Biomedical subjects

A Forner Cordero

Publications and source records attributed to A Forner Cordero.

5 recordsLinked to original sources

PubMed2005

Energy analysis of human stumbling: the limitations of recovery.

This study has analyzed the segmental energy changes in the recovery from a stumble induced during walking on a treadmill. Three strategies emerged according to the behavior of the perturbed limb, elevating, lowering, and delayed lowering. These three strategies showed different changes in the segmental energy with respect to normal gait. In the elevating strategy, the energy loss induced by the stumble was restored during the perturbed step and reached normal levels during the recovery step. The largest energy changes occurred in the lowering and delayed lowering strategies during the double stance (DS) phase. Moreover, in some of these trials there was energy absorption during the double stance phase for several strides after the perturbation. The most challenging perturbations had longer duration or occurred at mid-swing, triggering delayed lowering or lowering strategies, because more strides and larger energy changes were needed to recover, suggesting a trade-off between stability and energy efficiency.

Adult↗

PubMed2004

Mechanical model of the recovery from stumbling.

Several strategies have been described as a reaction to a stumble during gait. The elevating strategy, which tries to proceed with the perturbed step, was executed as a response to a perturbation during early swing. The lowering strategy, bringing the perturbed leg to the ground and overtaking the obstacle with the contralateral limb, was executed more frequently when the perturbation appeared at mid or late swing. The goal of this paper is to analyze which mechanical factors determine the most advantageous strategy. In order to determine these factors, a mechanical model of the recovery was developed and used to analyze a series of perturbation experiments. It was assumed that the goal of the recovery reaction was to control the trunk as an inverted pendulum during the double-stance phase. In order to be able to control the trunk angle, one foot should be up front and one foot should be behind the hips; otherwise it would be impossible to generate the required trunk torques. The trunk dynamics were expressed in terms of the ground reaction forces and their application point. A larger step (elevation strategy) gives the opportunity to dissolve the perturbation in one step. A small step (lowering strategy) necessarily results in a second quick step, after which the perturbation energy can be dissipated in the second double-stance phase. If a recovery step is too slow, it becomes impossible to counteract the forward flexion of the trunk. It is suggested that a measure of the ability to recover from a stumble could be based on the ability to perform quick steps.

Adult↗

PubMed2004

Use of pressure insoles to calculate the complete ground reaction forces.

A method to calculate the complete ground reaction force (GRF) components from the vertical GRF measured with pressure insoles is presented and validated. With this approach it is possible to measure several consecutive steps without any constraint on foot placement and compute a standard inverse dynamics analysis with the estimated GRF.

Computer Simulation↗

PubMed2003

Multiple-step strategies to recover from stumbling perturbations.

This study has analysed the recovery from an induced stumble whilst walking on a treadmill. Four stumbling conditions were tested; at early swing with short and long durations and at mid and late swing with short duration. The experiment set-up, including the possibility of being stumbled, did not alter the normal gait patterns and the recovery strategies depended on the perturbation conditions. For the early swing perturbation, delayed lowering and elevating strategies were performed using the perturbed leg. A lowering strategy was seen for mid and late swing perturbations. An elevating strategy consisted of an elevation of the swing limb while a lowering one consisted of bringing the foot quickly to the ground. There were two groups of reactions to the experimental perturbation of gait. In the first, there was an effort to complete the disturbed step as normally as possible, so the following steps were less constrained to maintain treadmill speed. In the second group of reactions, the perturbed step was aborted and the recovery effort transferred to the contralateral limb. In many cases, several steps were needed to regain normal gait pattern. The study of recovery reactions from gait perturbations should include at least three steps after the perturbed one.

Adult↗

PubMed2003

Surface electromyography analysis for variable gait.

The surface electromyographic (SEMG) signal obtained during gait is often presented as the SEMG profile, the average SEMG activation pattern during one gait cycle. A disadvantage of this method is that it omits the step-to-step variability of the timing of the muscle activation patterns that might be relevant information as a performance measure of motor control and balance. In this paper, a method was used in which every step in the gait cycle could be analysed with respect to the timing of the muscle activation. For this purpose, the approximated generalised likelihood (AGLR) algorithm was implemented and tested. Results of the simulations show that the AGLR was much more accurate than a standard threshold criterion. Timing parameters could be calculated from a SEMG recording during gait and a measure for symmetry and coordination could be extracted. The amplitude distribution within and outside defined bursts is also presented to avoid the less precise classification into on and off patterns.

Algorithms↗