STS Task Research Articles

Pelvic and Lower Limb Kinematics in Individuals With Chronic Low Back Pain During Sit-to-Stand Function: A Cross-Sectional Study

ObjectivesThe aim of this study was to investigate the 3-dimensional movement kinematics of pelvic and lower limb joints in CLBP subjects, compared to healthy individuals, utilizing a functional data analysis (FDA) approach. MethodsIn this study, a 7-camera Qualisys motion capture system was employed to record the kinematics of the pelvic, hip, knee, and ankle joints in 20 patients with low back pain (LBP) and 20 control subjects on both sides during the sit-to-stand motion. An FDA statistical approach was utilized to compare the data collected over time between the 2 groups. The STS task was divided into two distinct phases: the prelift off phase (pre-Lo) and the postlift off phase (post-Lo). ResultsDuring the “pre-Lo phase” of the STS motion, our statistical analysis revealed that the only significant difference between the two groups was a decreased medial rotation (P = .00) in the hip joint position of LBP patients on their dominant side, in comparison to healthy subjects. As for the “post-Lo phase,” the LBP group exhibited a more anterior pelvic tilt position (P = .00) and increased pelvic counterclockwise rotation (P = .03) in the sagittal and transverse planes when compared to the control group. Regarding hip joints, the LBP group demonstrated a more flexed position (indicative of reduced extension) on both the dominant (P = .00) and nondominant (P = .00) sides, coupled with diminished abduction (P = .04) and internal rotation (P = .03) of the hip on the dominant side. In relation to the knee and ankle joints, the results indicated a more adducted knee position (P = .00) and decreased ankle joint flexion (P = .02) on the dominant side in CLBP subjects when compared to the healthy group during the STS motion. ConclusionOur findings indicate that patients with CLBP exhibited distinct kinematic patterns in the pelvic and lower limb joints during the STS motion. These kinematic alterations primarily manifest in the joints of the dominant limb, with most of the differences observed during the second phase (postlift off phase) of the motion. It appears that these changes in pelvic and lower limb joint kinematics should be taken into account when planning future rehabilitation programs for CLBP patients engaged in this task.

Exploring Dimensionality Reduction Techniques in Multilingual Transformers

In scientific literature and industry, semantic and context-aware Natural Language Processing-based solutions have been gaining importance in recent years. The possibilities and performance shown by these models when dealing with complex Human Language Understanding tasks are unquestionable, from conversational agents to the fight against disinformation in social networks. In addition, considerable attention is also being paid to developing multilingual models to tackle the language bottleneck. An increase in size has accompanied the growing need to provide more complex models implementing all these features without being conservative in the number of dimensions required. This paper aims to provide a comprehensive account of the impact of a wide variety of dimensional reduction techniques on the performance of different state-of-the-art multilingual siamese transformers, including unsupervised dimensional reduction techniques such as linear and nonlinear feature extraction, feature selection, and manifold techniques. In order to evaluate the effects of these techniques, we considered the multilingual extended version of Semantic Textual Similarity Benchmark (mSTSb) and two different baseline approaches, one using the embeddings from the pre-trained version of five models and another using their fine-tuned STS version. The results evidence that it is possible to achieve an average reduction of 91.58% pm 2.59% in the number of dimensions of embeddings from pre-trained models requiring a fitting time 96.68% pm 0.68% faster than the fine-tuning process. Besides, we achieve 54.65% pm 32.20% dimensionality reduction in embeddings from fine-tuned models. The results of this study will significantly contribute to the understanding of how different tuning approaches affect performance on semantic-aware tasks and how dimensional reduction techniques deal with the high-dimensional embeddings computed for the STS task and their potential for other highly demanding NLP tasks.

High-gain observer-based nonlinear control scheme for biomechanical sit to stand movement in the presence of sensory feedback delays.

Sit-to-stand movement (STS) is a mundane activity, controlled by the central-nervous-system (CNS) via a complex neurophysiological mechanism that involves coordination of limbs for successful execution. Detailed analysis and accurate simulations of STS task have significant importance in clinical intervention, rehabilitation process, and better design for assistive devices. The CNS controls STS motion by taking inputs from proprioceptors. These input signals suffer delay in transmission to CNS making movement control and coordination more complex which may lead to larger body exertion or instability. This paper deals with the problem of STS movement execution in the presence of proprioceptive feedback delays in joint position and velocity. We present a high-gain observer (HGO) based feedback linearization control technique to mimic the CNS in controlling the STS transfer. The HGO estimates immeasurable delayed states to generate input signals for feedback. The feedback linearization output control law generates the passive torques at joints to execute the STS movement. The H2 dynamic controller calculates the optimal linear gains by using physiological variables. The whole scheme is simulated in MATLAB/Simulink. The simulations illustrate physiologically improved results. The ankle, knee, and hip joint position profiles show a high correlation of 0.91, 0.97, 0.80 with the experimentally generated reference profiles. The faster observer dynamics and global boundness of controller result in compensation of delays. The low error and high correlation of simulation results demonstrate (1) the reliability and effectiveness of the proposed scheme for customization of human models and (2) highlight the fact that for detailed analysis and accurate simulations of STS movement the modeling scheme must consider nonlinearities of the system.

Assisted Spatial Sit-to-Stand Prediction-Part 1: Virtual Healthy Elderly Individuals

AbstractSit-to-stand (STS) motion is a key determinant of functional independence for the senior people. This paper extends a predictive dynamics formulation previously reported to predict the assisted STS motion, i.e., the motion with a mechanical assistance, unilateral grab-rail bar which is placed on the right side of the virtual-individuals with a vertical orientation. The formulation is able to predict kinetics and kinematics not only in the sagittal plane, but also in frontal and transverse planes. Two different objective functions are tested: The first one is the dynamic effort and the second one is the dynamic effort plus the difference between right and left side support reaction forces (SRFs). Results show that sagittal plane kinematics and kinetics are not affected by the introduction of the grab-rail bar, whereas some significant differences are seen in the medial/lateral and anterior/posterior components of kinematics and kinetics. The healthy elderly group places a priority to the stability during an assisted STS task. The placement of the grab-rail bar on the right side results in a significant decrease in the left knee joint torque. Results in this study are consistent with those reported from the literature.

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

BackgroundSit-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 questionAre there any differences in the movement time, joint angles, and peak joint moments of STS in typically developing (TD) children? MethodsMotion 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). ResultsChildren 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. SignificanceDifferent 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.

Linguistic analysis of datasets for semantic textual similarity

Abstract Semantic Textual Similarity (STS), which measures the equivalence of meanings between two textual segments, is an important and useful task in Natural Language Processing. In this article, we have analyzed the datasets provided by the Semantic Evaluation (SemEval) 2012–2014 campaigns for this task in order to find out appropriate linguistic features for each dataset, taking into account the influence that linguistic features at different levels (e.g. syntactic constituents and lexical semantics) might have on the sentence similarity. Results indicate that a linguistic feature may have a different effect on different corpus due to the great difference in sentence structure and vocabulary between datasets. Thus, we conclude that the selection of linguistic features according to the genre of the text might be a good strategy for obtaining better results in the STS task. This analysis could be a useful reference for measuring system building and linguistic feature tuning.

Mechanical work, kinematics, and kinetics during sit-to-stand in children with and without spastic diplegic cerebral palsy

BackgroundSit-to-stand (STS) is one of the most common fundamental activity in daily life. The pathology of the neuromuscular control system in children with spastic diplegic cerebral palsy (SDCP) could contribute to atypical movement patterns leading to the inefficiency performance including the STS task. However, there was also a lack of evidence about kinematics, kinetics, and especially mechanical work during the STS task in children with SDCP aged 7–12 years old. Research questionWhat were the differences in mechanical work, kinematics and kinetics during STS task between children with SDCP and typically developing (TD) children? MethodsEleven children with SDCP (GMFCS I-II) and eleven age and gender-matched control TD children with an age range of 7–12 years were enrolled. Motion analysis and force plate systems were used to collect data. All participants performed the STS task from an adjustable chair. Independent sample t-test and two-way analysis of variance were used in this study. ResultsThe children with SDCP took a longer time and used more mechanical work during STS than TD children. At the beginning of the STS task, children with SDCP showed more trunk flexion and posterior pelvic tilting; in addition, during the STS task they also presented more trunk, hip, and knee flexion than TD children. However, the children with SDCP showed less ankle dorsiflexion compared with TD children. For the kinetic variables, asymmetry was found in children with SDCP. The maximum hip and knee extension moment, plantar flexion moment, and peak vertical ground reaction force (GRF) of the non-dominant leg were higher than the values of the dominant leg in these children. SignificanceEven though, children with SDCP who are able to independently STS. They were also a mechanically less efficient performance during STS task. Therefore, this task still needs to be trained during rehabilitation sessions.

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.

Sex difference in age-related changes in knee extensor strength and power production during a 10-times-repeated sit-to-stand task in Japanese elderly.

BackgroundFor middle-aged and elderly women, age-related decline in an index representing power production during STS task (STS-PI), calculated by using an equation reported previously, has been shown to be greater than that in the force generation capability of lower extremity. Whether this is specific to women remains unclear. This study examined how the age-related changes in knee extensor strength and power production during STS differ between Japanese men and women aged 65 years or older.MethodsThe time taken for a 10-times-repeated STS test (STS time) and force developed during maximal voluntary isometric knee extension (KE-F) were determined in Japanese younger-old (262 men and 285 women) aged 65–74 years and older-old (96 men and 89 women) aged 75–90 years. STS-PI was calculated using the following equation: STS-PI = (body height − 0.4) × body mass × 10/STS time.ResultsKE-F and STS-PI were significantly greater in the younger-old than in the older-old group (p < 0.0001) and in men than in women (p < 0.0001). STS-PI and KE-F, expressed as the percentages of the mean value of the corresponding variable for the younger-old group (%STS-PI and %KE-F, respectively), were negatively correlated to chronological age in both men (r = −0.386 and r = −0.269, respectively, p < 0.0001) and women (r = −0.504 and r = −0.294, respectively, p < 0.0001). Regression slopes in the relationship between age and %KE-F were not significantly different between men (−1.521) and women (−1.618). However, regression slope in the relationship between age and %STS-PI was significantly steeper in women (−3.108) than in men (−2.170) (p < 0.05). In OOG, %KE-F had no significant effect of sex, but %STS-PI was significantly lower in women than in men (p < 0.001).ConclusionsIn Japanese men and women aged 65 years or over, age-related loss in power production during STS is steeper in women than in men, with greater magnitude than that in knee extensor strength. This suggests a higher priority of improving power generation capability during whole-body movement such as STS in older women than in older men.

Activation of the vastus medialis oblique and vastus lateralis muscles in asymptomatic subjects during the sit-to-stand procedure.

[Purpose] The purpose of this study was to examine the vastus medialis oblique to vastus lateralis ratio in two pelvic tilt positions while performing the sit-to-stand task. [Subjects and Methods] Activation of the vastus medialis oblique and the vastus lateralis muscles of 46 healthy subjects (25 males, 21 females) were recorded by surface electromyography during the STS task with anterior pelvic tilt (sit with thoracolumbar spine extended and pelvis in an anterior tilt) and neutral pelvic tilt (sit with thoracolumbar spine relaxed and pelvis in the neutral tilt position) positions. Changes in vastus medialis oblique, vastus lateralis activation and the vastus medialis oblique/vastus lateralis ratio were analyzed. [Results] Vastus medialis oblique and vastus lateralis muscle activation significantly increased in neutral pelvic tilt position, but the vastus medialis oblique/vastus lateralis ratio was not statistically different. [Conclusion] The sit-to-stand procedure with neutral pelvic tilt position increased activation of the vastus medialis oblique and vastus lateralis, usefully strengthening the quadriceps, but did not selectively activate the vastus medialis oblique muscle.

Analysis of the neuromuscular activity during rising from a chair in water and on dry land

PurposeThe purpose of the present study was to analyze the neuromuscular responses during the performance of a sit to stand [STS] task in water and on dry land. Scope10 healthy subjects, five males and five females were recruited for study. Surface electromyography sEMG was used for lower limb and trunk muscles maximal voluntarty contraction [MVC] and during the STS task. ResultsMuscle activity was significantly higher on dry land than in water normalized signals by MVC from the quadriceps-vastus medialis [17.3%], the quadriceps – rectus femoris [5.3%], the long head of the biceps femoris [5.5%], the tibialis anterior [13.9%], the gastrocnemius medialis [3.4%], the soleus [6.2%]. However, the muscle activity was higher in water for the rectus abdominis [−26.6%] and the erector spinae [−22.6%]. ConclusionsThis study for the first time describes the neuromuscular responses in healthy subjects during the performance of the STS task in water. The differences in lower limb and trunk muscle activity should be considered when using the STS movement in aquatic rehabilitation.

Comparison of the Power Knee and C-Leg during step-up and sit-to-stand tasks

For U.S. military service members with transfemoral amputations there are different prosthetic knee systems available that function differently. For example the C-Leg® (C-Leg, Otto Bock Healthcare, GmbH, Duderstadt, Germany) is a passive microprocessor knee, and the Power Knee™ (PK, Ossur, Reykjavík, Iceland) provides active positive power generation at the knee joint. This study examined both step-up and sit-to-stand tasks performed by service members using C-Leg and PK systems to determine if the addition of positive power generation to a prosthetic knee can improve symmetry and reduce impact to the remaining joints. For both tasks, average peak sagittal knee powers and vertical ground reaction forces (GRFs) were greater for the intact limb versus the amputated limb across PK and C-Leg groups. For the sit-to-stand task, peak knee power of the amputated limb was greater for PK users versus C-Leg users. Vertical GRFs of the intact limb were greater for the C-Leg versus the PK. The performance of the PK relative to the C-Leg during a STS task illustrated few differences between components and no effect on the intact limb.

Weight-Bearing and Effort Distributions at the Lower Limbs during the Five-Repetition Sit-to-Stand Test in Hemiparetic and Healthy Individuals

Background. The weight-bearing (WB) and effort distributions during the five-repetition sit-to-stand test (5R-STS) were assessed in healthy and hemiparetic subjects and were compared to the distributions obtained for a single STS task (1-STS).Methods. Eighteen hemiparetic subjects and 12 controls were included. The WB distribution and time were computed using the vertical ground reaction forces. The knee muscles' effort distribution was quantified with the electromyographic (EMG) data of the STS transfers expressed relatively to the EMG values of maximal strength assessments.Results. In both groups, the time, WB, and effort distributions did not differ between repetitions of the 5R-STS test. The WB and effort distributions of the first repetition were more asymmetrical than those for the 1-STS for the hemiparetic subjects only.Conclusions. Since no changes were found between repetitions, the 5R-STS test might not be demanding enough. The hemiparetic subjects adopt different WB and effort distribution strategies according to the number of STSs to complete.

Energy Expenditure during Non-weight-bearing Walking Using Elbow Crutches

Results The maximum forward excursion of the CoP was sequentially increased through control, soft collar and hard collar conditions. Mean maximum anterior position of CoP and 222.19 mm hard, 218.16 mm soft, 216.39 mm control collar. A significant difference was found (p < 0.05), and post hoc testing identified significant differences between hard and soft collars, and the hard collar and no collar conditions. No significant difference was found between no collar and soft collar conditions. Discussion As movement of the neck was progressively restricted, the strategy for StS was altered, with the body initiating more forward movement during performance of the task. By limiting neck movement anterior displacement of the CoP was increased, potentially making the subject less stable. Increased forward momentum is an important element in the efficiency of the StS task. Slowing of StS is known to occur with ageing and the total muscle effort required is consequently increased. Current evidence identifies falls in elderly people occurring in transition between sitting and standing, and wearing of a collar may further compromise safety in these individuals. Further evaluation of the effects of collars on centres of pressure in representative groups may identify strategies to minimise risk.

Control of body mass transfer as a function of speed of ascent in sit-to-stand

The purpose of this study was to test the hypothesis that a progressive variation in the speed of ascent would result in differences in the horizontal and vertical motions of the body center of mass (CM) and in the governing impulse-momentum relationship. A motion analysis system and two force platforms were used to examine the STS task among 10 healthy adults at each of three self-selected speeds. As the speed of ascent became faster, a progressively earlier time to the maximum vertical linear momentum and an increase in its magnitude occurred. In contrast, a relatively constant time to the maximum linear momentum, which was also the time when the propulsive impulse became the braking impulse, was found in the horizontal direction, and the propulsive impulse showed a disproportionately (1:3) smaller increase from slow to fast speeds than its vertical counterpart. The relative invariance in the horizontal motion suggested that different neuromuscular control strategies may have been employed in the horizontal and vertical directions to accomplish the different tasks of balance control in one direction and changing the gravitational potential energy in the other direction.