Appendix
The definition of the referential frames follows that of the ISB. The angles were computed as
projection angles.
Trunk angles:
1. Definition of the referential frame
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X t : antero-posterior axis from back to front
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Yt : longitudinal axis positive when directed towards the head
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Zt : medio-lateral axis from the left to the right
2. Definition of the position of reference
Subject stands still on his feet
3. Angles computation
trunk flexion/extension
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angle between the vectors Ytref and Yt projected in the sagittal plane ( Xtref , Ytref )
medio/lateral inclination
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- angle between the vectors Ytref and Yt projected in the frontal plane ( Ytref , Ztref )
internal/external rotation
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- angle between the vectors Xtref and Zt projected in the transverse plane ( Xtref , Ztref )
Figure 1: illustration of the referential frames
Upperarm angles:
1. Definition of the referential frame
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Xu : perpendicular to the two other vectors directed forwards
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Y u : longitudinal axis directed from the elbow joint centre to the shoulder joint centre
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Z u : elbow flexion axis directed medio-laterally
2. Angles computation
shoulder flexion/extension
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angle between the vectors Yt and Y u projected in the sagittal plane ( X t , Yt )
abduction/adduction
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angle between the vectors Yt and Y u projected in the frontal plane ( Yt , Zt )
humeral internal/external rotation
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-angle between the vectors (Yu  Xt )  Yu and Xu
Forearm angles:
1. Definition of the referential frame

Xf : perpendicular to the two other vectors directed forwards
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Yf : longitudinal axis directed from the elbow joint centre to the shoulder joint centre
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Zf : elbow flexion axis directed medio-laterally
2. Angles computation
flexion/extension
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angle between the vectors Y u and Yf
pronation/supination
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angle between the vectors Xf and Z h projected in the plane ( Xf , Zf )
Hand angles:
1. Definition of axes needed
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Y h : longitudinal axis directed from distal to proximal
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Zw : wrist axis directed from the ulna to the radius
2. Angles computation
flexion/extension
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angle between the vectors Yf and Y h projected in the plane perpendicular to Zw
radial/ulnar deviation
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angle between the vectors Yf and Y h projected in the plane ( Yf , Zw )