Calibration of an instrumented couch with a motioncapture system in measuring force applied and distance during manual therapy

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Adit Chiradejnant
Duangporn Suriyaamarit
Mathawee Kaewprasert


Objective: This study aimed to (i) describe an instrumented couch which would be able to synchronize with the motion-capture system in details; (ii) calibrate this device in measuring applied forces on its surface and distance.

Study design: The criterion-related validity and test-retest reliability.

Methods: The criterion-related validity and reliability of the couch were investigated in two

conditions: empty couch and a couch with dead weight of known mass 70 kg., in three directions (vertical, medial-lateral and caudad-cephalad directions). The motion-capture system was also investigated by using the grid paper size 40×40 cm2. Pearson’s correlation and the intraclass correlation coefficient (2, 1) were used to analyze the validity and the reliability of the couch in measuring the applied force and motion-capture system in measuring the distance. The percentage error was calculated for both the couch and the motion-capture system.

Results: The Pearson’s correlation of the couch and the motion-capture system in this study was 1.00 (p<0.05). The intraclass correlation coefficient (2, 1) of the couch was 1.00 (p<0.05). The average percentage error of the couch in measuring the applied force and the motioncapture system in measuring the distance ranged from 0.41-1.12% and 0%, respectively.

Conclusion: The instrumented couch and the motion-capture system are appropriate to investigate both amount of force applied and displacement during manual therapy.


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