Search Results (5)

The effectiveness of railway brakes strongly depends on their thermal condition. A computer simulation and experimental investigations on a full-scale dynamometric stand were chosen as an adequate analysis of the heat transfer process in brakes. The article introduces a two-dimensional, axisymmetric numerical model of the tested disc brake. Boundary conditions related to the heat generated in the friction brake and heat transferred to the environment are also presented. The transient heat transfer problem was solved using the in-house computer program of the finite element method. The article presents simulations and experimental investigations of the intensive braking of a train with an initial high speed. Temperature responses of the disc brake on the friction surface and at other selected points are shown. In addition, a thermal imaging camera was used to assess the temperature distribution on the friction surface of the disc. The results of experimental and simulation tests were preliminarily compared. Similar maximum temperature values were obtained at the end of braking with a particular discrepancy in temperature responses during the analyzed process. Full article

Background: Kickboxing is a combat sport that is complex in technique, tactics, and movement structure, and requires an adequate level of motor skills as a foundation for activities during competitions. General physical fitness, defined as the effect of the externalization of motor skills, is the basis for athletic training regardless of the sport. The aim of this study was to determine the effect of modified training based on the principles of CrossFit on the development of general physical fitness in a group of kickboxers compared to a control group. Methods: The study was experimental in nature and was conducted in a group of 60 kickboxers, divided into experimental and control groups. Participants were selected by purposive sampling, and the criteria were training experience, sports skill level (minimum class 1 athletes), and consent to participate in the experiment. The intervention in the study group involved the introduction of CrossFit-based training into a conventional kickboxing training program. General and special physical fitness of the athletes were diagnosed. Results: Statistically significant differences were found in general fitness in terms of abdominal strength (p < 0.001), pull-ups (p < 0.001), dynamometric measurement of handgrip force (p < 0.001) (kg), clap push-ups (p < 0.001), standing long jump (p < 0.001), shuttle run (p < 0.001), sit-and-reach (p < 0.001), and tapping (p < 0.001). Furthermore, changes in special fitness were also demonstrated for the special kickboxing fitness test (SKFT) (p < 0.02), the total number of punches (p < 0.001), punching speed (p < 0.001), and hip turning speed (p < 0.001). There was also a correlation between characteristics of general fitness and special fitness (p < 0.001). Conclusions: The experimental training program based on the principles of CrossFit training had a positive effect on the general and special kickboxing physical fitness. Full article

The current study examined the back plate position impact on the block phase movement pattern and total starting performance with a distinction for sex. Thirty-eight swimmers performed starts changing the back plate position (preferred position, one position forward and one position backward), with the data being assessed using a 3D dynamometric central and a video camera. In males, the 15 m start time was 0.1 s shorter for the preferred position compared with the backward position (p < 0.05). Regardless of the back plate positioning, the swimmers spent a similar time on the block. A more forward position of the back plate postponed the rear foot take-off and consequently reduced the front foot stand duration. A back plate position effect was revealed for those variables with a larger effect size in males whereas in females, a change of about two positions was needed to reach a significance level. Probably due to the specification of physical domains, a greater impact on the changes introduced was noted for males. Therefore, whilst searching for the optimal starting position, adjustments to the back plate placement might affect a greater number of males than females. To reinforce the starting optimization during the training process and its monitoring, the effect of personal preference toward the starting block setting was also considered. Full article

Pompe disease is a multisystemic disorder with the hallmark of progressive skeletal muscle weakness that often results in difficulties in walking and balance. However, detailed characterization of gait and postural regulation with this disease is lacking. The objective of this investigation was to determine if differences exist between the gait and postural regulation of LOPD patients and a matched control group. The gaits of 16 patients with LOPD were assessed using a gait analysis mobile system (RehaGait) and a dynamometric treadmill (FDM-T 1.8). The Interactive Balance System (IBS) was used to evaluate postural regulation and stability. All measures were compared to individual reference data. Demographic (age, gender), morphological (body height, body mass) and clinical data (muscle strength according to the Medical Research Council Scale (MRC Scale), as well as the 6-min walking test and a 10-m fast walk) were also recorded. Compared to individual reference data, LOPD patients presented with reduced gait velocity, cadence and time in single stand. A total of 87% of LOPD patients had abnormalities during posturographic analysis presenting with differences in postural subsystems. This study provides objective data demonstrating impaired gait and posture in LOPD patients. For follow-up analysis and as outcome measurements during medical or physiotherapeutic interventions, the findings of this investigation may be useful. Full article

Various diseases are associated with the impaired control of the medio-lateral (ML) position of the centre of feet pressure (CoP), and several manoeuvres have been proposed for enhancing the CoP symmetry. Here, we assessed in healthy standing subjects the feasibility and outcome of a novel protocol entailing a reaction to a continuous asymmetric ML displacement (10 cm) of the support base. The periodic perturbation consisted of a fast half-cycle (0.5 Hz) followed by a slow half-cycle (0.18 Hz). One hundred successive horizontal translation cycles were delivered in sequence. Eyes were open or closed. CoP was recorded before, after, and during the stimulation by a dynamometric platform fixed onto the translating platform. We found that the post-stimulation CoP was displaced towards the direction of the fast half-cycles. The displacement lasted several tens of seconds. Vision did not affect the amplitude or duration of the post-stimulation effect. The magnitude of post-stimulation CoP displacement was related to the perturbation-induced ML motion of CoP recorded during the stimulation. Over the successive perturbation cycles, the time-course of this motion revealed an adaptation phenomenon. Vision moderately reduced the adaptation rate. The findings support the feasibility of the administration of a simple asymmetric balance perturbation protocol in clinical settings to help patients recover the symmetry of the CoP. This protocol needs to be further validated in older populations and in patients. Full article