Effects of volleyball match-induced fatigue on knee joint position sense

Abstract

It has been suggested that a greater number of injuries during the last third of practice sessions or matches could be related to alteration of lower limb neuromuscular control due to neuromuscular fatigue. This fatigue-related effect can be mediated by changes in joint proprioception. In athletes, the use of functional fatigue protocols could have the advantage of mimicking the demands of sporting activity, thus reflecting more specifically the changes in neuromuscular control and proprioception observed in sport settings. The purpose of the present study was to assess the effect of fatigue induced by a volleyball match on knee joint position sense in elite volleyball players. Seventeen female volleyball players aged 18.9±4.2 years from the Portuguese national team volunteered for the study. Knee joint position sense was evaluated by an open kinetic chain technique and active knee positioning, and was reported using absolute, relative, and variable angular errors. Joint position sense measures were obtained before and immediately after a simulated volleyball match of five sets. To ensure that the match was sufficiently intense to induce fatigue, the perceived exertion or exercise intensity was assessed at the end of the match using Borg’ s rating of perceived exertion (RPE) scale. All participants completed the volleyball match (90min duration), reaching or exceeding 15 on the RPE scale (15.59±0.71; range 15–17), equivalent to “hard/heavy work”. After the volleyball match, a significant increase in absolute (2.11°) and relative (1.71°) angular errors was detected. Match-induced fatigue significantly exacerbated the overestimation of the test position. Moreover, the reliability and accuracy in estimating knee angles decreased from rest to the fatigued state, as shown by the increase (264%) in variable error. Our results show that fatigue induced by a volleyball match has a marked effect on knee joint position sense in elite female volleyball players. Knee joint position sense was less accurate and less consistent after the volleyball match. Fatigue induced by a simulated competitive volleyball match resulted in proprioceptive deficits, decreasing sensorimotor system acuity in female volleyball players.     

Impact of hockey skate design on ankle motion and force production

Dynamic forces and range of motion (ROM) were measured during on-ice skating using a standard hockey skate and a modified skate (MS) with an altered tendon guard and eyelet configuration. The objective of this study was to determine if these modifications resulted in biomechanical and performance changes during on-ice skating skills. The right skate of each type was instrumented with a calibrated strain gauge force transducer system to measure medial?Clateral and vertical forces during ice skating. In addition, a goniometer was placed about the ankle and rear foot to measure ROM during skating. Ten subjects executed three skills: forward skating, crossovers inside foot and crossovers outside foot. The MS demonstrated significant gains of 5°?C9° in dorsi-plantarflexion ROM (p?<?0.05). Total peak force occurred later during plantarflexion, suggesting a more prolonged and effective force generation with the MS during a given skating stride. A 14?C20?% increase (p?>?0.05) in mean work and power output was noted with the MS, although no improved times were observed during the skating skills. Potentially, some players may need a period of familiarization to take advantage of the design alterations of the MS.     

Relationships between intrinsic motivation, physical self-concept and satisfaction with life: a longitudinal study

In this study, we examined the relationships between intrinsic motivation, physical self-concept, and satisfaction with life using cross-lagged panel models analysed via structural equation models. The sample consisted of 293 participants (148 men, 145 women) aged 18-70 years who performed diverse types of physical exercise. Three alternative models were tested. The data were better represented by a model in which physical self-concept mediates the relationships between intrinsic motivation and satisfaction with life. Specifically, the direct effects of intrinsic motivation on physical self-concept, and of physical self-concept on satisfaction with life were significant, with the amount of explained variance increasing over time. In conclusion, people who perform physical exercise regularly, and who have fun over time will tend to have a better physical self-perception and, consequently, more psychological well-being.     

Dimensional studies of specific microscopic fibre structures in deteriorated parchment before and during shrinkage

This paper reports the first systematic study of the dimensions of morphological changed microscopic collagen fibres in historical and new reference parchments with the aim to improve the knowledge on deterioration and the diagnosis of their damage in connection with conservation activities. The dimensions of fibres from the parchments were measured before and during shrinkage, with special emphasis on fibres with degradation characteristics designated as “pearls on a string” and “butterflies”. In addition, measurements of the total shrinkage of the length of fibres and pieces of parchment were also carried out. The observations support the assumption that in vivo transformation of the fibre structure by natural ageing is similar to that taking place when heating parchment and fibres in water. Based on statistical cluster analysis, four subpopulations of pearls representing different stages of deterioration are found. Moreover, the dimensional changes in the specific structures observed at room temperature can be related to specific temperatures in the interval of shrinkage suggesting that the hydrothermal stability of the fibres may be predicted on the basis of the ratio between length and width of the so-called pearls (P_l/P_w). The total shrinkage measured is drastic, in average around 56% for fibres and 43 to 48% for pieces of parchment depending on the direction of the skin. The total shrinkage of fibres corresponds to a mean change in the ratio P_l/P_w from around 10 to around 2.3. Finally, relations between the measured dimensions at the microscopic level with those of collagen at nanoscopic and molecular levels including known and potential chemical splitting points strongly indicate that the formation of the butterfly-like fragments formed by cleavage of two adjacent pearls in the fibre can be ascribed to chemical modification of specific tripeptides in the collagen molecule.     

Contribution of historical Spanish inventions to the knowledge of olive oil industrial heritage

This article presents new research, which has the objective of quantifying the knowledge produced by historical technological innovations in the field of olive oil industrial heritage. It studies inventions related to the mechanical processes of the extraction of olive oil between 1826 and 1966, which are recorded in the Historical Archive of the Spanish Patent and Trademark Office. It uses a new adaptation of the methodology of knowledge management (KM) defined by Nonaka and Takeuchi. We have obtained the knowledge value of each innovation according to the level of technological knowledge registered at the time, while distinguishing between the historical evolution of inventions relating to milling and those relating to pressing. In the first analysis, the results show a recession in the quantitative level of knowledge in the olive oil sector with respect to the technological potential of the time. However, when contrasted with the events relating to industrial heritage at the time, it is possible to account for this technological evolution and prove the validity of the methodology used. The results show that general evolution of the knowledge generated has decreased, particularly in the pressing process, although this is not the case in the milling process.     

Equalities and Gay and Lesbian Young People: Implications for educational psychologists

This paper describes the work of one Educational Psychology Service in examining educational issues around gay and lesbian young people, and exploring how educational psychologists may be able to make a positive contribution. Set within a whole service approach to equalities, the paper suggests concrete ways in which the profession can make a difference for this potentially vulnerable population of young people.     

Part-time education at tertiary level in the Netherlands

In Holland there are not many opportunities of obtaining a university degree through studying in the evenings and at weekends. Only a few faculties have facilities and even these are limited. It is known, however, that at the moment there are no less than 10,000 students with full-time jobs (approximately 10% of the total number of university students). Finding adequate accommodation for this group is one of the major problems in the present educational system at Dutch Universities.The most important aim of the investigation reported in this paper was to establish a profile of the evening (or working) students, on the basis of personal and background data, motivation and the problems they had to cope with. We presented to the working students questions about the structural aspects, the didactic processes and the organisational planning of a curriculum at a possible future Evening University of Holland.This report recommends that an early start be made on an educational institution, organised nation-wide but with local departments, which focuses especially on working students.Translation: Drs. Henny Corver