Comparative assessment of 3D joint marker sets for the biomechanical analysis of occupational tasks

This study involves the comparative assessment of three joint marker sets to estimate joint centres. One set consists of wide elastic bands for marking the joint centres of the ankle, knee, elbow, and wrist joints (band method), a second set uses two spherical markers on either side of the joint (ball method), and a third set defines the location of a local coordinate system from spherical markers placed near the joint (coordinate method). The three marker sets were compared relative to each other. The ball method and the coordinate method were the most similar (average differences ranged from 6 to 16 mm), which is due in part to the common markers in these sets. The band method and the coordinate method were generally the least similar (average differences ranged from 15 to 31 mm). However, the results support the assumption that the marker set consisting of elastic bands can be used as an alternative to other commonly used sets. It may even be better for certain applications because of the relatively small number of missing points. Since the bands encircle the joint they are less likely to be hidden from the view of the cameras than the two marker sets that use balls to mark the joints. Most movements filmed for ergonomic analysis are complex and the incidence of missing points with traditional marker sets is high. Therefore, the band method is a very practical alternative when studying complex occupational tasks.