Query: sit-to-stand lifts

title: Mechanical work, kinematics, and kinetics during sit to stand in children with and without spastic diplegic cerebral palsy.
abstract: Sit 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.  What were the differences in mechanical work, kinematics and kinetics during STS task between children with SDCP and typically developing (TD) children?  Eleven 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.  The 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.  Even 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.

title: Muscle thickness contribution to sit to stand ability in institutionalized older adults
abstract: Ultrasound is a low cost, safe and accessible tool to use on muscle mass assessment. The relations between muscle thickness and lower limb function have not been investigated in institutionalized elderly people. The purpose of the present study was to investigate the associations among sit to stand capacity, ultrasound measured rectus femoris muscle thickness, hand grip strength and anthropometrics in a population of institutionalized older adults. Twelve older adults (nine women and three men, mean age SD 86 7 years, body mass index 24 3 kg/m2) participated in this cross sectional study. Sit to stand capacity using five repetition sit to stand test, rectus femoris muscle thickness using B mode ultrasonography, handgrip and anthropometric were measured. The relationships of the variables were analyzed using Pearson correlation coefficient and multiple linear regression analysis. Significant bivariate correlations were found between rectus femoris muscle thickness and sit to stand test (p 0.05) Multiple linear regression analysis showed associations between rectus femoris muscle thickness and sit to stand test, after adjusting by body mass index and age (p 0.0001) Rectus femoris thickness in contraction adjusted by body mass index and age was predictors of physical performance. The independent variables shared 78.6% of variance in the sit to stand test. Rectus femoris muscle thickness measured with ultrasonography, body mass index and age could explain functionality in institutionalized older adults measured by five repetition sit to stand test.

title: Optimized scoring tool to quantify the functional performance during the sit to stand transition with a magneto inertial measurement unit.
abstract: Sit to stand is used as a qualitative test to evaluate functional performance, especially to detect fall risks and frail individuals. The use of various quantitative criteria would enable a better understanding of musculoskeletal deficits and movement strategy modifications. This quantification was proven possible with a magneto inertial unit which provides a compatible wearable device for clinical routine motion analysis.  Sit to stand movements were recorded using a single magneto inertial measurement unit fixed on the chest for 74 subjects in three groups healthy young, healthy senior and frail. MIMU data was used to compute 15 spatiotemporal, kinematic and energetic parameters. Nonparametric statistical test showed a significant influence of age and frailness. After reducing the number of parameters by a principal component analysis, an AgingScore and a FrailtyScore were computed.  The fraction of variance explained by the first principal component was 77.48 2.80% for principal component analysis with healthy young and healthy senior groups, and 74.94 2.24% with healthy and frail senior groups. By receiver operating characteristic curve analysis of this score, we were able to refine the analysis to differentiate between healthy young and healthy senior subjects as well as healthy senior and frail subjects. By radar plot of the most discriminate parameters, the motion's strategy could be characterized and be used to detect premature functional deficit or frail subjects.  Sit to stand measured by a single magneto inertial unit and dedicated post processing is able to quantify subject's musculoskeletal performance and will allow longitudinal investigation of aging population.

title: Control of the Sit To Stand Transfer of a Biped Robotic Device for Postural Rehabilitation
abstract: This paper deals with the control of the sit to stand transfer of a biped robotic device (either an autonomous biped robot or a haptic assistive exoskeleton for postural rehabilitation) The control has been synthesized, instead of considering the physiology, analyzing the basic laws of dynamics. The transfer of a human from sitting on a chair to an erect posture is an interesting case study, because it treats biped balance in a two phase dynamic setting, with an external force disturbance (the chair pelvis contact) affecting the center of pressure under the feet. At the beginning, a body is sitting, with a fixed pelvis moving with the hips going toward the supporting feet and, contemporaneously, releasing the load from the chair with ankles and knee torques. Then, after lift off, it reaches and maintains an erect posture. The paper objectives are threefold: identifying the major dynamical determinants of the exercise; sythesizing an automatic control for an autonomous device; proposing an innovative approach for the rehabilitation process with an exoskeleton. For this last objective, the paper extends the idea of the authors of a haptic exoskeleton for rehabilitation. It is driven to control the joints by electromiographical signals from the patient. The two spaces, cartesian (world) and joint, where, respectively, the automatic control and the patient operate, are considered and a technique to blend the two actions is proposed. The exoskeleton is programed to perform the exercise autonomously. Then, during the evolution of the phases of rehabilitation, we postulated to seamlessly move the control from one space (purely autonomous) to another (completely driven by the patient) choosing and keeping the postural tasks and joints (heaps, knees, or ankles) on which to apply each one of the two actions without interaction.

title: Quantifying sit to stand and stand to sit transitions in free living environments using the activPAL thigh worn activity monitor.
abstract: Standing up, sitting down and walking require considerable effort and coordination, which are crucial indicators to rehabilitation (e.g. stroke) and in older populations may indicate the onset of frailty and physical and cognitive decline. Currently, there are few reports robustly quantifying sit to stand and stand to sit transitions in free living environments. The aim of this study was to identify and quantify these transitions using the peak velocity of sit to stand and stand to sit transitions to determine if these velocities were different in a healthy cohort and a mobility impaired population.  Free living sit to stand and stand to sit acceleration data were recorded from 21 healthy volunteers and 34 stroke survivors using activPAL3(tm) monitors over a one week period. Thigh inclination velocity was calculated from these accelerometer data. Maximum velocities were compared between populations.  A total of 10,299 and 11,392 sit to stand and stand to sit transitions were recorded in healthy volunteers and stroke survivors, respectively. Healthy volunteers had significantly higher overall mean peak velocities for both transitions compared with stroke survivors [70.7deg/s 52.2 versus 44.2deg/s 28.0 for sit to stand, P 0.001 and 74.7deg/s 51.8 versus 46.0deg/s 31.9 for stand to sit; P 0.001] Mean peak velocity of transition was associated with increased variation in peak velocity across both groups.  There were significant differences in the mean peak velocity of sit to stand and stand to sit transitions between the groups. Variation in an individual's mean peak velocity may be associated with the ability to perform these transitions. This method could be used to evaluate the effectiveness of interventions following injury such as stroke, as well as monitor decline in functional ability.

title: Individuals with mild to moderate hip osteoarthritis exhibit altered pelvis and hip kinematics during sit to stand.
abstract: Performance of the sit to stand (STS) task is compromised in individuals with advanced hip osteoarthritis (OA) Understanding how STS performance is altered in individuals with mild to moderate hip OA may inform interventions to improve function and slow disease progression.  Do trunk, pelvis, and hip biomechanics differ during a STS task between individuals with mild to moderate hip OA and a healthy, age matched control group?  Thirteen individuals with mild to moderate symptomatic and radiographic hip OA and seventeen healthy, age matched controls performed a standardized STS task. Data were acquired using a three dimensional motion capture system. The primary outcome measures were task duration, sagittal and frontal plane trunk, pelvis, and hip joint angles, and sagittal and frontal plane trunk and hip joint moments. Comparisons of lower limb measures were between the most affected side in the hip OA group and a randomly chosen limb for the control group, termed the index limb, prior to and following lift off from the chair.  Participants with mild to moderate hip OA took longer to perform the STS task compared to controls. Prior to lift off, the hip OA group exhibited greater posterior pelvic tilt, greater pelvic rise on the index side and less hip joint flexion relative to controls. Following lift off, the hip OA group exhibited greater pelvic rise on the index side compared to controls.  Individuals with mild to moderate hip OA exhibit subtle alterations in movement strategy compared to healthy controls when completing a STS task similar, to a small extent, to adaptations reported in advanced stages of the disease. Interventions to target these features and prevent further decline in physical function may be warranted in the management of mild to moderate hip OA while the opportunity remains.

title: SLAK Completely Supports Sit to Stand*
abstract: Current soft actuators are favorable for wearable applications because of their intrinsic safety  and ergonomic comfort  However, they cannot provide the torque to completely support everyday movements such as sit to stand  High torques, sometimes sufficient for complete support, are important for people with complete spinal cord injuries, rehabilitation of stiff joints, and protecting workers in dangerous environments from injury. This talk reports the design and preliminary results on a simple high torque actuator, the pleated pneumatic interference actuator (PPIA) that is used in a sit to stand (STS) orthosis  the soft lifting assistor for the knee (SLAK) PPIAs are based on Nesler et al.'s [4] PIA and made from fabric reinforced rubber bladders. In our previous work  the constraints required to laterally stabilize the single PPIA behind the leg limited its range of motion (ROM) well below that required for STS. The 1.35 kg SLAK eliminates the lateral constraints. Instead, it has three parallel PPIAs made of sealed firehose lengths inserted into a 1000D Cordura fabric sleeve. At 320 kPa the SLAK was shown to completely support standing over 94 of the STS motion  a very significant improvement over the 67 of the STS motion of our previous design  The SLAK does so with a torque of 3.8 Nm at 7.9 deg increasing parabolically to 320 Nm at 82 deg knee flexion. When worn, the SLAK generates a torque over the knee's complete ROM, even providing a torque to support the knee in full extension. However, this is not reflected in the data due to the shifting of the SLAK on the smooth test leg, particularly at low flexion angles. At these angles the significant shear component generated by the PPIA's torque caused the two ends of the PPIA to move away from each other, misaligning it completely away from the knee joint and preventing it from applying measurable torque. Future work will resolve this problem, and characterize the power and speed performance of the SLAK.

title: Physics based sit to stand three dimensional motion prediction considering seat pan contact
abstract: Sit to stand (STS) is one of the most demanding tasks in mechanical terms in daily lives. Many elderlies, people with lower limb injuries, and patients with neurological disorders or musculoskeletal abnormalities have difficulties during this task. In literature, most studies were carried out through experiments. Experiment based methods are time consuming and tedious. In addition, seat pan contact forces were ignored or analyses started after lift off instance. In this study, a three dimensional physics based formulation for the entire STS motion was presented. This formulation was based on joint space, where resultant joint torques instead of activations of individual muscles are considered to reduce computational time. Both ground reaction forces and the seat pan contact forces were considered, and resultant joint torques were predicted with recursive Lagrangian dynamics. A 56 degree of freedom (DOF) digital human model was used, and time and chair height were altered to study cause and effect. First, bilateral symmetry was assumed, and results were compared with the experimental results in literature to validate the proposed formulation. As time and chair height increased, the motion became less demanding in mechanical terms. After 2.5 s, resultant peak joint torques at the knee and ankle joints were found to be relatively equivalent to static torque components. An asymmetric STS motion example was also investigated.

title: Model based control for exoskeletons with series elastic actuators evaluated on sit to stand movements
abstract: BackgroundCurrently, control of exoskeletons in rehabilitation focuses on imposing desired trajectories to promote relearning of motions. Furthermore, assistance is often provided by imposing these desired trajectories using impedance controllers. However, lower limb exoskeletons are also a promising solution for mobility problems of individuals in daily life. To develop an assistive exoskeleton which allows the user to be autonomous, i.e. in control of his motions, remains a challenge. This paper presents a model based control method to tackle this challenge.MethodsThe model based control method utilizes a dynamic model of the exoskeleton to compensate for its own dynamics. After this compensation of the exoskeleton dynamics, the exoskeleton can provide a desired assistance to the user. While dynamic models of exoskeletons used in the literature focus on gravity compensation only, the need for modelling and monitoring of the ground contact impedes their widespread use. The control strategy proposed here relies on modelling of the full exoskeleton dynamics and of the contacts with the environment. A modelling strategy and general control scheme are introduced.ResultsValidation of the control method on 15 non disabled adults performing sit to stand motions shows that muscle effort and joint torques are similar in the conditions with dynamically compensated exoskeleton and without exoskeleton. The condition with exoskeleton in which the compensating controller was not active showed a significant increase in human joint torques and muscle effort at the knee and hip. Motor saturation occurred during the assisted condition, which limited the assistance the exoskeleton could deliver.ConclusionsThis work presents the modelling steps and controller design to compensate the exoskeleton dynamics. The validation seems to indicate that the presented model based controller is able to compensate the exoskeleton.

title: The sit to stand muscle power test: An easy, inexpensive and portable procedure to assess muscle power in older people
abstract: Skeletal muscle power has been demonstrated to be a stronger predictor of functional limitations than any other physical capability. However, no validated alternatives exist to the usually expensive instruments and/or time consuming methods to evaluate muscle power in older populations. Our aim was to validate an easily applicable procedure to assess muscle power in large cohort studies and the clinical setting and to assess its association with other age related outcomes.  Forty community dwelling older adults (70 87years) and 1804 older subjects (67 101years) participating in the Toledo Study for Healthy Aging were included in this investigation. Sit to stand (STS) velocity and muscle power were calculated using the subject's body mass and height, chair height and the time needed to complete five STS repetitions, and compared with those obtained in the leg press exercise using a linear position transducer. In addition, STS performance, physical (gait speed) and cognitive function, sarcopenia (skeletal muscle index (SMI) and health related quality of life (HRQoL) were recorded to assess the association with the STS muscle power values.  No significant differences were found between STS velocity and power values and those obtained from the leg press force velocity measurements (mean difference+ 95% CI=0.02+ 0.05m*s 1 and 6.9+ 29.8W, respectively) (both p>0.05) STS muscle power was strongly associated with maximal muscle power registered in the leg press exercise (r=0.72; p<0.001) In addition, cognitive function and SMI, and physical function, were better associated with absolute and relative STS muscle power, respectively, than STS time values after adjusting by different covariates. In contrast, STS time was slightly more associated with HRQoL than STS muscle power measures.  The STS muscle power test proved to be a valid, and in general, a more clinically relevant tool to assess functional trajectory in older people compared to traditional STS time values. The low time, space and material requirements of the STS muscle power test, make this test an excellent choice for its application in large cohort studies and the clinical setting. HIGHLIGHTSSit to stand power was calculated from: sit to stand time, chair height, body mass and height.Sit to stand power was similar to that obtained from a validated instrument in the leg press exercise.Sit to stand power was independently associated with physical and cognitive function, sarcopenia and quality of life.