行走模式对人体下肢三维步态、肌电信号的影响

目的:揭示人体在主动和被动两种行走模式下的步态特征与下肢主要肌群的肌电信号变化规律.方法:选取12名在校男大学生,通过Greenjog履带式自发力跑台和h/p/cosmos电动跑台建立主动式和被动式行走模型,先后在两种模式下以3种递增速度即慢速(2 km/h)、常速(4 km/h)、和快速(6 km/h)进行一次性步行...     

Computational Models to Synthesize Human Walking

The synthesis of human walking is of great interest in biomechanics and biomimetic engineering due to its predictive capabilities and potential applications in clinical biomechanics, rehabilitation engineering and biomimetic robotics. In this paper, the various methods that have been used to synthesize humanwalking are reviewed from an engineering viewpoint. This involves a wide spectrum of approaches, from simple passive walking theories to large-scale computational models integrating the nervous, muscular and skeletal systems. These methods are roughly categorized under four headings： models inspired by the concept of a CPG （Central Pattern Generator）, methods based on the principles of control engineering, predictive gait simulation using optimisation, and models inspired by passive walking theory. The shortcomings and advantages of these methods are examined, and future directions are discussed in the context of providing insights into the neural control objectives driving gait and improving the stability of the predicted gaits. Future advancements are likely to be motivated by improved understanding of neural control strategies and the subtle complexities of the musculoskeletal system during human locomotion. It is only a matter of time before predictive gait models become a practical and valuable tool in clinical diagnosis, rehabilitation engineering and robotics.     

Reflections on clinical gait analysis

Clinical gait analysis allows the measurement and assessment of walking biomechanics, which facilitates the identification of abnormal characteristics and the recommendation of treatment alternatives. The predominant methods for this analysis currently include the tracking of external markers placed on the patient, the monitoring of patient/ground interaction (e.g. ground reaction forces), and the recording of muscle electromyographic (EMG) activity, all during gait. These data allow the computation of stride and temporal parameters, joint/segment kinematics, joint kinetics, and EMG plots that are used to gain a better understanding of a patient's walking difficulties. Gait interpretation involves a systemic evaluation of each of these types of data, noting both corroborating and conflicting information while identifying functionally significant deviations from the normal. Understanding the etiology of these abnormalities allows the formulation of a treatment plan that may involve physical therapy, bracing, and/or surgery. This process is challenging because of the complexity of the motion, neuromuscular involvement of the patient (e.g. dynamic spasticity), variability of treatment outcome, and on occasion, uncertainty about the quality of the gait data. The experience of the interpretation team with respect to gait biomechanics, a particular patient population, and the effectiveness of different treatment modalities is the principal determinant of the success of this approach. The clinical gait analysis process continues to evolve positively. It has become more comprehensive and meaningful because of an improved understanding of normal gait biomechanics and more rigorous data collection/reduction protocols that complement accumulated clinically relevant experience.     

Quadrupedal locomotion in squirrel monkeys (Cebidae: Saimiri sciureus): a cineradiographic study of limb kinematics and related substrate reaction forces

Quadrupedal locomotion of squirrel monkeys on small-diameter support was analyzed kinematically and kinetically to specify the timing between limb movements and substrate reaction forces. Limb kinematics was studied cineradiographically, and substrate reaction forces were synchronously recorded. Squirrel monkeys resemble most other quadrupedal primates in that they utilize a diagonal sequence/diagonal couplets gait when walking on small branches. This gait pattern and the ratio between limb length and trunk length influence limb kinematics. Proximal pivots of forelimbs and hindlimbs are on the same horizontal plane, thus giving both limbs the same functional length. However, the hindlimbs are anatomically longer than the forelimbs. Therefore, hindlimb joints must be more strongly flexed during the step cycle compared to the forelimb joints. Because the timing of ipsilateral limb movements prevents an increasing amount of forelimb retraction, the forelimb must be more protracted during the initial stance phase. At this posture, gravity acts with long moment arms at proximal forelimb joints. Squirrel monkeys support most of their weight on their hindlimbs. The timing of limb movements and substrate reaction forces shows that the shift of support to the hindlimbs is mainly done to reduce the compressive load on the forelimb. The hypothesis of the posterior weight shift as a dynamic strategy to reduce load on forelimbs, proposed by Reynolds ([1985]) Am. J. Phys. Anthropol. 67:335-349; [1985] Am. J. Phys. Anthropol. 67:351-362), is supported by the high correlation of ratios between forelimb and hindlimb peak vertical forces and the range of motion of shoulder joint and scapula in primates.     

Pendular activity of human upper limbs during slow and normal walking

When walking at normal and fast speeds, humans swing their upper limbs in alternation, each upper limb swinging in phase with the contralateral lower limb. However, at slow and very slow speeds, the upper limbs swing forward and back in unison, at twice the stride frequency of the lower limbs. The change from “single swinging” (in alternation) to “double swinging” (in unison) occurs consistently at a certain stride frequency for agiven individual, though different individuals may change at different stride frequencies. To explain this change in the way we use our upper limbs and individual variations in the occurrence of the change, the upper limb is modelled as a compound pendulum. Based on the kinematic properties of pendulums, we hypothesize that the stride frequency at which the change from “single swinging” to “double swinging” occurs will be at or slightly below the natural pendular frequency (NPF) of the upper limbs. Twenty-seven subjects were measured and then filmed while walking at various speeds. The mathematically derived NPF of each subject's upper limbs was compared to the stride frequency at which the subject changed from “single swinging” to “double swinging.” The results of the study conform very closely to the hypothesis, even when the NPF is artificially altered by adding weights to the subjects' hands. These results indicate that the pendulum model of the upper limb will be useful in further investigations of the function of the upper limbs in human walking. © 1994 Wiley-Liss, Inc.