Magneto-Inertial Measurement Unit sensors (MIMU) display high potential for the quantitative evaluation of upper limb kinematics, as they allow monitoring ambulatory measurements. The sensor-to-segment calibration step, consisting of establishing the relation between MIMU sensors and human segments, plays an important role in the global accuracy of joint angles. The aim of this study was to compare sensor-to-segment calibrations for the MIMU-based estimation of wrist, elbow, and shoulder joint angles, by examining trueness (“close to the reference”) and precision (reproducibility) validity criteria. Ten subjects performed five sessions with three different operators. Three classes of calibrations were studied: segment axes equal to technical MIMU axes (TECH), segment axes generated during a static pose (STATIC), and those generated during functional movements (FUNCT). The calibrations were compared during the maximal uniaxial movements of each joint, plus an extra multi-joint movement. Generally, joint angles presented good trueness and very good precision in the range 5°–10°. Only small discrepancy between calibrations was highlighted, with the exception of a few cases. The very good overall accuracy (trueness and precision) of MIMU-based joint angle data seems to be more dependent on the level of rigor of the experimental procedure (operator training) than on the choice of calibration itself.

No abstract

No abstract

The purpose of this study was to develop a relationship to evaluate the grip force (force) using the electromyogram (EMG) of the flexor digitorum superficialis (FDS) and of the extensor digitorum (ED) according to the flexion-extension wrist angle (θ) and to the pronation-supination forearm angle (θ). Fifteen participants had to exert 3 levels of grip forces in 4 positions of the wrist combined with 3 positions of the forearm. The relationship is: force = 0.0045· θ· EMG(FDS) + 0.48· EMG(FDS)-0.0014 · θ · EMG(ED) -0.0016 · θ · EMG(ED) + 0.4· EMG(ED) This relationship can be used to estimate grip force for levels of strength lower than 50% of the maximal voluntary contraction.

As a marked increase in the number of musculoskeletal disorders was noted in many industrialized countries and more specifically in companies that require the use of hand tools, the French National Research and Safety Institute (INRS) launched in 1999 a research project on the topic of integrating ergonomics into hand tool design, and more particularly to a design of a boning knife. After a brief recall of the difficulties of integrating ergonomics at the design stage, the present paper shows how 3 design methodological tools--Functional Analysis, Quality Function Deployment and TRIZ--have been applied to the design of a boning knife. Implementation of these tools enabled us to demonstrate the extent to which they are capable of responding to the difficulties of integrating ergonomics into product design.