A geometric analysis of muscle mechanical power with applications to human gait.
ABSTRACT The interpretation and assessment of the biomechanical behaviour underlying complex movements such as human walking often requires that different time-series representations of the data be mentally combined. Geometrically based data presentation techniques (e.g. phase diagrams) which have been used in the past can sometimes reveal such information more easily through the link of mechanical behaviour to single plot geometries. Yet, examples such as phase or angle-angle diagrams are limited to movement description only (i.e. kinematics). In the present work, a method is introduced which graphs the factors of the muscle mechanical power equation (i.e. net muscle moment of force and relative joint angular velocity). The resulting planar space is called the "power plane" and it offers direct and simultaneous access to the relationship between specific variables associated with both movement and movement cause about a joint from the very plot geometry. In particular, the shape of the power portrait can reveal information about external influences and multiarticular interaction. The power plane diagram extends the phase diagram and is shown to reveal common patterning at the knee joint across various types of human gait which is not evident from the very different time-series plots.
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ABSTRACT: The Masai Barefoot Technology (MBT) shoe was developed as a walking device to improve gait stability and reduce the joint load. Kinematic changes with MBT shoes have been reported; however, kinetic characteristics with MBT shoes have not been adequately assessed. The purpose of this study was to investigate the immediate effects of using MBT footwear on the kinetic and kinematic changes in the lower extremity in healthy males. Fourteen healthy male subjects (mean age: 25.6 ± 5.1 years) underwent three-dimensional gait analysis. Ground reaction forces (GRF) during the shock absorption phase were significantly decreased with MBT shoes compared with stable shoes. Gait with the MBT shoes showed significantly decreased knee extension angle in the early stance phase, a decreased hip extension angle, and an increased ankle dorsiflexion angle in the late stance phase. The peak value of the ankle planter moment, ankle negative power, and vertical component of the GRF significantly decreased with MBT shoes in the late stance phase compared with stable shoes. Therefore, MBT shoes could assist with shock absorption in the early stance phase and maintain the progression force while reducing joint moment and power. The results of this study suggest that MBT shoes might be effective to improve shock absorption, increase knee extensor muscle activity, and assist ankle push-off.Gait & posture 01/2012; 35(4):567-72. · 2.58 Impact Factor
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ABSTRACT: The purpose of this study was to test the hypothesis that limb propulsion is mainly associated with the interaction of a number of muscle power bursts developed throughout the stance phase and that the control actions are mainly achieved by the contralateral limb through different power-burst interactions. We also hypothesized that the power activities of the propulsion limb would be related to those of the control limb. Sixty gait trials of 20 subjects with dominant right hands and right legs were chosen for analysis. Each trial represents a performance of an able-bodied gait. Data were assessed using an eight-camera, high-speed, video-based system synchronized to two force plates. The muscle powers and their related mechanical energies were calculated at each joint and in each plane of the lower limbs by use of an inverse dynamic technique. The Pearson correlation method was used to determine the relationships within each limb by use of the data identified by principal component analysis, whereas a canonical correlation analysis was performed to illustrate the interaction between the limbs. Gait propulsion was an activity initiated by the hip shortly after heel-strike and maintained throughout the stance phase. Control was the main task of the left limb as evidenced by the power absorption bursts at the hip and knee. The left limb power generations were generally secondary to control activities and were possibly involved in adjustments to correct the other limb's propulsion. Interlimb interaction further emphasized the functional relationship between forward progression and control tasks developed by each limb and highlighted the importance of the frontal and transverse plane actions during gait. These results do not support the hypothesis that the ankle was a major contributor to forward progression.American Journal of Physical Medicine & Rehabilitation 12/2001; 80(11):821-30. · 1.73 Impact Factor