Influence of regression model and initial intensity of an incremental test on the relationship between the lactate threshold estimated by the maximal-deviation method and running performance

Abstract

This study investigated the influence of the regression model and initial intensity during an incremental test on the relationship between the lactate threshold estimated by the maximal-deviation method and performance in elite-standard runners. Twenty-three well-trained runners completed a discontinuous incremental running test on a treadmill. Speed started at 9 km · h^?1 and increased by 1.5 km · h^?1 every 4 min until exhaustion, with a minute of recovery for blood collection. Lactate–speed data were fitted by exponential and polynomial models. The lactate threshold was determined for both models, using all the co-ordinates, excluding the first and excluding the first and second points. The exponential lactate threshold was greater than the polynomial equivalent in any co-ordinate condition (P < 0.001). For both models, the lactate threshold was lower when all co-ordinates were used than when the first and the first and second points were excluded (P < 0.001). 10-km race pace was correlated with both the exponential and polynomial lactate thresholds for all the co-ordinate conditions (r ≥ 0.75, P < 0.001 and r ≥ 0.56, P < 0.05, respectively). The results suggest that the exponential lactate threshold should be used instead of the polynomial equivalent since it is more strongly associated with performance and is independent of the initial intensity of the test.     

The effect of periodized resistance training on accelerative sprint performance

The purpose of this study was to assess the effect of periodized resistance training on accelerative sprint performance. Sixteen physically active men participated in a randomized controlled study. An experimental group (n = 10) completed an 8-week periodized resistance training intervention, while a control group (n = 6) did not train. Pre- and post-training measures of 20-m straight-line sprint time, including a 10-m split, maximum strength, and explosive strength, were recorded. Flight time, stance time, stride length, and stride frequency were quantified from digitized video recordings of the first three strides of the 20-m sprint. Resistance training resulted in significant increases in maximum strength (parallel back squat: 19%) and explosive strength (6–10%). However, both groups increased 0–10 m sprint times (experimental group = 6%; control group = 3%) while 10–20 m times were reduced (experimental group = 7%; control group = 4%), highlighting the mechanical differences between the distinct sprint phases. The change during the 0–10 m interval was accompanied by a reduction in stride frequency during the first three strides. Strength coaches should be aware that the potential benefits of increased muscular strength during short sprints are likely to be affected by mechanical specificity and that improvements in sprinting performance may not occur immediately after a period of resistance training.     

Characteristics of the start in women's World Cup skeleton

This study characterizes key elements of the start in elite female World Cup skeleton athletes. The top 20 female competitors in three World Cup races were videotaped within a calibrated space to allow the following components of the start to be quantified: (1) acceleration (velocity at 15-m mark, time to 15-m mark), (2) capacity (time to load, total number of steps to load), and (3) load (velocity at 45-m mark). A correlation analysis was used to establish the relationship between the variables of interest and overall start time (15- to 65-m mark). Velocity at the 15-m mark accounted for 86% of the variance in overall start time at St. Moritz and 85% at Sigulda. A stepwise regression analysis revealed that approximately 89% of the variation in start time could be explained by velocity at the 15-m mark, time to load, and velocity at the 45-m mark. Of the variables analysed in this study, rapid acceleration to attain a high velocity at the 15-m mark was the most important component of a fast overall start time. The importance of the time to load and velocity at the 45-m mark vary according to the different track characteristics.     

Is passive drag dependent on the interaction of kayak design and paddler weight in flat-water kayaking?

Abstract

Drag is one of the major factors that influences kayaking performance. To focus on the drag of the kayak’s hull shape and the paddlers’ weight per se, the passive drag (D_p) was measured on a flat-water sprint course for one paddler with added weights. D_p was measured by an electromechanical towing device using a load cell, at incremental and constant velocities from 2.78 to 5.56 m/s. Three kayaks of different sizes and shapes (Nelo® K1 Quattro-M, ML, and L) were used and the paddlers’ body weight was adjusted with weights so the total paddler weight in the kayak was 65, 75, and 85 kg. The mean D_p increased by the power function of D = kvⁿ (mean R² = .990; SD .006). The D_p went from 21.37?±?1.29 N at 2.78 m/s to 89.32?±?6.43 N at 5.56 m/s. For the two lighter weighted kayaks (65 and 75 kg), the lowest D_p was observed with different kayak sizes (M, ML, or L) depending on the target velocity. The manufacturers suggest that paddlers should select a kayak size according to their body weight to minimise drag; however, the results of this study suggest that target velocities, and thus competition distance should also be factored into kayak selection.     

Measures of instruction for creative engagement: Making metacognition,modeling and creative thinking visible

The purpose of the current study was to estimate reliability, internal consistency and construct validity of the Measure of Instruction for Creative Engagement (MICE) instrument. The MICE uses an iterative process of evidence collection and scoring through teacher observations to determine instructional domain ratings and overall scores. The results demonstrated the sound inter-observer reliability, teacher stability and score validity of the MICE. We found (a) a low proportion of rater variance (0.14–5.99%), (b) moderate to highly correlated within-teacher ratings ranging from r(17) = 0.663, p < 0.01 to r(17) = 1.000, p < 0.01 and (c) a statistically-significant difference between classroom teachers and teaching artists, t(56) = 7.37, p = 0.000. These results relate to the development of classroom environment instruments and the substantive development of pedagogy that supports creative thinking and behaviours, both of which are a priority for enhancing teacher accountability and student learning.     

Reputation and reality: ranking major disciplines in Australian universities

League tables that rank universities may use reputational measures, performance measures, or both. Each type of measure has strengths and weaknesses. In this paper, we rank disciplines in Australian universities both by reputation, using an international survey of senior academics, and with actual performance measures. We then compare the two types of measures to see how closely they match. The criterion we use for both sets of measures is ‘international academic standing’. We find a high correlation between the survey results and the various measures of research performance. We also find a correlation between the quality of student intake and the survey rankings, but the satisfaction levels of recent graduates do not correlate well with the rankings by academics. We then construct an overall measure of performance, which gives very similar rankings to the survey results, especially for the top-ranked institutions.

Using a hypertext environment for teaching process writing: An evaluation study of three student groups

The present research consisted of a comprehensive evaluation of a hypertext model for teaching process writing at the junior high and high school level. Interests were to determine how two teachers and three different age groups of students used and reacted to the model, specifically, its embedded design features of model stories, note cards, idea buttons, mini-lessons, branching buttons, and cut-and-paste-tools. Results showed applications of the embedded features to vary based on teacher attitudes, feature attributes (e.g., ease of use and appeal), and student characteristics. Older students made more usage of many of the features, but were less positive about the hypertext model given their greater involvement with completing writing assignments rather than with exploring new forms of writing. The implications of the results are discussed regarding the instructional design and classroom implementation of new technologies for teaching process writing strategies.This study was conducted as a doctoral dissertation completed by the first author at the University of Memphis under the supervision of the second and third authors.     

Economic stress, parenting, and child adjustment in Mexican American and European American families

To assess the impact of economic hardship on 111 European American and 167 Mexican American families and their 5th-grade (M age=11.4 years) children, a family stress model was evaluated. Structural equation analyses revealed that economic hardship was linked to indexes of economic pressure that were related to depressive symptoms for mothers and fathers of both ethnicities. Depressive symptoms were linked to marital problems and hostile parenting. Paternal hostile parenting was related to child adjustment problems for European Americans, whereas marital problems were linked to child adjustment problems for Mexican Americans. Maternal acculturation was associated with both higher marital problems and lower hostile parenting. The utility of the model for describing the effects of economic hardship in Mexican Americans is noted.     

Visually impaired children: Development and implications for education

This paper examines some of the models used for conceptualizing the possible developmental implications of blindness and severe visual impairment. It takes up the question of the significance in infancy of certain skills and proficiencies, especially motor, that may be impeded by the lack of vision. The paper then addresses such issues for the school age child as access to literacy, with the emphasis being on ways of mitigating the potentially educationally handicapping consequences of visual disability. Educational technology is cited as one of the principal means available to teachers for meeting these challenges, and examples are given of procedures and devices that are being explored. A central argument is that for psychologists, teachers, and educational technologists the search must be to pinpoint the specific and changing needs of the individual learner.