Maximal-intensity isometric and dynamic exercise performance after eccentric muscle actions

A well-documented observation after eccentric exercise is a reduction in maximal voluntary force. However, little is known about the ability to maintain maximal isometric force or generate and maintain dynamic peak power. These aspects of muscle function were studied in seven participants (5 males, 2 females). Knee extensor isometric strength and rate of fatigue were assessed by a sustained 60 s maximal voluntary contraction at 80 degrees and 40 degrees knee flexion, corresponding to an optimal and a shortened muscle length, respectively. Dynamic peak power and rate of fatigue were assessed during a 30 s Wingate cycle test. Plasma creatine kinase was measured from a fingertip blood sample. These variables were measured before, 1 h after and 1, 2, 3 and 7 days after 100 repetitions of the eccentric phase of the barbell squat exercise (10 sets x 10 reps at 80% concentric one-repetition maximum). Eccentric exercise resulted in elevations in creatine kinase activity above baseline (274+/-109 U x l(-1); mean +/- s(x)) after 1 h (506+/-116 U x l(-1), P < 0.05) and 1 day (808+/-117 U x l(-1), P < 0.05). Isometric strength was reduced (P < 0.05) for 7 days (35% at 1 h, 5% at day 7) and the rate of fatigue was lower (P < 0.05) for 3 days at 80 degrees and for 1 day at 40 degrees. Wingate peak power was reduced to a lesser extent (P < 0.05) than isometric strength at 1 h (13%) and, although the time course of recovery was equal, the two variables differed in their pattern of recovery. Eccentrically exercised muscle was characterized by an inability to generate high force and power, but an improved ability to maintain force and power. Such functional outcomes are consistent with the proposition that type II fibres are selectively recruited or damaged during eccentric exercise.     

Is movement variability important for sports biomechanists?

This paper overviews the importance for sports biomechanics of movement variability, which has been studied for some time by cognitive and ecological motor skills specialists but, until quite recently, had somewhat been overlooked by sports biomechanists. The paper considers biomechanics research reporting inter- and intra-individual movement variability in javelin and discus throwing, basketball shooting, and locomotion. The overview does not claim to be comprehensive and we exclude such issues as the theoretical background to movement and coordination variability and their measurement. We overview evidence, both theoretical and empirical, of inter-individual movement variability in seeking to achieve the same task goal, in contrast to the concept of “optimal” movement patterns. Furthermore, even elite athletes cannot reproduce identical movement patterns after many years of training, contradicting the ideas of motor invariance and “representative” trials. We contend that movement variability, far from being solely due to neuromuscular system or measurement “noise” – as sports biomechanists may have previously supposed – is, or could be, functional. Such functionality could allow environmental adaptations, reduce injury risk, and facilitate changes in coordination patterns. We conclude by recommending that sports biomechanists should focus more of their research on movement variability and on important related topics, such as control and coordination of movement, and implications for practice and skill learning.     

Symbolic,identity, and probe delayed matching of sounds by the bottlenosed dolphin

The short-term memory for sounds of the bottlenosed dolphin was tested using symbolic, identity, and probe forms of the delayed matching-to-sample (DMS) task. The forms differed in the number (one or two) or nature (symbolic or identity matches of sample sounds) of postdelay test stimuli available as memory retrieval cues. Although symbolic DMS was difficult to learn, the final performance level was approximately equal to that for identity or probe DMS. On all tasks, the dolphin’s responses were above 80% correct through to delays of 90 sec and, in some cases, through to delays of 180 and 240 sec, the “limits” being governed mainly by the dolphin’s reluctance to continue being tested at long delays. Encoding of sample stimuli into their learned symbolic representation was hypothesized to have reduced symbolic DMS to a recognition memory task, resulting in the observed equivalence of performance with the other two recognition memory tasks. The probe DMS results, unlike those for identity or symbolic DMS, showed no significant proactive interference effects from samples of prior trials. Instead, proactive interference was traceable to the probe value of the prior trial. Overall, the auditory DMS data for the dolphin were functionally similar to results reported for monkeys tested on symbolic, identity, and probe visual DMS tasks.     

Conservation of stained glass windows with protective glazing: Main results from the European VIDRIO research programme

The methodology of protecting the European stained glass windows against environmental risk (e.g. meteorological factors, air pollution, microorganisms) by means of an external glazing is not new. In spite of many scientific studies carried out in the last 20 years, some questions were still up for discussion. The European VIDRIO (2002–2005) project gave an answer to these questions. The research carried out by the different project partners established a new multidisciplinary approach aimed at evaluating the efficiency of the protective glazing systems and their effects on stained glass windows conservation, and finally at assessing the most appropriate strategy to preserve stained glass windows. Scientific results showed that the so-called isothermal glazing (i.e. ventilation by the air coming from the inside of the building) protected efficiently the ancient stained glass window from environmental attack (i.e. rain, pollutants, condensation, thermal shocks) with very limited secondary effects. The scientific research highlighted that its efficiency was strongly related to the technical design of the protective system. In particular, the ventilation and the size of the interspace had to be carefully considered. The research developed within the VIDRIO project was turned into general recommendations to the owners and practitioners on the best practice for the stained glass windows future conservation.     

Effects of signaled reward in instrumental conditioning: Enhanced learning on DRL and DRH schedules of reinforcement

The effects of signaled reward were examined using DRL and DRH schedules of reinforcement. In each case, one group of rats received a brief cue between the reinforced response and the reward, and a second group received brief cues at random times. With the DRL schedule (Experiment 1), signaled reward decreased response rate, increased response efficiency (number of responses per reinforcer), and increased resistence to satiation relative to the control group. With the DRH schedule (Experiment 2), signaled reward increased response rate, efficiency, and resistance to satiation. These results refute an overshadowing explanation of the effects of signaled reward and suggest that food-correlated cues enhance learning of the reinforcement contingencies.