Reliability of the virtual elevation method to evaluate rolling resistance of different mountain bike cross-country tyres

Although a low rolling resistance is advantageous in mountain bike cross-country racing, no studies have used the virtual elevation method to compare tyres from different manufacturers as used in international competitions so far. The aims of this study were to assess the reliability of this method, to compare the off-road rolling resistance between tyres and to calculate the influence on off-road speed.

Nine 29-in. mountain bike cross-country tyres were tested on a course representing typical ground surface conditions 5 or 6 times. The coefficient of rolling resistance was estimated with the virtual elevation method by 3 investigators and corresponding off-road speeds were calculated.

The virtual elevation method was highly reliable (typical error = 0.0006, 2.8%; limits of agreement <0.0005, r ≥ 0.98). The mean coefficient of rolling resistance was 0.0219 and differed from 0.0205 to 0.0237 (P < 0.001) between tyres. The calculated differences in off-road speed amounted to 2.9–3.2% (0% slope) and 2.3–2.4% (10% slope) between the slowest and the fastest tyre.

The reliability of the method and the differences in rolling resistance between the tyres illustrate the value of testing tyres for important competitions on a representative ground surface using the virtual elevation method.     

Kicking Performance in Young U9 to U20 Soccer Players: Assessment of Velocity and Accuracy Simultaneously

Purpose: The purpose of this study was to compare the kicking performance of young soccer players in the U9 to U20 age groups. Method: Three hundred and sixty-six Brazilian players were evaluated on an official pitch using three-dimensional kinematics to measure (300 Hz) ball velocity (V_ball), foot velocity (V_foot), V_ball/V_foot ratio, last stride length, and distance between the support foot and the ball. Simultaneously, a two-dimensional procedure was also conducted to compute (60 Hz) the mean radial error, bivariate variable error, and accuracy. Possible age-related differences were assessed through one-way analysis of variance and magnitude-based inferences. Results: Ball velocity increased by 103% (p < .001, η² = .39) from the U11 age group (48.54 ± 8.31 km/hr) to the U20 age group (98.74 ± 16.35 km/hr). Foot velocity presented a 59% increase (p < .001, η² = .32) from the U11 age group (49.08 ± 5.16 km/hr) to U20 (78.24 ± 9.49 km/hr). This finding was due to improvement in the quality of foot–ball impact (V_ball/V_foot ratio) from U11 (0.99 ± 0.13 a.u.) to U20 (1.26 ± 0.11 a.u.; p < .001, η² = .25). Parameters such as mean radial error and accuracy appeared to be impaired during the growth spurt (U13–U15). Last stride length was correlated, low to moderately high, with V_ball in all age groups (r = .36–.79). Conclusions: In summary, we concluded that simple biomechanical parameters of kicking performance presented distinct development. These results suggest that different training strategies specific for each age group could be applied. We provide predictive equations to aid coaches in the long-term monitoring process to develop the kick in soccer or search for talented young players.     

A study of learning and motivation in a new media enriched environment for middle school science

This study examines middle school students’ learning and motivation as they engaged in a new media enriched problem-based learning (PBL) environment for middle school science. Using a mixed-method design with both quantitative and qualitative data, we investigated the effect of a new media environment on sixth graders’ science learning, their motivation, and the relationship between students’ motivation and their science learning. The analysis of the results showed that: Students significantly increased their science knowledge from pretest to posttest after using the PBL program, they were motivated and enjoyed the experience, and a significant positive relationship was found between students’ motivation scores and their science knowledge posttest scores. Findings were discussed within the research framework.     

Visual Guidance in Infants' Reaching toward Suddenly Displaced Targets

This experiment evaluated the role of visual input about the location of a target object and the location of the hand in reaching by infants and adults. 5- and 9-month-old infants were presented with illuminated toys to reach for in a dark room. On no-switch trials, the toy remained illuminated throughout the infant's reach, whereas on switch trials the first-lit toy was replaced during the reach by a second-lit toy at a different position. On approximately half of the trials of each type a luminescent marker was attached to the reaching hand. Adult subjects (tested without the hand marker) fully compensated to the second-lit toy on switch trials, during a second reaching segment. On switch trials, 9-month-olds partially adjusted to the second-lit toy when wearing the hand marker and did not adjust without it. On no-switch trials, 9-month-olds reached just as accurately with or without the hand marker. 5-month-olds were generally inaccurate in their reaching and were unaffected by the presence or absence of the hand marker. The findings suggest that during the development of reaching there is an increase in visual guidance during the approach phase of reaches.     

Inclusive education and social inequality: an update of the question and some geographical considerations

The aim of this article is to review the current state of inclusive education in the world and to suggest a few relevant considerations. The first section “Two parallel concerns” retraces the inescapable connections between the educational aspects of inclusive education and more general concerns regarding inequality. The second section “Inclusive education in academic publications” scrutinizes academic publications and identifies two major themes among their contents: at first sight the internal transformations occurring in schools attract attention, but subsequently the territorial environment also gives rise to some concern. The third section “Inclusive education in the publications of international organizations” notes our search criteria for sifting through the documentation of the World Bank, OECD and UNESCO. The IBE/UNESCO workshops reflect varied, though converging interpretations of the concept of inclusive education in different parts of the world. All the official publications, however, tend to concentrate on the internal dynamics of schools, and there are not many that take a look at relations between inclusive education and public policy. Our last section “The geographical dimension of inclusive education” puts forward a few arguments in favour of paying more attention to inclusive education at the local and national levels. The main reasons for highlighting the local dimension arise from the combined factors of social deprivation, the need to co-ordinate measures taken in schools and the possibility of allowing a significant opening for community participation. The main reasons for paying attention to the national dimension relate to possible synergies between inclusive education and the expansion of education (for example, is schooling progressing at the same pace at different educational levels?), as well as between inclusive education and social protection (for example, do the many educational conditions applied to cash transfers have consistent pedagogic implications?).