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.     

Changes in swimming technique during time to exhaustion at freely chosen and controlled stroke rates

Abstract

The aim of this study was to assess technical changes during constrained swimming in time-to-exhaustion tests. Ten swimmers of national standard performed a maximal 400-m front crawl and two sets of exhaustion tests at 95%, 100%, and 110% of mean 400-m speed. In the first set (free), swimmers had to maintain their speeds until exhaustion and mean stroke rate was recorded for each test. In the second set (controlled), the same speed and individual corresponding stroke rate were imposed. The durations of the exhaustion tests, relative durations of the stroke phases, and arm coordination were analysed. For each speed in the “controlled” set, the exhaustion tests were shorter. Moreover, variables were consistent, suggesting a stabilization of stroke technique. Under the free condition, stroke rate increased to compensate for the decrease in stroke length. At the same time, swimmers reduced the relative duration of their non-propulsive phases in favour of the propulsive phases. Thus, swimmers changed their arm coordination, which came close to an opposition mode. These two constraints enable swimmers both to maintain their stroking characteristics and develop compensatory mechanisms to maintain speed. Moreover, stroke rate can be seen as a useful tool for controlling arm technique during paced exercise.     

Kinesthetic Perception of the Vertical as a Function of Sport Experience

Abstract

Near-infrared spectroscopy is currently used to assess changes in the oxygen saturation of the muscle during exercise. The primary purpose of this study was to assess the reliability of near-infrared spectroscopy in determining muscle oxygen saturation (StO₂) in the vastus lateralis during cycling and the gastrocnemius during running for exercise intensities at lactate threshold and maximal effort. Test-retest reliability was determined from an intraclass correlation coefficient obtained from a one-way analysis of variance. Reliability of muscle StO₂ for the gastrocnemius at lactate threshold was R = .87, and R= .88 at maximal effort. Reliability of muscle StO₂ for the vastus lateralis at lactate threshold was R= .94 and R = .99 at maximal effort.     

Toddlers Use the Number Feature in Determiners During Online Noun Comprehension

Function words support many aspects of language acquisition. This study investigated whether toddlers understand the number feature of determiners and use it for noun comprehension. French offers an ideal “test case” as number is phonetically marked in determiners but not in nouns. Twenty French‐learning 24‐month‐olds completed a split‐screen experiment. Looking times to target pictures were measured under 3 trial types varying in the degree to which the determiner matched the number displayed in the object(s). Children looked longer when the determiner matched the object(s), and were confused in trials of clear mismatch. Importantly, their processing resembled that of French adults ( D. Dahan, D. Swingley, M. K. Tanenhaus, & J. S. Magnuson, 2000 ). Thus, children understand the determiner number feature early in acquisition and use this knowledge to constrain online comprehension.     

The effect of practice on Raven's Advanced Progressive Matrices

Sixty-seven participants (39 men and 28 women), ranging in age from 26 to 79 years, were administered Raven's Advanced Progressive Matrices (APM) on three occasions. Although total APM scores were found to be highly reliable across the three occasions, the reliabilities of most individual items were extremely low. A single-factor model remained a borderline adequate fit (explaining approximately 20% of the variance) for the interitem correlation matrix on all three occasions. Total APM scores increased significantly across the three occasions (approximately two items per occasion). Improvements in total score across the occasions happened within a context of subjects changing both correct and incorrect responses from the previous occasion. The number of items left unanswered was found to be unrelated to both APM score on any given occasion and the amount of gain in score made across occasions. These findings suggest that the improvements in performance were not based on the acquisition of a strategy design to respond to more items or on the retention of item-specific information, but rather, the improvement reflected learning, something common to the types of items found in the APM.     

REACTION TIME AND INTELLIGENCE

The limited capacity theory is often cited to account for negative correlations between choice reaction time and different IQ measures. It is claimed, since working memory has strictly limited capacity to process a great amount of vital information and STM information decays if not rehearsed, that speed is an indispensable condition of efficient dealing with cognitive tasks. It ensures good performance before important information is forgotten. In the present experiment a special kind of task was applied‐one which supposedly puts a substantial load on the system of working memory. It was hypothesized that subjects dealing well with this task would also obtain high scores on general ability tests. The data obtained from 48 psychology students in the self‐paced, computer assisted study did not confirm this hypothesis. The data are interpreted as posing a challenge for the limited capacity theory, which must either be reformulated or replaced by better elaborated theoretical constructions.