (significant increases in E-area, SDrd, Range AP, and Range ML with moderate-to-large effect sizes), which is consistent with previous findings (Donath et al., 2016;Muehlbauer et al., 2012). In our study, the significant main effects of postural task and environmental conditions for all sway measures demonstrated that sway is highly sensitive to task constraints (e.g., base of support) and environmental constraints (e.g., properties of the surface of support) (Newell, 1986). ...
Article
Background: Previous studies have yielded conflicting results on the facilitative effects of concurrent visual feedback (CVFB) on postural control. In addition, these effects have generally been assessed only during a single postural task, and their scope has been limited to training sessions in the acquisition phase but not in the later retention phase. One explanation for these conflicting results is that assessing postural control during a single postural task, such as quiet stance, may not be sufficiently challenging for the postural control system to infer balance abilities. We aimed to address these shortcomings by diversifying postural tasks and environmental conditions and by including acquisition and retention phases in the experiments. Research questions: Does the provision of CVFB of the instantaneous COP position improve performance on a variety of postural tasks compared to no-CVFB controls? Are the effects of the CVFB retained the following day? Do the observed effect sizes differ in magnitude between the environmental and task conditions under CVFB? Methods: Forty healthy young adults were randomly assigned to CVFB and no-CVFB control groups. The subjects performed three postural tasks: quiet, tandem, and single-leg stance, under two environmental conditions based on the stiffness of the supporting ground surface. Seven measures of postural sway, including ellipse area, mean speed, and sample entropy, were examined. Results: The provision of CVFB significantly increased sample entropy and sway-path length of the normalized posturogram. In addition, ellipse area, standard deviation of resultant distance, and range in the anteroposterior direction were significantly reduced in the CVFB group compared to the no-CVFB controls; however, these effects were not retained the following day without the addition of CVFB augmentation. The postural sway measures under CVFB were affected by task and environmental constraints, with varying effect sizes. Significance: This study demonstrated environment and task-specific changes in postural sway measures under CVFB, which facilitated postural control in a variety of postural tasks. Providing CVFB significantly increased sample entropy, indicating less regular postural sway. The features of CVFB that attract external attention and reduce cognitive overload are possible explanations for these findings.
... One possible explanation for the absence of a fatigue effect could be due to the requirements of the FL task. The FL position, for example, involves greater activation (% MVIC) in both agonist and antagonist muscles (SOL: 26 %, GL: 12 %, and TA: 5 %) and greater co-contraction index (TA-SOL: 6.5 and TA-GL: 7.8), as compared with quiet standing [SOL: 10% and TA: 2 % (Donath et al., 2016); and TA-SOL: 2.4 (our calculation based on Donath et al., 2016)], which could limit the extent of agonist/antagonist modulation available to increase ankle stiffness to compensate for fatigue. Thus, in the present study, the fatigue-induced increase in sway velocity may instead indicate the use of more corrective actions at the ankle independent of stiffness, as COP sway velocity has been shown to be highly correlated with COM sway acceleration during quiet standing (Masani et al., 2014). ...
... One possible explanation for the absence of a fatigue effect could be due to the requirements of the FL task. The FL position, for example, involves greater activation (% MVIC) in both agonist and antagonist muscles (SOL: 26 %, GL: 12 %, and TA: 5 %) and greater co-contraction index (TA-SOL: 6.5 and TA-GL: 7.8), as compared with quiet standing [SOL: 10% and TA: 2 % (Donath et al., 2016); and TA-SOL: 2.4 (our calculation based on Donath et al., 2016)], which could limit the extent of agonist/antagonist modulation available to increase ankle stiffness to compensate for fatigue. Thus, in the present study, the fatigue-induced increase in sway velocity may instead indicate the use of more corrective actions at the ankle independent of stiffness, as COP sway velocity has been shown to be highly correlated with COM sway acceleration during quiet standing (Masani et al., 2014). ...
Article
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Aims The main aim of this study was to determine sex differences in postural control changes with ankle muscle fatigue during a standing forward leaning (FL) task under different vision conditions. The secondary aim was to examine sex differences in the effect of fatigue on soleus (SOL) H-reflex amplitude, a measure of motoneuron excitability with activation of Ia afferents. Methods Fifteen healthy young adult males (mean age: 28.0 years) and 16 healthy young adult females (mean age: 26.1 years) were asked to perform four consecutive FL tasks [30 s; two with eyes open (EO) and two with eyes closed (EC)] before, and immediately following a fatiguing exercise consisting of alternating ankle plantarflexion (6 s) and dorsiflexion (2 s) maximal isometric contractions, and at 5 and 10 min of recovery. Center of pressure (COP) sway variables (mean position, standard deviation, ellipse area, average velocity, and frequency), an ankle co-contraction index, and a ratio of SOL H-reflex to the maximum amplitude of the compound muscle action potential (M-max) were obtained during the FL tasks. A rating of perceived fatigue (RPF) was also documented at the different time points. Results Time to task failure (reduction of 50% in maximal voluntary isometric contraction torque of ankle plantar flexors) and the increase in RPF value were not significantly different between males and females. Both sex groups showed similar and significant increases (p < 0.05) in mean COP sway velocity with no significant changes in co-contraction indices. No significant effects of fatigue and related interactions were found for SOL H/M-max ratio. Discussion The absence of a significant sex difference in postural control change (sway and co-contraction) with fatigue could be explained by similar perceived (RPF) and performance fatigability (exercise duration) between males and females in the present study. Fatigue did not lead to significant changes in SOL spinal motoneuron excitability with activation of Ia afferents.
... In unperturbed conditions, balance is thought to be regulated mainly by spinal and brainstem structures 5 , with minimal implication of the cortex, in agreement with CKC being undetectable in most of the participants (< 25% per feature) in such conditions based on 10 min of EEG recordings. When standing on a foam block, the ability to sense pressure distribution and body orientation decreases 27 , while the effectiveness of ankle torque produced for postural stabilization is reduced 28,29 , leading to an increase in muscle activity 30 . Closing the eyes further suppresses visual information, leaving only vestibular information intact to maintain balance. ...
Article
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Maintaining an upright stance requires the integration of sensory inputs from the visual, vestibular and somatosensory-proprioceptive systems by the central nervous system to develop a corrective postural strategy. However, it is unclear whether and how the cerebral cortex monitors and controls postural sways. Here, we asked whether postural sways are encoded in ongoing cortical oscillations, giving rise to a form of corticokinematic coherence (CKC) in the context of standing balance. Center-of-pressure (CoP) fluctuations and electroencephalographic cortical activity were recorded as young healthy participants performed balance tasks during which sensory information was manipulated, by either removal or alteration. We found that postural sways are represented in ongoing cortical activity during challenging balance conditions, in the form of CKC at 1–6 Hz. Time delays between cortical activity and CoP features indicated that both afferent and efferent pathways contribute to CKC, wherein the brain would monitor the CoP velocity and control its position. Importantly, CKC was behaviorally relevant, as it predicted the increase in instability brought by alteration of sensory information. Our results suggest that human sensorimotor cortical areas take part in the closed-loop control of standing balance in challenging conditions. Importantly, CKC could serve as a neurophysiological marker of cortical involvement in maintaining balance.
... It appears that these two balance tests represent their unique postural positions. Both positions involve tests challenging neuromuscular coordination while standing on one leg (37). ...
... Moreover, as previously reported in the literature, different types of ankle injuries can develop different motor strategies for balance [37][38][39]. On the other hand, and which could explain our finding, numerous authors have reported how balance tasks of greater difficulty increase muscle activation [40][41][42]. This finding leads us to believe that this task posed a greater challenge in static balance in the operated limb for our participants. ...
Article
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Ankle fractures can lead to issues such as limited dorsiflexion, strength deficits, swelling, stiffness, balance disorders, and functional limitations, which complicate daily activities. This study aimed to describe neuromuscular adaptations at 6 and 12 months post-surgery during static and dynamic balance tasks, specifically using the Y-Balance Test (YBT). Additionally, the relationship between neuromuscular patterns, balance, and musculoskeletal deficits was evaluated. In 21 participants (14 at 6 months and 21 at 12 months) with bimalleolar fractures, hip strength, ankle dorsiflexion, ankle functionality, and static and dynamic balance were assessed using electromyography of five lower limb muscles (tibialis anterior, peroneus longus, lateral gastrocnemius, biceps femoris, and gluteus medius). A significant interaction effect (limb × proximal [hip]—distal [ankle] muscle) (F = 30.806, p < 0.001) was observed in the anterior direction of the Y-Balance Test (YBTA) at 6 months post-surgery. During the YBTA and YBT posteromedial (YBTPM), it was found that a lower dorsiflexion range of movement was associated specifically at 6 months with greater activation of the lateral gastrocnemius. However, these differences tended to diminish by 12 months. These findings suggest that neuromuscular patterns differ between operated and non-operated limbs during the YBTA at 6 months post-surgery. The Y-Balance Test, particularly its anterior direction, effectively highlighted these neuromuscular changes. This is a preliminary study; further research is needed to explore these findings in depth.
... Similarly, despite their intended aim to improve ADL competence through simulated skills, current 'functional training' methods demonstrate minimal ecological ADL improvements [199][200][201][202]. This lack of transfer in both traditional balance training and functional training approaches suggests issues such as insufficient variability in protocols and inappropriate progression, with an overemphasis on exercise load rather than applied skill practice [83,96,[203][204][205][206][207][208][209][210][211][212][213][214][215][216][217]. ...
Article
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This article challenges the prevalent approach in exercise science for improving functional performance in older adults. It argues that contemporary exercise research and practice adhere to an outdated paradigm that undermines the principle of specificity in training and assessment. The author supports this central critique by examining fundamental issues including conceptual imprecision, paradigmatic limitations, and misapplications of core theories of motor learning. Additional evidence from exercise science literature demonstrates how these issues compromise the effectiveness of interventions by violating the specificity principle. To address these limitations, the author proposes a preliminary framework titled 'The Emergence of Skilled Mobility in Ageing' (ESMA), which aligns training and evaluation with individual task environment constraints. This framework recognises the critical role of adaptive variability and representative practice design in optimising coordination, skills, and mobility. The proposed preliminary framework has significant implications for interdisciplinary collaboration and knowledge translation through focused and ecologically valid assessments and interventions. Overall, this article identifies key gaps in the current exercise science paradigm for older adults and offers an integrated solution that promotes specificity and real-world functioning. Future research will focus on the development and validation of this framework.
... Indeed, several age-related neural changes, both peripherally and centrally have the potential to modulate balance function. For example, previous work suggests that age-induced reduction in postural stability receives contributions from decreased coordination of muscle activity 40 , alteration in sensory integration 41 , or potential changes in the processing of somatosensory afferents 42 . Importantly, our data suggests that muscle composition and balance stability, two factors commonly reported to predict fall risks 12,43,44 , are independent predictors of such risks. ...
Article
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While the simultaneous degradation of muscle composition and postural stability in aging are independently highly investigated due to their association with fall risk, the interplay between the two has received little attention. Thus, the purpose of this study is to explore how age-related changes in muscle composition relate to postural stability. To that aim, we collected posturography measures and ultrasound images of the dominant Vastus Lateralis and Biceps Brachii from 32 young (18–35 year old) and 34 older (65–85 year old) participants. Muscle properties were quantified with echo-intensity and texture-based metrics derived from gray-level co-occurrence matrix analysis, and postural stability with the variability of the center of pressure during bipedal stance tasks. Ultrasound parameters revealed that young muscle possessed lower echo-intensity and higher homogeneity compared to the elderly. Echo-intensity and muscle thickness, and several texture-based parameters possessed outstanding young versus older classification performance. A canonical correlation analysis demonstrated a significant relationship between ultrasound and postural measures only within the young group (r = 0.53, p < 0.002), where those with ‘better’ muscle composition displayed larger postural sways. Our results indicate that, in older individuals, postural stability and muscle composition, two common fall risk factors, are unrelated. In view of this decoupling, both may contribute independently to fall risk. Furthermore, our data support the view that texture-based parameters provide a robust alternative to echo-intensity in providing markers of muscle composition.
... Regarding ankle muscle activation during quiet standing, preadolescents have exhibited elevated levels of Tibialis Anterior (TA) activity and increased ankle muscle co-activation during challenging balance tasks [24], a pattern that persists in late adolescents, particularly in the anterior-posterior (AP) sway direction [25]. In adults, studies have demonstrated that enhanced ankle muscle co-activation (e.g., TA/SOLEUS or TA/MG) serves as a strategic mechanism to enhance postural stability through heightened ankle stiffness [26][27][28]. This phenomenon suggests that joint stiffening may represent a mechanism for reducing COP displacement during demanding balance tasks. ...
... In unperturbed conditions, balance is thought to be regulated mainly by spinal and brainstem structures (5), with minimal implication of the cortex, in agreement with the absence of CKC in such conditions. When standing on a foam block, the ability to sense pressure distribution and body orientation decreases (26), while the effectiveness of ankle torque produced for postural stabilization is reduced (27,28), leading to an increase in muscle activity (29). Closing the eyes further suppresses visual information, leaving only vestibular information intact to maintain balance. ...
Preprint
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Maintaining an upright stance requires the integration of sensory inputs from the visual, vestibular and somatosensory-proprioceptive systems by the cortex to develop a corrective postural strategy. However, it is unclear whether and how the cerebral cortex monitors and controls postural sways. Here, we asked whether postural sways are encoded in ongoing cortical oscillations, giving rise to a form of corticokinematic coherence (CKC) in the context of standing balance. Center-of-pressure (CoP) and center of mass (CoM) fluctuations and electroencephalographic cortical activity were recorded as young healthy participants performed balance tasks during which sensory information was manipulated, by either removal or alteration. We found that postural sways are represented in ongoing SM1 cortical activity during challenging balance conditions, in the form of CKC at 1-6 Hz that was stronger for CoP compared with CoM fluctuations. Time delays between cortical activity and CoP features indicated that both afferent and efferent pathways contribute to CKC, wherein the brain would monitor the CoP velocity and control its position. Importantly, CKC was behaviorally relevant, as it predicted the increase in instability brought by alteration of sensory information. Our results demonstrate that human sensorimotor cortical areas take part in the closed-loop control of standing balance in challenging conditions. They demonstrate that CKC could serve as a neurophysiological marker of cortical involvement in maintaining balance.
... The change in the relation between ankle and hip kinematics was reflected in the decrease of the slope on the angular acceleration plane in older people. Older people tend to take a hip strategy in which the COM acceleration is controlled by moving the upper segment relative to the lower limb, which suggests the compensation mechanisms for the decline of the ankle strategy [29,36]. If increased angular acceleration in the ankle joint depends on less suppression from the hip joint, functional changes might be also observed in the hip joint. ...
Article
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Inter-joint interactions are involved in human standing. These interactions work not only for global kinematics that control the center of mass (COM) of the entire body, but also for local kinematics that control joint angular movements. Age-related changes in these interactions are thought to cause unstable standing postures in older people. Interactions of global kinematics are known to be deficient owing to aging. However, it is unclear whether the interaction of local kinematics is affected by aging. We investigated the age-related changes in inter-joint interactions, especially local kinematics, during standing. Differences were investigated in these two inter-joint interactions between older and younger adults in three different postures: normal, eyes-closed, and foam-surface standings. The inter-joint interaction for local kinematics was computed using the induced-acceleration analysis with a double-inverted pendulum model and quantified using an uncontrolled manifold approach. Consistent with previous studies, the inter-joint interaction for COM acceleration (global kinematics) deteriorated in older adults. In contrast, the interactions for angular accelerations in the ankle and hip joints (local kinematics) were slightly better in the older adults. Moreover, the individual components of angular acceleration which were induced by net torques from homonymous and remote joints were significantly increased in older adults. Thus, global and local inter-joint interactions are driven by distinct neural mechanisms and the interaction of local kinematics can compensate for the increment of each component of joint angular acceleration in older adults.
... The actual muscle contribution and timing of activation remain unclear. A large number of studies utilized the electromyographic (EMG) analysis to describe the latency and intensity of activation in many different balance tasks [8][9][10][11][12][13][14][15]. Still, to our knowledge, only Morey-Klapsing et al. distinguished the muscle response to medial vs lateral imbalances in a one-legged stance [16]. ...
Article
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Introduction Single-leg stance has been extensively studied for functional evaluation, therapeutic exercise, sports training, and fall prevention. However, the motor strategies of the supporting limb have been investigated only at the ankle level. It is not known, at the hip, how the muscular system reacts to medial and lateral imbalances. We hypothesize, based on a myofascial chain approach, that the balance is managed by the front and back spiral chains. The aim of this work was to perform a preliminary experimental analysis to verify the spiral chain hypothesis, testing a method to investigate the motor strategies underlying equilibrium. Methods Five healthy subjects (i.e. without neurological or orthopedic pathologies affecting the upright position) underwent perturbations of their monopodal balance while a surface electromyographic analysis of gluteus maximus, gluteus medius, adductor longus (ADD), tibialis anterior (TA), and peroneus longus (PL) was executed. The percentage of electrical activation with respect to maximal contraction was calculated for each muscle investigated. The coordination in activation between the hip and ankle muscles was analyzed by the Pearson correlation coefficient. Results Of the studied muscles, TA (43% of maximal contraction) and gluteus medius (28%) had the average highest reaction to lateral imbalance and the highest correlation coefficient (0.89, p-value<0.01); PL (35%) and ADD (16%) were the most relevant in counteracting the medial imbalance (correlation coefficient=0.83, p-value<0.01). Conclusion The study was performed on a few subjects, and the muscles of the lower limb were only partially investigated. However, the consistency of the results with former experimental studies provided preliminary evidence of the adequacy of the method adopted. The correlation of hip and ankle muscle activations was in line with the spiral chain hypothesis.
... To perform this, core muscles such as the internal oblique and the dominant side multifidus and proximal medial gastrocnemius muscles are activated to maintain stability. 19 The improvement of the SLS were not significant but the test scores are impressive. ...
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Parkinson's disease (PD) affects gait and postural stability. Tai Chi (TC) is recommended for PD for management of the condition, however biomechanical understanding to its effects on gait and postural stability is limited. This study aimed to examine the effects of an online 12-week biomechanical-based TC intervention on gait and posture in people with PD. Fifteen individuals in early-stage PD were recruited (Hoehn & Yahr stages 1–2). The TC intervention program was 60 min session, three times weekly for 12 weeks. The pre- and post-intervention test in obstacle crossing, timed-up-and-go (TUG) test, and single leg standing (SLS) with eyes open (EO) and closed (EC) were conducted. Gait speed, crossing stride length, clearance height of the heel and toe, anterior-posterior (AP) and medial-lateral (ML) displacement and velocity of the center of mass (COM) and separation of the COM-center of pressure (COP) were analyzed. The participants significantly improved their pre-vs. post-TC intervention performance on TUG test (p = 0.002). During obstacle crossing, the participants significantly increased crossing stride length of the trailing foot, increased AP COM displacement and decreased ML COM-COP separation (p < 0.05); the maximal dorsiflexion angle of the leading limb significantly increased and maximal plantarflexion angle of the trailing limb significantly decreased (p < 0.05). A 12-week biomechanical-based online TC training was effective towards improvement of gait and postural stability among people in the early-stage of PD. The TC program and online training could be applied for management of PD.
... Further, whether this information can help early identification of defects in neurodegenerative diseases featuring balance impairment is an open issue [30,259,260]. As a final plain remark, we recommend the use of compliant surface for balance rehabilitation, not least because it entrains a definite adaptation process, contrary to standing on hard support [261,262]. ...
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The ground reaction force (GRF) recorded by a platform when a person stands upright lies at the interface between the neural networks controlling stance and the body sway deduced from centre of pressure (CoP) displacement. It can be decomposed into vertical (VGRF) and horizontal (HGRF) vectors. Few studies have addressed the modulation of the GRFs by the sensory conditions and their relationship with body sway. We reconsidered the features of the GRFs oscillations in healthy young subjects (n = 24) standing for 90 s, with the aim of characterising the possible effects of vision, support surface and adaptation to repeated trials, and the correspondence between HGRF and CoP time-series. We compared the frequency spectra of these variables with eyes open or closed on solid support surface (EOS, ECS) and on foam (EOF, ECF). All stance trials were repeated in a sequence of eight. Conditions were randomised across different days. The oscillations of the VGRF, HGRF and CoP differed between each other, as per the dominant frequency of their spectra (around 4 Hz, 0.8 Hz and ECS ≈ EOS. Adaptation had no effect except in ECF condition. Specific rhythms of the GRFs do not transfer to the CoP frequency, whereas the magnitude of the forces acting on the ground ultimately determines body sway. The discrepancies in the time-series of the HGRF and CoP oscillations confirm that the body’s oscillation mode cannot be dictated by the inverted pendulum model in any experimental conditions. The findings emphasise the robustness of the VGRF “postural rhythm” and its correspondence with the cortical theta rhythm, shed new insight on current principles of balance control and on understanding of upright stance in healthy and elderly people as well as on injury prevention and rehabilitation.
... As such, it cannot be assumed that the observed relationship between mechanical properties with static balance parameters will generalise to dynamic balance. Furthermore, young adults mainly use muscles encompassing the ankle joint to minimise postural sway during quiet standing (Donath et al., 2016) with the ankle muscles but primarily the knee extensors more important contributors during dynamic lower extremity reaching tasks (Hoch et al., 2011;Norris and Trudelle-Jackson, 2011). Given the information above, the present work aimed to scrutinise the relationship between muscle mechanical properties of the ankle plantar flexors [lateral gastrocnemius (GL)] and knee extensors [vastus lateralis (VL)] with static (COP displacements during quiet standing) and dynamic (reach distances for the Y-balance test) balance parameters, separately. ...
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There is emerging evidence that mechanical properties of in vivo muscle tissues are associated with postural sway during quiet standing. However, it is unknown if the observed relationship between mechanical properties with static balance parameters generalise to dynamic balance. Thus, we determined the relationship between static and dynamic balance parameters with muscle mechanical properties of the ankle plantar flexors [lateral gastrocnemius (GL)] and knee extensors [vastus lateralis (VL)] in vivo. Twenty-six participants (men = 16, women = 10; age = 23.3 ± 4.4 years) were assessed for static balance [centre of pressure (COP) movements during quiet standing], dynamic balance (reach distances for the Y-balance test) and mechanical properties (stiffness and tone) of the GL and VL measured in the standing and lying position. Significant (p < .05) small to moderate inverse correlations were observed between the mean COP velocity during quiet standing with stiffness (r = −.40 to −.58, p = .002 to .042) and tone (r = −0.42 to −0.56, p = 0.003 to 0.036) of the GL and VL (lying and standing). Tone and stiffness explained 16%–33% of the variance in the mean COP velocity. Stiffness and tone of the VL measured in the lying (supine) condition were also inversely significantly correlated with Y balance test performance (r = −0.39 to −0.46, p = 0.018 to 0.049). These findings highlight that individuals with low muscle stiffness and tone exhibit faster COP movements during quiet standing, indicative of reduced postural control but also reveal that low VL stiffness and tone are associated with greater reach distances in a lower extremity reaching task, indicative of greater neuromuscular performance.
... This appears to be driven, in part, by a loss of leg proprioception (Anson et al., 2017;Henry & Baudry, 2019) and insufficient torque production by the ankle musculature (Cattagni, Scaglioni, Laroche, Grémeaux, & Martin, 2016;Lord, Clark, & Webster, 1991;Lord & Ward, 1994). To compensate for these lower limb sensorimotor impairments, older adults typically increase their level of ankle muscle co-contraction during standing balance tasks (Benjuya, Melzer, & Kaplanski, 2004;Donath, Kurz, Roth, Zahner, & Faude, 2016;Hortobágyi et al., 2009;Nagai et al., 2011;Vette et al., 2017). However, co-contraction appears more maladaptive than compensatory: it does not lead to reductions in postural sway (Nagai et al., 2011;Warnica, Weaver, Prentice, & Laing, 2014) and may even impede adaptive responses to postural perturbations (Falk et al., 2022;Nelson-Wong et al., 2012). ...
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Emerging evidence highlights that arm movements exert a substantial and functionally relevant contribution on quiet standing balance control in young adults. Ageing is associated with "non-functional" compensatory postural control strategies (i.e., lower limb co-contraction), which in turn, may increase the reliance on an upper body strategy to control upright stance. Thus, the primary purpose of this study was to compare the effects of free versus restricted arm movements on balance performance in young and older adults, during tasks of different difficulty. Fifteen young (mean ± SD age; 21.3 ± 4.2 years) and fifteen older (mean ± SD age; 73.3 ± 5.0 years) adults performed bipedal, semi-tandem and tandem balance tasks under two arm position conditions: restricted arm movements and free arm movements. Centre of pressure (COP) amplitude and frequency were calculated as indices of postural performance and strategy, respectively. Especially in older adults, restriction of arm movement resulted in increased sway amplitude and frequency, which was primarily observed for the mediolateral direction. Further, increasing balance task difficulty raised the arm restriction cost (ARC; a new measure to quantify free vs. restricted arm movement differences in postural control) that was more prominent in older adults. These findings indicate the ARC provides a measure of reliance on the upper body for balance control and that arm movement is important for postural control in older adults, especially during tasks of greater difficulty.
... Co-contraction strategy (that allows increasing the muscle stiffness and as such stabilizing the joints) is commonly used by young individuals when they are required to maintain balance in conditions of increased postural instability (Donath et al., 2016;Wang et al., 2023). Similarly, co-contraction is frequently described in the elderly (Arsenault et al., 2022;Błaszczyk et al., 1997;Bleuse et al., 2006) and individuals with neurological disorders (Aruin & Almeida, 1997;Garland et al., 1997;Massion et al., 1999). ...
Article
The objective of the study was to investigate the effect of leg supports on the anticipatory and compensatory postural adjustments of sitting subjects exposed to external perturbations in the anterior-posterior direction. Ten young participants received perturbations applied to the upper body while sitting on a stool with an anterior or posterior leg support and when using a footrest. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Anticipatory activities were observed in the tibialis anterior, biceps femoris, and erector spinae muscles in the anterior leg support condition. Early onset of muscle activity was observed in the tibialis anterior, biceps femoris, rectus femoris, and erector spinae muscles in the posterior leg support condition compared to the feet support condition. Moreover, to maintain balance participants utilized co-contraction of muscles as the main mechanism of balance control in sitting regardless of the availability of the anterior or posterior leg support. There was no effect of a leg support on center of pressure displacements. The outcome of the study provides a background for future investigations of the effect of leg supports on control of balance in sitting when perturbed.
... This corresponds to other studies also showing low levels of activity in the thigh muscles during standing balance exercises. 32,33 Considering the lack of loaded movement around the hip and knee joint this may not be surprising, however increasing the demand on postural control may also induce an increase in the degrees of hip and knee flexion significantly for the most challenging device, i.e. the BOSU as a compensation for the reduced ability of the ankle to control postural stability. These changes in the need for stabilisation and slight increase in hip and knee joint flexion increase the external moment, and as such place more demand on force production in the knee and hip extensors, thereby explaining the small, yet significantly increased levels of muscle activation in the hamstrings and quadriceps during single-leg stance on the BOSU. ...
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Background In injury prevention or rehabilitation programs, exercises that facilitate enhanced hamstring activity may be beneficial when aiming to enhance knee joint stability during movements in sports with higher risk of acute knee injury. Information about neuromuscular activation of the hamstring muscles in commonly used exercises may improve exercise selection and progression in programs for knee injury prevention or rehabilitation. Purpose To investigate (1) how balance devices with progressing degrees of instability influence the activity of muscles controlling the knee joint in typical balance exercises with different demands on postural control, and (2) if any between-sex differences exist. Study design Cross-sectional study. Methods Twenty habitually active healthy adults (11 males) participated in this cross-sectional study. Single-leg stance, single-leg squat and single-leg landing were performed on the floor and two different balance devices imposing various levels of challenge to postural control. Three-dimensional motion analysis was used to obtain hip and knee joint angles, and as primary outcomes, and peak normalized EMG activity from the hamstrings and quadriceps muscles was measured for comparison between exercises. Results The more challenging in terms of maintaining stable balance the devices were, the higher hamstring muscle activity levels were observed. There was a clear progression across balance devices from single-leg stance to single-leg squat and further to single-leg landing displaying increasing hamstring activity levels. The change in medial hamstring activity across all devices when changing from single-leg squat to single-leg landing was significantly higher for the female participants than for the males reaching a higher level of activity. Conclusion The muscle activity of the hamstrings and quadriceps increased when the motor task was more dynamic. Specifically, single-leg landings were effective in increasing the hamstring muscle activity over the single-leg stance to single-leg squat exercises, and muscle activity was significantly increased with the most unstable device. Increases in hamstring muscle activation was greater in female subjects than males with increasing instability of the balance devices. Trial identifier Not registered. Level of evidence 3
... The smaller the amplitude of body sway, the closer the COG stays to the second sacral body and reduces the need for lower extremity muscles to assist with maintaining balance. This leads to decreasing the potential for loss of balance and possibly falls [14,15]. ...
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The tsunami of medical wearables is not too far off the shore. With the proliferation of laboratory designs, for example, arterial pulse wave monitoring, continuous stress monitoring, and a sensor bracelet for impaired hand control [1-3], nearing completion in the lab but not yet ready for the medical market, there is a large void currently for consumer wearables to occupy. A fine example of this intentional crossover is Wearable X. In May 2017 Wearable X launched its first direct to consumer product, Nadi X, a line of activated yoga apparel [4]. Its patented technology with integrated sensors and haptic feedback (vibration) allows the user to literally "feel" how to move into each pose & posture verification at the end of each sequence. The sensors utilize accelerometers found in many current products, such as mobile phones, heart rate measuring devices, and Fitbit devices. Accelerometers measure the proper acceleration of a particular body, in the case of Nadi X, the lower limbs. Acceleration is the rate of change of speed with respect to time. In physics terms, s=d/t, with d being distance [5]. As for the haptic feedback in the Nadi X, it consists of vibrations through 10 haptic motors located in the hips, knees, and ankles; this is powered by the battery pack that clips in behind the left knee. A typical example of this is the slight vibrations from a smartphone that is given to the user when a button on the touchscreen is tapped [6]. Yet haptics is far more than just feeling a vibration. It is a myriad of sensations interpreted by the user [7]. The stimulation of Pacininan corpuscles, which are the mechanoreceptors that lie deep within the skin, is responsible for giving the sensation of vibration, specifically, high-frequency (20-1000 Hz) vibrations [8]. In the case of the Nadi X, it guides the wearer where to focus. i.e. "ground down through the back of your calves'' this is paired with further audio instructions i.e. "Lift up through the back of your hips", which in a one on one class, is sometimes paired with physical adjustments. For each user, there is probably a different feeling evoked, quite possibly a different emotion surfacing. Yes, haptic feedback is far more than just a vibration. It is the combination of these sensors and the haptic feedback during the performance of a yoga pose that is key to the Nadi X pants potentially crossing into the medical wearable realm. So why would this fact matter with regards to the medical realm? An excellent question indeed, and a question asked by Wearable X CEO, Billie Whitehouse, that lead to her collaboration with this author in a pilot study just recently concluded and currently undergoing data analysis. This pilot study examined if the Nadi X can help the user reduce low back pain using a yoga pose. The particular post utilized was the Chair Pose (Utkatasana) and is demonstrated in figure 1. In our discussions prior to commencing the study, Ms. Whitehouse shared her rationale for wanting to understand the landscape in order to move Nadi X into the medical wearables market, "We see an opportunity for Nadi X in the physical therapy space specifically because of the work we have done with Yoga. The long term goal is to collaborate across the country with medical professionals to ensure that Nadi X can support the efforts for reducing lower back pain. We engaged in this pilot study with Spectrum Ergonomics to test our hypothesis about how Nadi X can be effective as a physical therapy tool and potentially (in the future) a medical wearable technology platform".
... below and 2 cm medial to the anterior superior iliac spine), lumbar erector spinae (LES; 2 cm lateral to the third lumbar vertebra), and the medial head of gastrocnemius (GS; 2 cm medial to the midline and below the five finger distances from the posterior surface of the knee joint in the popliteal fossa) 13,14) . Maximal voluntary activity (MVC) in each muscle was measured to standardize the muscle activity for 3 s after each practice movement. ...
Article
[Purpose] Previous studies have not compared brain activity during voluntary axial muscle contraction with that during voluntary limb muscle contraction. This study aimed to investigate differences in brain activation patterns during voluntary contraction of the axial and lower limb muscles. [Subjects and Methods] Three tasks were performed by 20 healthy male participants (24.2 ± 3.7 years): voluntary axial muscle contraction task; voluntary lower limb muscle contraction task; and an upright sitting task which required no voluntary contraction. Brain activity was measured in the motor-related regions, in addition, muscle activity was also measured in the axial and limb muscles. Comparisons of brain activity between tasks were conducted.[Results] Significant interactions were found for SMA and M1 brain activities. The SMA activated in the voluntary axial muscle contraction task than in the other tasks. Contrastingly, M1 activated in both the axial and lower limb muscle voluntary contraction tasks. [Conclusion] In conclusion, the SMA was specifically involved in voluntary axial muscle contraction, while M1 was involved in both voluntary contraction of the axial and lower limb muscles.
... That's why we used a foam pad. Airex foam pad (6 ×50×41 cm) is commonly used in laboratory conditions to test balance control [48,49]. We tried to modify laboratory conditions close to realistic conditions. ...
Article
Background: To prevent the risk of stair descent falls and associated injuries in the older adults, it is important to understand the factors that affect this frequent locomotion of daily living. The fact that falls are in most cases the result of the interaction between intrinsic and extrinsic factors is very often underestimated when designing test protocols. Research question: This study aimed at evaluating balance control during and immediately after step down onto an unstable surface. Methods: Physically active men and women aged 60-69 years (n = 28) and 70-79 years (n = 18) were asked to perform a step down onto a foam pad and stand still for 30 s (restabilization phase). Centre of pressure (CoP) velocity and standard deviation of CoP sway in anteroposterior and mediolateral direction were evaluated during the step down (CoP VAP, CoP VML, CoP SDAP, CoP SDML) and in the first 5 s of restabilization (CoP VAP5, CoP VML5, CoP SDAP5, CoP SDML5). In addition, time to complete step was investigated. Results: Participants aged 70-79 years presented worse ML balance control after step down onto an unstable surface than their younger counterparts. This was represented by the significantly higher values of CoP SDML5 and CoP VML5 (p = 0.022 and p = 0.017). No other significant differences were detected. Significance: Age is associated with a more significant ML center of pressure velocity and sway after step down onto a foam pad in physically active older adults. Exercises aimed at improving ML balance control in unstable conditions should be the subject of physical interventions even in older adults with overall good state of health and physical fitness.
... Ziel der Trainingstherapie ist die Verringerung der oben genannten Einschränkungen, weshalb neben einem Krafttraining der extrinsischen Fußmuskulatur vor allem ein sensomotorisches Training effektiv scheint [10]. Das sensomotorische Training auf reduzierter oder labiler Unterstützungsfläche sowie mittels Reduktion der visuellen Kontrolle soll die posturale Kontrolle verbessern und steuert neben dem Rumpf und der gesamten unteren Extremität besonders die extrinsische Fußmuskulatur an [11]. ...
Article
Sprunggelenksdistorsionen sind eine der häufigsten Verletzungen im Sport und können sich als chronische Sprunggelenksinstabilitäten manifestieren. Die Prävention und Rehabilitation besteht zumeist aus einem Kraft-, Beweglichkeits- und Sensomotoriktraining um hauptsächlich die sprunggelenksumgebende Muskulatur zu erreichen. Dieser narrative Review soll aufzeigen, ob und wie ein Training der intrinsischen Fußmuskulatur Rehabilitation ergänzen kann.
... They were asked to sit upright during each condition and baseline recording but allowed to lean back between measurements to avoid fatigue. We choose the sitting position because quiet stance is always affected by keeping postural control, which, depending on the task, has been found to increase muscle activity in the back (Donath et al., 2016). We did not expect the time of leaning against the back of the chair to influence muscle activity in the subsequent trial because the participants sat relaxed and did not engage in other muscle-tensioning activities. ...
Article
Embodiment theories have proposed a reciprocal relationship between emotional state and bodily reactions. Besides large body postures, recent studies have found emotions to affect rather subtle bodily expressions, such as slumped or upright sitting posture. This study investigated back muscle activity as an indication of an effect of positive and negative emotions on the sitting position. The electromyography (EMG) activity of six back muscles was recorded in 31 healthy subjects during exposure to positive and negative affective pictures. A resting period was used as a control condition. Increased muscle activity patterns in the back were found during the exposure to negative emotional stimuli, which was mainly measured in the lumbar and thorax regions. The positive emotion condition caused no elevated activity. The findings show that negative emotions lead to increased differential muscle activity in the back and thus corroborate those of previous research that emotion affects subtle bodily expressions.
... Previous studies have confirmed that as the difficulty of balancing tasks increases, muscle activity of the lower limbs may also increase (Donath et al 2016, Gebel et al 2019. Li et al observed the EMG power spectral density difference in the theta band (4-7 Hz) (2019b). ...
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Objective. Standing balance forms the basis of daily activities that require the integration of multi-sensory information and coordination of multi-muscle activation. Previous studies have confirmed that the cortex is directly involved in balance control, but little is known about the neural mechanisms of cortical integration and muscle coordination in maintaining standing balance. Approach. We used a direct directed transfer function (dDTF) to analyze the changes in the cortex and muscle connections of healthy subjects (15 subjects: 13 male and 2 female) corresponding to different standing balance tasks. Main results. The results show that the topology of the EEG brain network and muscle network changes significantly as the difficulty of the balancing tasks increases. For muscle networks, the connection analysis shows that the connection of antagonistic muscle pairs plays a major role in the task. For EEG brain networks, graph theory-based analysis shows that the clustering coefficient increases significantly, and the characteristic path length decreases significantly with increasing task difficulty. We also found that cortex-to-muscle connections increased with the difficulty of the task and were significantly stronger than the muscle-to-cortex connections. Significance. These results show that changes in the difficulty of balancing tasks alter EEG brain networks and muscle networks, and an analysis based on the directed network can provide rich information for exploring the neural mechanisms of balance control.
... Muscle activity was measured using a wireless surface electromyograph (Trigno Research+ System) with a sampling frequency of 2000 Hz. In accordance with previous studies that measured muscle activity during postural control [18,19], electrodes were placed on the left side of the internal oblique (IO; approximately 2 cm below the line connecting both the anterior superior iliac spine), elector spinae group (ES; 2 cm lateral to the midline between the L4-L5 spinous processes), tibialis anterior (TA; proximal one-third of the line connecting the tip of the fibula to the medial capsule), and soleus (SOL; half of the lower leg and lateral to the Achilles tendon) muscles. The electrodes were placed as per the SENIAM recommendations (www.seniam.org) ...
Article
Background Previous studies have reported existence of coordinated brain and muscle activity patterns that affect postural control. However, differences in these activity patterns that affect postural control are still unclear. The purpose of this study was to clarify brain and muscle activity pattern affecting postural control. Research question Does the difference in brain and muscle activity patterns during postural control affect postural control ability? Method Nineteen healthy men (mean age: 24.8 ± 4.1 years, height: 171.8 ± 5.5 cm, and weight: 63.5 ± 12.5 kg) performed a postural control task on a balance board, and their brain and muscle activities and body sway during the task were measured using functional near-infrared spectroscopy, surface electromyography, and three-dimensional accelerometry. Hierarchical cluster analysis was conducted to extract subgroups based on brain and muscle activities and postural control, and correlation analysis was performed to investigate the relationship between brain activity, muscle activity, and postural control. Results Two subgroups were found. Subgroup 1 (n = 9) showed higher brain activity in the supplementary motor area (p = 0.04), primary motor cortex (p = 0.04) and stable postural control in the mediolateral (p < 0.01) planes, and subgroup 2 (n = 10) showed higher muscle activity in the tibialis anterior (p < 0.01), a higher shank muscles co-contraction (p = 0.02) and unstable postural control. Furthermore, the supplementary motor area activity is negatively correlated with body sway of mediolateral plane (r = −0.51, p = 0.02), and tibialis anterior activity is positively correlated with body sway on the mediolateral plane (r = 0.62, p = 0.004). Significance Higher brain activity in motor-related areas, lower activity in the lower limb muscles and lower co-contraction of shank muscles were observed in stable postural control. These results will facilitate the planning of new rehabilitation methods for improving postural control ability.
... It has been shown that static postural stability is often compromised with advancing age (8,9), reflected, e.g., by greater postural sway of older adults compared to young adults (10,11). Concerning specific assessment of side-by-side stance, healthy older adults showed significantly greater medio-lateral (ML) sway, during semi-tandem stance greater anterio-posterior (AP) and ML sway and during tandem stance greater AP sway compared to young controls (12). ...
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Neurological diseases are associated with static postural instability. Differences in postural sway between neurological diseases could include “conceptual” information about how certain symptoms affect static postural stability. This information might have the potential to become a helpful aid during the process of finding the most appropriate treatment and training program. Therefore, this study investigated static postural sway performance of Parkinson's disease (PD) and multiple sclerosis (MS) patients, as well as of a cohort of healthy adults. Three increasingly difficult static postural tasks were performed, in order to determine whether the postural strategies of the two disease groups differ in response to the increased complexity of the balance task. Participants had to perform three stance tasks (side-by-side, semi-tandem and tandem stance) and maintain these positions for 10 s. Seven static sway parameters were extracted from an inertial measurement unit that participants wore on the lower back. Data of 47 healthy adults, 14 PD patients and 8 MS patients were analyzed. Both healthy adults and MS patients showed a substantial increase in several static sway parameters with increasingly complex stance tasks, whereas PD patients did not. In the MS patients, the observed substantial change was driven by large increases from semi-tandem and tandem stance. This study revealed differences in static sway adaptations between PD and MS patients to increasingly complex stance tasks. Therefore, PD and MS patients might require different training programs to improve their static postural stability. Moreover, this study indicates, at least indirectly, that rigidity/bradykinesia and spasticity lead to different adaptive processes in static sway.
... Therefore, it is reasonable to assume that task-difficulty was lower for 2WB when compared to 1WB in phase 1. This assumption is supported by previous studies showing that enhancing the difficulty of postural tasks is associated with longer sway paths (Donath, Kurz, Roth, Zahner, & Faude, 2016). The lower task complexity during training might in turn have led to a ceiling effect that also prevented larger improvements in 2WB compared to both other groups. ...
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Prior motor experience is thought to aid in the acquisition of new skills. However, studies have shown that balance training does not promote learning of a subsequent balance task. These results stand in contrast to the learning-to-learn paradigm, which is well described for other tasks. We therefore tested if a coordinative affinity between tasks is needed to achieve a learning-to-learn for balance control. Three groups trained different motor tasks during training phase1 (coordination ladder (COOR); bipedal wobble board (2WB); single-leg wobble board (1WB)). During training phase2, all groups trained a tiltboard balance task. Task-specific and transfer effects were evaluated for phase1. A potential learning-to-learn effect was evaluated by comparing the acquisition rates from phase2 for the tiltboard task that was used for training and testing. The results indicate task-specific adaptations after phase1 for 1WB. In contrast, 2WB showed similar improvements than 1WB and COOR (effect sizes: −0.31 to −0.38) when tested on the wobble board with bipedal stance indicating no task-specific improvement for 2WB. For phase2, the linear regression analysis showed larger adaptations for 1WB and 2WB when compared to COOR. This effect implies some uncertainty due to overlapping confidence intervals. Task-specific adaptations after phase1 were found for 1WB but not 2WB. It is discussed that the difficulty of the training task could explain these contrasting results. During phase2, larger adaptations were found for both groups that trained balance tasks during phase1. Thus, despite some uncertainty, prior balance training appears to promote adaptations of a subsequently learned balance task. • Highlights • Prior balance training augments the learning of a new balance task if the two tasks share certain coordinative features. • The concept of “learning to learn” can probably be applied to postural control, although further studies are needed. • Balance training results (partly) in task-specific adaptations with no immediate transfer to other (but unrelated) balance tasks.
... Fear of falling, decreased muscle strength, and decreased proprioception are the main factors that cause falls. A study reported that the elderly showed lower muscle use efficiency and greater postural swings in standing balance tasks, which means that the elderly has a greater risk of falls (21). Lelard et al. (22) considered that any form of physical activities can increase confidence in maintaining balance, and that strength and proprioception training is the most suitable balance exercises for healthy elderly people. ...
... Falls in older age are a major public health problem due to their high prevalence, significant impact on health and quality of life, and high cost [1][2][3][4][5] . Impairments in balance and lower limb muscle strength are intrinsic factors for an increased risk of falls in older adults [6][7][8] . This is because, during the aging process, it is natural for there to be a decrease in muscle strength, with strength declines being detected in the abductors, hip adductors, and knee extensors. ...
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Objectives: This study aimed to assess the immediate and short-term effects of the Balance Exercise Circuit (BEC) on muscle strength, postural balance, and quality of life, with the aim of preventing falls in older adults. Methods: Twenty-two volunteers participated in this randomized controlled crossover study. Group A performed BEC training in the initial 3 months and received no intervention in the following 3 months. Group B received no intervention during the first 3 months and then participated in BEC training for the next 3 months. In addition, participants were followed for an additional 3 months. Muscle strength, postural balance, functional mobility, and quality of life were assessed, respectively, using an isokinetic dynamometer, force platform, TUG test, and the WHOQOL. Results: After 3 months of training, Group A presented improved balance and rate of force development (RFD), while Group B presented improvements in RFD, TUG performance, and WHOQOL physical and psychological domains. Regarding the short-term effects, the participants maintained the training effects in WHOQOL balance, RFD, and the social domain. In addition, the number of falls decreased during follow-up. Conclusion: The BEC intervention improved muscle strength, postural balance, and quality of life in older adults, in addition to reducing the risk of falls. Trial registration: Brazilian Registry of Clinical Trials (ReBEC) - RBR-5nvrwm.
... For instance, differences in kinematic patterns of landing could be present. Even in static balance task, different strategies in task execution between the legs might be present (reflected in different kinematic patterns and/or muscle activity), and not necessarily reflected in CoP movements [37]. Future studies should consider the differences in kinematic patterns of landing between the preferred and non-preferred leg. ...
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In this study, 90 (51 males, 39 females) tennis players performed single-leg quiet stance and single-leg landing tasks. For the static standing task, center-of pressure (CoP) velocities, amplitudes, frequency and area were calculated. For the landing tasks, time to stabilization as well as dynamic postural stability index were considered. The analysis of differences between the legs was done based on two methods for a priori determination of leg preference, one based on the preference of kicking a ball and one based on the preference for single-leg jumping. An additional analysis was done based on the leg dominance (determined post hoc), based on the observed performance of the tasks. In case of the classification based on kicking a ball, there was a statistically significantly lower CoP anterior-posterior velocity and anterior-posterior amplitude in static balance task (p ≤ 0.017; 0.17 ≤ d ≤ 0.28) for the preferred leg. The CoP frequency was higher in the preferred leg for both directions (p ≤ 0.002; 0.10 ≤ d ≤ 0.22). For the landing task, CoP medial-lateral time to stabilization was statistically significantly shorter for the preferred leg (0.28 ± 0.38 s) compared to the non-preferred leg (0.47 ± 0.60 s) (p = 0.012; d = 0.38). There were no differences between the legs for the landing task. Moreover, there were no differences between the legs when we used the preference based on jumping for either of the tasks (d ≤ 0.14). The differences between legs in terms of observed dominance were larger than the differences based on the preference, which stresses the need for clear distinction of limb preference and limb dominance in research and practice. Regarding the effect of leg preference, small differences in static balance may exist between the legs (when the preference is based on kicking a ball).
... Better posture control ability and less sway existed in balance measures among young participants, compared to older adults [26,38]. Older adults had higher electrophysiological costs for a given balance task and so can be considered less efficient from a neuromuscular viewpoint [39]. There may be less variance in the sway variable in young adults because their physical function and fitness are at a higher level. ...
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Purpose: Regular physical activity (PA) strengthens muscles and improves balance and coordination of human body. The aim of this study was to examine whether objectively measured physical activity (PA) and sedentary behaviors were related to static balance in young men and women. Design and setting: Cross-sectional community study. Participants: 86 healthy adults (50% women) aged 21.26 ± 2.11 years. Method: PA variables, including moderate-to-vigorous PA (MVPA), light PA (LPA), sedentary time (SED), and sedentary breaks, were measured by accelerometers on wrist (ActiGraph WGT3X-BT). The static balance was tested in the bipedal stance with eyes open or closed. The movement of the center of pressure, including total sway path length (SP), sway velocity (SV), and sway area (SA), was recorded with a three-dimensional force platform (Kistler 9287CA). The associations between PA (MVPA/LPA/SED/sedentary breaks) and static balance (SP/SV/SA) were analyzed using mixed linear regression analyses, with adjustments for condition (eyes open/closed), sex, age, body mass index (BMI), total device wearing time, and PA*condition. Data were analyzed with SPSS 24.0. Results: Better performance was observed in eyes-open condition (p < 0.05). MVPA was negatively associated with SA (p = 0.030), and SED was positively associated with SA after adjustments, respectively (p = 0.0004). No significance was found in the association of light PA, SED, or sedentary breaks with other static balance variables, respectively (p > 0.05). Conclusion: Increasing MVPA and less SED are associated with lower sway area measured by force platform, indicating more PA may related to better static balance in young adults.
... All these involutions degrade the motor output and motor component of the postural balance system (Bok et al., 2013;Cattagni et al., 2014;Menz, 2015). On the basis of these motor alterations, for a given postural balance condition, the effort required to control body balance is greater in older subjects than in young subjects and needs greater electromyographic activity to produce appropriate torque (Billot et al., 2010;Nagai et al., 2011;Skurvidas et al., 2012;Donath et al., 2016). It can be assumed that below a certain level of muscle strength (ability to produce strength), the increase in electromyographic activity to compensate for the age-related reduction in motor output is no longer possible and postural balance is negatively affected (Paillard, 2017b). ...
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In frail older subjects, the motor output of the antigravity muscles is fundamental in resisting falls. These muscles undergo accelerated involutions when they are inactive and the risk of falling increases during leisure and domestic physical activity. In order to reduce their risk of falling, frail older subjects limit their physical activities/exercises. The problem is that the less they exercise, the less they are able to exercise and the greater the risk in exercising. Hence, a vicious circle sets up and the antigravity muscles inevitably continue to deteriorate. This vicious circle must be broken by starting a reconditioning program based on developing the strength of antigravity muscles (especially lower-limb muscles). To begin with, for each increase in muscle strength, postural balance is improved. Once this increase reaches the threshold beyond which postural balance no longer improves, it seems appropriate to implement exercises aimed at concomitantly improving motor output and postural balance in order to counteract or even reverse the involution process of the postural balance system. Methods and strategies toward this end are proposed in this present communication. However, the transfer effects between strength increase and postural balance ability are not yet totally known and future research should evaluate the relationship between muscle strength and postural balance throughout rehabilitation programs (i.e., program follow-ups) in frail older subjects in order to advance knowledge of this relationship.
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Purpose of study. Disorders of postural function are an important problem in the field of geriatric health. According to statistics from the city of St. Petersburg every third elderly person has experienced a fall. To analyze the existing methods of correction of postural function in older age groups and evaluate their effectiveness. Material and methods. The literature review was conducted using the databases eLibrary, PubMed, Google Scholar over the past 10 years, only full-text articles were included in the review. Keywords and their combinations in Russian and English used for conducting the search: «postural function » (postural function), «correction» (correction), «the elderly» (the elderly). The criteria for including articles in the review were: full-text articles; year of publication from 2014 to 2024; works including meta-analyses, systematic and analytical literature reviews, clinical guidelines. In addition, the review included the domestic work of 2011. since it contains conceptual information. Exclusion criteria: matching of works in different databases. Resalts. 28 full-text articles were selected, the analysis of which shows a tendency towards the active introduction and use of high-tech equipment with biofeedback technology and virtual reality in the rehabilitation of elderly patients with impaired postural function. Conclusion. As a result of the review, the main methods of correcting postural function in older age groups are highlighted.
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Purpose: Postural control deteriorates with age, especially under dual-task conditions. It is currently unknown how a challenging virtual reality weight-shifting task affects lower back muscle activity. Hence, this study investigated erector spinae neuromuscular control during mediolateral weight-shifting as part of an exergame during single- (ST) and dual-task (DT) conditions in young and older adults. Methods: Seventeen young and 17 older adults performed mediolateral weight-shifts while hitting virtual wasps in a virtual environment with and without a serial subtraction task (DT). Center of mass position was recorded in real-time using 3D motion capturing. Electromyography recorded bilateral activation of the lumbar longissimus and iliocostalis muscles. Results: Weight-shifting (p < 0.03) and targeting the wasps (p < 0.005) deteriorated with age and DT. Relative muscle activation during both quiet stance and weight-shifting increased with age, while the DT-effect did not differ consistently between age-groups. However, bilateral muscle co-contraction decreased with DT in young adults only. When switching direction and targeting the wasps, variability of muscle activation increased with age and DT and proved related to worse targeting performance. These effects were mainly visible at the non-dominant body side. Conclusion: Older adults showed a higher erector spinae muscle contribution to perform weight-shifts with increased variability at the end of a shift, whereby muscle activity was modulated less well in older than in young adults in response to DT. Hence, the current findings point to the potential for developing postural training in which older adults learn to fine-tune trunk muscle activity to improve weight-shifting and reduce fall risk.
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Zur Therapie und Prophylaxe von Sprunggelenkdistorsionen wird meist die extrinsische Fußmuskulatur trainiert. Ein spezielles Training der intrinsischen Fußmuskeln findet kaum statt. Wie wichtig „Short-Foot Exercises“ oder ein Zehentraining nach einem Supinationstrauma sind, zeigt ein Review der Hochschule Furtwangen. Die Kernaussage: Das Trainieren der kurzen Fußmuskeln kann die subjektive Instabilität, Balance, Somatosensibilität und Funktionalität signifikant verbessern. Für Praxistipps ist die Qualität der Evidenz jedoch noch zu gering.
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Challenging balance training that targets age-related neuromuscular and motor coordination deficits is needed for effective fall prevention therapy. Goal-directed training can provide intrinsically motivating balance activities but may not equally challenge balance for all age groups. Therefore, the purpose of this research was to quantify age-specific effects of dynamic balance training with real-time visual feedback. Kinematics, muscle activity, and user perceptions were collected for forty healthy adults (20 younger, 18-39 years; 20 older, 58-74 years), who performed a single balance training session with or without real-time visual feedback. Feedback involved controlling either a physical mobile robot or screen-based virtual ball through a course with standing tilt motions from an instrumented wobble board. Dynamic balance training was more challenging for older compared to younger adults, as measured by significantly higher dorsiflexor and knee extensor muscle activity and ankle co-contractions (50%-80%, p<0.05). Older participants also performed more motion while training without feedback compared to younger adults (22%-65%, p<0.05). Robotic and virtual real-time visual feedback elicited similar biomechanical adaptations in older adults, reducing motions to similar levels as younger adults and increasing ankle co-contractions (p<0.05). Despite higher muscular demand, perceived physical exertion and high enjoyment levels (Intrinsic Motivation Inventory >0.80) were consistent across groups. However, robotic visual feedback may be more challenging than virtual feedback based on more frequent balance corrections, lower perceived competence, and lower game scores for older compared to younger adults. These findings collectively support the feedback system's potential to provide engaging and challenging at-home balance training across the lifespan.
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When a person stands upright quietly, the position of the Centre of Mass (CoM), the vertical force acting on the ground and the geometrical configuration of body segments is accurately controlled around to the direction of gravity by multiple feedback mechanisms and by integrative brain centres that coordinate multi-joint movements. This is not always easy and the postural muscles continuously produce appropriate torques, recorded as ground reaction force by a force platform. We studied 23 young adults during a 90 s period, standing at ease on a hard (Solid) and on a compliant support (Foam) with eyes open (EO) and with eyes closed (EC), focusing on the vertical component of the ground reaction force (VGRF). Analysis of VGRF time series gave the amplitude of their rhythmic oscillations (the root mean square, RMS) and of their frequency spectrum. Sway Area and Path Length of the Centre of Pressure (CoP) were also calculated. VGRF RMS (as well as CoP sway measures) increased in the order EO Solid ≈ EC Solid < EO Foam < EC Foam. The VGRF frequency spectra featured prevailing frequencies around 4–5 Hz under all tested conditions, slightly higher on Solid than Foam support. Around that value, the VGRF frequencies varied in a larger range on hard than on compliant support. Sway Area and Path Length were inversely related to the prevailing VGRF frequency. Vision compared to no-vision decreased Sway Area and Path Length and VGRF RMS on Foam support. However, no significant effect of vision was found on VGRF mean frequency for either base of support condition. A description of the VGRF, at the interface between balance control mechanisms and sway of the CoP, can contribute information on how upright balance is maintained. Analysis of the frequency pattern of VGRF oscillations and its role in the maintenance of upright stance should complement the traditional measures of CoP excursions in the horizontal plane.
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Apathy is a stressor and debilitating common condition for both stroke survivors and their caregivers. However, its effects on the postural control of these patients have not yet been investigated. Improved postural stability through withdrawing attention from postural control by concurrent cognitive task (i.e. dual-task condition) has been reported previously, but the effect of apathy, as a confounding factor, remains unknown. This study aimed to examine the effects of apathy and dual-task condition on postural control of chronic stroke survivors from biomechanical and neurophysiological perspectives. Twenty non-apathetic stroke survivors, 20 apathetic stroke survivors, and 20 sex-, age-, weight-, and height-matched healthy subjects were assessed using different postural sway measures and electromyography activity of ankle and hip muscles while quietly standing on rigid and foam surfaces under single-task, easy dual-task, and difficult dual-task conditions. The results showed postural instability and neuromuscular stiffening of stroke survivors, particularly apathetic stroke survivors, compared with healthy controls as evidenced by significantly greater postural sway measures and increased co-contraction of ankle muscles as well as hip muscles. Notably, concurrently performing a cognitive task significantly reduced postural instability and neuromuscular stiffening in chronic stroke survivors even in those with apathy. In conclusion, apathy exacerbates postural control impairments in chronic stroke survivors promoting an inefficient conscious mode of postural control. It is recommended that distracting the attention away from postural control by performing a concurrent cognitive task can be considered an effective strategy while designing interventions for improving postural control in apathetic stroke survivors.
Article
Background Abnormal stepping strategies have been associated with handheld tasks in subjects with chronic low back pain (LBP). However, their dominant ankle reactions remain unclear while holding a tray following a perturbation. Research question Are there differences in the reaction times of the ankle muscles during handheld tasks between subjects with and without LBP following a treadmill-induced slip perturbation? Methods Thirty-seven right limb dominant subjects with LBP and 37 subjects without LBP participated in the study. Each subject was introduced to a slip perturbation (1.37 m/sec velocity for 8.22 cm) with and without a handheld tray in random order. Subjects were allowed to recover by stepping forward for a 0.12 second duration while bilateral tibialis anterior (TA) and gastrocnemius (GA) muscle reaction times were measured by electromyography (EMG). Results The EMG results indicated that the groups demonstrated significant interactions on the limb sides and muscles (F = 4.86, p = 0.03). The dominant TA reaction time was significantly faster in the LBP group (t = 2.14, p = 0.03) while holding a tray. Significance The LBP group demonstrated faster reaction times on the dominant TA muscles during perturbations. Clinicians need to consider dominance-dependent compensatory ankle dorsiflexion strategies in LBP patients to help enhance dynamic balance and control.
Article
During upright standing, individuals often use co-contraction muscle activity at the ankle joint when encountering increased postural difficulty; however, this strategy has been shown to be maladaptive. The purpose of the current investigation was to examine the effect of sloped standing on postural sway and muscle co-contraction at the ankle joint as a function of postural difficulty. Twelve young (21.67 ± 1.11 years) adults performed upright standing on flat, declined, and inclined support surfaces. Center of pressure displacements indexed postural sway while electromyography data were collected for the tibialis anterior and gastrocnemius medialis muscles. A co-contraction index and a nonlinear coupling metric (cross-approximate entropy) were computed between ankle dorsiflexor and plantar flexor muscles (tibialis anterior/gastrocnemius medialis) activity. The results showed that higher degrees of postural difficulty led to increased amounts of sway as well as increased sway regularity. Lower co-contraction index was observed for higher degrees of postural difficulty; however, increased dynamic coupling occurred with deviations from the flat standing condition. Overall, increased postural difficulty as manipulated by sloped standing (in either inclined or declined conditions) resulted in individuals adopting a more regular sway trajectory that may be due, in part, to a stronger dynamic coupling strategy occurring at the neuromuscular level.
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Background Balance is an important determinant of physical function and falls risk. The ability to withstand external perturbations is important when walking on icy or uneven surfaces, whether the perturbations are bilateral or unilateral. Research question This study sought to determine the effect of unilateral and bilateral standing perturbations on leg muscle activity in healthy older adults. Methods Participants experienced unilateral and bilateral standing perturbations of the treadmill. Surface electromyography (EMG) from lower limb muscles was recorded unilaterally. EMG onset latency and root mean square (RMS) amplitude of the muscle bursts were calculated. Results Older adults demonstrated a combined ankle/hip strategy, along with pre-activation and co-contraction of muscles in response to unilateral and bilateral stance perturbations. As well, older adults demonstrated higher levels of EMG, but no difference in the latency of burst onset, in bilateral than unilateral perturbation types. Significance When the stance limb was perturbed in the bilateral condition, the older adults responded with a Gastrocs EMG burst nearly 100% of the maximum EMG. The high level of EMG used, especially in the Gastrocs, during the bilateral perturbations may reduce the safety factor for falls in older adults. Older adults responded to the different perturbation demands by modulating EMG amplitude as opposed to the onset timing of EMG.
Thesis
La scoliose idiopathique est la déformation du rachis la plus fréquente. Bien que le diagnostic soit clinique, le suivi et les prises de décisions thérapeutiques (traitement orthopédique et/ou chirurgical), reposent sur des critères d’évaluation radiographiques structurels. La littérature a montré qu’il existait dans la scoliose idiopathique des modifications de l’orientation de la tête, du tronc et du bassin dans les 3 plans de l’espace, associés à des troubles du contrôle postural, compromettant ainsi la stabilité en statique. Il existe également une modification de la position du centre de masse lié à la déformation, pouvant donc affecter la stabilité dynamique au cours de la marche. La problématique de ce travail était de caractériser les compensations posturales et fonctionnelles par approches biomécaniques des scolioses idiopathiques de l’adolescent (SIA), en vue d’améliorer la prise en charge clinique et plus particulièrement les stratégies chirurgicales.Dans notre 1ère étude, une modification significative de l’équilibre de la marche, mesuré par la marge de stabilité dynamique, était mise en évidence dans les déformations rachidiennes. Dans notre 2ème étude, appliquée uniquement à la SIA sévère avec indication de chirurgie, aucune modification de leur équilibre dynamique n’a été mise en évidence, témoin du caractère performant de la marche de ces patients. Dans la 3ème étude, l’approche analytique en baropodométrie dynamique et statique a mis en évidence des stratégies d’équilibrations spatiales, croisées et bilatérales, dans le but de symétriser les paramètres fonctionnels de la marche. Ces stratégies étaient liées à la localisation de la déformation et aux déséquilibres structuraux dans le plan frontal. Les déformations dans le plan sagittal avaient surtout un impact dans la modulation de l’amorti et de la propulsion au cours de la marche avec une influence particulière de la position du bassin.
Article
Objectives To compare neck, trunk, and lower extremity muscle activity in standing in persons with neck pain (NP) to healthy controls and determine associations with postural sway. Methods Participants included 25 persons with NP and 25 controls. Surface electromyography was recorded bilaterally from neck (sternocleidomastoid, SCM; splenius capitis, SC; upper trapezius, UT), trunk (erector spinae, ES), and lower extremity (rectus femoris, RF; biceps femoris, BF; tibialis anterior, TA; medial gastrocnemius, GN) muscles. Postural sway was measured using a force platform in narrow stance with eyes open/closed, on firm/soft surfaces. Results Compared to controls, the NP group demonstrated higher activity in all muscles, except UT and had higher amplitude ratios for neck muscles (SCM, SC) for all tasks (p < .05). No between-group difference was found in amplitude ratios for lower extremity muscles, except for GN. Lower extremity activity was moderately correlated with larger postural sway for both groups (r = 0.41–0.66, p < .05). There were no correlations between sway and neck and trunk muscle activity (p > .05). Conclusion Increased muscle activity with NP is associated with increased postural sway. Both groups used similar postural control strategies, but the increased neck activity in the NP group is likely related to the NP disorder rather than postural instability.
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Background An age-related decline in standing balance control in the medio-lateral direction is associated with increased risk of falls. A potential approach to improve postural stability is to change initial foot position (IFP). Research questions In response to a lateral surface perturbation, how are lower extremity muscle activation levels different and what are the effects of different IFPs on muscle activation patterns and postural stability in younger versus older adults? Methods Ten younger and ten older healthy adults participated in this study. Three IFPs were tested [Reference (REF): feet were placed parallel, shoulder-width apart; Toes-out with heels together (TOHT): heels together with toes pointing outward; Modified Semi-Tandem (M-ST): the heel of the anterior foot was placed by the big toe of the posterior foot]. Unexpected lateral translations of the standing surface were applied. Electromyographic (EMG) activity of the lower extremity muscles, standard deviation (SD) of the body’s CoM acceleration (SD of CoMAccel), and center of pressure (CoP) sway area were compared across IFPs and age. Results Activation levels of the muscles serving the ankle and gluteus medius were greater than for the knee joint muscles and gluteus maximus in the loaded leg across all IFPs in both groups. TOHT showed greater EMG peak amplitude of the soleus and fibularis longus compared to REF, and had smaller SD of CoMAccel and CoP sway area than M-ST. Compared to younger adults, older adults demonstrated lower EMG peak amplitude and delayed peak timing of the fibularis longus and greater SD of CoMAccel and CoP sway area in all IFPs during balance recovery. Significance During standing balance recovery, ankle muscles and gluteus medius are important active responders to unexpected lateral surface perturbations and a toes-out IFP could be a viable option to enhance ankle muscle activation that diminishes with age to improve postural stability.
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Background: The aging process results in a number of functional (e.g., deficits in balance and strength/power performance), neural (e.g., loss of sensory/motor neurons), muscular (e.g., atrophy of type-II muscle fibers in particular), and bone-related (e.g., osteoporosis) deteriorations. Traditionally, balance and/or lower extremity resistance training were used to mitigate these age-related deficits. However, the effects of resistance training are limited and poorly translate into improvements in balance, functional tasks, activities of daily living, and fall rates. Thus, it is necessary to develop and design new intervention programs that are specifically tailored to counteract age-related weaknesses. Recent studies indicate that measures of trunk muscle strength (TMS) are associated with variables of static/dynamic balance, functional performance, and falls (i.e., occurrence, fear, rate, and/or risk of falls). Further, there is preliminary evidence in the literature that core strength training (CST) and Pilates exercise training (PET) have a positive influence on measures of strength, balance, functional performance, and falls in older adults. Objective: The objectives of this systematic literature review are: (a) to report potential associations between TMS/trunk muscle composition and balance, functional performance, and falls in old adults, and (b) to describe and discuss the effects of CST/PET on measures of TMS, balance, functional performance, and falls in seniors. Data sources: A systematic approach was employed to capture all articles related to TMS/trunk muscle composition, balance, functional performance, and falls in seniors that were identified using the electronic databases PubMed and Web of Science (1972 to February 2013). Study selection: A systematic approach was used to evaluate the 582 articles identified for initial review. Cross-sectional (i.e., relationship) or longitudinal (i.e., intervention) studies were included if they investigated TMS and an outcome-related measure of balance, functional performance, and/or falls. In total, 20 studies met the inclusionary criteria for review. Study appraisal and synthesis methods: Longitudinal studies were evaluated using the Physiotherapy Evidence Database (PEDro) scale. Effect sizes (ES) were calculated whenever possible. For ease of discussion, the 20 articles were separated into three groups [i.e., cross-sectional (n = 6), CST (n = 9), PET (n = 5)]. Results: The cross-sectional studies reported small-to-medium correlations between TMS/trunk muscle composition and balance, functional performance, and falls in older adults. Further, CST and/or PET proved to be feasible exercise programs for seniors with high-adherence rates. Age-related deficits in measures of TMS, balance, functional performance, and falls can be mitigated by CST (mean strength gain = 30 %, mean effect size = 0.99; mean balance/functional performance gain = 23 %, mean ES = 0.88) and by PET (mean strength gain = 12 %, mean ES = 0.52; mean balance/functional performance gain = 18 %, mean ES = 0.71). Limitations: Given that the mean PEDro quality score did not reach the predetermined cut-off of ≥6 for the intervention studies, there is a need for more high-quality studies to explicitly identify the relevance of CST and PET to the elderly population. Conclusions: Core strength training and/or PET can be used as an adjunct or even alternative to traditional balance and/or resistance training programs for old adults. Further, CST and PET are easy to administer in a group setting or in individual fall preventive or rehabilitative intervention programs because little equipment and space is needed to perform such exercises.
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Examined the prevalence of lateral preferences in 1,932 female and 1,375 male volunteers (aged 17–35 yrs) as measured by the Lateral Preference Inventory (LPI). Females showed more right-sidedness than males for feet, hands, and ears, but not for eyes. The 16 items that make up the LPI are sufficiently brief and self-explanatory so that they can easily be incorporated into existing inventories, to allow a quick assessment of all 4 dimensions of laterality. The handedness subscale, comprised of only 4 items, can easily be inserted into a variety of other information-gathering instruments. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Spinal pain can result in unilateral atrophy of spinal muscles. Understanding side-to-side muscle activity during exercises can help clinicians address these deficits. This study determined if variations of bridging exercises specifically activated side-to-side trunk-muscle activity. Using surface electromyography on 20 healthy subjects (16 females), age 25.45 (± 3.57) years, height 166 (± 0.8) cm, weight 63.35 (± 12.70) kg, muscle activity of left and right lumbar multifidus, iliocostalis lumborum thoracis (ICLT), rectus abdominis (RA) and external oblique (EO) was recorded during eight bridging exercises with stable, unstable and unilateral (left-leg off the ground) conditions. There were significant side-to-side differences in abdominal-muscle activity during all unstable exercises (mean difference range from 3.10 %MVC for RA to 9.86 %MVC for EO), and during all unilateral exercises (mean difference range from 3.22 %MVC for RA to 9.41 %MVC for EO), with the exception of RA in exercise-7. For the back muscles, there were significant side-to-side differences for multifidus during all unilateral exercises (mean difference range 5.35 %MVC to 11.72 %MVC), with the exception of exercise-5. None of the bilateral exercises (stable or unstable) produced side-to-side differences for multifidus. For ICLT only exercise-3 produced significant side-to-side differences with a mean difference of 5.5 %MVC. In all cases where significant differences were noted, the left side of the muscles demonstrated the higher values. The results suggest that specific exercises (unilateral/unstable) can target specific sides of trunk muscles.
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A continuously greying society is confronted with specific age-related health problems (e.g., increased fall incidence/injury rate) that threaten both the quality of life of fall-prone individuals as well as the long-term sustainability of the public health care system due to high treatment costs of fall-related injuries (e.g., femoral neck fracture). Thus, intense research efforts are needed from interdisciplinary fields (e.g., geriatrics, neurology, and exercise science) to (a) elucidate neuromuscular fall-risk factors, (b) develop and apply adequate fall-risk assessment tools that can be administered in clinical practice, and (c) develop and design effective intervention programs that have the potential to counteract a large number of fall-risk factors by ultimately reducing the number of falls in the healthy elderly. This paper makes an effort to present the above-raised research topics in order to provide clinicians, therapists, and practitioners with the current state-of-the-art information.
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This systematic review update includes 54 randomised controlled trials and confirms that exercise as a single intervention can prevent falls (pooled rate ratio 0.84, 95% CI 0.77-0.91). Meta-regression revealed programs that included balance training, contained a higher dose of exercise and did not include walking training to have the greatest effect on reducing falls. We therefore recommend that exercise for falls prevention should provide a moderate or high challenge to balance and be undertaken for at least 2 hours per week on an ongoing basis. Additionally, we recommend that: falls prevention exercise should target both the general community and those at high risk for falls; exercise may be undertaken in a group or home-based setting; strength and walking training may be included in addition to balance training but high risk individuals should not be prescribed brisk walking programs; and other health-related risk factors should also be addressed.
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Demographic change in industrialized countries produced an increase in the proportion of elderly people in our society, resulting in specific healthcare challenges. One such challenge is how to effectively deal with the increased risk of sustaining a fall and fall-related injuries in old age. Deficits in postural control and muscle strength represent important intrinsic fall risk factors. Thus, adequate training regimens need to be designed and applied that have the potential to reduce the rate of falling in older adults by countering these factors. Therefore, the purpose of this review is to compare traditional and recent approaches in the promotion of balance and strength in older adults. Traditionally, balance and resistance training programmes proved to be effective in improving balance and strength, and in reducing the number of falls. Yet, it was argued that these training protocols are not specific enough to induce adaptations in neuromuscular capacities that are specifically needed in actual balance-threatening situations (e.g. abilities to recover balance and to produce force explosively). Recent studies indicated that perturbation-based or multitask balance training and power/high-velocity resistance training have the potential to improve these specific capacities because they comply with the principle of training specificity. In fact, there is evidence that these specifically tailored training programmes are more effective in improving balance recovery mechanisms and muscle power than traditional training protocols. A few pilot studies have even shown that these recently designed training protocols have an impact on the reduction of fall incidence rate in older adults. Further research is needed to confirm these results and to elucidate the underlying mechanisms responsible for the adaptive processes.
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The risk of sustaining a fall is particularly high in children and seniors. Deficits in postural control and muscle strength either due to maturation, secular declines or biologic aging are two important intrinsic risk factors for falls. During life span, performance in variables of static postural control follows a U-shaped curve with children and seniors showing larger postural sway than healthy adults. Measures of dynamic postural control (i.e. gait speed) as well as isometric (i.e. maximal strength) and dynamic muscle strength (i.e. muscular power) follow an inverted U-shaped curve during life span, again with children and seniors showing deficits compared to adults. There is evidence that particularly balance and resistance training are effective in counteracting these neuromuscular constraints in both children and seniors. Further, these training regimens are able to reduce the rate of sustaining injuries and falls in these age groups. An intergenerational intervention approach is suggested to enhance the effectiveness of these training programs by improving compliance and increasing motivation of children and seniors exercising together. Thus, the objectives of this mini-review are: (1) to describe the epidemiology and etiology of falls in children and seniors; (2) to discuss training programs that counteract intrinsic fall risk factors by reducing the rate of falling, and (3) to present an intergenerational approach that has the potential to make training programs even more effective by including children and seniors together in one exercise group.
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The aim of this study was to assess the relative torque (a percentage of the maximal capacity of torque production) at the ankle joint in young and elderly adults during different postural tasks of increasing difficulty. Seven young (approximately 22 years old) and seven older (approximately 80 years old) men took part in this investigation. Maximal agonist torque was estimated from resultant and antagonist torques in both populations in plantar-flexion (PF) and dorsi-flexion (DF). The sum of PF and DF maximal agonist torques was considered as the maximal capacity of torque production. The centre of pressure (CoP) displacement was analysed during Normal Quiet Stance, Romberg and One Leg Balance. During maximal contractions and postural tasks, the electromyographic (EMG) activity was simultaneously recorded on the triceps surae and tibialis anterior muscles. We observed that the maximal capacity of torque production was negatively correlated with the CoP displacement, whatever the population and the postural tasks. The relative torque during all postural tasks was positively correlated with the CoP displacement in both populations. Moreover, older adults needed more EMG activity than young adults to produce the same torque. From this knowledge, one can assume that increasing strength in the muscles of the ankle joint may improve postural stability in older adults; this might have implications in the prevention of falls in elderly persons and in rehabilitation programs for elderly people who have already fallen.
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Reliability is a population-specific property, but to the authors' knowledge there has been no study to determine the test-retest reliability of the postural stability measures such as center of pressure (COP) measures in the population of patients with musculoskeletal disorders (MSDs), while their clinical applications have been presented in literature. So, 33 patients with low back pain (LBP), anterior cruciate ligament (ACL) injury and functional ankle instability (FAI) randomly completed postural measurements with three levels of difficulty (rigid surface-eyes open, rigid surface-eyes closed, and foam surface-eyes closed) in two sessions. COP data were used to calculate standard deviation of amplitude, standard deviation of velocity, phase plane portrait, mean total velocity and area (95% confidence ellipse). Relative reliability of these measures was assessed using intraclass correlation coefficient (ICC) and absolute reliability using standard error of measurement (SEM) and coefficient of variation (CV). Also, minimal metrically detectable change (MMDC) was calculated to quantify intervention effects. Among different COP parameters, mean total velocity in all conditions of postural difficulty showed high to very high reliability, with ICC range of 0.74-0.91, SEM range of 0.09-0.40cm/s, CV range of 5.31-8.29% and MMDC range of 0.19-0.79cm/s. Phase plane portrait in anteroposterior-mediolateral (AP-ML) and ML direction were other best parameters with respect to the level of reliability. Mean total velocity and phase plane portrait parameters are suggested as good candidates to use for quantification and assessment of balance performance and identifying those with MSDs.
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This study examines the roles of somatosensory and vestibular information in the coordination of postural responses. The role of somatosensory information was examined by comparing postural responses of healthy control subjects prior to and following somatosensory loss due to hypoxic anesthesia of the feet and ankles. The role of vestibular information was evaluated by comparing the postural responses of control subjects and patients with bilateral vestibular loss. Postural responses were quantified by measuring 1) spatial and temporal characteristics of leg and trunk EMG activation; 2) ankle, knee, and hip joint kinematics, and 3) surface forces in response to anterior and posterior surface translations under different visual and surface conditions. Results showed that neither vestibular nor somatosensory loss resulted in delayed or disorganized postural responses. However, both types of sensory deficits altered the type of postural response selected under a given set of conditions. Somatosensory loss resulted in an increased hip strategy for postural correction, similar to the movement strategy used by control subjects while standing across a shortened surface. Vestibular loss resulted in a normal ankle strategy but lack of a hip strategy, even when required for the task of maintaining equilibrium on a shortened surface. Neither somatosensory nor vestibular loss resulted in difficulty in utilizing remaining sensory information for orientation during quiet stance. These results support the hypothesis that cutaneous and joint somatosensory information from the feet and ankles may play an important role in assuring that the form of postural movements are appropriate for the current biomechanical constraints of the surface and/or foot. The results also suggest that vestibular information is necessary in controlling equilibrium in a task requiring use of the hip strategy. Thus, both somatosensory and vestibular sensory information play important roles in the selection of postural movement strategies appropriate for their environmental contexts.
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We studied the extent to which automatic postural actions in standing human subjects are organized by a limited repertoire of central motor programs. Subjects stood on support surfaces of various lengths, which forced them to adopt different postural movement strategies to compensate for the same external perturbations. We assessed whether a continuum or a limited set of muscle activation patterns was used to produce different movement patterns and the extent to which movement patterns were influenced by prior experience. Exposing subjects standing on a normal support surface to brief forward and backward horizontal surface perturbations elicited relatively stereotyped patterns of leg and trunk muscle activation with 73- to 110-ms latencies. Activity began in the ankle joint muscles and then radiated in sequence to thigh and then trunk muscles on the same dorsal or ventral aspect of the body. This activation pattern exerted compensatory torques about the ankle joints, which restored equilibrium by moving the body center of mass forward or backward. This pattern has been termed the ankle strategy because it restores equilibrium by moving the body primarily around the ankle joints. To successfully maintain balance while standing on a support surface short in relation to foot length, subjects activated leg and trunk muscles at similar latencies but organized the activity differently. The trunk and thigh muscles antagonistic to those used in the ankle strategy were activated in the opposite proximal-to-distal sequence, whereas the ankle muscles were generally unresponsive. This activation pattern produced a compensatory horizontal shear force against the support surface but little, if any, ankle torque. This pattern has been termed the hip strategy, because the resulting motion is focused primarily about the hip joints. Exposing subjects to horizontal surface perturbations while standing on support surfaces intermediate in length between the shortest and longest elicited more complex postural movements and associated muscle activation patterns that resembled ankle and hip strategies combined in different temporal relations. These complex postural movements were executed with combinations of torque and horizontal shear forces and motions of ankle and hip joints. During the first 5-20 practice trials immediately following changes from one support surface length to another, response latencies were unchanged. The activation patterns, however, were complex and resembled the patterns observed during well-practiced stance on surfaces of intermediate lengths.(ABSTRACT TRUNCATED AT 400 WORDS)
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We examined how young and older adults adapt their posture to static balance tasks of increasing difficulty. Participants stood barefoot on a force platform in normal quiet, Romberg-sharpened and one-legged stance. Center of pressure (CoP) variations, electromyographic (EMG) activity of ankle and hip muscles and kinematic data were recorded. Both groups increased postural sway as a result of narrowing the base of support. Greater CoP excursions, EMG activity and joint displacements were noted in old compared to younger adults. Older adults displayed increased hip movement accompanied by higher hip EMG activity, whereas no similar increase was noted in the younger group. It is concluded that older adults rely more on their hip muscles when responding to self induced perturbations introduced by increased task constraints during quiet standing.
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The objective of this study was to measure the electromyographic (EMG) activity of the soleus, bicep femoris, rectus femoris, lower abdominal, and lumbosacral erector spinae (LSES) muscles with a variety of (a) instability devices, (b) stable and unstable (Dyna Disc) exercises, and (c) a fatiguing exercise in 16 highly conditioned individuals. The device protocol had participants assume standing and squatting postures while balancing on a variety of unstable platforms (Dyna Disc, BOSU ball, wobble board, and a Swiss ball) and a stable floor. The exercise protocol had subjects performing, static front lunges, static side lunges, 1-leg hip extensions, 1-leg reaches, and calf raises on a floor or an unstable Dyna Disc. For the fatigue experiment, a wall sit position was undertaken under stable and unstable (BOSU ball) conditions. Results for the device experiment demonstrated increased activity for all muscles when standing on a Swiss ball and all muscles other than the rectus femoris when standing on a wobble board. Only lower abdominals and soleus EMG activity increased while squatting on a Swiss ball and wobble board. Devices such as the Dyna Disc and BOSU ball did not exhibit significant differences in muscle activation under any conditions, except the LSES in the standing Dyna Disc conditions. During the exercise protocol, there were no significant changes in muscle activity between stable and unstable (Dyna Disc) conditions. With the fatigue protocol, soleus EMG activity was 51% greater with a stable base. These results indicate that the use of moderately unstable training devices (i.e., Dyna Disc, BOSU ball) did not provide sufficient challenges to the neuromuscular system in highly resistance-trained individuals. Since highly trained individuals may already possess enhanced stability from the use of dynamic free weights, a greater degree of instability may be necessary.
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Literature that provides progression models based on core muscle activity and postural manipulations is scarce. The purpose of this study was to investigate the core muscle activity in a series of balance exercises with different stability levels and additional elastic resistance. A descriptive study of electromyography (EMG) was performed with forty-four healthy subjects that completed 12 exercises in a random order. Exercises were performed unipedally or bipedally with or without elastic tubing as resistance on various unstable (uncontrolled multiaxial and uniaxial movement) and stable surfaces. Surface EMG on the lumbar multífidus spinae (LM), thoracic multífidus spinae (TM), lumbar erector spinae (LE), thoracic erector spinae (TE) and gluteus maximus (GM), on the dominant side of the body were collected to quantify the amount of muscle activity and were expressed as a % of the maximum voluntary isometric contraction (MVIC). Significant differences (p<.001) were found between exercises. The three unipedal standing exercises with additional elastic resistance generated the greatest EMG values, ranging from 19%MVIC to 30%MVIC. Postural manipulations with additional elastic resistance and/or unstable devices increase core muscle activity. An adequate exercise progression based on global core EMG could start with seated positions, progressing to bipedal standing stance (i.e., from either multiaxial or stable surface to uniaxial surface). Following this, unipedal standing positions may be performed (i.e., from either multiaxial or stable surface to uniaxial surface) and finally, elastic resistance must be added in order to increase EMG levels (i.e., from stable surface progressing to any of the used unstable surfaces). Copyright © 2015 Elsevier B.V. All rights reserved.
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Available evidence suggests that young adults and seniors use different strategies to adjust for increasing body sway during quiet standing. Altered antagonist muscle co-activation and different ankle muscle coordination patterns may account for this finding. Consequently, we aimed at addressing whether aging leads to changes in neuromuscular coordination patterns as well as co-activation during quiet stance. We additionally investigated whether a bout of high intensity interval training additionally alters these patterns. Twenty healthy seniors (age: 70 ± 4 y) and twenty young adults (age: 27 ± 3 y) were enrolled in the present study. In between the testing procedures, four consecutive high-intensity intervals of 4 min duration at a target exercise intensity of 90 to 95% HRmax were completed on a treadmill. The total center of pressure (COP) path length displacement served as standing balance performance outcome. In order to assess ankle-muscle coordination patterns, amplitude ratios (AR) were calculated for each muscle (e.g. tibialis anterior (TA) [%] = (TA × 100) / (gastrocnemius medialis (GM) + soleus (SOL) + peroneus longus (PL) + TA) in order to assess the inter-muscular coordination of the ankle-muscles. The co-activation was calculated for the SOL and TA muscles computing the co-activation index (CAI = 2 × TA / TA + SOL). Seniors showed an inverted ankle muscle coordination pattern during single limb stance with eyes open (SLEO), compared to young adults (rest: GM, S: 15 ± 8% vs Y: 24 ± 9%; p = 0.03; SOL, S: 27 ± 14% vs Y: 37 ± 18%; p = 0.009; TA, S: 31 ± 13% vs Y: 13 ± 7%; p = 0.003). These patterns did not change after a high-intensity training sessions. A moderate correlation between amplitude ratios of TA-contribution and postural sway was observed for seniors during SLEO (r = 0.61). Ankle co-activation was twofold elevated in seniors compared to young adults during SLEO (p < 0.001). These findings were also not affected by high intensity training. Increased ankle co-activation in the anterior-posterior plane and inverted ankle muscle coordination pattern merely occurred during single-leg stance. Seniors with decreased postural control showed higher TA contributions during SLEO. These neuromuscular changes are not affected by acute exhaustive exercise.
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In clinical evaluation, we used to evaluate the fall risk according to elderly falling experience or the balance assessment tool. Because of the tool limitation, sometimes we could not predict accurately. In this study, we first analyzed 15 healthy elderly (without falling experience) and 15 falling elderly (1∼3 time falling experience) balance performance in previous research. After 1 year follow up, there was only 1 elderly fall down during this period. It seemed like that falling experience had a ceiling effect on the falling prediction. But we also found out that using single leg standing time could be more accurately to help predicting the fall risk, especially for the falling elderly who could not stand over 10 seconds by single leg, and with a significant correlation between the falling experience and single leg standing time (r = -0.474, p = 0.026). The results also showed that there was significant body sway just before they falling down, and the COP may be an important characteristic in the falling elderly group.
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Ankle sprains are a common sports injury. The literature focuses on the application of neuromuscular training for the improvement of balance, injury prevention and rehabilitation. However, there is a dearth of knowledge about the appropriate prescription of exercises using unstable platforms and surfaces. The purpose of this study was to devise an ankle rehabilitation or training program with exercise progression based on the extent of muscle activation, employing platforms with different levels of stability and additional resistance. A descriptive study of electromyography (EMG) during ankle exercises was performed with a convenience sample of healthy subjects. Forty-four subjects completed 12 exercises performed in a random order. Exercises were performed unipedally or bipedally with or without elastic tubing as resistance on various unstable (uncontrolled multiaxial and uniaxial movement) and stable surfaces. Surface EMG from the tibialis anterior (TA), peroneus longus (PL) and soleus (SOL) were collected to quantify the amount of muscle activity. Significant differences were found between exercise conditions for PL (p<.001), TA (p=.011), and SOL (p<.001). The greatest EMG activity for all muscles occurred with an upright unipedal stance on a soft stability surface with resistance. The least EMG activity for the TA and SOL were in a seated position and for the PL in an erect bipedal position without resistance. Based on the level of ankle muscle activation, exercises for the ankle should progress from bilateral exercises on exercise balls (lowest intensity), to a unipedal position on a soft surface in combination with elastic tubing (highest intensity) in order to achieve progressively greater ankle muscle activation.
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Approximately 30% of people over 65 years of age living in the community fall each year. This is an update of a Cochrane review first published in 2009. To assess the effects of interventions designed to reduce the incidence of falls in older people living in the community. We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (February 2012), CENTRAL (The Cochrane Library 2012, Issue 3), MEDLINE (1946 to March 2012), EMBASE (1947 to March 2012), CINAHL (1982 to February 2012), and online trial registers. Randomised trials of interventions to reduce falls in community-dwelling older people. Two review authors independently assessed risk of bias and extracted data. We used a rate ratio (RaR) and 95% confidence interval (CI) to compare the rate of falls (e.g. falls per person year) between intervention and control groups. For risk of falling, we used a risk ratio (RR) and 95% CI based on the number of people falling (fallers) in each group. We pooled data where appropriate. We included 159 trials with 79,193 participants. Most trials compared a fall prevention intervention with no intervention or an intervention not expected to reduce falls. The most common interventions tested were exercise as a single intervention (59 trials) and multifactorial programmes (40 trials). Sixty-two per cent (99/159) of trials were at low risk of bias for sequence generation, 60% for attrition bias for falls (66/110), 73% for attrition bias for fallers (96/131), and only 38% (60/159) for allocation concealment.Multiple-component group exercise significantly reduced rate of falls (RaR 0.71, 95% CI 0.63 to 0.82; 16 trials; 3622 participants) and risk of falling (RR 0.85, 95% CI 0.76 to 0.96; 22 trials; 5333 participants), as did multiple-component home-based exercise (RaR 0.68, 95% CI 0.58 to 0.80; seven trials; 951 participants and RR 0.78, 95% CI 0.64 to 0.94; six trials; 714 participants). For Tai Chi, the reduction in rate of falls bordered on statistical significance (RaR 0.72, 95% CI 0.52 to 1.00; five trials; 1563 participants) but Tai Chi did significantly reduce risk of falling (RR 0.71, 95% CI 0.57 to 0.87; six trials; 1625 participants).Multifactorial interventions, which include individual risk assessment, reduced rate of falls (RaR 0.76, 95% CI 0.67 to 0.86; 19 trials; 9503 participants), but not risk of falling (RR 0.93, 95% CI 0.86 to 1.02; 34 trials; 13,617 participants).Overall, vitamin D did not reduce rate of falls (RaR 1.00, 95% CI 0.90 to 1.11; seven trials; 9324 participants) or risk of falling (RR 0.96, 95% CI 0.89 to 1.03; 13 trials; 26,747 participants), but may do so in people with lower vitamin D levels before treatment.Home safety assessment and modification interventions were effective in reducing rate of falls (RR 0.81, 95% CI 0.68 to 0.97; six trials; 4208 participants) and risk of falling (RR 0.88, 95% CI 0.80 to 0.96; seven trials; 4051 participants). These interventions were more effective in people at higher risk of falling, including those with severe visual impairment. Home safety interventions appear to be more effective when delivered by an occupational therapist.An intervention to treat vision problems (616 participants) resulted in a significant increase in the rate of falls (RaR 1.57, 95% CI 1.19 to 2.06) and risk of falling (RR 1.54, 95% CI 1.24 to 1.91). When regular wearers of multifocal glasses (597 participants) were given single lens glasses, all falls and outside falls were significantly reduced in the subgroup that regularly took part in outside activities. Conversely, there was a significant increase in outside falls in intervention group participants who took part in little outside activity.Pacemakers reduced rate of falls in people with carotid sinus hypersensitivity (RaR 0.73, 95% CI 0.57 to 0.93; three trials; 349 participants) but not risk of falling. First eye cataract surgery in women reduced rate of falls (RaR 0.66, 95% CI 0.45 to 0.95; one trial; 306 participants), but second eye cataract surgery did not.Gradual withdrawal of psychotropic medication reduced rate of falls (RaR 0.34, 95% CI 0.16 to 0.73; one trial; 93 participants), but not risk of falling. A prescribing modification programme for primary care physicians significantly reduced risk of falling (RR 0.61, 95% CI 0.41 to 0.91; one trial; 659 participants).An anti-slip shoe device reduced rate of falls in icy conditions (RaR 0.42, 95% CI 0.22 to 0.78; one trial; 109 participants). One trial (305 participants) comparing multifaceted podiatry including foot and ankle exercises with standard podiatry in people with disabling foot pain significantly reduced the rate of falls (RaR 0.64, 95% CI 0.45 to 0.91) but not the risk of falling.There is no evidence of effect for cognitive behavioural interventions on rate of falls (RaR 1.00, 95% CI 0.37 to 2.72; one trial; 120 participants) or risk of falling (RR 1.11, 95% CI 0.80 to 1.54; two trials; 350 participants).Trials testing interventions to increase knowledge/educate about fall prevention alone did not significantly reduce the rate of falls (RaR 0.33, 95% CI 0.09 to 1.20; one trial; 45 participants) or risk of falling (RR 0.88, 95% CI 0.75 to 1.03; four trials; 2555 participants).No conclusions can be drawn from the 47 trials reporting fall-related fractures.Thirteen trials provided a comprehensive economic evaluation. Three of these indicated cost savings for their interventions during the trial period: home-based exercise in over 80-year-olds, home safety assessment and modification in those with a previous fall, and one multifactorial programme targeting eight specific risk factors. Group and home-based exercise programmes, and home safety interventions reduce rate of falls and risk of falling.Multifactorial assessment and intervention programmes reduce rate of falls but not risk of falling; Tai Chi reduces risk of falling.Overall, vitamin D supplementation does not appear to reduce falls but may be effective in people who have lower vitamin D levels before treatment.
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Since normative surface EMG (SEMG) values for muscles acting at the knee joint are available for people with haemophilia, increasing interest is noticeable for other joints affected by haemophilic arthropathy. Adequate activity of shank muscles is an important key for appropriate postural control. The aim of this study was to determine differences in muscle activation patterns of lower leg muscles between people with and without haemophilia during upright standing. SEMG of tibialis anterior (TA), fibularis longus (FL), lateral (LG) and medial (MG) heads of gastrocnemius, and soleus (SO) muscles of both sides were recorded in 25 haemophilic patients (H) and 25 non-haemophilic control subjects (C) while standing on even ground. The Gilbert-Score was used to assign sides to major (H-MA) and minor (H-MI) affected ankle joints in H. To normalize the SEMG amplitudes, amplitude ratios (percentage of cumulated activity) were calculated. Compared to controls, TA ratios showed higher and MG reduced levels in both H groups (P < 0.01). In the H-MA subgroup of H, FL also joined the TA behaviour whereas SO had similar activation direction as MG. Although possible descending influences from the knee joints cannot be excluded, this can be interpreted as a compensational mechanism due to the severity of the orthopaedic status of the ankle, which with increasing heaviness is accompanied by reduced plantar flexion capability. However, ankle joint integrity appears to be reduced in H, with TA and MG seeming to play key roles for neuromuscular control of upright posture.
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Center of pressure (COP) path length evaluation was commonly applied to measure postural sway and usually obtained from gold standard force plates. Thus, we comparatively investigated the feasible and less-expensive GKS® balance system (GKS) with the Kistler® force platform (KIS). 34 non-specifically trained but active adults (14 males, 20 females, age: 25.4±4.8 years; weight: 69.3±12.3 kg; height: 1.75±0.09 m, sports activity: 5.8±3.6 hours per week) were randomly tested on both devices during double and single limb stance with opened and closed eyes. Irrespective of the analysed time frame, repeated measures analyses of variances revealed higher path length readings for GKS compared to KIS for 30 s (F=6.8, p=0.01) and 10 s (F=21.2, p=0.001). Large effect sizes of the COP path length differences between GKS and KIS decreased from easy tasks (double limb, eyes open; d(30-s)=2.55, d(10-s)=2.04) to the most severe task (single limb, eyes closed; d(30-s)=0.02, d(10-s)=0.23). According to Bland and Altman, the limits of agreements indicated a high random variability component (between 29%, double limb, eyes open and 67%, single limb, eyes closed). The overall intraclass correlation coefficients (ICC) across all four standing balance tasks were moderate for the 30 s- (0.57) as well as the 10 s-analysis (0.65). In conclusion, the COP path length displacements obtained from the GKS balance system seem to differ with a considerable random variability from Kistler force platform data. Thus, measurements of the evaluated devices should not be used interchangeably. Further methodological investigations regarding balance measures seem warranted.
Article
The study investigated age-related changes in the thickness of the deep and superficial abdominal muscles of 103 healthy women who could walk independently The participants were classified into five age groups: young (n=26; 20-24 years), young adult (n=26; 25-44 years), middle-aged (n=16; 45-64 years), young-old (n=16; 65-74 years), and old-old (n=19; 75-85 years). The muscle thicknesses of the right rectus abdominis, external oblique, internal oblique, and transversus abdominis were measured using ultrasound imaging. The rectus abdominis was significantly thicker in the young group compared with the young adult, middle-aged, young-old, and old-old groups (p<0.05). The external oblique and internal oblique muscles were significantly thicker in the young group compared with the middle-aged, young-old, and old-old groups (p<0.05). However, there were no significant differences in the thickness of the transversus abdominis between groups. The results suggest that age-related muscle atrophy occurs from an early age in superficial abdominal muscles, such as rectus abdominis, and that age-related atrophy is less in deep abdominal muscles such as the transversus abdominis.
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Compared with resistance training, information concerning the progressive configuration of balance training (BT) is rare and lacks scientific validation. Therefore, a study was designed to determine participants' ability to perform balance exercises with increasing level of difficulty. The task required the participants (N = 20) to stand as stable as possible on a computerized balance platform. The experiment was performed on 3 testing days using different stance and sensory conditions. On each day, bipedal, step, tandem, and monopedal stands were performed 3 times while sensory conditions changed from firm ground, eyes opened (day 1) over foam ground, eyes opened (day 2) to firm ground, eyes closed (day 3). The results showed that total center of pressure displacements significantly increased when the use of sensory information (comparison between testing days: all p < 0.001) or when the base of support (comparison within testing days: all p < 0.001) was gradually reduced. Based on the observed pattern of increased postural sway across all testing conditions and the levels of trial variability, exercises were categorized into several stages of training. Findings indicate that balance performance decreased in response to an increased level of task difficulty introduced by narrowing the base of support and by limiting the use of sensory information. Practitioners can use the derived exercise ranking to select exercises for BT appropriate to the level of participants' balance ability and to implement progression in balance training.
Article
How aging affects body sway and joint coordination during quiet standing was investigated under two visual feedback conditions provided on a monitor screen: fixed and moving cursor representing the center of pressure (COP) position measured by a platform. The across-time joint motion variance of ankle, knee, hip, mid-trunk, and cervical spine leading to COP displacement was analyzed using the uncontrolled manifold approach. The body sway was assessed by the COP displacement. Young and older adults showed greater ankle joint contribution to COP displacement than the other joints. However, older adults showed larger variability of knee and mid-trunk joint motions than young adults. During the moving condition, the ankle joint contribution decreased and hip joint contribution increased for both groups, but the COP displacement increased only for the older adults. We conclude that joint coordination and body sway during quiet standing can be modified by providing COP visual feedback and that joint coordination is affected by aging.
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Falls affect a significant number of older Australians and present a major challenge to health care providers and health systems. The purpose of this statement is to inform and guide exercise practitioners and health professionals in the safe and effective prescription of exercise for older community-dwelling people with the goal of preventing falls. Falls in older people are not random events but can be predicted by assessing a number of risk factors. Of particular importance are lower limb muscle strength, gait and balance, all of which can be improved with appropriate exercise. There is now extensive evidence to demonstrate that many falls are preventable, with exercise playing a crucial role in prevention. Research evidence has identified that programs which include exercises that challenge balance are more effective in preventing falls than those which do not challenge balance. It is important for exercise to be progressively challenging, ongoing and of sufficient dose to maximise its benefits in reducing falls. Other (non-exercise) interventions are necessary for certain people with complex medical conditions or recent hospitalisation and risk factors relating to vision and the use of psychotropic medications. Qualified exercise professionals are well placed to implement the research evidence and to prescribe and supervise specific exercise aimed at preventing falls in both healthy older community-dwelling people and those with co-morbidities.
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Although electromyography (EMG) is a common method to evaluate muscle activity, studies utilizing EMG in haemophilic patients are rare. The haemophilic arthropathy, resulting in altered afferent information is expected to cause disturbed activation and inter-muscular coordination patterns in haemophilic subjects. The aim of this study was to determine differences of selected knee muscles between haemophilic patients and non-haemophilic subjects during upright standing. Surface EMG (SEMG) amplitudes of rectus femoris, vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) muscles of both sides were measured in 27 haemophilic patients (H) and 26 control subjects (C) while standing on an even surface. Data from both sides were pooled in C, but data of H were subdivided further according to major (H-MA) and minor (H-MI) affected joints. To normalize the data, amplitude ratios (percentage of cumulated activity) were calculated as well. Regardless of whether H-MA or H-MI was compared with C, amplitudes of all extensor muscles reached significantly higher levels in H (P < 0.05). SEMG amplitude ratios also differed between H and C. Independent of subgroup, BF showed significantly reduced activation ratios (P < 0.01). Only the ratios of VM and VL of H-MA could replicate the observed amplitude differences to C (P < 0.05). These findings show that while standing, haemophiliacs maintain the necessary stability demands through increased extensor activities and modulated coordination patterns. Although all thigh muscles of haemophiliacs are characterized by distinct atrophy, increased amplitude levels could be proved for the knee extensor muscles only. Therefore, general atrophy-related effects cannot explain these results.
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Electromyograms (EMGs) need to be normalized if comparisons are sought between trials when electrodes are reapplied, as well as between different muscles and individuals. The methods used to normalize EMGs recorded from healthy individuals have been appraised for more than a quarter of a century. Eight methods were identified and reviewed based on criteria relating to their ability to facilitate the comparison of EMGs. Such criteria included the magnitude and pattern of the normalized EMG, reliability, and inter-individual variability. If the aim is to reduce inter-individual variability, then the peak or mean EMG from the task under investigation should be used as the normalization reference value. However, the ability of such normalization methods to facilitate comparisons of EMGs is questionable. EMGs from MVCs can be as reliable as those from submaximal contractions, and do not appear to be affected by contraction mode or joint kinematics, particularly for the elbow flexors. Thus, the EMG from an isometric MVC is endorsed as a normalization reference value. Alternatively the EMG from a dynamic MVC can be used, although it is recognized that neither method is guaranteed to be able to reveal how active a muscle is in relation to its maximal activation capacity.
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The aim of the present study was to determine whether force plate variables in single- and dual-task situations are able to predict the risk of multiple falls in a community-dwelling elderly population. Two hundred and seventy elderly persons (225 females, 45 males; age, 73+/-7 years) performed balance assessment with and without vision. Seven force plate variables were assessed to predict the risk of multiple falls; maximum displacement in the anteroposterior and medial-lateral directions (Max-AP, Max-ML), mean displacement in the medial-lateral direction (MML), the root mean square amplitude in anteroposterior and medial-lateral directions (RMS-AP, RMS-ML), the average speed of displacement (V), and the area of the 95th percentile ellipse (AoE). Falls were prospectively recorded during the following year. A total of 437 registered falls occurred during monitoring period. The force plate variable RMS-ML in the single-task condition (odds ratio, 21.8) predicted multiple falls together with the following covariables: history of multiple falls (odds ratio, 5.6), use of medications (fall-risk medications or multiple medicine use; odds ratio, 2.3), and gender (odds ratio, 0.34). Multiple fallers had a narrower stance width than non-fallers.