Biomedical subjects

T Karcnik

Publications and source records attributed to T Karcnik.

7 recordsLinked to original sources

PubMed2003

Using motion analysis data for foot-floor contact detection.

A simple, fast and straightforward method was developed for automatically deriving foot-floor contact information from tracking motion analysis system markers attached to the shoes of the subjects. The method was based on an accurate calibration of the motion analysis system prior to the experiments and a trivial off-line threshold-based algorithm using dedicated foot-attached marker positions and velocities as inputs. The main purpose of the method was to obtain the results almost instantaneously. The accuracy was poorer when compared with the classic, man-assisted and time-consuming methods, but the average error was less than 0.1 s compared with the force plate or pressure insole/foot switch-based methods. The method eliminates the need for foot switches when a motion analysis system is already being used. As encumbrance is reduced for the subjects, the method is also applicable to pathological gait patterns.

Biomechanical Phenomena↗

PubMed2001

Stability analysis of four-point walking.

The aim of the experiment reported here was to determine the static and dynamic stability of two-point stance phases when walking on hands and knees at different speeds. In addition, we defined the methods and predicted the consequences of including two-point stance phases into crutch assisted functional electrical stimulation (FES) walking. Crawling on hands and knees was performed at three speeds by five healthy male persons. With twelve joint-position markers placed on the subject, we determined two stability indices for every instant of gait. We analysed the peak values of these two indices during the two-point stance phases. The results indicate that we have to ensure the proper position of the centre of gravity to increase the speed of walking. To reach speeds, lower than 0.6 m/s, it is not necessary to include statically unstable phases. The shift of the centre of gravity towards and across the leading stability edge can result in getting into the dynamically unstable state. Considering the results we can effectively introduce two-point stance phases into crutch assisted FES walking and therefore increase the speed and energy effectiveness of walking

Biomechanical Phenomena↗

PubMed1999

Stability and velocity in incomplete spinal cord injured subject gaits.

We have defined 2 indices describing gait kinematic and dynamic stability. We assessed their values in the gaits of 5 different paraparetic subjects. The indices are correlated to the gait velocity to prove the close relationship between overall gate velocity and stability. Based on stability analysis and certain kinematic parameters, some possible ways of increasing the average gait velocity are explained.

Algorithms↗

PubMed1997

Improvement in step clearance via calf muscle stimulation.

The aim is to study the influence of electrically stimulated calf muscles on the effectiveness of the swinging leg movement. The study is carried out with a group of patients with incomplete spinal cord injuries both under stationary conditions and during crutch-assisted walking. Before stimulation is applied to the ankle plantar flexors, the knee extensors are inactivated. In each cycle, after ankle plantar flexor stimulation, peroneal stimulation is started, triggering the flexion reflex. From a biomechanical point of view, functional electrical stimulation (FES) of the ankle plantar flexors results in increased ground clearance of the lower extremity. Additionally, the FES-assisted lifting of the heel results in the elimination of extensor tone and thus shortens the swing time.

Adolescent↗

PubMed1997

Effects of respiratory muscle training and electrical stimulation of abdominal muscles on respiratory capabilities in tetraplegic patients.

Thirteen tetraplegic patients were included in the study of the effects of respiratory muscle training and of electrical stimulation of the abdominal muscles on their respiratory capabilities. Each patient was subjected for three 1 month lasting periods of the study: for inspiratory muscle training, expiratory muscle training and for a period without training. The sequence of these three periods was random for each patient. Respiratory tests (RT) measuring forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were conducted before and following each monthly period. Measurements were taken under four sets of conditions: the patients' unassisted efforts, their efforts combined with pressure manually applied by a therapist to the upper part of their abdomen, and their efforts accompanied by electrical stimulation (ES) of the abdominal muscles during the early phase of expirium, once triggered by the therapist and once by the patients themselves. RT values were increasing following respiratory muscle training and inspiratory training apparently had a slightly greater effect than its expiratory counterpart. The increments of values of RT were statistically significant (P < 0.05) after the inspiratory muscle training. RT measurements were greater when the patient's voluntary effort was combined with ES of abdominal muscles than when it was not. This study concludes that respiratory muscle training is a potentially effective approach and that ES of the abdominal muscles has potentials to improve coughing in tetraplegic patients.

Abdominal Muscles↗

PubMed1997

Influence of electrically stimulated ankle plantar flexors on the swinging leg.

The influence of functional electrically stimulated ankle plantar flexors on the swinging lower extremity was studied in incomplete spinal cord injured persons. Stimulation sequences with different time and frequency parameters were delivered to ankle plantar flexors and knee extensors and to the peroneal nerve. The results of kinematic assessment showed that stimulated calf muscles provide noticeable forward and upward propulsion to the swinging leg.

Adolescent↗

PubMed1997

Stability and energy criteria in healthy and paraplegic subject gait.

The functional electrical stimulation (FES) assisted gait of paraplegic patients is inferior to that of healthy subjects. The difference can be observed in terms of speed, upright balance, biomechanical energy consumption, and generation of propulsion forces in the direction of walking. The biomechanical structure of paraplegic subjects is the same as that of normal ones; however, the mode of walking differs significantly because of the reduced number of activated muscles and primitive control. The healthy subject is utilizing a 2-point dynamically stable gait. The paraplegic patient is using 4-channel FES and utilizing a 4-point statically stable gait. We believe that the FES gait can be improved if converted into a semidynamically or dynamically stable gait. The gait is considered statically stable if the center of gravity (COG) projection on the ground (PCOG) is inside the supporting area. For a quadruped, this is only possible if it is utilizing a creeping crawl gait. In this paper, the relationship between PCOG and the supporting area are discussed as a criterion for dynamic stability assessment. Results are shown for 3 different modes of 2-point and 4-point gaits.

Biomechanical Phenomena↗