KINEMATIC ANALYSES OF THE DISCUS THROWING COMPETITIONS AT THE WORLD ATHLETICS CHAMPIONSHIPS 1993

Purpose of the paper This paper wants to discus possibilities and limitations of applied kinematic performance diagnostics of discus throwing as an example for other athletic disciplines. On the basis of kinematic analyses of the finalists at the WAC 94 added to a data base including 260 throws of world class athletes the applicability of traditional kinematic approaches is called into question. &f&& Analyses were performed with a PEAK PERFORMANCE motion analysis system. The video fields were digitized manually. 17 body landmarks were taken to define the locations of 12 body segments. Timing Parameters The analysis of phase durations is a good indicator for the stability of individual movement rhythm and timing. Highest importance is usually awarded to the last three phases of the throw. 11 is true that the often formulated demand for a possibly short airborne phase can be supported by mechanical considerations but individual variations (see table 2) avoid a significant correlation between this parameter and throwing distance (r= -.0076, p= ,919) as well as release velocity (I= ,0193, p= ,891) . The same comes true for transition and delivery phase. No significant correlation to release parameters could be identified. These variations occur interindividually with astonishing uniform individual timing patterns. If we compare the men's medallists we find a high constancy in individual movement patterns as far as timing is concerned. Release Characteristics Of all release parameters velocity oi release appears to be the most important. The assumption of a direct linear relation between release velocity and throwing distance cannot be maintained. Quadratic regressions indicate an area for release velocities and not as expected for maximum velocities. If we summarize all data available on release velocity and throwing distance the correlation turns out to be r=.55. Correcting throwing distance for the influence of wind by calculating ballistic distance increases the correlation to I= .90. The negative coefficient for velocity and the difference between ballistic and official distance (r=-64) indicates a decreasing influence of the wind conditions with increasing release velocities. Thus increasing throwing distance by increasing release velocity is primarily an intraindividual problem of movement coordination on a high speed level. This result comes true not only for discus throwing but can also be observed in other throwing events and even athletic jumping events as well. Nevertheless individual styles profed to be rather repeatable and typical for a specific athlete. Discussion The present kinematic analysis of discus throwing increased the existing data base of the discipline. Timing Characteristics how extreme interindividual variabilities but high intraindividual constancy without significant relations to throwing distance. None of the timing variations can be recommended as the best solution. Release parameters revealed no further insights into throwing techniques. As release velocity contributes about 80% to the variance-of the ballistic distance it is the most important release parameter. The influence of the wind conditions appears to decrease statistically with increasing release velocity on the one hand but on the other hand avoids a higher correlation between release velocity and the official distance. Regression analysis revealed that release velocity must rather be optimized than maximized. This might be due to the individual athletes' ability to control the discus release at high velocities. History of the discus' acceleration described as change of discus velocity during the crucial phases of the turn again revealed interindividual variations without showing a common tendency or even a solution to be called the best. It must be questioned whether a kinematic analysis of top level athletes' techniques leads to further insights into the discipline itself. The kinematic data are nothing else than a descriptions of the athletes' movements in a more objective way. Those analyses did not yet identify the ideal technique. This means a dilemma for any trainer as he has no criteria to separate between mistakes and individual variations of movement technique

ANALYSIS OF FACTORS INFLUENCING THE START PUSH IN WHEELCHAIR RACING

The purpose of this study was (1) to identify muscle strength potentials of wheelchair racing athletes of different performance levels and (2) to identify factors which determine the successful initial push during start. Kinematic and force data were sampled for analysis. Initial acceleration was found to be dependent on the length of the propulsion path as well as on the position of the hands on the hand rim. Favourable handrim positions could be identified for the start. Hand positions preferred by the athletes produced comparable force values but highest power output compared to alternative positions given through the protocol!. The stiffness of the wrist joint prior to release contributed considerably to the acceleration of the wheelchair-athlete system

The role of fire in the formation of soil organic matter in tropical and subtropical climatic zones

Comunicación oral presentada en el European Geosciences Union General Assembly 2016 Vienna, Austria | 17–22 April 2016In tropical and subtropical areas, natural and prescribed vegetation fires lead to a considerable input of charcoal into soils. Whereas it is well accepted that an immediate effect of charcoal input represents the enhancement of the aromaticity of the soil organic matter (SOM) in particular of the topsoils, our knowledge about the long-term impact of this material on the humification processes is still scarce. Analyzing the SOM along various profiles of soils in Southern, Central and Northern Brazil indicated an ubiquitous presence of pyrogenic organic matter (PyOM) down to the C horizons. Interestingly, in several soils lower charcoal contributions were found in the topsoils than in the deeper horizons. Solid-state 13C and 15N NMR revealed that this PyOM is highly carboxylated. Most tentatively, charcoal was efficiently oxidized and biodegraded at the surface turning it into a more humus-like substance. However, some of the degradation products must have been transported into deeper soil regions where they were selectively preserved. Possibly, the oxygen depletion in subsoils or the interaction of oxidized PyOM with the mineral phase have increased its biochemical recalcitrance resulting in a preferential degradation of SOM derived from fire-unaffected sources. Our data clearly show that frequent charcoal addition can have a higher long-term impact on SOM of deeper soil horizons than commonly assumed. It may even represent an essential factor for defining the properties of such subsoil.Peer reviewe

Chemical composition and biological stability of pyrogenic C from a natural fire

2 pages, 1 figure, 3 references.-- Comunicación oral presentada en la Session 1. Pyrogenic C: Dstribution and Stability, en European Science Foundation-Exploratory Workshop, celebrado del 5-7 de noviembre 2013, en Sevilla, España.The work presented here is a synthesis of an article series conducted on natural charcoal in the environment (Alexis et al., 2007, Alexis et al. 2010, Alexis et al., 2012). The objective was to characterize the alteration of OM resulting from thermal alteration and to follow the fate of the produced pyrogenic C in soil.Peer reviewe

Ferrihydrite–humic associations: magnetic hyperfine interactions

7 pages, 6 figures, 1 table, 18 references.Humic–iron oxide associations are believed to exist in various surface environments, such as soils and surface waters, and may add substantially to the stability of organic matter under oxidizing surface conditions. However, a nondestructive, solid-state characterization of such associations is still lacking. In this paper synthetic coprecipitates between humic material (dissolved organic matter; DOM) obtained from a Podzol and synthetic ferrihydrite are examined using X-ray diffraction (XRD) patterns and Fe-specific Mössbauer spectra at temperatures between 4.2 K and room temperature. Lepidocrocite formed in the absence of DOM. However, DOM induced the formation of a four (XRD)-line ferrihydrite that contained 96 mg C/kg. In contrast to a pure four-line ferrihydrite, which was completely magnetically ordered at 4.2 K, the synthesized DOM–ferrihydrite was not fully ordered at 4.2 K and had a magnetic hyperfine field 1 to 2 T lower than the pure ferrihydrite. Such an effect was not observed when DOM was only surface-adsorbed. We conclude that organic components of the DOM coprecipitated with the ferrihydrite. Their interaction with the Fe atoms of the oxide prevents complete spin freezing at 4.2 K. Solid-state 13C nuclear magnetic resonance (NMR) spectra suggested that O-alkyl C of the DOM was mainly responsible for the interaction with the Fe in the oxide.Deutsche Forschungsgemeinschaft financial support.Peer reviewe

REFLEX RESPONSES TO LOCAL SOLEUS MUSCLE VIBRATION

The aims of the present work was i. to investigate the acute effects of prolonged vibratory stimulation on short-latency stretch reflexes (SLR) of soleus muscle, ii. to assess effects of vibration on parameters of the H-reflex and M-wave stimulus-response curves. There were no changes in the EMG of SLR. During vibration H-reflex amplitudes decreased but H-reflex threshold current increased. None of the H-reflex parameters showed timedependent changes. In contrast, maximum M-wave magnitude (MMAX) decreased after 30min of sustained vibration. The analysis suggests differential effects of presynaptic inhibition on ��-motoneurons. The vibration parameters have no effect on excitability of afferent and efferent fibers. The depression of the MMAX after vibratory stimulation may be related to neuromuscular transmission failure and/or reduced sarcolemmal excitability

EVALUATION OF PASSIVELY INDUCED SHOULDER STRETCH REFLEX USING AN ISOKINETIC DYNAMOMETER IN MEN

The purpose of the current study was to determine shoulder internal rotator muscles\u27 reflex latencies (SLR) under variable conditions in 20 healthy, specifically trained male participants. Sets of different external shoulder rotation stretches were applied via an isokinetic dynamometer. SLR latencies were determined from sEMG readings as the time from external shoulder rotation stretches application to onset of muscle activity. The amount of muscular response to the perturbation was evaluated via a peak-to-peak analysis. SLR latencies and amplitudes of the pectoral muscle and the anterior deltoid were affected by the investigated muscle and the level of pre-innervation torque. Our results indicated faster muscular stretch response than reported in previous studies which can be attributed to training induced adaptions of the shoulder muscles and capsule

Variability in oxidative degradation of charcoal: influence of production variables and environmental exposure

<p>Charcoal is a key component of the Black Carbon (BC) continuum, where BC is characterized as a recalcitrant, fire-derived, polyaromatic material. Charcoal is an important source of palaeoenvironmental data, and of great interest as a potential carbon sink, due to its high apparent environmental stability. However, at least some forms of charcoal are clearly susceptible to environmental alteration and degradation over relatively short timescales. Although these processes have importance for the role of charcoal in global biogeochemistry, they remain poorly understood.</p> <p>Here we present results of an investigation into the susceptibility of a range of charcoal samples to oxidative degradation in acidified potassium dichromate. The study examines both freshly-produced charcoal, and charcoal exposed to environmental conditions for up to 50,000 years. We compare the proportion of carbon present in different forms between the samples, specifically with respect to the relative chemical resistance of these forms. This was undertaken in order to improve understanding of the post-depositional diagenetic changes affecting charcoal within environmental deposits.</p> <p>A wide range in chemical compositions are apparent both within and between the sample groups. In freshly-produced charcoal, material produced at 300 °C contains carbon with more labile forms than charcoal produced at ≥400 °C, signifying a key chemical change over the 300–400 °C temperature range. Charcoal exposed to environmental depositional conditions is frequently composed of a highly carboxylated aromatic structure and contains a range of carbon fractions of varying oxidative resistance. These findings suggest that a significant number of the environmental charcoals have undergone post-depositional diagenetic alteration. Further, the data highlight the potential for the use of controlled progressive oxidative degradation as a method to characterize chemical differences between individual charcoal samples.</p&gt

Sozialwissenschaftliche Unternehmensberatung

In Abgrenzung zur 'traditionellen', eher betriebswirtschaftlich orientierten Unternehmensberatung stellt der Autor in seinem Beitrag das systemische Beratungskonzept vor. Er geht von der Einsicht aus, daß Begriffe wie 'Komplexität', 'Vernetzung' und 'System' keine 'akademischen Worthülsen sind, sondern Stichworte für einen notwendigen Paradigmawechsel im Managementdenken und -handeln.' Systemische Beratung zeichnet sich dadurch aus, das Unternehmen als 'Ganzes' in den Blick zu bekommen. Dieser Form von Unternehmensberatung geht es nicht um das Anbieten von maßgeschneiderten, d. h. auf die spezifische unternehmerische Problemsituation zugeschnittene Lösungen, sondern um Anregungen zur selbstgesteuerten Klärungshilfe. Als Felder sozialwissenschaftlicher Unternehmensberatung - sie werden anhand praktischer Beispiele erläutert - nennt der Autor: (1) Techniken der Selbstklärung (2) Persönlichkeitsklärung (3) Kommunikationsklärung und (4) Systemklärung. (BE