Cortical activity associated with the maintenance of balance during unstable stances.

Background: Humans continuously maintain and adjust posture during gait, standing, and sitting. The difficulty of postural control is reportedly increased during unstable stances, such as unipedal standing and with closed eyes. Although balance is slightly impaired in healthy young adults in such unstable stances, they rarely fall. The brain recognizes the change in sensory inputs and outputs motor commands to the musculoskeletal system. However, such changes in cortical activity associated with the maintenance of balance following periods of instability require further clarified. Methods: In this study, a total of 15 male participants performed two postural control tasks and the center of pressure displacement and electroencephalogram were simultaneously measured. In addition, the correlation between amplitude of center of pressure displacement and power spectral density of electroencephalogram was analyzed. Results: The movement of the center of pressure was larger in unipedal standing than in bipedal standing under both eye open and eye closed conditions. It was also larger under the eye closed condition compared with when the eyes were open in unipedal standing. The amplitude of high-frequency bandwidth (1-3 Hz) of the center of pressure displacement was larger during more difficult postural tasks than during easier ones, suggesting that the continuous maintenance of posture was required. The power spectral densities of the theta activity in the frontal area and the gamma activity in the parietal area were higher during more difficult postural tasks than during easier ones across two postural control tasks, and these correlate with the increase in amplitude of high-frequency bandwidth of the center of pressure displacement. Conclusions: Taken together, specific activation patterns of the neocortex are suggested to be important for the postural maintenance during unstable stances.

Differences in upper body posture between patients with lumbar spine syndrome and healthy individuals under the consideration of sex, age and BMI.

BACKGROUND: Work-related forced postures, such as prolonged standing work, can lead to complaints in the lower back. Current research suggests that there is increased evidence of associations between patients with low back pain (LBP) and reduced lordosis in the lumbar spine and generally less spinal tilt in the sagittal plane. The aim of this study is to extend the influence of LBP to other parameters of upper body posture in standing, taking into account the rotational and frontal planes. METHODS: The study included a no-LBP group (418 males, 412 females, aged 21-65 years) and an LBP group (138 subjects: 80 females, 58 males, aged 18-86 years) with medically diagnosed lumbar spine syndrome (LSS). The "ABW BodyMapper" back scanner from ABW GmbH in Germany was used for posture assessment using video raster stereography. Statistical analyses employed two-sample t-tests or Wilcoxon-Mann-Whitney-U tests to assess the relationship between the LBP/no-LBP groups and back posture parameters. Linear and logarithmic regressions were used with independent variables including group, sex, height, weight and body mass index (BMI). Significance level: α = 0.05 (95% confidence). RESULTS: The regression analysis showed that sagittal parameters of the spine (sagittal trunk decline, thoracic and lumbar bending angle, kyphosis and lordosis angles) depend primarily on sex, age, BMI, height and/or weight but not on group membership (LBP/no-LBP). In the shoulder region, a significant dependency between group membership and scapular rotation was found. In the pelvic region, there were only significant dependencies in the transverse plane, particularly between pelvic torsion and BMI, weight, height and between pelvic rotation and group membership, age and sex. CONCLUSION: No difference between the patients and healthy controls were found. In addition, sex appears to be the main influencing factor for upper body posture. Other influencing factors such as BMI, height or weight also seem to have a significant influence on upper body posture more frequently than group affiliation.

Do Postural and Walking Stabilities Change over a Decade by Aging? A Longitudinal Study.

BACKGROUND: Previous studies have demonstrated that the center of gravity (COG) is more unstable in the elderly than in young people. However, it is unclear whether aging itself destabilizes the COG. This study aimed to investigate changes in COG sway and gait kinematics over time by a longitudinal study of middle-aged and elderly adults. METHODS: This study included 198 healthy middle-aged and elderly people who underwent stabilometry at ten-year intervals. The participants' mean age at baseline was 62.9 ± 6.5 years, and 77 (39%) of them were male. The results of stabilometry (mean velocity, sway area, postural sway center in the medial-lateral direction [X center], and postural sway center in the anterior-posterior direction [Y center]), and results of exercise tests (the height-adjusted maximum stride length [HMSL] and the 10 m walk test [10MWT]) were analyzed. The destabilized group with 11 participants, whose mean velocity exceeded 3 cm/s after 10 years, was compared with the stable group with 187 participants, whose mean velocity did not exceed 3 cm/s. RESULTS: Mean velocity increased significantly over ten years (open-eye, from 1.53 ± 0.42 cm to 1.86 ± 0.67 cm, p < 0.001); however, the sway area did not change significantly. X center showed no significant change, whereas Y center showed a significant negative shift (open-eye, from -1.03 ± 1.28 cm to -1.60 ± 1.56 cm, p < 0.001). Although the results of 10MWT and initial HMSL did not differ significantly, the HMSL in the destabilized group at ten years was 0.64, which was significantly smaller than the 0.72 of others (p = 0.019). CONCLUSIONS: The ten-year changes in COG sway in middle-aged and elderly adults were characterized by a significant increase in mean velocity but no significant difference in sway area. Because the destabilized group had significantly smaller HMSL at ten years, instability at the onset of movement is likely to be affected by COG instability.

Effect of Active Muscles on Astronaut Kinematics and Injury Risk for Piloted Lunar Landing and Launch While Standing.

While astronauts may pilot future lunar landers in a standing posture, the response of the human body under lunar launch and landing-related dynamic loading conditions is not well understood. It is important to consider the effects of active muscles under these loading conditions as muscles stabilize posture while standing. In the present study, astronaut response for a piloted lunar mission in a standing posture was simulated using an active human body model (HBM) with a closed-loop joint-angle based proportional integral derivative controller muscle activation strategy and compared with a passive HBM to understand the effects of active muscles on astronaut body kinematics and injury risk. While head, neck, and lumbar spine injury risk were relatively unaffected by active muscles, the lower extremity injury risk and the head and arm kinematics were significantly changed. Active muscle prevented knee-buckling and spinal slouching and lowered tibia injury risk in the active vs. passive model (revised tibia index: 0.02-0.40 vs. 0.01-0.58; acceptable tolerance: 0.43). Head displacement was higher in the active vs. passive model (11.6 vs. 9.0 cm forward, 6.3 vs. 7.0 cm backward, 7.9 vs. 7.3 cm downward, 3.7 vs. 2.4 cm lateral). Lower arm movement was seen with the active vs. passive model (23 vs. 35 cm backward, 12 vs. 20 cm downward). Overall simulations suggest that the passive model may overpredict injury risk in astronauts for spaceflight loading conditions, which can be improved using the model with active musculature.

Measuring Muscle Activity in the Trunk, Pelvis, and Lower Limb Which Are Used to Maintain Standing Posture in Patients With Adult Spinal Deformity, With Focus on Muscles that Contract in the Compensatory Status.

STUDY DESIGN: Prospective single-center study. OBJECTIVE: This study aimed to investigate the muscle activity of the trunk, pelvis, and lower limb, which are used to maintain a standing posture in elderly patients with spinal deformities. We also elucidated the mechanism of compensation against spinal deformity in terms of muscle activity. METHODS: Any patient scheduled to undergo surgery for adult spinal deformity was included. Surface electromyography and radiography were performed preoperatively. The following four representative alignments were defined as compensations: 1. pelvic retroversion, 2. reduction in thoracic kyphosis, 3. hyperextension of the lumbosacral junction, and 4. knee flexion. Individual muscle activity was compared with and without compensation. The patients were stratified into three groups according to the severity of spinal compensation, and differences in muscle activity were compared. RESULTS: This study included 76 patients (7 men and 69 women, average age 69.4 years). Our results revealed that pelvic retroversion and knee flexion were compensations that required trunk muscle activity. In contrast, reduction of thoracic kyphosis and hyperextension of the lumbosacral junction did not require much trunk muscle activity. There was a significant difference in the muscle activity of the pelvis and lower limbs according to the severity of the deformity. CONCLUSIONS: In terms of muscle activity, compensation for regional alignment changes in the adjacent spine is economical. However, extra-spinal compensations, such as pelvic retroversion and knee flexion, are non-economical. According to compensation recruitment, the muscle activity of the pelvis and lower limbs increased with the severity of the spinal deformity.

Spinopelvic Imbalance Is Associated With Increased Sway in the Center of Gravity: Validation of the "Cone of Economy" Concept in Healthy Subjects.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: To investigate the effects of pelvic compensation on standing balance in healthy volunteers. METHODS: The 180 healthy volunteers were recruited at a basic health checkup. The inclusion criteria were: 1) age ≥ 65 years, 2) underwent a whole spine radiograph and stabilometry, 3) well-balanced standing posture with a sagittal vertical axis <50 mm, and 4) a visual analog scale of lower back pain of <20 mm. Based on the pelvic incidence (PI) and lumbar lordosis (LL) mismatch, subjects were divided into harmonious (PI-LL ≤ 10°) or unharmonious (PI-LL > 10°) groups. RESULTS: Participants in the unharmonious group were significantly older compared with the harmonious group (70.2 ± 4.4 vs. 72.0 ± 4.6 years, P < .01). The PI minus LL values were -2.2° ± 7.5° and 16.6° ± 7.0° in the harmonious and unharmonious groups, respectively (P < .001). Anteroposterior LNG/TIME (average center of pressure sway speed) was significantly greater in the unharmonious group with both open and closed eyes (1.04 ± 0.38 cm/s vs. 1.25 ± 0.47 cm/s, P < .001 and 1.22 ± 0.54 cm/s vs. 1.58 ± 0.77 cm/s, P < .001, respectively). Lateral LNG/TIME was significantly greater in the unharmonious group only with closed eyes (1.24 ± 0.54 cm/s vs. 1.47 ± 0.79 cm/s, P = .03). CONCLUSIONS: Healthy elderly subjects with poor spinopelvic harmony had relatively unstable standing balance. The "cone of economy" was demonstrated, showing that unharmonious spinopelvic balance had a non-economic effect on standing.

Effects of the whole-body vibration direction on the cognitive response of standing subjects.

This study aims to investigate the effect of whole-body vibration along different axes on the response time (RT) of standing subjects during a customised psychomotor vigilance task (PVT). Twenty-five subjects were exposed to harmonic vibration with amplitude of 0.7 m/s2 RMS and frequencies between 1.5 Hz and 12.5 Hz. ANOVA was used to assess if the difference of RT with and without vibration had a statistical relevance. Results showed that the RT was statistically affected by the vibration only at frequencies below 2 Hz. The vibration at higher frequencies had a minor effect on the RT. The RTs during the vibration exposure was, on average, 15% higher than the RT post exposure. Practitioner summary: This study investigates the effects of whole-body vibration (WBV) along different axes on the response time (RT). We measured the RTs to a psychomotor vigilance task of 25 standing subject exposed to WBV. The cognitive response was statistically affected by the WBV and, on average RT have increased of 15%.

Neglected problem: Influence of school bag on lumbar segment in children.

Background and Objectives: School bag (SB) load causes significant changes in the height and symmetry of the intervertebral discs at each level of the spine from T12-L1 to L5-S1. This study aims to determine the change in the size of the lumbar segment angle at a particularly critical point L3-L4 of the spine in relation to the load of the average weight of SB in healthy male children (students) at standing and after 2-minute gait. Methods: 47 boys, aged 12.2 ± 0.92 years, underwent photogrammetric measurements in the sagittal plane in statics and dynamics, walking on a laboratory treadmill. Measurements were repeated with the weight of SB with a constant load of 6,251 kg, which represents 13.78% of the average body weight of our sample. The lumbar angle (LA) connecting the point of the big toe, the lumbar point L3-L4 and the processus spinosus C7 was measured. In gait, LA was measured in the phases of the middle support and the initial contact of the heel. Results: T-test of paired samples was used to estimate the change in LA at standing from 4.953° and walking phases from 6.295° to 7.332° in relation to the unloaded state, and the value of the effect size (ES) indicates that the impact of SB load is significant. Conclusions: Cumulatively, microtraumas caused by SB load significantly affect the increase in intervertebral pressure at the L3-L4 point, which is susceptible to degenerative processes and which can be the cause of lumbar syndrome (LS). Preventive measures are needed in order to lighten SB in this population and introduce up to 10% of students' body weight into the safe zone.

Human Standing Posture Motion Evaluation by the Visual Simulation of Multi-Directional Sea-Waves.

Crew fatigue from standing posture motion, caused by ship motion, can lead to marine accidents. Therefore, the mechanism of fatigue in crew members ought to be elucidated. The standing posture of humans is maintained by postural state detection through the visual, vestibular, and somatosensory systems. Humans can adjust their posture through corrective postural reactions (CPR) generated after anticipatory postural adjustments (APAs) by using information from these sensory systems. APAs refer to skills acquired by learning from past motions and perturbations and are prepared by the central nervous system based on visual information before the actual perturbation occurs. We hypothesized that APAs would decrease fatigue in crew members by stabilizing their standing posture motions. We aimed to clarify the human standing posture control influenced by APAs based on visual information. To this end, we presented wave images with different wave directions to the participants using a visual simulator and analyzed their standing posture motion. We found that the participants stabilized their standing posture based on the projected wave directions. This showed that the participants predicted ship motion from the wave images and controlled their center of pressure (COP) through APAs. Individual differences in standing postural motion may indicate the subjective variation of APAs based on individual experiences. This study was limited to males aged 20-23 years. To generalize this study, randomized controlled trials should be performed with participants of multiple age groups, including men and women.

Standing Posture in Motor and Cognitive Dual-Tasks during Smartphone Use: Linear and Nonlinear Analysis of Postural Control.

Analysis of the center of pressure (CoP) during cognitive or motor dual-tasking is widely used to characterize postural control. Most studies use traditional measures of CoP to quantify postural control, but given its complexity, nonlinear analysis of CoP is of growing interest in the area. This study aims to analyze CoP behavior in healthy young adults during standing posture performance while simultaneously performing motor or cognitive tasks on a smartphone, using linear and nonlinear analysis of CoP. Thirty-six healthy participants (23.08 ± 3.92 years) were found eligible for this study. They performed a single task (ST), cognitive dual-task (cog-DT), and motor dual-task (mot-DT). The total excursion of CoP, displacement of CoP in the anterior-posterior and medial-lateral directions, mean total velocity of CoP, and mean anterior-posterior and medial-lateral velocities of CoP were measured with a force plate. Approximate entropy (ApEn) of the anterior-posterior (ApEn-AP) and medial-lateral (ApEn-ML) displacement of CoP were also calculated. The results showed that dual-task costs for the total excursion, displacement in the anterior-posterior direction, mean total velocity, and mean anterior-posterior velocity of CoP were greater during the cog-DT than the mot-DT (p < 0.05). In the nonlinear analysis of the CoP, there was no difference (p > 0.05) between the cog-DT and mot-DT for ApEn values of the anterior-posterior and medial-lateral time series of the CoP. Both linear and nonlinear analyses showed differences between the cog-DT and ST (p < 0.05), revealing a decline in postural control during the cog-DT compared with the ST. In conclusion, performing a cog-DT causes sway impairments and lower postural control efficacy compared with motor single and dual-tasks. Furthermore, both linear and nonlinear analyses were able to distinguish between conditions.

Effects of Noisy Galvanic Vestibular Stimulation on the Muscle Activity and Joint Movements in Different Standing Postures Conditions.

Objective: Noisy galvanic vestibular stimulation (nGVS) is an effective method for stabilizing posture; however, little is known regarding the detailed muscle activity and joint movement in the standing posture. This study aimed to clarify the changes in the lower limb muscle activity and joint angular velocity by nGVS intervention using the simultaneous assessment method of inertial measurement units and surface electromyography (EMG). Methods: Seventeen healthy participants were assessed for their physical responses under four conditions (standing on a firm surface with eyes-open/eyes-closed, and a foam surface with eyes-open/eyes-closed) without stimulation (baseline) and with stimulation (sham or nGVS). Noise stimuli were applied for 30 s at a level below the perceptual threshold. The body control response was evaluated using EMG activity and angular velocity of the lower limbs. Result: Regarding the change from baseline for each parameter, there was a significant interactive effect of EMG activity in the muscle type × intervention and EMG activity and angular velocity in the condition × intervention. Post hoc analysis revealed that the angular velocity was significantly decreased in the abduction-adduction direction in the standing on a foam surface with eyes-closed condition compared to that with eyes-open in the nGVS intervention. Conclusion: Our results suggest that nGVS altered physical responses in different standing postural conditions. The present study is exploratory and therefore the evidence should be investigated in future studies specifically target those muscle activities and joint motion parameters.

Muscle actions on crossed and non-crossed joints during upright standing and gait: A comprehensive description based on induced acceleration analysis.

The multibody nature of the musculoskeletal system makes each applied force potentially accelerate all body segments. Hence, muscles' actions on the kinematics of crossed and non-crossed joints should be estimated based on multibody dynamics. The objective of this study was to systematically investigate the actions of main lower limb muscles on the sagittal-plane angular kinematics of the hip, knee, and ankle joints, during upright standing and gait. Subject-specific simulations were performed to compute the muscle-tendon forces based on three-dimensional kinematic data collected from 10 able-bodied subjects during walking at preferred speed and during relaxed standing posture. A subject-scaled model consisting of the lower limb segments, 19 degrees of freedom and 92 Hill-type muscle-tendon units was used. Muscle-induced joint angular accelerations were estimated by Induced Acceleration Analysis in OpenSim. A comprehensive description of the estimated joint accelerations induced by lower limb muscles was presented, for upright standing and for the whole gait cycle. The observed muscle actions on crossed and non-crossed joints were phase- and task-specific. The main flexors and extensors for each joint were reported. Particular biarticular muscles presented actions opposite to their anatomical classification for specific joints. Antagonist muscle actions were revealed, such as the hitherto unknown opposite actions of the soleus and gastrocnemius at the ankle, and of the iliopsoas and soleus at the knee and ankle, during upright standing. Agonist actions among remote muscles were also identified. The presented muscle actions and their roles in joint kinematics of bipedal standing and walking contribute to understanding task-specific coordination.

Sling suspension therapy is an effective treatment method of juvenile spinal osteochondrosis in adolescent girls.

BACKGROUND: Juvenile spinal osteochondrosis (JSO) affects vertebral endplates and may cause intervertebral discs alterations. The condition is typically related to pain, and weakness and shortening of trunk muscles. Sling suspension therapy (SST) has been shown to reduce lumbar pain effectively. It is, however, unclear whether SST is superior to other treatment methods in reducing pain, correcting posture, and activating trunk stabilizers in JSO. OBJECTIVE: In this study, we intended to compare the effectiveness of two different exercise modalities; Sling Suspension Therapy and Gym Ball Exercise in the treatment of JSO in adolescent girls. METHODS: A randomised controlled single centre clinical trial was carried out in an inpatient rehabilitation unit at a sanatorium. Forty adolescent girls (age 16.3 ± 0.47 yrs.), who were diagnosed with JSO (according to ICD-10 Version: 2016 - M 42.0) were randomly assigned into two groups: Group 1 - Sling suspension therapy (SST), Group 2 - Gym ball exercises (GBE). Both groups received interventions for 3 weeks, 15 sessions, and 30 minutes a day for 5 consecutive days a week. Back pain, endurance of trunk muscles and standing posture were evaluated pre- and post-interventions. RESULTS: Both groups demonstrated significant improvement in all measured outcomes. SST was more effective in reducing pain (p< 0.05), increasing the endurance of trunk muscles (p< 0.05) and improving the standing posture (p< 0.05) compared to GBE (p< 0.05). CONCLUSIONS: Sling suspension therapy is more effective compared with Gym ball exercises in the treatment of juvenile spinal osteochondrosis in adolescent girls in terms of back pain, posture and endurance of trunk muscles.

Evaluation of Postural Sway in Post-stroke Patients by Dynamic Time Warping Clustering.

Post-stroke complications are the second most frequent cause of death and the third leading cause of disability worldwide. The motor function of post-stroke patients is often assessed by measuring the postural sway in the patients during quiet standing, based on sway measures, such as sway area and velocity, which are obtained from temporal variations of the center of pressure. However, such approaches to establish a relationship between the sway measures and patients' demographic factors have hardly been successful (e.g., days after onset). This study instead evaluates the postural sway features of post-stroke patients using the clustering method of machine learning. First, we collected the stroke patients' multi-variable motion-capture standing-posture data and processed them into t s long data slots. Then, we clustered the t-s data slots into K cluster groups using the dynamic-time-warping partition-around-medoid (DTW-PAM) method. The DTW measures the similarity between two temporal sequences that may vary in speed, whereas PAM identifies the centroids for the DTW clustering method. Finally, we used a post-hoc test and found that the sway amplitudes of markers in the shoulder, hip, knee, and center-of-mass are more important than their sway frequencies. We separately plotted the marker amplitudes and frequencies in the medial-lateral direction during a 5-s data slot and found that the post-stroke patients' postural sway frequency lay within the bandwidth of 0.5-1.5 Hz. Additionally, with an increase in the onset days, the cluster index of cerebral hemorrhage patients gradually transits in a four-cluster solution. However, the cerebral infarction patients did not exhibit such pronounced transitions over time. Moreover, we found that the postural-sway amplitude increased in clusters 1, 3, and 4. However, the amplitude of cluster 2 did not follow this pattern, owing to age effects related to the postural sway changes with age. A rehabilitation doctor can utilize these findings as guidelines to direct the post-stroke patient training.

State-Space Characterization of Balance Capabilities in Biped Systems with Segmented Feet.

The human ability of keeping balance during various locomotion tasks is attributed to our capability of withstanding complex interactions with the environment and coordinating whole-body movements. Despite this, several stability analysis methods are limited by the use of overly simplified biped and foot structures and corresponding contact models. As a result, existing stability criteria tend to be overly restrictive and do not represent the full balance capabilities of complex biped systems. The proposed methodology allows for the characterization of the balance capabilities of general biped models (ranging from reduced-order to whole-body) with segmented feet. Limits of dynamic balance are evaluated by the Boundary of Balance (BoB) and the associated novel balance indicators, both formulated in the Center of Mass (COM) state space. Intermittent heel, flat, and toe contacts are enabled by a contact model that maps discrete contact modes into corresponding center of pressure constraints. For demonstration purposes, the BoB and balance indicators are evaluated for a whole-body biped model with segmented feet representative of the human-like standing posture in the sagittal plane. The BoB is numerically constructed as the set of maximum allowable COM perturbations that the biped can sustain along a prescribed direction. For each point of the BoB, a constrained trajectory optimization algorithm generates the biped's whole-body trajectory as it recovers from extreme COM velocity perturbations in the anterior-posterior direction. Balance capabilities for the cases of flat and segmented feet are compared, demonstrating the functional role the foot model plays in the limits of postural balance. The state-space evaluation of the BoB and balance indicators allows for a direct comparison between the proposed balance benchmark and existing stability criteria based on reduced-order models [e.g., Linear Inverted Pendulum (LIP)] and their associated stability metrics [e.g., Margin of Stability (MOS)]. The proposed characterization of balance capabilities provides an important benchmarking framework for the stability of general biped/foot systems.

Static and dynamic pelvic kinematics after one-stage bilateral or unilateral total hip arthroplasty.

INTRODUCTION: The pelvis rotates simultaneously around both hips along sagittal, frontal and transversal planes and its kinematics change in patients after total hip arthroplasty (THA). Consequently, it is reasonable to expect different pelvic kinematic profiles in bilateral or unilateral THA. Therefore, the aim of this study was to compare pelvic kinematics in patients with bilateral or unilateral THA. METHODS: 40 patients undergoing bilateral (n = 20) or unilateral (n = 20) THA were evaluated for pelvic kinematics during standing and walking tasks using an optoelectronic system. Mean pelvic orientation was assessed during standing, whereas the Gait Variable Score (GVS), maximum and minimum peaks, range and values of pelvic tilt, obliquity and rotation during Heel-Strike and Toe-Off phases of gait cycle were calculated during walking. Data were collected the day before and at seven days after surgery. RESULTS: At baseline, no between-group differences were found. At 7 days, GVS for pelvic tilt (p = 0.029) and rotation (p = 0.046) were closer to normative data in bilateral patients, who also revealed lower maximum peak of anterior tilt (p = 0.013) and lower range of pelvic tilt during gait (p = 0.031) with respect to unilateral cases. No between-group differences were found for pelvic orientation during standing at any time-point. CONCLUSIONS: Bilateral patients revealed more physiological pelvic kinematics than unilateral cases. These findings underline the advantage of patients undergoing 1-stage bilateral THA and may be helpful in selecting personalised rehabilitative approaches.

Compensation for standing posture by whole-body sagittal alignment in relation to health-related quality of life.

AIMS: The aim of this study is to test the hypothesis that three grades of sagittal compensation for standing posture (normal, compensated, and decompensated) correlate with health-related quality of life measurements (HRQOL). METHODS: A total of 50 healthy volunteers (normal), 100 patients with single-level lumbar degenerative spondylolisthesis (LDS), and 70 patients with adult to elderly spinal deformity (deformity) were enrolled. Following collection of demographic data and HRQOL measured by the Scoliosis Research Society-22r (SRS-22r), radiological measurement by the biplanar slot-scanning full body stereoradiography (EOS) system was performed simultaneously with force-plate measurements to obtain whole body sagittal alignment parameters. These parameters included the offset between the centre of the acoustic meatus and the gravity line (CAM-GL), saggital vertical axis (SVA), T1 pelvic angle (TPA), McGregor slope, C2-7 lordosis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), PI-LL, sacral slope (SS), pelvic tilt (PT), and knee flexion. Whole spine MRI examination was also performed. Cluster analysis of the SRS-22r scores in the pooled data was performed to classify the subjects into three groups according to the HRQOL, and alignment parameters were then compared among the three cluster groups. RESULTS: On the basis of cluster analysis of the SRS-22r subscores, the pooled subjects were divided into three HRQOL groups as follows: almost normal (mean 4.24 (SD 0.32)), mildly disabled (mean 3.32 (SD 0.24)), and severely disabled (mean 2.31 (SD 0.35)). Except for CAM-GL, all the alignment parameters differed significantly among the cluster groups. The threshold values of key alignment parameters for severe disability were TPA > 30°, C2-7 lordosis > 13°, PI-LL > 30°, PT > 28°, and knee flexion > 8°. Lumbar spinal stenosis was found to be associated with the symptom severity. CONCLUSION: This study provides evidence that the three grades of sagittal compensation in whole body alignment correlate with HRQOL scores. The compensation grades depend on the clinical diagnosis, whole body sagittal alignment, and lumbar spinal stenosis. The threshold values of key alignment parameters may be an indication for treatment. Cite this article: Bone Joint J 2020;102-B(10):1359-1367.

Standing-Posture Recognition in Human-Robot Collaboration Based on Deep Learning and the Dempster-Shafer Evidence Theory.

During human-robot collaborations (HRC), robot systems must accurately perceive the actions and intentions of humans. The present study proposes the classification of standing postures from standing-pressure images, by which a robot system can predict the intended actions of human workers in an HRC environment. To this end, it explores deep learning based on standing-posture recognition and a multi-recognition algorithm fusion method for HRC. To acquire the pressure-distribution data, ten experimental participants stood on a pressure-sensing floor embedded with thin-film pressure sensors. The pressure data of nine standing postures were obtained from each participant. The human standing postures were discriminated by seven classification algorithms. The results of the best three algorithms were fused using the Dempster-Shafer evidence theory to improve the accuracy and robustness. In a cross-validation test, the best method achieved an average accuracy of 99.96%. The convolutional neural network classifier and data-fusion algorithm can feasibly classify the standing postures of human workers.

Tuning of Standing Postural Responses to Instability and Cost Function.

Whole-body movements are performed daily, and humans must constantly take into account the inherent instability of a standing posture. At times these movements may be performed in risky environments and when facing different costs of failure. The aim of the study was to test the hypothesis that in upright stance participants continuously estimate both probability of failure and cost of failure such that their postural responses will be based on these estimates. We designed a snowboard riding simulation experiment where participants were asked to control the position of a moving snowboard within a snow track in a risky environment. Cost functions were provided by modifying the penalty of riding in the area adjacent to the snow track. Uncertainty was modified by changing the gain of postural responses while participants were standing on a rocker board. We demonstrated that participants continually evaluated the environmental cost function and compensated for additional risk with feedback-based postural changes, even when probability of failure was negligible. Results showed also that the participants' estimates of the probability of failure accounted for their own inherent instability. Moreover, participants showed a tendency to overweight large probabilities of failure with more biomechanically constrained standing postures that results in suboptimal estimates of risky environments. Overall, our results suggest that participants tune their standing postural responses by empirically estimating the cost of failure and the uncertainty level in order to minimize the risk of falling when cost is high.

Lower Limb Varicose Veins among Nurses: A Single Center Cross-Sectional Study in Mansoura, Egypt.

BACKGROUND: Lower limb varicose veins are common among nurses due to occupational and nonoccupational risk factors. AIMS: To estimate the prevalence of lower limbs varicosity and its associated risk factors. SETTINGS AND DESIGN: A cross-sectional descriptive study was carried out among 201 nurses at Mansoura University Hospital from January 1st to May 31st, 2018. METHODS: A questionnaire was used to collect sociodemographic data, risk factors for varicose veins, and occupational details. Varicose veins were diagnosed by Doppler ultrasound. STATISTICAL ANALYSIS: Univariate and logistic regression analyses were done. RESULTS: The prevalence of varicose veins was 18.4%. Significant independent predictors are being ≥25 years old, working in emergency rooms and ICU/operative rooms, and using oral contraceptives with adjusted odds ratios [95% Confidence Interval (CI)] of [8.7 (2.6-28.4)], [10.8 (2.6-45.9)], [16.2 (3.9-67.4)], and [4.2 (1.3-13.2)], respectively. CONCLUSIONS: Independent predictors, other than age, are modifiable and those with highest AOR are occupationally related.