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In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy
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Transverse pelvic rotation during quiet human stance.
Michael Günther1, Daniel Otto, Otto Müller
1Eberhard-Karls-Universität, Orthopädische Klink, Biomechaniklabor, Tübingen, Deutschland, Germany. guenther@tat.physik.uni-tuebingen.de
Gait & Posture
|July 24, 2007
Summary
Quiet stance biomechanics remain unclear. This study found ground reaction torque stabilizes body rotation by counteracting high-frequency pelvic angle shifts, rather than through simple rotational stiffness. This offers insights into postural control mechanisms.
Area of Science:
- Biomechanics
- Human postural control
- Human kinetics
Background:
- The precise mechanisms governing stable two-legged quiet stance are not fully understood.
- Investigating the body's rotational stability during quiet standing is crucial for understanding human locomotion and balance.
Purpose of the Study:
- To investigate biomechanical parameters characterizing the mechanisms of body rotation around the longitudinal axis during quiet stance.
- To test the hypothesis that the pelvis is coupled to the ground by rotational stiffness from both legs, with ground reaction torque proportional to pelvic angle.
Main Methods:
- Ten subjects stood quietly on force platforms measuring transverse ground reaction torque (GRT).
- Hip kinematics were recorded using marker tracking in the sagittal plane.
- Pelvic rotation in the transverse plane was calculated from hip marker coordinates.
Main Results:
- The hypothesis that transverse GRT is proportional to pelvic angle was rejected.
- Transverse GRT was identified as a stabilizing mechanism for higher-frequency pelvic angle deflections (>1 Hz).
- A stiffness coefficient of approximately 2.4 Nm/degrees was found between transverse GRT and the relative displacement of high- and low-frequency pelvic angle components.
Conclusions:
- Quiet stance involves a rotational stabilizing mechanism where ground reaction torque actively corrects rapid pelvic oscillations.
- Findings suggest a more dynamic control of body rotation than simple passive stiffness.
- Implications for understanding the control and localization of active body rotation during stance are discussed.
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