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A comparison of neck bending and flexion measurement methods for assessment of ergonomic risk

Zare M., Biau S., Gourlay A., Roquelaure Y.

International Journal of Occupational Safety and Ergonomics

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2015

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Vol. 21, No. 3

330--335

EN

Head movements of workers were measured in the sagittal plane in order to establish a precise and accurate assessment method to be used in real work situations. Measurements were performed using two inclinometers connected to an embedded recording system. Two quantitative analysis methods were tested, i.e., measurement of bending with an inclinometer attached to the head, and measurement of flexion/extension by using an additional inclinometer located at C7/T1. The results were also compared with a video observation method (qualitative). The results showed that bending measurements were significantly different from those of flexion/extension for angles between 0° and 20°, and angles >45°. There were also significant differences between workers for flexion >45°, reflecting individual variability. Additionally, several limitations of observational methods were revealed by this study.

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An analytical expression for the D.I.P.–P.I.P. flexion interdependence in human fingers

Van-Zwieten K. J., Schmidt K. P., Bex G. J., Lippens P. L., Duyvendak W.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 1

129--135

EN

Empirical evidence shows that a strong correlation exists between the flexion angles of the distal and proximal interphalangeal (D.I.P., P.I.P.) joints of the human finger. Several authors measured this functional dependence, stating that the interdependence of D.I.P. and P.I.P. flexion is different for healthy individuals and patients displaying pathologies. The purpose of our study is to find an analytical expression for this correlation. Methods: Following closely the anatomical in situ relations, we developed a two-dimensional kinematical model which expresses analytically the D.I.P.–P.I.P. angle correlation. Numerical values for the model were extracted from one healthy and one pathological case data set. Results: The analytical form of the model allows for any P.I.P. angle not only to calculate the corresponding D.I.P. angle, but after first order differentiation with respect to the P.I.P. angle, it also shows the rate of change of the D.I.P. flexion. The model reproduces well the differences in the angular correlation of D.I.P. flexion of the two healthy-pathological data sets. Displaying the rate of change of D.I.P. flexion versus P.I.P. flexion provides an additional, clear-cut discriminatory tool between normal and pathological states. Conclusions: Information on differences between normal and pathological flexion of fingers is more pronounced and easier accessible from the derivatives of the D.I.P.–P.I.P. flexion behaviour than from direct angular correlation data. The analytical form of our model allows one to establish the rate of change of the D.I.P. angles, resulting in a better analysis of the situations at hand.

3

Analysis of muscles behaviour. Part 2 The computational model of muscles group acting on the elbow joint

Wojnicz W., Wittbrodt E.

Acta of Bioengineering and Biomechanics

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2010

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Vol. 12, no. 1

3-10

EN

The purpose of this paper is to present the computational model of muscles’ group describing the movements of flexion/extension at the elbow joint in the sagittal plane of the body when the forearm is being kept in the fixed state of supination/pronation. The method of evaluating the muscle forces is discussed in detail. This method is the basis for the quantitative and qualitative verification of the proposed computational model of muscles’ group. Applying this computational model, the forces of real muscles belonging to the muscles’ group can be evaluated without using any optimization technique.

4

Adjustable mechanical stability of the balanced tibiofemoral joint in flexion/extension: a novel measuring method in vitro

Knosel M., Kubein-Meeesenburg C., Stuhmer H., Nagerl H., Mansour M., Fanghänel J.

Acta of Bioengineering and Biomechanics

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2004

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Vol. 6, nr 2

3-15

EN

A number of muscles which pull over the tibiofemoral joint (possessing maximally four kinematic degrees of freedom) is larger than necessary in order to produce static equilibria in the physiologic positions of the tibiofemoral joint. Consequently, it should be possible to balance the knee in any arbitrary position by a set of combinations of isotonic muscular forces. The corresponding equilibria of the same flexional status should be differentiated by their degree of stability. Here, we describe a novel method which allows measuring the isotonic stability in flexion/extension in vitro for examining the above theses derived theoretically. By in vitro experiments we could show for the first time that not only a) the same position in flexion can be held in differing static equilibria by correspondingly differing combinations of muscular forces, but also b) the varying degree of stability ranges from stable and indifferent to unstable. These features were related a) to rotations of the resultant muscular force in the main functional plane and b) translations of its force line in parallel to this plane in the direction of abduction/adduction. By that we are able to present a hypothesis of how nature deals with an apparent antagonism of mechanically stable posture and mechanical instability of the joint demanded in the case of fast motion.