Preparation time influences ankle and knee joint control during dynamic change of direction movements

The influence of preparation time on ankle joint biomechanics during highly dynamic movements is largely unknown. The aim of this study was to evaluate the impact of limited preparation time on ankle joint loading during highly dynamic run-and-cut movements. Thirteen male basketball players performed 45°-sidestep-cutting and 180°-turning manoeuvres in reaction to light signals which appeared during the approach run. Both movements were executed under (1) an easy condition, in which the light signal appeared very early, (2) a medium condition and (3) a hard condition with very little time to prepare the movements. Maximum ankle inversion angles, moments and velocities during ground contact, as well as EMG signals of three lower extremity muscles, were analysed. In 180°-turning movements, reduced preparation time led to significantly increased maximum ankle inversion velocities. Muscular activation levels, however, did not change. Increased inversion velocities, without accompanying changes in muscular activation, may have the potential to destabilise the ankle joint when less preparation time is available. This may result in a higher injury risk during turning movements and should therefore be considered in ankle injury research and the aetiology of ankle sprains.     

Best Practices for Preschool Music Education: Supporting Music-Making Throughout the Day

Early Childhood Education Journal - Active engagement in music has numerous academic and social benefits for young children and music-making is included in many early childhood standards and...     

Retrospective and prospective short-term memory in delayed response tasks in rats

Separate groups of rats were trained and tested on asymmetrically and symmetrically reinforced successive delayed matching-to-sample (DMTS) or delayed discrimination (DD) tasks in Experiment 1. Each rat received training and testing on symmetrically reinforced DMTS and DD tasks in Experiment 2. The only difference between each task was that the rats had to respond correctly to a light or tone test stimulus, S₂, if it matched a light or tone sample stimulus, S₁, in DMTS, but could respond to either S₂ if S₁ had been a particular stimulus in DD. Only correct leverpresses were reinforced in the asymmetrically reinforced version of each task. Both correct presses and correct omissions were reinforced in the symmetrically reinforced version of each task. Response biases to leverpress during tests for delayed responding to S₁ were reduced in both symmetrically reinforced tasks, but only in the DD task did such contingencies produce consistently poorer performance in responding to either S, in Experiment 1. Declines in accuracy of performance that occurred in both experiments were greater to the visual than to the auditory S₁ only in the DMTS tasks with increased intervals between S₁ and S₂. A third experiment, in which rats had to respond to S₂ if it matched S₁ (DMTS) or if S₂ mismatched S, (DMmTS), was carried out. Modality of S₁ similarly affected accuracy of delayed responding in each task, as in the first two experiments. Methodological and theoretical implications of these results are discussed in terms of Honig and Thompson’s (1982) dual-process theory of working memory.