6.2 Signals of the Muscles and Motions

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Fig. 6.9: The total force of the three knee bends of the patient (above), The result of the two-

dimensional photogrammetric analysis of the three joint angles (below).

Synchronisation

The measured data sets of the technical uncoupled measurement systems had to be

synchronised to get a correct temporal correlation between the two measured vari-

ables force and joint angle. The precondition for this procedure are characteristic at-

tributes and phases of the course of the signals of the measured variables which had

to be defined [36].

The periodic course of the knee angle is obvious (bottom Figure 6.9, lined), how-

ever in the course of the total force an approximate periodic course could be detected

if some phases of the biomechanical behavior during the knee bends were described

(cf. Figure 6.10). The periodic course in both force and joint angle data is also referred

to as a characteristic pattern. By means of a detailed biomechanical comparison of the

force and the knee angle curve seven phases could be defined for the patient data (cf.

Figure 6.10):

1.

P1: Upright stand phase

2.

P2: Descending phase

3.

P3: Deceleration phase - contraction of muscle force

4.

P4: Deceleration - acceleration phase - center of mass slowed to halt and muscle

activation for the following upward direction

5.

P5: Reduction of muscle force phase