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.     

Ready to learn? Children's pre-academic achievement in pre-Kindergarten programs

We examined children's growth in school-related learning and social skills over the pre-Kindergarten (pre-K) year in state-funded programs designed to prepare children for kindergarten. We expected that children's gains in academic and social skills could be attributed to variations in the structural and classroom process dimensions of program quality. Nearly 3000 (n = 2800) children were randomly selected, four per classroom, from approximately 700 randomly selected, state-funded pre-Kindergarten classrooms in eleven states. Enrollment in pre-K appeared related to gains in academic skills. Children showed larger gains in academic outcomes when they experienced higher-quality instruction or closer teacher–child relationships. Gains were not related to characteristics of the child or program (i.e., ratio, teacher qualifications and program location and length). These findings have implications for a range of state and local policy and program development efforts as well as for theories of contextual influences on development.     

“How are running shoes assessed? A systematic review of characteristics and measurement tools used to describe running footwear”

Background: Many footwear characteristics are argued as risk factors for running related injuries (RRI). Several footwear assessment tools are available; however, their use in studies of RRI is unknown. Objective: This systematic review evaluated the characteristics and methods of assessing footwear in studies of RRI. Design: Five online databases were searched for studies on adult runners, in running style footwear, who experienced running-related pain or injury. The methodological quality of included articles was independently assessed by two raters using a modified Downs and Black checklist. Study and participant characteristics, footwear assessment tools used, and footwear characteristics reported were extracted for qualitative synthesis. Results: Twenty-four articles were included in the review. Low risk of bias was determined for 11 (44%) of the included studies. Twenty-eight different footwear characteristics were grouped into four categories: nomenclature, measurements, qualitative features, and subjective features. Fifteen different methods for assessing the 28 footwear characteristics were reported among the included studies. Only three methods were described previously, as valid and reliable. Conclusion: Differences in assessing footwear may mask the link between footwear characteristics and injury risk. Systematic footwear assessments and nomenclature are needed to evaluate the effects of footwear characteristics on RRI.     

Physical activity and school recess time: differences between the sexes and the relationship between children's playground physical activity and habitual physical activity

The aims of this study were: (1) to observe participation in moderate-to-vigorous physical activity (MVPA) during school recess periods; (2) to determine the relative importance of physical activity during recesses to overall daily physical activity; and (3) to examine differences in physical activity between the sexes during unstructured recess periods. The participants were 22 school children (10 boys, 12 girls) aged 8 - 10 years (mean = 8.9, s = 0.7) in the third and fourth grades. Daily totals for the physical activity variables were calculated by summing the values for each hour of 14 h of physical activity measurements (08:00 to 22:00 h). Recess times (minutes) were as follows: morning 10:30 to 11:00 h and afternoon 15:30 to 16:00 h. We did not differences between boys and girls in daily total accelerometer counts or the overall time spent in MVPA. However, girls were significantly (P < 0.05) more involved (38%) in MVPA during recess time than boys (31%). Participation in MVPA during recess contributes significantly more (P < 0.05) for girls (19%) than boys (15%) to the total amount of physical activity suggested by international health-related physical activity guidelines, while the percentage of time engaged in MVPA during recess time at school accounts for a small amount of the daily MVPA (6% for boys and 8% for girls). The results of this study suggest that school recess time is an important setting to promote MVPA and contributes to daily physical activity in young children, especially in girls.