Is the occurrence of the sticking region the result of diminishing potentiation in bench press?

In this study we investigated if the occurrence of the sticking region was a result of diminishing potentiation (coinciding delayed muscle activation) or the result of a mechanically poor region in which the muscles can produce less force. A regular one-repetition maximum (1RM) free-weight bench press was compared with isometric bench presses performed at 12 different positions. A lower force at the sticking region compared to the other regions in the isometric bench presses would confirm the mechanically-poor-position hypothesis. Twelve resistance-trained males (age 21.7 ± 1.3 years, mass 78 ± 5.8 kg, height 1.81 ± 0.05 m) were tested in 1RM and in isometric contractions in bench press in 12 different positions, indicated by the vertical distance between barbell and sternum, covering the whole range of motion during the concentric phase. Barbell kinematics and muscle activity were registered. In both types of executions a region of lower force output was observed, which supports the mechanically-poor-position hypothesis. Electromyographic activity of four muscles showed the same pattern in the isometric and 1RM attempts. It was concluded that diminishing effect potentiation could not explain the existence of the sticking region.     

Imitation jumps in ski jumping: Technical execution and relationship to performance level

ABSTRACT

Imitation jumps are frequently used in training for ski jumping. Yet, the dynamics of these jumps differ considerably. Thus, the relevance of imitation jumps for ski jumping performance is not elucidated. The aim of this study was to investigate the relationship between the technical execution of imitation jumps and ski jumping performance level. We compared the imitation jumps of 11 ski jumpers of different performance levels using a Spearman correlation transform of time traces of the kinetics (measured using force cells and motion capture) of imitation jumps. The kinetic aspects that were related to performance centred on the moment arm of ground reaction force to the centre of mass before the onset of the push-off, angular momentum early in push-off, thigh angle during the main period of push-off and vertical velocity towards the end of push-off. We propose that the thigh angle may be a key element allowing high development of linear momentum while preparing for appropriate aerodynamic position. Furthermore, the findings suggest that the kinetic development prior to (and during) push-off is more important than the kinematic end state at take-off.     

How do elite ski jumpers handle the dynamic conditions in imitation jumps?

We examined the effect of boundary conditions in imitation ski jumping on movement dynamics and coordination. We compared imitation ski jumps with – and without – the possibility to generate shear propulsion forces. Six elite ski jumpers performed imitation jumps by jumping from a fixed surface and from a rolling platform. The ground reaction force vector, kinematics of body segments, and EMG of eight lower limb muscles were recorded. Net joint dynamics were calculated using inverse dynamics. The two imitation jumps differed considerably from each other with regard to the dynamics (moments, forces), whereas the kinematics were very similar. Knee power was higher and hip power was lower on the rolling platform than on the fixed surface. Mean EMG levels were very similar for both conditions, but differences in the development of muscle activity were indicated for seven of eight muscles. These differences are reflected in a subtle difference of the alignment of ground reaction force with centre of mass: the ground reaction force runs continuously close to but behind the centre of mass on the rolling platform and fluctuates around it on the fixed surface. This likely reflects a different strategy for controlling angular momentum.     

The BASES Expert Statement on Exercise and Cancer Survivorship

Abstract

Research examining the proximal-to-distal sequencing of segments of the body involved in overarm throwing has been equivocal: some studies have found support for the concept while others have not. The aim of the present study, therefore, was to determine if there is a proximal-to-distal sequence in the timing of the movements of joints and the distal endpoints of segments in overarm throwing. The three-dimensional kinematics of a penalty throw in experienced team handball players (n = 11) were recorded and analysed with regard to the timing of events. We analysed the timing of the maximal velocity of the distal endpoints of six segments and the maximal angular velocity in 11 joints, as well as the initiation of these joint movements. A temporal proximal-to-distal sequence was observed only for the initiation of the joint movements. No such sequence was found for maximal velocity of the joints and distal endpoints of segments.     

Task Experience as a Boundary Condition for the Negative Effects of Irrelevant Information on Learning

Research on multimedia learning has shown that learning is hampered when a multimedia message includes extraneous information that is not relevant for the task, because processing the extraneous information uses up scarce attention and working memory resources. However, eye-tracking research suggests that task experience might be a boundary condition for this negative effect of extraneous information on learning, because people seem to learn to ignore task-irrelevant information over time. We therefore hypothesised that extraneous information might no longer hamper learning when it is present over a series of tasks, giving learners the chance to adapt their study strategy. This hypothesis was tested in three experiments. In experiments 1a/1b, participants learned the definitions of new words (from an artificial language) that denoted actions, with matching pictures (same action), mismatching pictures (another action), or without pictures. Mismatching pictures hampered learning compared with matching pictures. Experiment 2 showed that task experience may indeed be a boundary condition to this negative effect on learning: the initial negative effect was no longer present when learners gained experience with the task. This suggests that learners adapted their study strategy, ignoring the mismatching pictures. That hypothesis was tested in experiment 3, using eye tracking. Results showed that attention to the pictures waned with task experience, and that this decrease was stronger for mismatching than for matching pictures. Our findings demonstrate the importance of investigating multimedia effects over time and in relation to study strategies.     

Research Methods

Klaus Krippendorf, CONTENT ANALYSIS: AN INTRODUCTION TO ITS METHODOLOGY (Beverly Hills, CA: Sage, 1980---$16.00/$7.95)

Karl Erik Rosegren, ADVANCES IN CONTENT ANALYSIS (Beverly Hills, CA: Sage, 1981---$25.00/$12.50)

Nick L. Smith, COMMUNICATION STRATEGIES IN EVALUATION: NEW PERSPECTIVES IN EVAUATION, VOLUME 3 (Beverly Hills, CA: Sage, 1982---$22.50)

Jerome Johnston and James Ettema, POSITIVE IMAGES: BREAKING STEREOTYPES WITH CHILDREN'S TELEVISION (Beverly Hills: Sage Publications, 1982---$22.95/$10.95)     

Biomechanical analysis of traction at the shoe-surface interface on third-generation artificial turf

The existing knowledge of traction on artificial turf is based almost exclusively on mechanical devices. While most attention has traditionally been concentrated on rotational traction, sports such as soccer predominantly involve translational movements. The aim of the study was to investigate whether translational traction at the shoe-surface interface differed between various third-generation artificial turf systems in combination with different cleat configurations in vivo. Twenty-two male soccer players performed five short sprints with a 90° cut over a turf-covered force plate for each combination of three turf systems and three cleat configurations. The results showed that, despite various differences in other traction measures, traction coefficients were almost identical across turf systems and cleat configurations.