Journal of biomechanics
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Journal of biomechanics · Oct 2008
Effects of walking speed, strength and range of motion on gait stability in healthy older adults.
Falls pose a tremendous risk to those over 65 and most falls occur during locomotion. Older adults commonly walk slower, which many believe helps improve walking stability. While increased gait variability predicts future fall risk, increased variability is also caused by walking slower. ⋯ Maximum FM showed similar changes with speed (p<0.02). Both younger and older adults exhibited decreased instability by walking slower, in spite of increased variability. These increases in dynamic instability might be more sensitive indicators of future fall risk than changes in gait variability.
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Journal of biomechanics · Sep 2008
Cervical helical axis characteristics and its center of rotation during active head and upper arm movements-comparisons of whiplash-associated disorders, non-specific neck pain and asymptomatic individuals.
The helical axis model can be used to describe translation and rotation of spine segments. The aim of this study was to investigate the cervical helical axis and its center of rotation during fast head movements (side rotation and flexion/extension) and ball catching in patients with non-specific neck pain or pain due to whiplash injury as compared with matched controls. The aim was also to investigate correlations with neck pain intensity. ⋯ A general increase of axis irregularity that correlated to pain intensity was observed in the whiplash group. The rotation center was superiorly displaced in the non-specific neck pain group during side rotation, with the same tendency for the whiplash group. During ball catching, an anterior displacement (and a tendency to an inferior displacement) of the center of rotation and slower and more restricted upper body movements implied a changed movement strategy in neck pain patients, possibly as an attempt to stabilize the cervical spine during head movement.
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Journal of biomechanics · Jul 2008
A new technique to measure the dynamic contact pressures on the Tibial Plateau.
Studies of the load transfer role of the meniscus have been limited to static experimental and analytical approaches. The objective of this study was to develop an experimental technique to allow the contact pressures on the tibial plateau of cadaveric knees to be measured under dynamic physiological loads. ⋯ Meniscectomy resulted in a 267% increase in average contact pressure, a 117% increase in peak contact pressure, and an 80% decrease in contact area, all measured at the point of maximum peak contact stress in the gait cycle. It is envisaged that the experimental model herein developed will allow for the screening of candidate materials prior to more expensive and time-consuming animal models.
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Journal of biomechanics · Jan 2008
Effects of a hip belt on transverse plane trunk coordination and stability during load carriage.
This study examined the transverse plane kinematics of the pelvis, thorax and head while participants walked at a range of speeds on a treadmill under three load conditions: no load, with a loaded backpack with no hip belt and with a loaded backpack with a hip belt. Research has suggested that one mechanism for adapting to heavy loads carried with no hip belt is to reduce the amplitudes and relative phase of transverse plane pelvic and thoracic rotations, in order to minimize rotational torque on the loaded upper body. Transverse plane rotation amplitudes of the pelvis, thorax, backpack and head were calculated from 3D kinematic data for 12 healthy subjects, walking at speeds of 0.5, 0.9, 1.3 and 1.7 ms(-1). ⋯ The backpack with the hip belt allowed significantly larger transverse plane rotation amplitudes, along with increased stability of the coordination pattern, than the backpack with no hip belt. Motion patterns of the backpack and thorax suggested that the backpack frame was used to assist with the deceleration and reversal of the loaded thorax, driven by the pelvis through the hip belt connection. Use of the frame in this way may have required less trunk muscle activation and allowed for improved pattern stability.
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Journal of biomechanics · Jan 2008
Effects of mechanical compression on metabolism and distribution of oxygen and lactate in intervertebral disc.
The objective of this study was to examine the effects of mechanical compression on metabolism and distributions of oxygen and lactate in the intervertebral disc (IVD) using a new formulation of the triphasic theory. In this study, the cellular metabolic rates of oxygen and lactate were incorporated into the newly developed formulation of the mechano-electrochemical mixture model [Huang, C.-Y., Gu, W. Y., 2007. ⋯ In contrast, static compression exhibited inverse effects on transport and metabolism of oxygen and lactate. The theoretical predictions in this study are in good agreement with those in the literature. This study established a new theoretical model for analyzing cellular metabolism of nutrients in hydrated, fibrous soft tissues under mechanical compression.