Analysis of standing up and sitting down in humans: definitions and normative data presentation

Dynamics of sit-to-stand and stand-to-sit motions based on the trajectory control of the centre of mass of the body: A bond graph approach

This paper presents a bond graph model for the dynamics of sit-to-stand (SiTSt) and stand-to-sit (StTSi) motions. It is hypothesized that, for these motions, the central nervous system (CNS) controls the trajectory of the centre of mass of the body (COMB). The model comprises two identical submodels: one submodel emulates the working of the CNS, and the other represents the human body. Reference trajectories of the COMB determined through experimentation are input to the submodel representing the working of CNS, which automatically determines the required joint angle trajectories. Based on the required and actual joint angle trajectories, proportional integral derivative controllers at the joints (j-PID) provide the required joint torques to actuate the human body submodel. Simulation results show that during SiTSt or StTSi motions, the centre of mass of the human body submodel follows the commanded trajectories. The joint angle trajectories from the submodel representing the working of CNS closely follow the respective experimental joint angle trajectories. Also, for each motion, joint angles, torques and powers are presented, which agree with earlier studies. These findings provide adequate confidence in proposed hypothesis and indicate the potential of developed model for other biomechanical investigations of SiTSt and StTSi motions.

Weight-bearing asymmetry during sit-to-stand after major lower-limb amputation: A systematic review and meta-analysis

Weight-bearing asymmetry during sit-to-stand (STS) can cause musculoskeletal problems in people with major lower-limb amputation. Does weight-bearing asymmetry differ between individuals with major lower-limb amputation and individuals without amputation? We conducted a systematic review and meta-analysis. We searched PubMed, Cochrane Library, Web of Science, and HAL up to June 2022 using keywords and inclusion/exclusion criteria. Article quality was assessed. Data for population, intervention, weight-bearing asymmetry, and biomechanical analysis were reported. Standardized mean differences (SMDs) were calculated from the outcomes when possible. We included 11 studies (102 people with amputation). Weight-bearing asymmetry was greater in people with amputation than those without amputation (SMD = 1.72 [1.30-2.14] p < 0.00001). It was greater for individuals with transtibial amputation (TTA) and with transfemoral amputation (TFA) than for those without amputation (SMD = 1.20 [0.76-1.65] p < 0.00001 and SMD = 5.32 [4.15-6.50] p < 0.00001, respectively). STS performance time was longer for people with amputation (SMD = 0.52 [0.23-0.81] p = 0.0004) than those without amputation. Trunk motion differed in those with amputation, and lower-limb kinematics differed considerably, especially for people with TFA. Weight-bearing is more asymmetric in people with amputation than in people without amputation. The differences in weight-bearing asymmetry and kinematics during STS between people with TTA and TFA suggest that different strategies are required to improve weight-bearing symmetry: improvements in active prosthetic knees in TFA and rehabilitation focused on weight-bearing in TTA.

Trunk biomechanical changes between the sit-to-stand and stand-to-sit performed at self-selected and fast speeds in stroke survivors

PURPOSE

To compare the trunk biomechanical characteristics between the sit-to-stand and stand-to-sit performed at self-selected and fast speeds in stroke survivors and healthy-matched controls.

METHODS

Thirty individuals (15 stroke survivors and 15 healthy-matched controls) were included. The following biomechanical characteristics were determined: peak of trunk forward flexion and time until the peak of trunk forward flexion, total duration, phase I (sit-to-stand: time spent from the beginning to seat-off; stand-to-sit: time spent from the beginning to seat-on) and II durations (sit-to-stand: time spent from seat-off to the end of the task; stand-to-sit: time spent from the seat-on to the end of the task). Two-way repeated measures ANOVA was used (α = 5%).

RESULTS

The maximum angle of trunk forward flexion and time spent until the maximum angle of trunk forward flexion in both tasks were significantly higher in stroke survivors. For both groups and speeds, phase I duration and peak of trunk forward flexion of the stand-to-sit were significantly higher than that of the sit-to-stand (11.41≤F ≤ 33.60; 0.001 ≤ p ≤ 0.002) and, phase II duration was significantly higher during the sit-to-stand than that of the stand-to-sit (21.27 ≤ F ≤ 65.10; p ≤ 0.001).

CONCLUSIONS

These results confirm specific trunk biomechanical characteristics between sit-to-stand and stand-to-sit in stroke survivors and healthy-matched controls.

Activity-Dependent Compensation at the Hip and Ankle at 8 Years After the Reconstruction of Isolated and Combined Posterior Cruciate Ligament Injuries

BACKGROUND

After posterior cruciate ligament reconstruction (PCLR), functional deficits at the knee can persist. It remains unclear if neighboring joints compensate for the knee during demanding activities of daily living.

PURPOSE

To assess long-term alterations in lower limb mechanics in patients after PCLR.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 28 patients who had undergone single-bundle unilateral isolated or combined PCLR performed stair navigation, squat, sit-to-stand, and stand-to-sit tasks at 8.2 ± 2.2 years after surgery. Motion capture and force plates were used to collect kinematic and kinetic data. Then, 3-dimensional hip, knee, and ankle kinematic data of the reconstructed limb were compared with those of the contralateral limb using statistical parametric mapping.

RESULTS

Side-to-side differences at the knee were primarily found during upward-driven movements at 8 years after surgery. The reconstructed knee exhibited lower internal rotation during the initial loading phase of stair ascent versus the contralateral knee (P = .005). During the sit-to-stand task, higher flexion angles during the midcycle (P = .017) and lower external rotation angles (P = .049) were found in the reconstructed knee; sagittal knee (P = .001) and hip (P = .016) moments were lower in the reconstructed limb than the contralateral limb. In downward-driven movements, side-to-side differences were minimal at the knee but prominent at the ankle and hip: during stair descent, the reconstructed ankle exhibited lower dorsiflexion and lower external rotation during the midcycle versus the contralateral ankle (P = .006 and P = .040, respectively). Frontal hip moments in the reconstructed limb were higher than those in the contralateral limb during the stand-to-sit task (P = .010); during squats, sagittal hip angles in the reconstructed limb were higher than those in the contralateral limb (P < .001).

CONCLUSION

Patients after PCLR exhibited compensations at the hip and ankle during downward-driven movements, such as stair descent, squats, and stand-to-sit. Conversely, residual long-term side-to-side differences at the knee were detected during upward-driven movements such as stair ascent and sit-to-stand.

CLINICAL RELEVANCE

After PCLR, side-to-side differences in biomechanical function were activity-dependent and occurred either at the knee or neighboring joints. When referring to the contralateral limb to assess knee function in the reconstructed limb, concentric, upward-driven movements should be prioritized. Compensations at the hip and ankle during downward-driven movements lead to biases in long-term functional assessments.

The influence of smoothness and speed of stand-to-sit movement on joint kinematics, kinetics, and muscle activation patterns

Background

Stand-to-sit (StandTS) is an important daily activity widely used in rehabilitation settings to improve strength, postural stability, and mobility. Modifications in movement smoothness and speed significantly influence the kinematics, kinetics, and muscle activation patterns of the movement. Understanding the impact of StandTS speed and smoothness on movement control can provide valuable insights for designing effective and personalized rehabilitation training programs.

Research question

How do the smoothness and speed of StandTS movement affect joint kinematics, kinetics, muscle activation patterns, and postural stability during StandTS?

Methods

Twelve healthy younger adults participated in this study. There were two StandTS conditions. In the reference condition, participants stood in an upright position with their feet positioned shoulder-width apart on the force plate. Upon receiving a visual cue, participants performed StandTS at their preferred speed. In the smooth condition, participants were instructed to perform StandTS as smoothly as possible, aiming to minimize contact pressure on the seat. Lower leg kinetics, kinematics, and coordination patterns of muscle activation during StandTS were measured: (1) angular displacement of the trunk, knee, and hip flexion; (2) knee and hip extensor eccentric work; (3) muscle synergy pattern derived from electromyography (EMG) activity of the leg muscles; and (4) postural sway in the anterior-posterior (A-P), medio-lateral (M-L), and vertical directions.

Results

Compared to the reference condition, the smooth condition demonstrated greater eccentric knee extensor flexion and increased joint work in both the knee and hip joints. Analysis of specific muscle synergy from EMG activity revealed a significant increase in the relative contribution of hip joint muscles during the smooth condition. Additionally, a negative correlation was observed between knee extensor and vertical postural sway, as well as hip extensor work and M-L postural sway.

Conclusion

Smooth StandTS facilitates enhanced knee eccentric control and increased joint work at both the hip and knee joints, along with increased involvement of hip joint muscles to effectively manage falling momentum during StandTS. Furthermore, the increased contributions of knee and hip joint work reduced postural sway in the vertical and M-L directions, respectively. These findings provide valuable insights for the development of targeted StandTS rehabilitation training.

A Novel CNN-BiLSTM Ensemble Model With Attention Mechanism for Sit-to-Stand Phase Identification Using Wearable Inertial Sensors

Sit-to-stand transition phase identification is vital in the control of a wearable exoskeleton robot for assisting patients to stand stably. In this study, we aim to propose a method for segmenting and identifying the sit-to-stand phase using two inertial sensors. First, we defined the sit-to-stand transition into five phases, namely, the initial sitting phase, the flexion momentum phase, the momentum transfer phase, the extension phase, and the stable standing phase based on the preprocessed acceleration and angular velocity data. We then employed a threshold method to recognize the initial sitting and the stable standing phases. Finally, we designed a novel CNN-BiLSTM-Attention algorithm to identify the three transition phases, namely, the flexion momentum phase, the momentum transfer phase, and the extension phase. Fifteen subjects were recruited to perform sit-to-stand transition experiments under a specific paradigm. A combination of the acceleration and angular velocity data features for the sit-to-stand transition phase identification were validated for the model performance improvements. The integration of the CNN, Bi-LSTM, and Attention modules demonstrated the reasonableness of the proposed algorithms. The experimental results showed that the proposed CNN-BiLSTM-Attention algorithm achieved the highest average classification accuracy of 99.5% for all five phases when compared to both traditional machine learning algorithms and deep learning algorithms on our customized dataset (STS-PD). The proposed sit-to-stand phase recognition algorithm could serve as a foundation for the control of wearable exoskeletons and is important for the further development of intelligent wearable exoskeleton rehabilitation robots.

The relationship between acceleration in sit-to-stand and falls in community-dwelling older adults: cross-sectional study

[Purpose] This study aimed to determine the relationship between acceleration parameters in the sit-to-stand (STS) movement and falls, and the strength of the association between acceleration in STS movements and falls in older adults. [Participants and Methods] In total, 330 older adults were included. Four acceleration parameters were measured in STS movement: maximum acceleration (MA), velocity (MV), power (MP), and stand-up time (ST). For the conventional STS tests, 5 times STS test (5xSTS) and ground reaction force (maximal rate of force development per body weight: RFD/w, peak reaction force per body weight: F/w, chair-rise time: T) were measured. Poisson regression analysis adjusted for confounding factors was used. [Results] In the model adjusted for confounders, significant associations were observed among MV (Prevalence ratio (PR): 0.75; 95% confidence interval (CI): 0.58-0.98), MP (PR: 0.67; 95% Cl: 0.68-0.93), RFD/w (PR: 0.70; 95% Cl: 0.56-0.87), and T (PR: 1.14; 95% Cl: 1.05-1.24). [Conclusion] Among the acceleration parameters, MP was most strongly associated with falls and was considered the most useful parameter for evaluation. In addition, comparisons with the conventional chair rise tests suggested that MP was stronger than the 5xSTS test and may be equally related to the RFD/w.

Sit-to-Stand Video Analysis-Based App for Diagnosing Sarcopenia and Its Relationship With Health-Related Risk Factors and Frailty in Community-Dwelling Older Adults: Diagnostic Accuracy Study

BACKGROUND

Probable sarcopenia is determined by a reduction in muscle strength assessed with the handgrip strength test or 5 times sit-to-stand test, and it is confirmed with a reduction in muscle quantity determined by dual-energy X-ray absorptiometry or bioelectrical impedance analysis. However, these parameters are not implemented in clinical practice mainly due to a lack of equipment and time constraints. Nowadays, the technical innovations incorporated in most smartphone devices, such as high-speed video cameras, provide the opportunity to develop specific smartphone apps for measuring kinematic parameters related with sarcopenia during a simple sit-to-stand transition.

OBJECTIVE

We aimed to create and validate a sit-to-stand video analysis-based app for diagnosing sarcopenia in community-dwelling older adults and to analyze its construct validity with health-related risk factors and frailty.

METHODS

A total of 686 community-dwelling older adults (median age: 72 years; 59.2% [406/686] female) were recruited from elderly social centers. The index test was a sit-to-stand video analysis-based app using muscle power and calf circumference as proxies of muscle strength and muscle quantity, respectively. The reference standard was obtained by different combinations of muscle strength (handgrip strength or 5 times sit-to-stand test result) and muscle quantity (appendicular skeletal mass or skeletal muscle index) as recommended by the European Working Group on Sarcopenia in Older People-2 (EWGSOP2). Sensitivity, specificity, positive and negative predictive values, and area under the curve (AUC) of the receiver operating characteristic curve were calculated to determine the diagnostic accuracy of the app. Construct validity was evaluated using logistic regression to identify the risks associated with health-related outcomes and frailty (Fried phenotype) among those individuals who were classified as having sarcopenia by the index test.

RESULTS

Sarcopenia prevalence varied from 2% to 11% according to the different combinations proposed by the EWGSOP2 guideline. Sensitivity, specificity, and AUC were 70%-83.3%, 77%-94.9%, and 80.5%-87.1%, respectively, depending on the diagnostic criteria used. Likewise, positive and negative predictive values were 10.6%-43.6% and 92.2%-99.4%, respectively. These results proved that the app was reliable to rule out the disease. Moreover, those individuals who were diagnosed with sarcopenia according to the index test showed more odds of having health-related adverse outcomes and frailty compared to their respective counterparts, regardless of the definition proposed by the EWGSOP2.

CONCLUSIONS

The app showed good diagnostic performance for detecting sarcopenia in well-functioning Spanish community-dwelling older adults. Individuals with sarcopenia diagnosed by the app showed more odds of having health-related risk factors and frailty compared to their respective counterparts. These results highlight the potential use of this app in clinical settings.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05148351; https://clinicaltrials.gov/study/NCT05148351.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.3390/s22166010.

Automatic Detection of Magnetic Disturbances in Magnetic Inertial Measurement Unit Sensors Based on Recurrent Neural Networks

This paper proposes a new methodology for the automatic detection of magnetic disturbances from magnetic inertial measurement unit (MIMU) sensors based on deep learning. The proposed approach considers magnetometer data as input to a long short-term memory (LSTM) neural network and obtains a labeled time series output with the posterior probabilities of magnetic disturbance. We trained our algorithm on a data set that reproduces a wide range of magnetic perturbations and MIMU motions in a repeatable and reproducible way. The model was trained and tested using 15 folds, which considered independence in sensor, disturbance direction, and signal type. On average, the network can adequately detect the disturbances in 98% of the cases, which represents a significant improvement over current threshold-based detection algorithms.

Upper extremity effort during the sit-to-stand task in able-bodied and in individuals with spinal cord injury: A preliminary study

OBJECTIVE

To investigate the association between the presence of spinal cord injury (SCI) on biomechanical variables by comparing individuals with SCI and able-bodied individuals during the sit-to-stand (STS) task assisted by a walker device. Specifically, we compared the upper-extremity joint angles and moments, trunk forward tilt angle, vertical forces of the instrumented walker, and ground reaction forces between groups.

DESIGN

Case-control study.

SETTING

Department of Orthopedics and Traumatology, UNICAMP-Brazil.

PARTICIPANTS

Six individuals with SCI and fourteen able-bodied individuals.

MAIN OUTCOME MEASURES

Kinematics and kinetics of the shoulder, elbow, and wrist joints; trunk forward tilt angle, vertical walker forces, and ground reaction forces (GRF) were analyzed during the STS task in two phases: before and after the seat-off event.

RESULTS

A higher peak elbow flexion angle and higher vertical walker forces were observed before the seat-off, whereas the lower peak vertical GRF was found, after the seat-off, in the SCI group compared with the control group.

CONCLUSIONS

SCI affects kinematics and kinetics variables during the STS task compared to able-bodied controls. Individuals with SCI adopted different standing-up strategies that affected the distribution of the forces in the upper and lower extremities of the human body.

Analysis of inter-joint coordination during the sit-to-stand and stand-to-sit tasks in stroke patients with hemiplegia

BACKGROUND

Inter-joint coordination is an important factor affecting postural stability, and its variability increases after fatigue. This study aimed to investigate the coordination pattern of lower limb joints during the sit-to-stand (Si-St) and stand-to-sit (St-Si) tasks in stroke patients and explore the influence of duration on inter-joint coordination.

METHODS

Thirteen stroke hemiplegia patients (five with left paretic and eight right paretic) and thirteen age-matched healthy subjects were recruited. The Si-St and St-Si tasks were performed while each subject's joint kinematics were recorded using a three-dimensional motion capture system. Sagittal joint angles of the bilateral hip, knee and ankle joints as well as the movement duration were extracted. The angle-angle diagrams for the hip-knee, hip-ankle and knee-ankle joint were plotted to assess the inter-joint coordination. The inter-joint coordination was quantified using geometric characteristics of the angle-angle diagrams, including perimeter, area and dimensionless ratio. The coefficient of variation (CV) was performed to compare variability of the coordination parameters.

RESULTS

There were no significant differences in the perimeter, area and dimensionless ratio values of the bilateral hip-knee, hip-ankle and knee-ankle inter-joints during Si-St and St-Si tasks in the stroke group. The perimeter values of bilateral hip-knee and knee-ankle inter-joints in the stroke group were lower (P<0.05) than in the healthy group during Si-St and St-Si tasks. Although no significant bilateral differences were found, the inter-joint coordination in stroke patients decreased with the increased movement duration of both Si-St and St-Si tasks. Additionally, the CV of the hip-knee inter-joint area during the Si-St task in the stroke group was less than (P<0.05) that in the healthy group.

CONCLUSION

Stroke patients exhibit different inter-joint coordination patterns than healthy controls during the Si-St and St-Si tasks. The duration affects joint coordination, and inter-joint coordination is limited on the hemiplegic side joint pairs, which may lead to inconsistency in the rhythm of the left and right leg inter-joint movements and increase the risk of falls. These findings provide new insights into motor control rehabilitation strategies and may help planning targeted interventions for stoke patients with hemiplegia.

Concurrent and discriminant validity and reliability of an Android App to assess time, velocity and power during sit-to-stand test in community-dwelling older adults

INTRODUCTION

Nowadays, smartphones are equipped with the most sophisticated hardware which provides the opportunity to develop specific smartphone apps to analyze kinetic and kinematic parameters during sit-to-stand test in a clinical setting. The aims were to ascertain whether a new Android video-analysis based-App is comparable to the previously validated Apple-App for measuring time, velocity and power during sit-to-stand test, to determine its reliability and discriminant validity.

METHODS

One-hundred sixty-one older adults (61-86 years) were recruited from an elderly social center. Sit-to-stand variables were simultaneously recorded through the Android and Apple-App. Their validity and inter-rater, intra-rater, and test-retest reliability was tested using an intraclass correlation coefficient (ICC_2-1). Low gait speed (< 1.0 m/s), low physical performance (Short Physical Performance Battery < 10 points), and sarcopenia (EWGSOP2 guideline) were used to determine discriminant validity which was reported as the area under the curves (AUC) and their effect sizes (Hedges' g) for independent sample t-test.

RESULTS

Excellent reproducibility (ICC_2-1 > 0.85) and strong agreement (ICC_2-1 > 0.90) between operating systems for sit-to-stand variables derived from the App was found. Older adults classified as sarcopenic (11.2%), low physical performance (15.5%), or reduced gait speed (14.3%) showed worse sit-to-stand time, velocity and power with large effect sizes (Hedges' g: > 0.8) compared to their respective counterpart. These variables showed the acceptable-to-excellent ability to identify low gait speed, low physical performance, and sarcopenic older adults (AUC-range: 0.73-0.82).

CONCLUSION

The new Sit-to-Stand App running on the Android operating system is comparable to the previously validated Apple App. Excellent reproducibility and acceptable-to-excellent discriminant validity were found.

Design and evaluation of the pneumatic leg prosthesis ERiK to assist elderly amputees with sit-down and stand-up movements

Standing up using one leg is a challenging task for those with a transfemoral amputation, particularly for elderly users with a low activity level. Active prostheses are generally not accessible to this group and available passive prostheses do not support standing up. This article presents the design and evaluation of the "Energy Restoring Intelligent Knee" (ERiK), which stores energy during sit-down in a pneumatic cylinder and returns it during stand-up. We hypothesized that the system would reduce the time needed to perform transitions and also enable higher load sharing by the prosthetic leg. However, the results of an experimental study with seven participants with transfemoral amputation contradict these hypotheses: the participants could neither move faster nor make more use of the prosthetic leg to share their body weight during transitions. We observed that a major obstacle to the useful functionality of the leg was the absence of ankle dorsiflexion - the foot tended to slip during stand-up initiation, such that only low pre-pressures and therefore support levels could be set. The rather binary action of the pneumatics also complicated movement initiation. The lessons learned from this study may be helpful to those seeking to create better designs in the future.

Can a powered knee-ankle prosthesis improve weight-bearing symmetry during stand-to-sit transitions in individuals with above-knee amputations?

BACKGROUND

After above-knee amputation, the missing biological knee and ankle are replaced with passive prosthetic devices. Passive prostheses are able to dissipate limited amounts of energy using resistive damper systems during "negative energy" tasks like sit-down. However, passive prosthetic knees are not able to provide high levels of resistance at the end of the sit-down movement when the knee is flexed, and users need the most support. Consequently, users are forced to over-compensate with their upper body, residual hip, and intact leg, and/or sit down with a ballistic and uncontrolled movement. Powered prostheses have the potential to solve this problem. Powered prosthetic joints are controlled by motors, which can produce higher levels of resistance at a larger range of joint positions than passive damper systems. Therefore, powered prostheses have the potential to make sitting down more controlled and less difficult for above-knee amputees, improving their functional mobility.

METHODS

Ten individuals with above-knee amputations sat down using their prescribed passive prosthesis and a research powered knee-ankle prosthesis. Subjects performed three sit-downs with each prosthesis while we recorded joint angles, forces, and muscle activity from the intact quadricep muscle. Our main outcome measures were weight-bearing symmetry and muscle effort of the intact quadricep muscle. We performed paired t-tests on these outcome measures to test for significant differences between passive and powered prostheses.

RESULTS

We found that the average weight-bearing symmetry improved by 42.1% when subjects sat down with the powered prosthesis compared to their passive prostheses. This difference was significant (p = 0.0012), and every subject's weight-bearing symmetry improved when using the powered prosthesis. Although the intact quadricep muscle contraction differed in shape, neither the integral nor the peak of the signal was significantly different between conditions (integral p > 0.01, peak p > 0.01).

CONCLUSIONS

In this study, we found that a powered knee-ankle prosthesis significantly improved weight-bearing symmetry during sit-down compared to passive prostheses. However, we did not observe a corresponding decrease in intact-limb muscle effort. These results indicate that powered prosthetic devices have the potential to improve balance during sit-down for individuals with above-knee amputation and provide insight for future development of powered prosthetics.

Biopsychosocial Factors Related to Postural Sway During Sit-to-Stand Movement in Children and Adolescents With Down Syndrome: A Cross-Sectional Study

We investigated factors related to postural sway during sit-to-stand movement in children and adolescents with Down syndrome (DS). Our assessment of participants followed the biopsychosocial model. Body function and structure were represented by muscle strength and postural sway during sit-to-stand movement, which were assessed by manual muscle testing and kinetics analysis, respectively. The Gross Motor Function Measure and Pediatric Balance Scale depicted the activity component. In addition, we included these relevant contextual factors: age, Home Observation for Measurement of the Environment, family income, and maternal schooling. A correlation analysis verified a suspected association between biopsychosocial and postural sway variables. There were significant separated correlations between postural sway in the three phases of the sit-to-stand movement, and age, GMFM-88 dimension D, and muscle strength. Thus, postural control in sit-to-stand movement was related to biopsychosocial factors involving different life aspects of children and adolescents with DS, and these factors should be addressed in rehabilitation therapy intended to improve postural control among these individuals.

RGB-Depth Camera-Based Assessment of Motor Capacity: Normative Data for Six Standardized Motor Tasks

BACKGROUND

Instrumental motion analysis constitutes a promising development in the assessment of motor function in clinical populations affected by movement disorders. To foster implementation and facilitate interpretation of respective outcomes, we aimed to establish normative data of healthy subjects for a markerless RGB-Depth camera-based motion analysis system and to illustrate their use.

METHODS

We recorded 133 healthy adults (56% female) aged 20 to 60 years with an RGB-Depth camera-based motion analysis system. Forty-three spatiotemporal parameters were extracted from six short, standardized motor tasks-including three gait tasks, stepping in place, standing-up and sitting down, and a postural control task. Associations with confounding factors, height, weight, age, and sex were modelled using a predictive linear regression approach. A z-score normalization approach was provided to improve usability of the data.

RESULTS

We reported descriptive statistics for each spatiotemporal parameter (mean, standard deviation, coefficient of variation, quartiles). Robust confounding associations emerged for step length and step width in comfortable speed gait only. Accessible normative data usage was lastly exemplified with recordings from one randomly selected individual with multiple sclerosis.

CONCLUSION

We provided normative data for an RGB depth camera-based motion analysis system covering broad aspects of motor capacity.

Validity of an iPhone App to Detect Prefrailty and Sarcopenia Syndromes in Community-Dwelling Older Adults: The Protocol for a Diagnostic Accuracy Study

Prefrailty and sarcopenia in combination are more predictive of mortality than either condition alone. Early detection of these syndromes determines the prognosis of health-related adverse events since both conditions can be reversed through appropriate interventions. Nowadays, there is a lack of cheap, portable, rapid, and easy-to-use tools for detecting prefrailty and sarcopenia in combination. The aim of this study is to validate an iPhone App to detect prefrailty and sarcopenia syndromes in community-dwelling older adults. A diagnostic test accuracy study will include at least 400 participants aged 60 or over without cognitive impairment and physical disability recruited from elderly social centers of Murcia (Spain). Sit-to-stand muscle power measured through a slow-motion video analysis mobile application will be considered as the index test in combination with muscle mass (calf circumference or upper mid-arm circumference). Frailty syndrome (Fried's Phenotype) and sarcopenia (EWGSOP2) will both be considered as reference standards. Sensibility, specificity, positive and negative predictive values and likelihood ratios will be calculated as well as the area under the curve of the receiver operating characteristic. This mobile application will add the benefit for screening large populations in short time periods within a field-based setting, where space and technology are often constrained (NCT05148351).

The Effects of Specific Omega-3 and Omega-6 Polyunsaturated Fatty Acids and Antioxidant Vitamins on Gait and Functional Capacity Parameters in Patients with Relapsing-Remitting Multiple Sclerosis

Patients with multiple sclerosis (MS) are characterized by, among other symptoms, impaired functional capacity and walking difficulties. Polyunsaturated fatty acids (PUFAs) have been found to improve MS patients' clinical outcomes; however, their effect on other parameters associated with daily living activities need further investigation. The current study aimed to examine the effect of a 24-month supplementation with a cocktail dietary supplement formula, the NeuroaspisTM PLP10, containing specific omega-3 and omega-6 PUFAs and specific antioxidant vitamins on gait and functional capacity parameters of patients with MS. Fifty-one relapsing-remitting MS (RRMS) patients with low disability scores (age: 38.4 ± 7.1 years; 30 female) were randomized 1:1 to receive either a 20 mL daily dose of the dietary formula containing a mixture of omega-3 and omega-6 PUFAs (12,150 mg), vitamin A (0.6 mg), vitamin E (22 mg), and γ-tocopherol (760 mg), the OMEGA group (n = 27; age: 39 ± 8.3 years), or 20 mL placebo containing virgin olive oil, the placebo group (n = 24; age: 37.8 ± 5.3 years). The mean ± SD (standard deviation) Expanded Disability Status Scale (EDSS) score for the placebo group was 2.36 and for the OMEGA group 2.22. All enrolled patients in the study were on Interferon-β treatment. Spatiotemporal gait parameters and gait deviation index (GDI) were assessed using a motion capture system. Functional capacity was examined using various functional tests such as the six-minute walk test (6MWT), two sit-to-stand tests (STS-5 and STS-60), and the Timed Up and Go test (TUG). Isometric handgrip strength was assessed by a dynamometer. Leg strength was assessed using an isokinetic dynamometer. All assessments were performed at baseline and at 12 and 24 months of supplementation. A total of 36 patients completed the study (18 from each group). Six patients from the placebo group and 9 patients from the OMEGA group dropped out from the study or were lost to follow-up. The dietary supplement significantly improved the single support time and the step and stride time (p < 0.05), both spatiotemporal gait parameters. In addition, while GDI of the placebo group decreased by about 10% at 24 months, it increased by about 4% in the OMEGA group (p < 0.05). Moreover, performance in the STS-60 test improved in the OMEGA group (p < 0.05) and there was a tendency for improvement in the 6MWT and TUG tests. Long-term supplementation with high dosages of omega-3 and omega-6 PUFAs (compared to previous published clinical studies using PUFAs) and specific antioxidant vitamins improved some functional capacity and gait parameters in RRMS patients.

Toward Phase-Variable Control of Sit-to-Stand Motion with a Powered Knee-Ankle Prosthesis

This paper presents a new model and phase-variable controller for sit-to-stand motion in above-knee amputees. The model captures the effect of work done by the sound side and residual limb on the prosthesis, while modeling only the prosthetic knee and ankle with a healthy hip joint that connects the thigh to the torso. The controller is parametrized by a biomechanical phase variable rather than time and is analyzed in simulation using the model. We show that this controller performs well with minimal tuning, under a range of realistic initial conditions and biological parameters such as height and body mass. The controller generates kinematic trajectories that are comparable to experimentally observed trajectories in non-amputees. Furthermore, the torques commanded by the controller are consistent with torque profiles and peak values of normative human sit-to-stand motion. Rise times measured in simulation and in non-amputee experiments are also similar. Finally, we compare the presented controller with a baseline proportional-derivative controller demonstrating the advantages of the phase-based design over a set-point based design.

Sex and age influence on postural sway during sit-to-stand movement in children and adolescents: Cross-sectional study

We investigated the influence of sex and age in postural sway during sit-to-stand (STS) in children and adolescents of 5-15 years. We evaluated sway during STS in 86 typical participants. STS was divided into three phases: preparation, rising, and stabilization. We calculated for each phase: area, anterior-posterior, and medial-lateral velocity of center-of-pressure sway. We applied a stepwise multiple linear regression model to determine if age and sex might be predictors of postural sway during STS. Only age was associated with sway, accounting for between 6.5% and 14.6% of the variability in sway during STS. The age of the subject influences postural sway during STS, but in a small amount. This variable should be taken into account as a variable of control in the assessment of dynamic postural control. Moreover, postural stability during STS was not associated with the sex of the participants.

Kinematic analysis of the human body during sit-to-stand in healthy young adults

Sit-to-stand (STS) motion is one of the most important and energy-consuming basic motions in everyday life. Kinematic analysis provides information regarding what strategy or motion pattern is used by the healthy people, and through which, we can understand and obtain the law of the STS motion. The objective of this article is to study the law of STS motion through the experiment to determine a suitable description of STS motion in healthy adults, so as to provide a starting point and bases for future design and control of STS assistive devices.Thirty healthy adult subjects participated in this study and carried out STS motion experiment of standing up naturally. The STS motions were recorded using a high-definition camera. The experimentally collected kinematic data and a link segment model of the human body were used to obtain the coordinates of joints and to calculate the coordinates, velocity, and momentum of center of gravity; the postures of human body during STS are also obtained. The relationship between human body parameters and motion parameters is analyzed by using Pearson correlation method.The STS motion is divided into 4 phases; the phases are differentiated in terms of STS motion characteristics and postures, and momentum of center of gravity of human body. The main factors determining the differences in STS motion among individuals are horizontal distance between hip joint and ankle joint, lower leg length, thigh length, and the length of the transition period. The horizontal distance between hip joint and ankle joint is positively correlated with the duration from motion begin to trunk stops flexing forward (P = .021 < .05), but not so with the duration from motion begin to the end of phase 2 (P = .15 > .05).The results suggest that when designing the sit-to-stand assistive devices, one should pay attention to the whole-body posture control in STS motion, such as the posture guidance of trunk and lower leg, and should carry out specific training according to different STS phases. Sit-to-stand assistive devices should provide the same horizontal distance between hip joint and ankle joint for different individuals during the STS motion. Transition period should be properly controlled, and the degree of freedom of the lower leg should not be limited.

Trunk kinematics and muscle activation patterns during stand-to-sit movement and the relationship with postural stability in aging

BACKGROUND

Stand-to-sit (StandTS) movement is an important functional activity that can be challenging for older adults due to age-related changes in neuromotor control. Although trunk flexion, eccentric contraction of the rectus femoris (RF), and coordination of RF and biceps femoris (BF) muscles are important to the StandTS task, the effects of aging on these and related outcomes are not well studied.

RESEARCH QUESTION

What are the age-related differences in trunk flexion, lower extremity muscle activation patterns, and postural stability during a StandTS task and what is the relationship between these variables?

METHODS

Ten younger and ten older healthy adults performed three StandTS trials at self-selected speeds. Outcomes included peak amplitude, peak timing, burst duration, and onset latency of electromyography (EMG) activity of the RF and BF muscles, trunk flexion angle and angular velocity, whole body center of mass (CoM) displacement, center of pressure (CoP) velocity, and ground reaction force (GRF).

RESULTS

There were no age-related differences in weight-bearing symmetry, StandTS and trunk flexion angular velocity, or BF activity. In both groups, EMG peak timing of RF was preceded by BF. Compared to younger adults, older adults demonstrated shorter RF EMG burst duration, reduced trunk flexion, and reduced stability as indicated by the longer duration in which CoM was maintained beyond the posterior limit of base of support (BoS), greater mean anterior-posterior CoP velocity and larger standard deviation of CoM vertical acceleration during StandTS with smaller vertical GRF immediately prior to StandTS termination. Trunk flexion angle and RF EMG burst duration correlated with stability as measured by the duration in which the CoM stayed within the BoS.

SIGNIFICANCE

Decreased trunk flexion and impaired eccentric control of the RF are associated with StandTS instability in aging and suggest the importance of including StandTS training as a part of a comprehensive balance intervention.

A Novel Simplified System to Estimate Lower-Limb Joint Moments during Sit-to-Stand

To provide effective diagnosis and rehabilitation, the evaluation of joint moments during sit-to-stand is essential. The conventional systems for the evaluation, which use motion capture cameras, are quite accurate. However, the systems are not widely used in clinics due to their high cost, inconvenience, and the fact they require lots of space. To solve these problems, some studies have attempted to use inertial sensors only, but they were still inconvenient and inaccurate with asymmetric weight-bearing. We propose a novel joint moment estimation system that can evaluate both symmetric and asymmetric sit-to-stands. To make a simplified system, the proposal is based on a kinematic model that estimates segment angles using a single inertial sensor attached to the shank and a force plate. The system was evaluated with 16 healthy people through symmetric and asymmetric weight-bearing sit-to-stand. The results showed that the proposed system (1) has good accuracy in estimating joint moments (root mean square error < 0.110 Nm/kg) with high correlation (correlation coefficient > 0.99) and (2) is clinically relevant due to its simplicity and applicability of asymmetric sit-to-stand.

Sit-To-Stand Movement Evaluated Using an Inertial Measurement Unit Embedded in Smart Glasses-A Validation Study

Wearable sensors have recently been used to evaluate biomechanical parameters of everyday movements, but few have been located at the head level. This study investigated the relative and absolute reliability (intra- and inter-session) and concurrent validity of an inertial measurement unit (IMU) embedded in smart eyeglasses during sit-to-stand (STS) movements for the measurement of maximal acceleration of the head. Reliability and concurrent validity were investigated in nineteen young and healthy participants by comparing the acceleration values of the glasses’ IMU to an optoelectronic system. Sit-to-stand movements were performed in laboratory conditions using standardized tests. Participants wore the smart glasses and completed two testing sessions with STS movements performed at two speeds (slow and comfortable) under two different conditions (with and without a cervical collar). Both the vertical and anteroposterior acceleration values were collected and analyzed. The use of the cervical collar did not significantly influence the results obtained. The relative reliability intra- and inter-session was good to excellent (i.e., intraclass correlation coefficients were between 0.78 and 0.91) and excellent absolute reliability (i.e., standard error of the measurement lower than 10% of the average test or retest value) was observed for the glasses, especially for the vertical axis. Whatever the testing sessions in all conditions, significant correlations (p < 0.001) were found for the acceleration values recorded either in the vertical axis and in the anteroposterior axis between the glasses and the optoelectronic system. Concurrent validity between the glasses and the optoelectronic system was observed. Our observations indicate that the IMU embedded in smart glasses is accurate to measure vertical acceleration during STS movements. Further studies should investigate the use of these smart glasses to assess the STS movement in unstandardized settings (i.e., clinical and/or home) and to report vertical acceleration values in an elderly population of fallers and non-fallers.

Sit-to-Stand Muscular Activity for Different Seat Backrest Inclination Levels and Execution Speeds

The sit-to-stand transfer can be separated into a postural phase (trunk flexion) and a focal phase (whole-body extension). The aim of this study was to analyze the as yet little known whole-body muscular activity characterizing each phase of this task and its variations with backrest inclination and execution speed. Fifteen muscles of the trunk and lower limbs of 10 participants were investigated using surface EMG. Results showed that backrest-induced modifications were mostly confined to the postural phase: reclining the backrest increased its duration and the activity level of the sternocleidomastoideus, the rectus and obliquus externus abdominis, and the semitendinosus. Speed-induced variations were also predominant during the postural phase, which was shortened with an increased activity of most muscles at maximal speed.

Impact of dual task on postural sway during sit-to-stand movement in children with unilateral cerebral palsy

BACKGROUND

To verify the effect of dual-task on postural oscillation during sit-to-stand movement in children with Cerebral Palsy.

METHODS

17 children with spastic unilateral cerebral palsy and 20 typically-developing children, aged 5 to 12 years, performed the following tasks: Simple task: sit-to-stand with arms crossed against the chest; bimanual dual-task: sit-to-stand while carrying a tray; unimanual dual-task: sit-to-stand while holding a plastic cup with one hand. For data analysis, sit-to-stand was divided in three phases: preparation (phase 1), rising (phase 2), and stabilization (phase 3). Postural control was measured using a force plate, and the variables analyzed were: area, anterior-posterior and medial-lateral velocity, and STS duration. Analysis of variance was applied to test the effects of group; task conditions and interactions.

FINDINGS

Children with cerebral palsy presented higher values of postural oscillation when compared to their typical pairs. Bimanual and Unimanual dual tasks presented greater postural oscillation values in sit-to-stand phase 1 compared to simple task. In bimanual dual-task, children with cerebral palsy presented lower values of velocity in phases 3, and greater postural oscillation and duration of the task when compared to single-task and unimanual dual-tasks. I.

INTERPRETATION

The insertion of a secondary task seems to interfere differently children with cerebral palsy, depending on the specific demands of each task. Thus, the importance of inserting dual tasks in the interventions is emphasized, considering that they are executed extensively in the day to day, and can act as facilitators or challenge in the execution of functional tasks.

Metrics extracted from a single wearable sensor during sit-stand transitions relate to mobility impairment and fall risk in people with multiple sclerosis

BACKGROUND

Approximately half of the 2.3 million people with multiple sclerosis (PwMS) will fall in any three-month period. Currently clinicians rely on self-report measures or simple functional assessments, administered at discrete time points, to assess fall risk. Wearable inertial sensors are a promising technology for increasing the sensitivity of clinical assessments to accurately predict fall risk, but current accelerometer-based approaches are limited.

RESEARCH QUESTION

Will metrics derived from wearable accelerometers during a 30-second chair stand test (30CST) correlate with clinical measures of disease severity, balance confidence and fatigue in PwMS, and can these metrics be used to accurately discriminate fallers from non-fallers?

METHODS

Thirty-eight PwMS (21 fallers) completed self-report outcome measures then performed the 30CST while triaxial acceleration data were collected from inertial sensors adhered to the thigh and chest. Accelerometer metrics were derived for the sit-to-stand and stand-to-sit transitions and relationships with clinical metrics were assessed. Finally, the metrics were used to develop a logistic regression model to classify fall status.

RESULTS

Accelerometer-derived metrics were significantly associated with multiple clinical metrics that capture disease severity, balance confidence and fatigue. Performance of a logistic regression for classifying fall status was enhanced by including accelerometer features (accuracy 74%, AUC 0.78) compared to the standard of care (accuracy 68%, AUC 0.74) or patient reported outcomes (accuracy 71%, AUC 0.75).

SIGNIFICANCE

Accelerometer derived metrics were associated with clinically relevant measures of disease severity, fatigue and balance confidence during a balance challenging task. Inertial sensors could feasibly be utilized to enhance the accuracy of functional assessments to identify fall risk in PwMS. Simplicity of these accelerometer-based metrics could facilitate deployment for community-based monitoring.

Modified desk height helps children with cerebral palsy perform sit-to-stand

Aim: Children with cerebral palsy (CP) have difficulties performing activities that require the use of fundamental motor skills such as sit-to-stand (STS). In this study, we used a height adjustable chair and desk to investigate the role of desk support in STS and how it might benefit children with CP. Methods: Seventeen typically developing children (TDC), average age = 9.7 years, and 28 children with CP (Gross Motor Function Classification System [GMFCS] I and II), average age = 10.3 years, participated in the test. Elapsed time and body sway were measured using a pressure mat and load cell while each child performed a STS task. Two different desk heights were tested for time consumption and sway under the condition of hands-on-desk and arms-crossed. Results: We found that the elapsed time of hands-on-desk with the elbow flexion height was the shortest (p < 0.05). Sway amount was also significantly reduced for all children when they used the table for STS (p < 0.05). Conclusion: Results of this study may be a useful reference in rehabilitation training and designing a desk height beneficial for children with CP.Implications for RehabilitationBetter performance of sit-to-stand for a child with cerebral palsy could be made by a desk supportElapsed time during preparation period for sit-to-stand could be reduced by desk support for all CP childrenSway amount during sit-to-stand could be reduced by desk support, especially for the CP children with GMFCS level IIDesk height is an important parameter and should be studied in detail.

Classification of standing and sitting phases based on in-socket piezoelectric sensors in a transfemoral amputee

A transfemoral prosthesis is required to assist amputees to perform the activity of daily living (ADL). The passive prosthesis has some drawbacks such as utilization of high metabolic energy. In contrast, the active prosthesis consumes less metabolic energy and offers better performance. However, the recent active prosthesis uses surface electromyography as its sensory system which has weak signals with microvolt-level intensity and requires a lot of computation to extract features. This paper focuses on recognizing different phases of sitting and standing of a transfemoral amputee using in-socket piezoelectric-based sensors. 15 piezoelectric film sensors were embedded in the inner socket wall adjacent to the most active regions of the agonist and antagonist knee extensor and flexor muscles, i. e. region with the highest level of muscle contractions of the quadriceps and hamstring. A male transfemoral amputee wore the instrumented socket and was instructed to perform several sitting and standing phases using an armless chair. Data was collected from the 15 embedded sensors and went through signal conditioning circuits. The overlapping analysis window technique was used to segment the data using different window lengths. Fifteen time-domain and frequency-domain features were extracted and new feature sets were obtained based on the feature performance. Eight of the common pattern recognition multiclass classifiers were evaluated and compared. Regression analysis was used to investigate the impact of the number of features and the window lengths on the classifiers’ accuracies, and Analysis of Variance (ANOVA) was used to test significant differences in the classifiers’ performances. The classification accuracy was calculated using k-fold cross-validation method, and 20% of the data set was held out for testing the optimal classifier. The results showed that the feature set (FS-5) consisting of the root mean square (RMS) and the number of peaks (NP) achieved the highest classification accuracy in five classifiers. Support vector machine (SVM) with cubic kernel proved to be the optimal classifier, and it achieved a classification accuracy of 98.33 % using the test data set. Obtaining high classification accuracy using only two time-domain features would significantly reduce the processing time of controlling a prosthesis and eliminate substantial delay. The proposed in-socket sensors used to detect sit-to-stand and stand-to-sit movements could be further integrated with an active knee joint actuation system to produce powered assistance during energy-demanding activities such as sit-to-stand and stair climbing. In future, the system could also be used to accurately predict the intended movement based on their residual limb’s muscle and mechanical behaviour as detected by the in-socket sensory system.

The development of sit-to-stand in typically developing children aged 4 to 12 years: Movement time, trunk and lower extremity joint angles, and joint moments

BACKGROUND

Sit-to-stand (STS) movement is an important transition movement for daily life. STS movement is typically seen in children aged 1 year and older. According to the motor development process, the ability of children in different age groups to perform STS movement would be different before they meet the mutuality. However, it is still unclear whether there are changes in the STS movement of growing children and adults.

RESEARCH QUESTION

Are there any differences in the movement time, joint angles, and peak joint moments of STS in typically developing (TD) children?

METHODS

Motion analysis and the force plate system were used to analyze the STS movement in 77 healthy participants. All participants were asked to perform the STS movement using an adjustable bench with a self-selected pattern. Statistical analysis was done with respect to age (4-6, 7-9, 10-12, 18-25 years) and body height (1.00-1.20, 1.20-1.40, 1.40-1.60, 1.60-1.80 meters).

RESULTS

Children aged 4-6 years (or 1.0-1.20 m height) took less time to accomplish STS movement than adults (or 1.60-1.80 m height). Children aged 4-9 years performed STS movement by using more trunk and hip flexion and anterior pelvic tilt, but less knee flexion and ankle dorsiflexion than children aged 10-12 years and adults. At the final standing position, children aged 4-12 years exhibited more knee extension and more ankle plantar flexion than adults. In addition, children aged 4-12 years had more peak trunk-pelvic extension and less peak knee extension moments than adults.

SIGNIFICANCE

Different strategies to achieve the STS task were found among children aged 4-12 years in terms of total movement time, joint angle, and joint moments. Adult-like kinematic and kinetic STS patterns were not seen in children up to 12 years old.

Toward clinically-relevant joint moment estimation during sit to stand: a feasibility study

Conventional motion analysis system to measure joint moment during sit to stand is impractical to be used in clinics. Inertial sensor-based motion analysis system has been proposed to improve usability. In this study, we propose a simple system that can predict joint moment, especially maximum joint moment, with a minimum number of an inertial sensor attached and force plate; shank and thigh angles were estimated with a kinematic model and an effective joint moment analysis period. Through a validation experiment with eight subjects, the estimated joint moments were comparable to be actual joint moment measured by the conventional system, also the previous study with the inertial system.

Stand-to-Sit Kinematics of the Pelvis Is Not Always as Expected: Hip and Spine Pathologies Can Have an Impact

BACKGROUND

Stand-to-sit pelvis kinematics is commonly considered as a rotation around the bicoxofemoral axis. However, abnormal kinematics could occur for patients with musculoskeletal disorders, affecting the hip-spine complex. The aim of this study is to perform a quantitative analysis of the stand-to-sit pelvis kinematics using 3D reconstruction from biplanar x-rays.

METHODS

Thirty volunteers as a control group (C), 30 patients with hip pathology (Hip), and 30 patients with spine pathology (Spine) were evaluated. All subjects underwent standing and sitting full-body biplanar x-rays. Three-dimensional reconstruction was performed in each configuration and then translated such as the middle of the line joining the center of each acetabulum corresponds to the origin. Rigid registration quantified the finite helical axis (FHA) describing the transition between standing and sitting with two specific parameters. The orientation angle (OA) is the signed 3D angle between FHA and bicoxofemoral axis, and the rotation angle (RA) represents the signed angle around FHA.

RESULTS

The mean OA was -1.8° for the C group, 0.3° for Hip group, and -2.4° for Spine group. There was no significant difference in mean OA between groups. However, variability was higher for the Spine group with a standard deviation (SD) of 15.9° compared with 10.8° in the C group and 12.3° in the Hip group. The mean RA in the C group was 18.1° (SD, 9.0°). There was significant difference in RA between the Hip and Spine groups (21.1° [SD, 8.0°] and 16.4° [SD, 10.8°], respectively) (P = .04).

CONCLUSION

Hip and spine pathologies affect stand-to-sit pelvic kinematics.

Dual-task effects on postural sway during sit-to-stand movement in children with Down syndrome

BACKGROUND

Cognitive and postural tasks require common cognitive mechanisms, resulting in conflicts when both tasks are simultaneously performed. The presence of neuromotor dysfunctions, such as Down syndrome, may impair coordination processes required to perform dual-tasks. The objective of this study was to investigate the dual-task effects on postural sway during sit-to-stand movements in typical children and children with Down syndrome in a cross-sectional study.

METHODS

Twenty six typical children (10.2 ± 2.4 years) and 21 with Down syndrome (10.3 ± 2.3 years) performed sit-to-stand in the following conditions: (1) simple task; (2) dual-task bimanual activity (DT-Bim): sit-to-stand while carrying a tray using both hands; (3) dual-task unimanual dominant activity (DT-Uni-Dom): sit-to-stand while holding a plastic cup simulating water using the dominant hand; (4) dual-task unimanual non-dominant activity (DT-Uni-Nondom): sit-to-stand movement while holding a plastic cup simulating water. For data analysis, sit-to-stand was divided into three phases: preparation (phase 1), rising (phase 2), and stabilisation (phase 3). The following variables were calculated for each phase: anterior-posterior and medial-lateral amplitude of centre-of-pressure displacement, anterior-posterior and medial-lateral velocity of centre-of-pressure sway and area of centre-of-pressure sway.

RESULTS

Children with Down syndrome showed greater sway than typical children in all sit-to-stand phases. Typical children showed greater anterior-posterior amplitude in phase 2 of sit-to-stand during DT-Uni Nondom compared with DT-Uni Dom. Children with Down syndrome during simple task condition showed greater and faster values sway in phases 2 and 3 of sit-to-stand movement than in DT-Bim activity, DT-Uni Dom activity and DT-Uni Nondom activity. During the condition of DT-Bim activity, these children showed lower anterior-posterior velocity of sway in phase 2 than during DT-Uni Dom activity.

CONCLUSIONS

Children with Down syndrome showed greater postural sway during sit-to-stand than typical children. The addition of a concurrent motor task to sit-to-stand impacted postural sway in different intensities and in different ways across groups. Dual-tasks increased body sway in typical children in the DT-Uni Nondom condition compared with dominant one. In children with Down syndrome, dual-tasks decreased body sway, apparently resulting in a postural strategy of stiffness.

Do the center of mass strategies change with restricted vision during the sit-to-stand task?

BACKGROUND

The relationship between the visual sensory and center-of-mass characteristics during the sit-to-stand task is not well documented. Do the center of mass strategies change with restricted vision during the sit-to-stand task?

METHODS

The participants in this study were fifteen girls with congenital blindness (age (94.6 (5.6) months), mass (25.6 (2.0) kg), and height (1.3 (0.0) m)) and 30 healthy girls with no visual impairment who were divided randomly into two groups. The two experimental condition groups consisted of one in which the participants were assigned to keep their eyes open (age (95.8 (5.4) months), by mass (26.1 (5.1) kg), and by height (1.3 (0.0) m)) and the other in which the participants were assigned to keep their eyes closed (age (93.8 (0.0) months), by mass (24.2 (0.0) kg), and by height (1.1 (0.0) m)) for 20 min before the test. The center-of-mass displacement of the foot, leg, and thigh were calculated for dominance and non-dominance during the sit-to-stand performance at initiation, seat-off, and end events.

FINDINGS

Congenital blindness was associated with the non-dominant center-of-mass displacement of the foot increasing upwards during all events (initiation, p = 0.025; seat-off, p = 0.036; end, p = 0.034), as well the non-dominant center of mass of the foot moving anteriorly during the initiation point (p = 0.016). In addition, the center-of-mass displacements for the dominant and non-dominant feet (initiation, p = 0.006, and p = 0.016; seat-off, p = 0.006, and p = 0.014; end, p = 0.006, and p = 0.013, respectively) and legs (16.98%, p = 0.024, d = 0.95; and 17.88%, p = 0.032, d = 0.99, respectively) in the eyes-closed group shifted to a forward direction, and the center of mass of the non-dominant foot (initiation, p = 0.024; seat-off, p = 0.021; end, p = 0.012) moved significantly upwards. Furthermore, the whole body center of the mass velocity (anterior-posterior axis (initiation, p = 0.042; seat-off, p = 0.006; end, p = 0.005)) in the eyes-closed group was smaller than that in the eyes-open group.

INTERPRETATION

The findings show that the sit-to-stand center of the mass components in blind children may have clinical importance for the rehabilitation of these subjects.

Tracking Kinematic and Kinetic Measures of Sit to Stand using an Instrumented Spine Orthosis

Age related spinal deformity is becoming an increasingly prevalent problem, resulting in decreased quality of life. While spinal deformity can be corrected via surgical intervention, a large number of people with spinal fusions require follow-up surgery due to further degeneration. The identification of changes to a subjects kinematics and kinetics post-surgery are limited by a lack of methods to collect patient specific motion data over the course of surgical recovery. This paper introduces an Instrumented Spine Orthosis (ISO) that can capture the motions of the subjects torso without requiring the use of a control computer or other dedicated motion capture equipment. This system is used to collect the peak torso angles and velocities for a single subject performing sit-to-stand actions. The accuracy of the ISO is evaluated using motion capture, during different sit-to-stand protocols designed to highlight motion changes that have been seen in subjects with reduced mobility. This system was found to provide reliable measurements of these kinematic and kinetic torso measures across all tested motions, demonstrating the potential for the use of Instrumented Spine Orthotics to provide quantitative measures during the surgical recovery process.

The effect of time restricted visual sensory input on asymmetry of ground reaction force components in female children

The association between visual sensory and the asymmetry index of sit-to-stand ground reaction force characteristics is not fully understood. Therefore, the purpose of this study was to investigate asymmetry index of sit-to-stand ground reaction forces, their times-to-peak, vertical loading rate, impulses, and free moment in blind and sighted children. 15 female children with congenital blindness and 30 healthy girls with no visual impairments volunteered to participate in this study. The girls with congenital blindness were placed in one group and the girls with no visual impairments were randomly divided into two groups of 15. The two condition groups consisted of, one eyes open and the other, eyes closed. The participants in the eyes closed group were asked to close their eyes for 20 min before the test, whereas those in the eyes open group kept their eyes open. Kinematic and kinetic data were collected using an eight-camera motion analysis system synchronized with two force plates embedded in the floor. A MANOVA test was run for between-group comparisons. There were no distinctive biomechanical alternations in all axes of ground reaction forces and their times-to-peak, vertical loading rate, impulses and free moments in congenital blindness and eyes closed groups compared with the eyes open group. However, eyes closed was associated with increased total time and second phase duration of sit-to-stand performance by 69% (p = 0.008) and 62% (p = 0.008), respectively. These findings reveal that individuals who are visually restricted in the short term, do not develop stereotypical movement strategies for sit-to-stand.

Constrained Dynamic Optimization of Sit-to-Stand Motion Driven by Bézier Curves

The purpose of this work is twofold: first, to synthesize a motion pattern imitating sit-to-stand (STS) and second, to compare the kinematics and dynamics of the resulting motion to healthy STS. Predicting STS in simulation inspired the creation of three models: a biomechanical model, a motion model, and performance criteria as a model of preference. First, the human is represented as three rigid links in the sagittal plane. This model captures aspects of joint, foot, and buttocks physiology, which makes it the most comprehensive planar model for predicting STS to date. Second, candidate STS trajectories are described geometrically by a set of Bézier curves which seem well suited to predictive biomechanical simulations. Third, with the assumption that healthy people naturally prioritize mechanical efficiency, disinclination to a motion is described as a cost function of joint torques, and for the first time, physical infeasibility including slipping and falling. This new dynamic optimization routine allows for motions of gradually increasing complexity while the model's performance is improving. Using these models and optimal control strategy together has produced gross motion patterns characteristic of healthy STS when compared with normative data from the literature.

Thigh-Derived Inertial Sensor Metrics to Assess the Sit-to-Stand and Stand-to-Sit Transitions in the Timed Up and Go (TUG) Task for Quantifying Mobility Impairment in Multiple Sclerosis

Introduction: Inertial sensors generate objective and sensitive metrics of movement disability that may indicate fall risk in many clinical conditions including multiple sclerosis (MS). The Timed-Up-And-Go (TUG) task is used to assess patient mobility because it incorporates clinically-relevant submovements during standing. Most sensor-based TUG research has focused on the placement of sensors at the spine, hip or ankles; an examination of thigh activity in TUG in multiple sclerosis is wanting. Methods: We used validated sensors (x-IMU by x-io) to derive transparent metrics for the sit-to-stand (SI-ST) transition and the stand-to-sit (ST-SI) transition of TUG, and compared effect sizes for metrics from inertial sensors on the thighs to effect sizes for metrics from a sensor placed at the L3 level of the lumbar spine. Twenty-three healthy volunteers were compared to 17 ambulatory persons with MS (PwMS, HAI ≤ 2). Results: During the SI-ST transition, the metric with the largest effect size comparing healthy volunteers to PwMS was the Area Under the Curve of the thigh angular velocity in the pitch direction-representing both thigh and knee extension; the peak of the spine pitch angular velocity during SI-ST also had a large effect size, as did some temporal measures of duration of SI-ST, although less so. During the ST-SI transition the metric with the largest effect size in PwMS was the peak of the spine angular velocity curve in the roll direction. A regression was performed. Discussion: We propose for PwMS that the diminished peak angular velocity during SI-ST directly represents extensor weakness, while the increased roll during ST-SI represents diminished postural control. Conclusions: During the SI-ST transition of TUG, angular velocities can discriminate between healthy volunteers and ambulatory PwMS better than temporal features. Sensor placement on the thighs provides additional discrimination compared to sensor placement at the lumbar spine.

A model based analysis of optimality of sit-to-stand transition

Objective assessment of mobility and effectiveness of interventions remains an open issue. Timed Up and Go (TUG) and 30 Second Chair Stand (30SCS) tests are routinely used in assessing mobility of subjects, but they provide a single parameter. Instrumenting subjects with wearable sensors enables a detailed mobility assessment. Specifically, we argue that instrumented sit-to-stand (S2ST) posture transitions during the TUG and 30SCS tests can be used to assess the strength and balance of subjects. In this paper we develop a personalized three-segment model that quantifies torques/forces on the body and assesses optimality of each sit-to-stand transition. To characterize a S2ST transition we calculate action defined as an integral of mechanical energy over time. The theoretical optimal transition time can thus be determined for each person by finding the minimum action necessary for a S2ST transition. Our model assesses action during the S2ST transition using inputs from smartphone's inertial sensors, and calculates optimum S2ST transition time for a given body composition of a subject. Our experimental evaluation shows that healthy young subjects have posture transition times close to the optimal transition time generated by the model. We hypothesize that the optimality of posture transition provides an objective and potentially more accurate estimation of the mobility. We tested the model by evaluating optimum action and optimum S2ST transition time for 10 geriatric patients undergoing a mobility improvement program by comparing their performance with the optimum performance generated by the model. This paper presents the model and possible use of the results to assess long-term changes in mobility of users.

Safer chairs for elderly patients: design evaluation using electromyography and force measurement

A vast majority of patient fall events in hospitals involve the elderly. In inpatient care settings, despite the risk of fall, patients are encouraged to leave their bed, move around their room, and sit on their chair to progress in their healing. Despite the vital role of patient chair design in improving recovery, few studies have examined the ergonomic requirements of safe patient chairs. This study examined the impact of manipulating horizontal and vertical positions of armrests in a test chair on required physical effort during Stand-to-Sit-to-Stand (St-Si-St) transitions among 15 elderly women. Physical effort was measured using: (1) surface electromyography (sEMG); (2) force measurement by load cells; (3) video recording. Findings showed non-linear patterns of change in required physical effort due to changes in armrests' height and distance. It was also found that minimum effort is associated with armrests higher and farther apart than those in typical patient chairs. Practitioner Summary: Safe chairs are essential for inpatient recovery, yet their ergonomic features are not investigated. Impact of changes in chair armrests on required physical effort was examined using electromyography, force measurement and video recording. Armrests higher and farther apart than those in typical patient chairs may be safer for elderly patients.

Nondestructive Estimation of Muscle Contributions to STS Training with Different Loadings Based on Wearable Sensor System

Partial body weight support or loading sit-to-stand (STS) rehabilitation can be useful for persons with lower limb dysfunction to achieve movement again based on the internal residual muscle force and external assistance. To explicate how the muscles contribute to the kinetics and kinematics of STS performance by non-invasive in vitro detection and to nondestructively estimate the muscle contributions to STS training with different loadings, a wearable sensor system was developed with ground reaction force (GRF) platforms, motion capture inertial sensors and electromyography (EMG) sensors. To estimate the internal moments of hip, knee and ankle joints and quantify the contributions of individual muscle and gravity to STS movement, the inverse dynamics analysis on a simplified STS biomechanical model with external loading is proposed. The functional roles of the lower limb individual muscles (rectus femoris (RF), gluteus maximus (GM), vastus lateralis (VL), tibialis anterior (TA) and gastrocnemius (GAST)) during STS motion and the mechanism of the muscles' synergies to perform STS-specific subtasks were analyzed. The muscle contributions to the biomechanical STS subtasks of vertical propulsion, anteroposterior (AP) braking and propulsion for body balance in the sagittal plane were quantified by experimental studies with EMG, kinematic and kinetic data.

Noninvasive Estimation of Joint Moments with Inertial Sensor System for Analysis of STS Rehabilitation Training

An original approach for noninvasive estimation of lower limb joint moments for analysis of STS rehabilitation training with only inertial measurement units was presented based on a piecewise three-segment STS biomechanical model and a double-sensor difference based algorithm. Joint kinematic and kinetic analysis using a customized wearable sensor system composed of accelerometers and gyroscopes were presented and evaluated compared with a referenced camera system by five healthy subjects and five patients in rehabilitation. Since there is no integration of angular acceleration or angular velocity, the result is not distorted without offset and drift. Besides, since there are no physical sensors implanted in the lower limb joints based on the algorithm, it is feasible to noninvasively analyze STS kinematics and kinetics with less numbers and types of inertial sensors than those mentioned in other methods. Compared with the results from the reference system, the developed wearable sensor system is available to do spatiotemporal analysis of STS task with fewer sensors and high degree of accuracy, to apply guidance and reference for rehabilitation training or desired feedback for the control of powered exoskeleton system.

Progressive intervention strategy for the gait of sub-acute stroke patient using the International Classification of Functioning, Disability, and Health tool

BACKGROUND

The International Classification of Functioning, Disability, and Health (ICF) provides models for functions and disabilities. The ICF is presented as a frame that enables organizing physical therapists' clinical practice for application.

OBJECTIVE

The purpose of the present study was to describe processes through which stroke patients are assessed and treated based on the ICF model.

METHODS

The patient was a 65-year-old female diagnosed with right cerebral artery infarction with left hemiparesis. Progressive interventions were applied, such as those aiming at sitting and standing for the first two weeks, gait intervention for the third and fourth weeks, and those aiming at sitting from a standing position for the fifth and sixth weeks.

RESULTS

The ICF model provides rehabilitation experts with a frame that enables them to accurately identify and understand their patients' problems. The ICF model helps the experts understand not only their patients' body structure, function, activity, and participation, but also their problems related to personal and environmental factors.

CONCLUSIONS

The experts could efficiently make decisions and provide optimum treatment at clinics using the ICF model.