Comparison of kinematics in skilled and unskilled arms of the same recreational baseball players

Abstract

We examined mechanisms of coordination that enable skilled recreational baseball players to make fast overarm throws with their skilled arm and which are absent or rudimentary in their unskilled arm. Arm segment angular kinematics in three dimensions at 1000 Hz were recorded with the search-coil technique from the arms of eight individuals who on one occasion threw with their skilled right arm and on another with their unskilled left arm. Compared with their unskilled arm, the skilled arm had: a larger angular deceleration of the upper arm in space in the forward horizontal direction; a larger shoulder internal rotation velocity at ball release (unskilled arms had a negative velocity); a period of elbow extension deceleration before ball release; and an increase in wrist velocity with an increase in ball speed. It is suggested that some of these differences in arm kinematics occur because of differences between the skilled and unskilled arms in their ability to control interaction torques (the passive torque at one joint due to motion at adjacent joints). It is proposed that one reason unskilled individuals cannot throw fast is that, unlike their skilled counterparts, they have not developed the coordination mechanisms to effectively exploit interaction torques.     

Physiological variables and performance markers of serving soldiers from two “elite” units of the British Army

Abstract

The aim of this study was to compare selected physiological variables and performance markers of soldiers from two “elite” units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = ?0.57) and 29 km time-trial (r = ?0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = ?0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits.     

Faculty and Male Football and Basketball Players on University Campuses

Abstract

Four experiments examined the influence of observing a correct model (CM), a learning sequence model (LSM), and an incorrect model (IM) on the performance of two motor skills. The results of experiment 1 showed that the CM and LSM conditions facilitated performance on the first 10 trails, but not thereafter when compared to the IM group and a control group. Experiment 2 showed that performance estimation was improved by observing the CM and LSM conditions, indicating that information was conveyed by observing these models. Experiment 3 revealed pronounced modeling effects on a difficult motor skill for the CM and LSM conditions which were sustained throughout the 60 practice trials. Experiment 4 showed no differences in performance between a live model demonstrating correctly and a filmed model demonstrating correctly. The findings from the 4 experiments were discussed in terms of the information conveyed through observation and its function in the development of the cognitive components of a motor skill.     

Support Base Use in Two Dance Idioms

Abstract

Recovery pulse rates following a 3-min. step test were obtained from 686 junior high school and 1,332 high school age subjects who were students in 55 different secondary schools throughout the six districts of the AAHPER. The pulse rates were converted to cardiovasular efficiency scores and from these, national standards were established for the 9–14 age group and for the 15 19 age group. The standards consisted of six categories from excellent to very poor. In addition, it was found that junior high school subjects scored better than high school subjects; that neither temperature nor time of day of testing had a significant effect on test scores; and that at the high school level the senior high school subjects in the Central district achieved the best scores of the six districts while at the junior high level the Central and Southern districts ranked together as best.     

Meaningful interaction: toward a new theoretical approach to online instruction

ABSTRACT

Taking full advantage of the educative benefits of interaction in digital learning environments will require the development of new theoretical frameworks that can contribute to a richer understanding of interaction. Literary theory provides an excellent place to develop such a framework and advanced understanding. Literary theory enables us to reconceptualise online courses as ‘texts’, thereby equipping us with more sophisticated modes of analysis for the teaching and learning process. By rethinking online courses as texts, and better yet as what Roland Barthes has described as ‘writerly’ texts, we can improve interaction in the online classroom. More importantly, we can move toward a more meaningful form of interaction, where learners interact with course content at the level of meaning and meaning making, where interaction becomes a full participation in the production of a lesson’s meaning. Indeed, this aim of co-producing meaning should be the primary objective of all learning.