Acute effects of intense interval training on running mechanics

The aims of this study were to determine if there are significant kinematic changes in running pattern after intense interval workouts, whether duration of recovery affects running kinematics, and whether changes in running economy are related to changes in running kinematics. Seven highly trained male endurance runners (VO 2max = 72.3 +/- 3.3 ml kg -1 min -1 ; mean +/- s) performed three interval running workouts of 10 X 400 m at a speed of 5.94 +/- 0.19 m s -1 (356 +/- 11.2 m min -1 ) with a minimum of 4 days recovery between runs. Recovery of 60, 120 or 180 s between each 400 m repetition was assigned at random. Before and after each workout, running economy and several kinematic variables were measured at speeds of 3.33 and 4.47 m s -1 (200 and 268 m min -1 ). Speed was found to have a significant effect on shank angle, knee velocity and stride length (P ? 0.05). Correlations between changes pre- and post-test for VO 2 (ml kg -1 min -1 ) and several kinematic variables were not significant (P > 0.05) at both speeds. In general, duration of recovery was not found to adversely affect running economy or the kinematic variables assessed, possibly because of intra-individual adaptations to fatigue.     

Solving Bernstein's Problem: A Proposal for the Development of Coordinated Movement by Selection

In recent years, many established concepts in the theory of human motor development have undergone profound change, and our knowledge has increased greatly. Nevertheless, some outstanding problems remain unsolved. A central problem concerns the redundancy of effective movements, first pointed out by N. A. Bernstein. The human motor system is mechanically complex and can make use of large number of degrees of freedom. The controlled operation of such a system requires a reduction of mechanical redundancy, effectively by reducing the number of degrees of freedom. More recent work has shown that this problem is hard to solve explicitly by computing solutions to the equations of motion of the system. Equally challenging to traditional computational approaches is the fact the motor systems show remarkable adaptability and flexibility in the presence of changing biomechanical properties of motor organs during development and when faced with different environmental conditions or tasks. Solutions to these problems would have a large impact on a variety of issues in child development. In this article, we stress the importance of the somatic selection of neuronal groups in maps for the progressive transformation of a primary movement repertoire into a set of motor synergies and adaptive action patterns. We present results from computer simulations of a simple motor system that works according to such selectional principles. This approach suggests a provisional solution to Bernstein's problem and provides new parameters to guide experimental approaches to the development of sensorimotor coordination.     

What next? Three knowledge objectives for communication researchers

This essay identifies as knowledge objectives the need to (1) understand the interrelatedness of communicative contexts, (2) pinpoint more precisely the serial nature of communication, and (3) establish the relationship between laboratory and naturalist investigations     

Studies on the use of fear appeals: A summary and analysis

While a number of studies have been concerned with the effects of varying intensities of fear appeals on audience response, interpretation of the findings poses a number of problems. The author summarizes some of the major research thus far conducted, analyzes several of the problems involved in interpreting the findings of these studies, and provides some tentative suggestions for fruitful approaches to the study of the effects of fear‐arousing appeals.     

Explaining the academic performance of community college students who transfer to a senior institution

The academic performance of 361 community college students was investigated after their transfer to a comprehensive university. The predictor variables included personal, environmental, demographic, and pretransfer academic measures. The criterion was grade point average (GPA) at the senior institution. Analyses included moderated linear regression and a branching algorithm which forms subgroups to best explain criterion scores (AID-3). The academic pattern and performance at the community college was found to be very important to the relevance of specific factors related to the curriculum selected at the senior institution.     

The effect of l-citrulline and watermelon juice supplementation on anaerobic and aerobic exercise performance

Citrulline has been proposed as an ergogenic aid, leading to an interest in watermelon given its high citrulline concentration. The aim of this study was to determine the effects of a single, pre-exercise dose of l-citrulline, watermelon juice, or a placebo on the total maximum number of repetitions completed over 5 sets, time to exhaustion, maximal oxygen consumption (VO₂max), anaerobic threshold, and flow-mediated vasodilation. A randomised double-blind within-participants study design was used to examine these effects among 22 participants (n = 11 males). Supplementation included either a 7.5% sucrose drink containing 6 g of l-citrulline, 710 mL of watermelon juice (~1.0 g citrulline), or a 7.5% sucrose placebo drink. Supplementation was administered 1 or 2 h before exercise testing to investigate a timing effect. There was no significant effect between the three supplements for the total number of repetitions, time to exhaustion, VO₂max, anaerobic threshold, or flow-mediated vasodilation. There was also no interaction observed relative to gender or supplement timing (P > 0.05). A single dose of l-citrulline or watermelon juice as a pre-exercise supplement appears to be ineffective in improving exercise performance; however, greater doses of l-citrulline have been shown to be safe and are currently left unexamined.