A novel guideline for the analysis of linear acceleration mechanics - outlining a conceptual framework of 'shin roll' motion

Linear acceleration is a key performance determinant and major training component of many sports. Although extensive research about lower limb kinetics and kinematics is available, consistent definitions of distinctive key body positions, the underlying mechanisms and their related movement strategies are lacking. The aim of this 'Method and Theoretical Perspective' article is to introduce a conceptual framework which classifies the sagittal plane 'shin roll' motion during accelerated sprinting. By emphasising the importance of the shin segment's orientation in space, four distinctive key positions are presented ('shin block', 'touchdown', 'heel lock' and 'propulsion pose'), which are linked by a progressive 'shin roll' motion during swing-stance transition. The shin's downward tilt is driven by three different movement strategies ('shin alignment', 'horizontal ankle rocker' and 'shin drop'). The tilt's optimal amount and timing will contribute to a mechanically efficient acceleration via timely staggered proximal-to-distal power output. Empirical data obtained from athletes of different performance levels and sporting backgrounds are required to verify the feasibility of this concept. The framework presented here should facilitate future biomechanical analyses and may enable coaches and practitioners to develop specific training programs and feedback strategies to provide athletes with a more efficient acceleration technique.

Speed Rope Skipping - Performance and Coordination in a Four-Limb Task

This study investigated biomechanical characteristics of Speed Rope Skipping (RS) and estimated the contribution of the lower and upper limbs to overall performance. Lower (jumping), upper (turning), and whole-body (skipping) performance were examined in 23 rope skippers. All tests were recorded by 2 D video and nine skipping tests were performed in a 3 D motion capture system. Similar movement patterns were observed for the lower limbs in all participants, while handle trajectories differed in shape and symmetry according to performance. In general, turning unlike jumping performance was close to and significantly correlated with skipping performance. Therefore, it appears that lower extremity movement may be adapted to the limiting capacity of the upper extremity to maintain movement stability.

How Fit Are Special Operations Police Officers? A Comparison With Elite Athletes From Olympic Disciplines

The diverse tasks of special operations police (SOP) units place high physical demands on every officer. Being fit for duty requires a wide range of motor abilities which must be trained regularly and in a structured manner. But SOP operators have to plan and manage large proportions of their training alone, which makes it difficult to control. Therefore, this study aimed to highlight strengths and deficits of the SOP operators' fitness by comparing them to elite athletes, and to define future training goals. Retrospective data of 189 male SOP operators were used, who completed several isometric strength tests, a graded exercise test to determine maximal oxygen uptake, and countermovement jumps to determine leg muscle power. On the basis of a literature search, performance data were then compared to a total of 3,028 elite male athletes from 36 Summer Olympic disciplines. Pooled means and standard deviations were calculated for each discipline and effect sizes were used to analyze their similarities and differences to the SOP unit. On average, SOP operators were taller, heavier, and stronger than elite athletes. But both the ability to convert this strength into explosive movement and aerobic power was significantly less developed. From this point of view, SOP operators should consider polarized endurance training to work efficiently on improving aerobic performance. In addition, regular plyometric training seems necessary to improve leg muscle power and agility.

Inside a synesthete's head: a functional connectivity analysis with grapheme-color synesthetes

Grapheme-color synesthesia is a condition in which letters are perceived with an additional color dimension. To identify brain regions involved in this type of synesthesia and to analyze functional connectivity of these areas, 18 grapheme-color synesthetes and 18 matched controls were stimulated with letters and pseudo-letters presented in black and color in an event-related fMRI experiment. Based on the activation-differences between synesthetes and non-synesthetic controls regions of interest were defined. In a second analysis step functional connectivity was calculated using beta series correlation analysis for these seed regions. First we identified one seed region in the left inferior parietal (IPL) cortex (BA7) showing activation differences between grapheme-color synesthetes and controls. Furthermore, we found activation differences in brain areas involved in processing of letters and pseudo-letters, in particular the right IPL cortex (BA7), but also two more clusters in the right hemispheric BA 18 and BA 40. Functional connectivity analysis revealed an increased connectivity between the left IPL seed region and primary/secondary visual areas (BA 18) in synesthetes. Also the right BA 7 showed a stronger connectivity with primary/secondary visual areas (BA 18) in grapheme-color synesthetes. The results of this study support the idea that the parietal lobe plays an important role in synesthetic experience. The data suggest furthermore that the information flow in grapheme-color synesthetes was already modulated at the level of the primary visual cortex which is different than previously thought. Therefore, the current models of grapheme-color synesthesia have to be refined as the unusual communication flow in synesthetes is not restricted to V4, fusiform cortex and the parietal lobe but rather involves a more extended network.

The neural correlates of coloured music: a functional MRI investigation of auditory-visual synaesthesia

In auditory-visual synaesthesia, all kinds of sound can induce additional visual experiences. To identify the brain regions mainly involved in this form of synaesthesia, functional magnetic resonance imaging (fMRI) has been used during non-linguistic sound perception (chords and pure tones) in synaesthetes and non-synaesthetes. Synaesthetes showed increased activation in the left inferior parietal cortex (IPC), an area involved in multimodal integration, feature binding and attention guidance. No significant group-differences could be detected in area V4, which is known to be related to colour vision and form processing. The results support the idea of the parietal cortex acting as sensory nexus area in auditory-visual synaesthesia, and as a common neural correlate for different types of synaesthesia.

[Accidental intraartrial injection of diacethylmorphine (heroin) in drug addicts -- three case reports]

Accidental intrarterial injections are not uncommon in medical treatments. This is also true for uncontrolled injections by drug-addicts. Since 2002 a number of 600 heavy opiate addicts in Germany are substituted in a country-wide study with pure diacetylmorphine (Heroine). We report the course and outcome of three cases of accidental intraarterial injections of pure diacetylmorphine under controlled conditions. After initial symptoms of vasospasms, all cases were without symptoms within one hour and no obvious loss of tissue was observed. After discussing the literature about medical literature and treatment options in intraarterial injections it is concluded, that the cause of major complications after intraarterial injections may not be the pure diacetylmorphine but additional substances in impure "street-heroin" samples.

Acamprosate reduces motor cortex excitability determined by transcranial magnetic stimulation

Acamprosate is effective in reducing alcohol intake in weaned alcoholics. We were interested if acamprosate had an effect on the excitability of cortical motoneurons determined by transcranial magnetic stimulation (TMS). We studied 12 male healthy volunteers (mean age 29.5 years, SD = 4.8) who were either treated with 6 tablets of acamprosate (each containing 333 mg verum) per day or placebo (randomized cross-over design) for 1 week. TMS was performed after each treatment session including a paired stimulation paradigm. Motor evoked potentials (MEPs) of the placebo and verum group did not differ with respect to paired stimulation. However, motor threshold increased in the acamprosate group (verum: 61.5% (SD = 7.9) vs. placebo: 58.9% (SD = 8.8), p = 0.036). We conclude that acamprosate leads to a hypoexcitability of the motor cortex. This might be due to subcortical mechanisms, e.g. thalamocortical pathways since intracortical inhibition and facilitation was not affected.

Effects of acamprosate on memory in healthy young subjects

OBJECTIVE

Several studies have shown acamprosate (calciumacetylhomotaurinate) to increase abstinence rates in weaned alcoholics. Chronic alcoholics often suffer from cognitive deficits. Since acamprosate appears to interact with N-methyl-D-aspartate (NMDA) receptors, a subclass of glutamate receptors playing an important role in learning and memory processes, this study was performed in order to investigate different cognitive functions during administration of acamprosate.

METHOD

A randomized, double-blind, cross-over, placebo-controlled design, involving 12 healthy male volunteers was used. Acamprosate 2 g daily per os or placebo were administered for 7 days respectively, with a wash-out interval of 21 days between phases. Mood and different memory functions (i.e., working memory, delayed recall, recognition tasks) were assessed.

RESULTS

It was shown that a dose of acamprosate 2 g/day for 7 days may produce an impairment in delayed free recall. Recognition tasks, short term working memory and mood were not altered.

CONCLUSIONS

The present study supports the hypothesis that acamprosate impairs memory functions. This is in keeping with the concept of acamprosate acting as NMDA receptor antagonist. The limitations of the study are discussed.

Lack of psychotomimetic or impairing effects on psychomotor performance of acamprosate

The possible effects on psychomotor performance, concentration, attention, and mood of acamprosate (calciumacetylhomotaurinate) were assessed using a randomized, double-blind, cross-over, placebo-controlled design involving 12 healthy male volunteers. Acamprosate 2 g daily per os or placebo was administered for seven days and separated by washout intervals of at least 21 days. Objective tests evaluated psychomotor functions (simple reaction time measurement, binary choice reaction test, computerized visual searching task, sustained attention test). Mood was assessed using the Beck Depression Inventory and the Beschwerde-Liste to assess subjective physical impairment. Additionally, a visual 3-D illusion paradigm was applied to measure the psychotomimetic effect. A dose of acamprosate of 2 g/day for seven days was free of any significant effects on mood, concentration, attention, psychomotor performance and did not produce any subjective sedation, excitation or psychotomimetic effects.