Assessing pitcher and catcher influences on base stealing in Major League Baseball

A formal statistical analysis is performed to determine the extent to which pitchers and catchers can influence stolen-base attempts and successes. Two response proportions, attempt/opportunity and success/attempt, are modelled separately using mixed-effects logistic regression models applied to situations with a runner on first and other bases empty. Data include the first innings of all Major League Baseball games played between 1978 and 1990, which encompasses over 48,000 opportunities and 9000 attempts. Pitchers and catchers are entered as random effects and various other factors thought to influence stolen-base attempts and successes are entered as fixed effects. Variance components are estimated and hypotheses tests indicate that the population variance components for both pitchers and catchers are significant for both response proportions. The presence of variation among players at the respective positions is interpreted as evidence that stolen-base defence is a real skill exhibited to varying extents by different players. Furthermore, the variance component for pitchers is greater than that for catchers for both response proportions, indicating that pitchers have greater potential to affect stolen-base attempts and successes. Under usual conditions, it is estimated that 95% of pitchers have first-inning stolen-base success/attempt probabilities between 0.50 and 0.84, while 95% of catchers have probabilities between 0.59 and 0.79.     

Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing

The aims of the study were to: (1) adapt the "double-push" technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional "V2" skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 +/- 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 +/- 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.     

Effects of wear on static and dynamic failure loads of aluminium-based alloy climbing karabiners

In rock climbing, karabiners are used to arrest falls and consequently must be able to withstand dynamic loads. The current international standard for rating karabiner strength prescribes a quasi-static tensile test, which poorly simulates the dynamic nature of an actual climbing fall. In this study, a new method was developed to measure the dynamic failure loads of climbing karabiners. Both new and heavily worn karabiners were tested open and closed, and results from static and dynamic tests were compared. We found that the dynamic failure loads of closed karabiners were up to 50% lower than the failure loads in static tests, while for open karabiners, the static and dynamic values were similar. The reason for this behaviour is unclear; it is most likely due to the combined effects of different stress concentrations and loading regimes of the two tests. Irrespective of test type, karabiner strength decreased with wear level. Based on our results, we advise frequent inspection of permanently placed karabiners for signs of excessive wear. In addition, testing of climbing karabiners in a dynamic test in addition to the standard static test might be considered when developing new karabiner models.     

First names and popularity in grade school children

The relationship between first name desirability and popularity was studied using 780 boys and 768 girls from six elementary schools. Girls' popularity, as demonstrated by positive sociometric choices, was significantly related to the desirability of their first names. There is also a slight indication that boys' popularity with girls was influenced by the boys' first names. Sociometric rejections were not related to first name desirability for either boys or girls. The findings for girls remained significant when the effects of parental education and ethnicity were partialled out; the single finding for boys did not.     

What is modelled during observational learning?

In this article, we examine the question of what information is processed during observational learning by evaluating a variety of methods, theories, and empirical data. Initially, we review work involving neuroimaging techniques and infant imitation. We then evaluate data from behavioural experiments involving adults, wherein a variety of attempts have been made to isolate the critical or minimal information constraining the acquisition of coordination. This body of research has included comparisons between video and point-light displays, manipulations to the amount and type of information presented in the display, the collection of point-of-gaze data, and manipulations to the task context in terms of outcome goals. We conclude that observational learning is governed by specific features of the model's action (i.e. motions of the end effector) and the task (i.e. outcome constraints) and, in contrast with traditional theoretical modelling, more global aspects of a model (i.e. the relative motions within and between joints) do not appear to be the primary method for constraining action execution.     

Effects of time of day and distance upon accuracy and consistency of throwing darts

We examined variations in dart-throwing performance during the daytime in 12 participants. Two distances from the dartboard were investigated - the normal distance (short throws) and another 50% further away than this (long throws). Intra-aural temperature and subjective fatigue were measured, and errors in performance were assessed as the radial distances of throws from the bulls-eye and the standard deviation of these distances. Long-distance throws improved significantly throughout the daytime and correlated positively with intra-aural temperature (r= -0.49, P=0.002 and r= -0.49, P=0.002 for errors and standard deviation of errors, respectively), but not with subjective fatigue (r= -0.10, P=0.56 and r= -0.05, P=0.74 for errors and standard deviation of errors, respectively). Short-distance throws were associated less with intra-aural temperature (r= -0.46, P= 0.005 and r= -0.17, P=0.31 for errors and standard deviation of errors, respectively), and worsened with fatigue (r=+0.34, P= 0.040 for errors). Compared with the short-distance throws, the long-distance throws were performed significantly less well than could be accounted for by the increased distance (mean errors were increased 1.67-2.78 times and standard deviation of errors of errors 1.58-3.68 times), supporting the concept of a trade-off between force of contraction and accuracy of performance. Throwing darts can be used as a model for investigating factors that influence motor performance, and our results indicate that the effects of time of day upon performance depend upon the relative importance of force and accuracy.     

Biomechanical validation of a specific upper body training and testing drill in cross-country skiing

The aim of this study was to perform a biomechanical validation of a double poling imitation drill on a rollerboard. Six elite cross-country skiers performed three imitation drill trials at maximal speed at 13 degrees inclination and in double poling on roller skis on a paved road of 3 degrees. Pole and strap forces, elbow and hip angles and EMG activity of eight upper body muscles were measured. Force curves showed similar characteristics, except for impact force occurring only at pole plant in double poling on roller skis. Double poling on a rollerboard includes an eccentric roll-down phase not appearing in double polling on roller skis. Forces on the rollerboard were similar to those on roller skis. Courses of the elbow angles indicated similar shapes, except for the angle at the start of the propulsion phase and, consequently, during flexion (p < 0.01). Propulsion time and cycle duration were longer and frequency lower on the rollerboard (all p < 0.001). Muscle activities were not significantly different, except for stronger biceps brachii (p < 0.01) and weaker erector spinae activation (p < 0.05) on the rollerboard. Muscle coordination patterns showed similar onset and offset points of each muscle and comparable activations in both activities, except for biceps brachii. Two movement strategies on the rollerboard were found, which led to small differences in measured variables. The biomechanical validity of double poling on a rollerboard can be judged as moderately high, being aware of the differences in some variables that might be considered in training sessions on the rollerboard, particularly when using intervals with high number of repetitions.