User's Manual

Document MV0319P.N

MVN User Manual

120

Note that all representations of the joint angles are based on the same quaternion or rotation matrix.

The differences lie only in how the angles are extracted (represented) from this rotation. The

International Society of Biomechanics (ISB) has proposed standards for rotation sequences for the lower

[Wu et al, 2002ii] and upper body [Wu et al 2005iii].

19.8.1 Euler Extractions for the joint angles

In order to produce validated joint angle output, Xsens MVN works closely to the ISB and Grood and

Suntay recommendations

[i,ii,iii,vi]

. Almost all angles follow the ISB Euler angle extractions of Z

(flexion/extension), X (abduction/adduction) Y (internal/external rotation). The definitions of the origins

of the segments are somewhat different, since MVN uses MT’s placed on the segment, rather than

markers placed on bony landmarks. The origins and coordination axes are defined above.

19.8.2 Shoulder angle definitions

For joint angle calculations, the only difference for Euler extractions between MVN and ISB is for the

shoulder joint. MVN provides three different shoulder angle calculations, as can be seen in the data tree,

after a session has been recorded.

The shoulder joint angles provided are:

 Angles between C7 and the shoulder segment

 Euler rotation sequence ZXY

 Euler rotation sequence XZY