Helios de Rosario

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. Our method uses the measurement of several repetitions of a given movement to obtain the optimal average IHA path. The starting point is a change of variables, from time to a joint position magnitude (generally an angle). In this way, instead of operating with the time-dependent single-valued trajectory of the successive cycles, our model permits the representation of any motion variable (e.g. positions and their time derivatives) as a cloud of points dependent on the joint angle. This allows the averaging to be performed over the displacements and their derivatives before determining the mean IHA path. We thus avoid the nonlinear magnification of errors and variability inherent in the IHA computation. Moreover, the IHA path can be considered as a geometric attribute of the joint and the type of motion, rather than of each single movement execution. An experiment was performed that show the accuracy and usefulness of the method.

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. The results obtained suggest a sequential activation of lumbar vertebrae in the flexion–extension motion. On the other hand, the location of the pelvis IAR shows that the movement of the pelvis on the seat is not just a rolling motion but a rolling with some level of sliding. Finally, the location of the IAR in the thorax-pelvis relative motion shows a mismatch between the trunk IAR and the backrest axis of rotation in several office chairs. The proposed technique provides a new approach for the kinematic analysis of sitting posture. The results can be applied to the improvement of biomechanical models of seated posture as well as to define some design criteria of work seats based on the fit between the trunk and backrest movements.

Technology use, adoption and behavior in older adults: Results from the iStoppFalls project

ABSTRACT Technology use is a common constituent of modern life. However, little is known about older adults’ use of technology. This article presents a subset of data collected via the technology deployed in the iStoppFalls randomized control trial. The primary focus lies on questions about digital device/Internet use, ownership, length, and frequency as well as social networking. Data was collected from participants aged 65 years or older. Seventy-eight participants completed a specifically developed technology survey as part of the baseline assessment. Results showed that the majority of subjects owned a computer with men being its main user. Participants used technological devices on a daily basis for more than 1 year. The main reason for using technology was e-mail communication, search engines, text processing, and online shopping. Only a few participants used social network applications, with Google+ and Facebook being the most popular ones. Future work should consider an in-depth qualitative approach to further increase understanding of technology use in older adults.

A new non-invasive and low cost method for the characterisation of pronation patterns by using AR-markers and functional classification

The influence of three shoe criteria was evaluated during the gait of young children. Each criterion effect was identified on a large number of kinematic and dynamic values. A recent study presented how relevant shoe properties could reduce joint loading, in order to prevent injuries in adults (Boyer et al. 2012). The present study proposed a similar approach to quantify the influence of shoe properties on gait of young children, who need adapted shoes during growth. Heel height and sole stiffness principally influenced ankle and knee kinematics and dynamics whereas upper height largely influenced hip kinematics. The current study proposed a first assessment of kinematic and dynamic parameters of shod walking in young children. A large distribution of children’s age should explain the high variability observed on curve peaks. Future investigations may be done considering age groups in order to reduce this variability.

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. The resulting joint kinematic model is based on the real movement and accounts for nonfixed axes of rotation; therefore it could improve current models based on revolute pairs in those cases where joint movement implies displacement of the ICR. Previous authors have used the ICR to characterize human joint motion, but they only considered the fixed centrode. Such an approach is not adequate for reproducing motion because the fixed centrode by itself does not convey information about body position. The combination of the fixed and moving centrodes gathers the kinematic information needed to reproduce the position and velocities of moving bodies. To illustrate our method, we applied it to the flexion-extension movement of the head relative to the thorax. The model provides a good estimation of motion both for position variables (mean R(pos)=0.995) and for velocities (mean R(vel)=0.958). This approach is more realistic than other models of neck motion based on revolute pairs, such as the dual-pivot model. The geometry of the centrodes can provide some information about the nature of the movement. For instance, the ascending and descending curves of the fixed centrode suggest a sequential movement of the cervical vertebrae.

Ankle 3D-kinematics measurement by using a single camera and AR-markers

The study of ankle kinematics is very important for different applications such as sports, rehabilitation, or footwear design. Video-photogrammetry is considered to be the most accurate technique (Graf and Stefanyshyn 2012), although due to its instrumental complexity, it is normally limited to the laboratory. In recent applications for sports training and footwear selection, however, accuracy is less crucial than usability and adequacy for using outside the laboratory. This has promoted the creation of simpler techniques, such as markerless photogrammetry (Surer et al. 2011), or magnetic and inertial sensors (Cutti et al. 2009). 3D kinematics can alternatively be measured by simple and non-invasive instruments like Augmented Reality (AR) markers. These markers are used by robotic devices to detect the position and orientation of a plane pattern with a single camera (Zhang et al. 2002). Purpose of the study

My-active and healthy ageing (My-AHA): An ICT platform to detect frailty risk and propose intervention

Stemming from a holistic view of interrelated frailties, cognitive decline, physical frailty, depression and anxiety, social isolation and poor sleep quality, My-AHA proposes an ICT platform for early detection of pre-frailty and intervention to sustain active and healthy ageing and slowing or reversing further decline. The main aim of My-AHA is to reduce frailty risk by improving physical activity and cognitive function, psychological state, social resources, nutrition, sleep and overall well-being in older adults with pre-frailty symptoms. It will empower older citizens to better manage their own health, providing new ways of health monitoring and disease prevention through individualized profiling and personalized recommendations, feedback and support. An ICT-based platform will detect defined risks in the frailty domains early and accurately via non-stigmatising embedded sensors and data readily available in the daily living environment of older adults. When risk is detected (pre-frail), My-AHA will provide targeted ICT-based interventions. These interventions will follow an integrated approach to motivate users to participate in physical exercise, cognitively stimulating games and social networking to achieve long-term behavioural change, sustained by continued end user engagement with My-AHA. A randomized controlled study (RCT), involving 300 subjects receiving intervention, and 300 controls from many EU and non EU countries, to evaluate intercultural aspects, is ongoing in order to evaluate efficacy of the my-AHA platform. The ultimate aim is to deliver significant innovation in the area of active and healthy ageing through cooperation between European health care organizations, SMEs, and NGOs.1

Heuristic Models Applied to the Assessment and Redesign of Human Machine Interfaces Embedded in Light Rail Vehicles

Abstract This paper describes the utilization of a heuristic tool for analysing the intrinsic complexity and usability of an HMI (Human-Machine Interface) of the on board information system embedded into the light rail CITADIS (vehicle manufactured by Alstom Transport). The usefulness of this tool is assessing early designs of this kind of equipment, prior to its implementation in a functional platform, or even in the rolling stock.