A Deep Learning Model for Markerless Pose Estimation Based on Keypoint Augmentation: What Factors Influence Errors in Biomechanical Applications?

In biomechanics, movement is typically recorded by tracking the trajectories of anatomical landmarks previously marked using passive instrumentation, which entails several inconveniences. To overcome these disadvantages, researchers are exploring different markerless methods, such as pose estimation networks, to capture movement with equivalent accuracy to marker-based photogrammetry. However, pose estimation models usually only provide joint centers, which are incomplete data for calculating joint angles in all anatomical axes.

Positioning errors of anatomical landmarks identified by fixed vertices in homologous meshes.

Background: Human movement analysis is usually achieved by tracking markers attached to anatomical landmarks with photogrammetry. Such marker-based systems have disadvantages that have led to the development of markerless procedures, although their accuracy is not usually comparable to that of manual palpation procedures. New motion acquisition systems, such as 3D temporal scanners, provide homologous meshes that can be exploited for this purpose.

Protocol for Forearm Pronosupination Strength Measuring in Different Postures: Reliability and Influence of Relevant Factors.

Importance: Despite the importance of pronosupination strength, which is key in daily activities, current evaluation protocols are disparate, and results differ regarding the influence of factors such as gender, age, limb dominance, or posture.

Objective: To design a reliable device to measure pronation and supination torques in different forearm positions, considering the influence of gender, age, and limb dominance.

Design: Reliability study with analysis of intrarater and interrater repeatability and examination of the influence of different factors on the strength of pronation and supination.

Applications of Natural Language Processing for the Management of Stroke Disorders: Scoping Review.

Background: Recent advances in natural language processing (NLP) have heightened the interest of the medical community in its application to health care in general, in particular to stroke, a medical emergency of great impact. In this rapidly evolving context, it is necessary to learn and understand the experience already accumulated by the medical and scientific community.

Objective: The aim of this scoping review was to explore the studies conducted in the last 10 years using NLP to assist the management of stroke emergencies so as to gain insight on the state of the art, its main contexts of application, and the software tools that are used.

Accuracy of a 3D temporal scanning system for gait analysis: Comparative with a marker-based photogrammetry system.

Background: Combining the accuracy of marker-based stereophotogrammetry and the usability and comfort of markerless human movement analysis is a difficult challenge. 3D temporal scanners are a promising solution, since they provide moving meshes with thousands of vertices that can be used to analyze human movements.

Research Question: Can a 3D temporal scanner be used as a markerless system for gait analysis with the same accuracy as traditional, marker-based stereophotogrammetry systems?

Methods: A comparative study was carried out using a 3D temporal scanner synchronized with a marker-based stereophotogrammetry system.

A model to differentiate WAD patients and people with abnormal pain behaviour based on biomechanical and self-reported tests.

The prevalence of malingering among individuals presenting whiplash-related symptoms is significant and leads to a huge economic loss due to fraudulent injury claims. Various strategies have been proposed to detect malingering and symptoms exaggeration. However, most of them have been not consistently validated and tested to determine their accuracy in detecting feigned whiplash.

Relationship between neck motion and self-reported pain in patients with whiplash associated disorders during the acute phase.

Background: Biomechanical measures quantify motor control and functional deficits in Whiplash Associated Disorders (WAD), but few studies relate those measures to the clinical scales that are routinely used to assess patients. Most studies are limited to chronic neck pain, and report poor to moderate correlations.

Objective: To define a statistical model that relates measures of neck kinematics with clinical scales of neck pain, in WAD patients during the rehabilitation process in the acute phase (less than 3 months since the accident).

The My Active and Healthy Aging (My-AHA) ICT platform to detect and prevent frailty in older adults: Randomized control trial design and protocol.

Introduction: Frailty increases the risk of poor health outcomes, disability, hospitalization, and death in older adults and affects 7%-12% of the aging population. Secondary impacts of frailty on psychological health and socialization are significant negative contributors to poor outcomes for frail older adults.

Method: The My Active and Healthy Aging (My-AHA) consortium has developed an information and communications technology-based platform to support active and healthy aging through early detection of prefrailty and provision of individually tailored interventions, targeting multidomain risks for frailty across physical activity, cognitive activity, diet and nutrition, sleep, and psychosocial activities.

Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation.

The accurate location of the main axes of rotation (AoR) is a crucial step in many applications of human movement analysis. There are different formal methods to determine the direction and position of the AoR, whose performance varies across studies, depending on the pose and the source of errors. Most methods are based on minimizing squared differences between observed and modelled marker positions or rigid motion parameters, implicitly assuming independent and uncorrelated errors, but the largest error usually results from soft tissue artefacts (STA), which do not have such statistical properties and are not effectively cancelled out by such methods.

The design of a purpose-built exergame for fall prediction and prevention for older people.

Background: Falls in older people represent a major age-related health challenge facing our society. Novel methods for delivery of falls prevention programs are required to increase effectiveness and adherence to these programs while containing costs. The primary aim of the Information and Communications Technology-based System to Predict and Prevent Falls (iStoppFalls) project was to develop innovative home-based technologies for continuous monitoring and exercise-based prevention of falls in community-dwelling older people.

ICT-based system to predict and prevent falls (iStoppFalls): results from an international multicenter randomized controlled trial.

Background: Falls and fall-related injuries are a serious public health issue. Exercise programs can effectively reduce fall risk in older people. The iStoppFalls project developed an Information and Communication Technology-based system to deliver an unsupervised exercise program in older people's homes.

The reliability of humerothoracic angles during arm elevation depends on the representation of rotations.

The reliability of joint rotation measurements is an issue of major interest, especially in clinical applications. The effect of instrumental errors and soft tissue artifacts on the variability of human motion measures is well known, but the influence of the representation of joint motion has not yet been studied. The aim of the study was to compare the within-subject reliability of three rotation formalisms for the calculation of the shoulder elevation joint angles.

ICT-based system to predict and prevent falls (iStoppFalls): study protocol for an international multicenter randomized controlled trial.

Background: Falls are very common, especially in adults aged 65 years and older. Within the current international European Commission's Seventh Framework Program (FP7) project 'iStoppFalls' an Information and Communication Technology (ICT) based system has been developed to regularly assess a person's risk of falling in their own home and to deliver an individual and tailored home-based exercise and education program for fall prevention. The primary aims of iStoppFalls are to assess the feasibility and acceptability of the intervention program, and its effectiveness to improve balance, muscle strength and quality of life in older people.

Point of optimal kinematic error: improvement of the instantaneous helical pivot method for locating centers of rotation.

This paper proposes a variation of the instantaneous helical pivot technique for locating centers of rotation. The point of optimal kinematic error (POKE), which minimizes the velocity at the center of rotation, may be obtained by just adding a weighting factor equal to the square of angular velocity in Woltring׳s equation of the pivot of instantaneous helical axes (PIHA). Calculations are simplified with respect to the original method, since it is not necessary to make explicit calculations of the helical axis, and the effect of accidental errors is reduced.

Model of soft tissue artifact propagation to joint angles in human movement analysis.

This work describes the kinematic laws that govern the transmission of soft tissue artifact errors to kinematic variables in the analysis of human movements. Artifacts are described as relative translations and rotations of the marker cluster over the bone, and a set of explicit expressions is defined to account for the effect of that relative motion on different representations of rotations: the rotation around the screw axis, or rotation vector, and three Euler angle sequences (XY'Z, YX'Y″, ZX'Y″). Although the error transmission is nonlinear in all cases, the effect of artifacts is greater on Euler sequences than on the rotation vector.

Propagation of soft tissue artifacts to the center of rotation: a model for the correction of functional calibration techniques.

This paper presents a mathematical model for the propagation of errors in body segment kinematics to the location of the center of rotation. Three functional calibration techniques, usually employed for the gleno-humeral joint, are studied: the methods based on the pivot of the instantaneous helical axis (PIHA) or the finite helical axis (PFHA), and the "symmetrical center of rotation estimation" (SCoRE). A procedure for correcting the effect of soft tissue artifacts is also proposed, based on the equations of those techniques and a model of the artifact, like the one that can be obtained by double calibration.

Correction of joint angles from Kinect for balance exercising and assessment.

The new generation of videogame interfaces such as Microsoft's Kinect opens the possibility of implementing exercise programs for physical training, and of evaluating and reducing the risks of elderly people falling. However, applications such as these might require measurements of joint kinematics that are more robust and accurate than the standard output given by the available middleware. This article presents a method based on particle filters for calculating joint angles from the positions of the anatomical points detected by PrimeSense's NITE software.

Kinematic description of soft tissue artifacts: quantifying rigid versus deformation components and their relation with bone motion.

This paper proposes a kinematic approach for describing soft tissue artifacts (STA) in human movement analysis. Artifacts are represented as the field of relative displacements of markers with respect to the bone. This field has two components: deformation component (symmetric field) and rigid motion (skew-symmetric field).

Representation of planar motion of complex joints by means of rolling pairs. Application to neck motion.

We propose to model planar movements between two human segments by means of rolling-without-slipping kinematic pairs. We compute the path traced by the instantaneous center of rotation (ICR) as seen from the proximal and distal segments, thus obtaining the fixed and moving centrodes, respectively. The joint motion is then represented by the rolling-without-slipping of one centrode on the other.

Can human movement analysis contribute to usability understanding?

Nowadays human-machine interfaces are evaluated using different methodologies. These methodologies rarely consider the human movements involved in the interaction, and if so, the movements are considered in a simplistic manner. Another often neglected aspect is the relationship between the learning process and the use of the interface.

Optimal average path of the instantaneous helical axis in planar motions with one functional degree of freedom.

This paper presents a model for determining the path of the instantaneous helical axis (IHA) that optimally represents human planar motions with one functional degree of freedom (fDOF). A human movement is said to have one fDOF when all degrees of freedom (DOFs) are coordinated such that all the kinematic variables can be expressed, across movement repetitions, as functions of only one independent DOF, except for a small natural intercycle variability quantified as lower than a prespecified value. The concept of fDOF allows taking into account that, due to motor coordination, human movements are executed in a repeatable manner.

Kinematics of the trunk in sitting posture: an analysis based on the instantaneous axis of rotation.

This paper presents a new approach for analysing trunk kinematics in sitting posture based on the characterisation of thorax and pelvis motion by means of ranges of motion and instantaneous axes of rotation (IAR). These variables are estimated from videophotogrammetric data. An experiment was carried out in order to analyse three motions associated with the flexion-extension movement: the absolute motions of the pelvis and thorax and the relative motion between the thorax and pelvis.