Clinical gait analysis is a term that can be applied to numerous methods of evaluating a subject's walking pattern. These methods may include observation, videotaping, electromyography, kinematics, ...kinetics, and energetics. Modern gait analysis is based on the integration of these component methods of measurement to derive a complete analysis of gait. The data may then be used to help determine the treatment course of a patient with ambulatory problems or to document the effects of treatment. The purpose of this article is to provide an overview of the individual components of gait analysis. Emphasis will be placed on the type of information that can be derived from each component and how the information may be used clinically. Normal pediatric kinematics and kinetics are provided with literature references for phasic electromyography and temporal and stride variables. Two case examples illustrate the clinical utility of gait analysis information applied to cerebral palsy in surgical decision making and orthotic assessment. Guidelines are also provided for the referral of patients to a gait analysis laboratory.
Observational learning is considered powerful to promote (implicit) motor learning. While it is a common tool in practice, little is known about the effects of video instructions on movement ...execution. The aim of this study was to investigate the effects of watching biomechanically optimal (OPT) and suboptimal (SUBOPT) sidestep cutting (SSC) video instructions on movement execution. Ten male basketball players (age 15.5 ± 1.2 years, height 189.9 ± 3.1 cm, mass 75.4 ± 7.1 kg) from a Regional Talent Center performed anticipated 45° SSC tasks in baseline (BASE) followed by two counterbalanced experimental conditions. Subjects watched expert videos (matched by sex and height) of OPT and SUBOPT movement executions and were asked to imitate this to the best of their ability. Kine(ma)tic data was captured with 21 reflective markers and 2 force plates. After watching the videos, subjects displayed smaller ankle dorsiflexion angles (p < 0.001) and greater vertical ground reaction force (vGRF) (p = 0.012) in SUBOPT compared to OPT condition during initial contact (IC). Greater knee flexion and ankle dorsiflexion angles in the expert compared to subjects in the OPT condition were found (p < 0.001). Contrarily, subjects were able to imitate SUBOPT executions shown by the expert. This means that athletes worsen their movement execution when modelling a SUBOPT model. Coaches are advised to mainly use (1) OPT video instructions and (2) expert modelling with a relatively small gap in movement execution between the athlete and model.
Studies for effective golf coaching such as providing a causal relationship between the address posture and golf-swing behaviors are limited. This study investigated the effects of ball position on ...golf-swing behaviors. Twenty professional golfers performed golf swing at five different anteroposterior (forward/backward) ball positions: reference ball position (R0) and ±2.14 cm (golf ball radius) and ±4.17 cm (golf ball diameter) to the R0. Their swings were captured using a motion capture system with two force platforms. Statistical parametric mapping was used to compare the ground reaction forces and swing kinematics for different ball positions. The backward (closer to the golfer) ball positions were associated with more extended trunk, knee, and ankle angles in the sagittal plane during the entire golf swing (from address to impact) compared to that of the R0. The backward ball positions were generally associated with decreased horizontal ground reaction forces and pelvis and X-factor angles in the transverse plane during the downswing compared to that of the R0. Whereas, these patterns were reversed for the forward ball positions. These results demonstrate the value of ball position for coaching methods including the importance of a consistent ball position and reveal a consistent human control system for professionals which can provide valuable information for modeling the features of a digitized coaching tool.
Individuals with cerebral palsy frequently exhibit crouch gait, a pathological walking pattern characterized by excessive knee flexion. Knowledge of the knee joint moment during crouch gait is ...necessary for the design and control of assistive devices used for treatment. Our goal was to 1) develop statistical models to estimate knee joint moment extrema and dynamic stiffness during crouch gait, and 2) use the models to estimate the instantaneous joint moment during weight-acceptance. We retrospectively computed knee moments from 10 children with crouch gait and used stepwise linear regression to develop statistical models describing the knee moment features. The models explained at least 90% of the response value variability: peak moment in early (99%) and late (90%) stance, and dynamic stiffness of weight-acceptance flexion (94%) and extension (98%). We estimated knee extensor moment profiles from the predicted dynamic stiffness and instantaneous knee angle. This approach captured the timing and shape of the computed moment (root-mean-squared error: 2.64 Nm); including the predicted early-stance peak moment as a correction factor improved model performance (root-mean-squared error: 1.37 Nm). Our strategy provides a practical, accurate method to estimate the knee moment during crouch gait, and could be used for real-time, adaptive control of robotic orthoses.
This paper describes the design of a 7 degree-of-freedom (d.o.f) manipulator for underwater inspection applications. The functional requirements of an underwater manipulator for subsea inspection are ...discussed and the desired performance requirements identified. The inspection process of a weld joint using a manipulator is described and the desirable attributes of a 5 d.o.f manipulator for the inspection process established. A novel kinematic structure, for Underwater Robotic Vehicle (URV) operation, having a 2 d.o.f launching stages and a 5 d.o.f inspection stage is proposed for the manipulator. This configuration increases the dexterity, without compromising on the total reach of the manipulator. The kinematic structure of the 7 d.o.f, 2 stage, manipulator is presented. A hybrid power actuation is proposed for the manipulator to exploit the benefits of both hydraulic as well as electric actuators. Kinematic analysis of the manipulator is presented. The link dimensions of the inspection stage manipulator is done on the basis of kinematic performance indices of the manipulator. The novel kinematic structure and the hybrid power actuation strategy results in a power efficient, dexterous manipulator for underwater applications.
The objective of this paper is to establish a computer algorithm capable of simulating dynamics of variable configuration systems based on the unified matrix approach for multibody systems of N ...bodies connected by M generic hinges with M ≥ N. The system may have an arbitrary system topology, including chain, tree and closed-loop configuration. Hinge can be either a physical joint mechanism such as gimbal, ball-joint, or spring-damper, or a hypothetical connecting point of two adjacent bodies as in case of docking. Any change in configuration and constraint conditions has been modeled by a function dependent on time and states. The approach developed here is essentially based on the formulation of a matrix form of the linear algebraic equation to be solved simultaneously for the time derivatives of non-holonomic angular and linear momenta, and the internal non-working constraint torques and forces. The non-holonomic momenta are derived for each body referring to the angular and linear velocities with respect to the inertially fixed frame expressed in the body frame of each body. With this selection of the variables, the linear equation takes a form Ax=B, where the coefficient matrix A represents the system configuration and the constraint conditions. This approach has been proven useful in simulation, such as separation, connection, topology change, and change in constraint degrees-of-freedom.
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