JOINT CO-ORDINATE SYSTEM AND ATTITUDE VECTOR: INFLUENCE IN THE INTERPRETATION OF MOVEMENTS
AbstractINTRODUCTION: A rapid lateral braking movement and a rapid turning movement were recorded with two cameras Photo Sonics 16mm at 200 frames/s. The different Joint Coordinate Systems and the attitude vector has a better behavior in these practical cases as suggested by H. Woltring and has the same anatomical sense that the most usual Joint Coordinate Systems. RESULTS: Four body segments were defined: foot, leg, thigh and hip. Three markers define the 3D position of each segment. The position of the markers was selected following the criteria that the movement of muscles and skin had not a big influence on the measurements. To define the anatomical axes the anthropometrical model proposed by Vaughan et al. (1992) was used with some variations, because of the supposition that some markers belong 'to two body segments at the same time is not correct in the movements studied. CONCLUSIONS: In the two movements studied the angle's curves calculated with the attitude vector have a form similar to those of the curves calculated with JCS-1 and JCS+1 which the Joint Coordinate Systems recommended as standard in Cole et al. (1993) and ISB (1995), but the absolute value of the angles is displaced. It is clear that the selection of the JCS has influence in the angle's value and, in some cases, it can change the description of the movement. The order of rotations in JCS are 123 (+1), 231 (+2), 312 (+3), 132 (-1), 321 (-2),213 (-3). In lateral braking movement JCS+3 changes the hip flexion for hip extension and knee flexion for knee extension. And 71 JCS-3 changes hip adduction for hip abduction and hip internal rotation for hip external rotation. In the turning movement JCS+2 changes hip flexion, hip adduction, knee adduction and ankle supination. JCS+3 changes hip flexion, hip adduction, knee extension and knee internal rotation. JCS-3 changes hip adduction. If only these JCS had been used, the description of movement would have been incongruent. Although the attitude vector has some mathematical advantages, the matter of wh ich is the more anatomical is still open. The attitude vector represents the movement in one helical displacement around an axis The different JCS represent the movement in three ordered helical displacements around three consecutive axes. REFERENCES: Cole, G.K.; Nigg, B.M.; Ronsky, J.L.; Yeadon, M.R. (1993) Application of the Joint Coordinate System to the Three Dimensional Joint Attitude and Movement Representation: A Standardization Proposal. Transactions of the ASME, 115,344-349. ISB (1995) A joint coordinate system for the ankle complex. ISB News'letter, 59, 6-8. Kapandji, IA (1988) Cuaderno 2: Miembro Inferior. Cuadernos de fisiologia articular.(Edited by Masson S.A.). Barcelona. Vaughan, C.L; Davis, B.L.; O'Connor, J.C. (1992) Dynamics of human gait. Human Kinetics Books, Champaign, IIlinois Woltring, H.J. (1994) 3-D attitude representation of human joints: a standardization proposal. J. Biomech. 27,
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