TY - BOOK A1 - Schmidt, Thorsten Ingo A1 - Ulrich, Peter A1 - Büchner, Christiane A1 - Franzke, Jochen A1 - Jann, Werner A1 - Bauer, Hartmut A1 - Wagner, Dieter A1 - Brüning, Christoph A1 - Bickenbach, Christian A1 - Kuhlmann, Sabine A1 - Peters, Niklas A1 - Reichard, Christoph A1 - Tessmann, Jens A1 - Maaß, Christian A1 - Kern, Kristine A1 - Kochskämper, Elisa A1 - Gailing, Ludger A1 - Krzymuski, Marcin ED - Schmidt, Thorsten Ingo ED - Bickenbach, Christian ED - Gronewold, Ulfert ED - Kuhlmann, Sabine ED - Ulrich, Peter T1 - Kommunalwissenschaften an der Universität Potsdam BT - Rück- und Ausblick zum 30-jährigen Bestehen des Kommunalwissenschaftlichen Instituts (KWI) T3 - KWI-Schriften N2 - Zum dreißigjährigen Bestehen des Kommunalwissenschaftlichen Instituts an der Universität Potsdam vereint dieser Jubiläumsband kurze Aufsätze von ehemaligen und aktuellen Vorstandsmitgliedern, von Ehrenmitgliedern des Vorstands, langjährigen wissenschaftlichen Mitarbeitern des Instituts und aktuellen wissenschaftlichen Kooperationspartnern. Die insgesamt zwölf Beiträge befassen sich mit den Kommunalwissenschaften und der Geschichte des Kommunalwissenschaftlichen Instituts, mit aktuellen kommunalwissenschaftlichen Fragestellungen und wissenschaftlichen Kooperationen des KWI. Der vom KWI-Vorstand herausgegebene Band soll einen breiten Blick auf 30 Jahre Kommunalwissenschaften in Brandenburg und an der Universität Potsdam werfen und einen Ausblick auf zukünftige kommunalwissenschaftliche Forschung geben. T3 - KWI-Schriften - 15 KW - Kommunalwissenschaft KW - Institut KW - Brandenburg KW - Potsdam KW - Universität Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-636180 SN - 978-3-86956-581-1 SN - 1867-951X SN - 1867-9528 IS - 15 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Kayhan, Ezgi A1 - Matthes, Daniel A1 - Marriott Haresign, Ira A1 - Bánki, Anna A1 - Michel, Christine A1 - Langeloh, Miriam A1 - Wass, Sam A1 - Höhl, Stefanie T1 - DEEP: A dual EEG pipeline for developmental hyperscanning studies JF - Developmental Cognitive Neuroscience N2 - Cutting-edge hyperscanning methods led to a paradigm shift in social neuroscience. It allowed researchers to measure dynamic mutual alignment of neural processes between two or more individuals in naturalistic contexts. The ever-growing interest in hyperscanning research calls for the development of transparent and validated data analysis methods to further advance the field. We have developed and tested a dual electroencephalography (EEG) analysis pipeline, namely DEEP. Following the preprocessing of the data, DEEP allows users to calculate Phase Locking Values (PLVs) and cross-frequency PLVs as indices of inter-brain phase alignment of dyads as well as time-frequency responses and EEG power for each participant. The pipeline also includes scripts to control for spurious correlations. Our goal is to contribute to open and reproducible science practices by making DEEP publicly available together with an example mother-infant EEG hyperscanning dataset. KW - Developmental hyperscanning KW - Dual EEG analysis KW - Adult-child interaction KW - Phase Locking Value KW - PLV KW - Cross-frequency PLV KW - FieldTrip Y1 - 2022 U6 - https://doi.org/10.1016/j.dcn.2022.101104 SN - 1878-9307 VL - 54 SP - 1 EP - 11 PB - Elsevier CY - Amsterdam, Niederlande ER - TY - THES A1 - Lenz, Josefine T1 - Thermokarst dynamics in central-eastern Beringia T1 - Thermokarstdynamik im zentral-östlichen Beringia BT - insights from permafrost and lacustrine sediment cores BT - Einblicke durch Permafrost- und Seesedimentkerne N2 - Widespread landscape changes are presently observed in the Arctic and are most likely to accelerate in the future, in particular in permafrost regions which are sensitive to climate warming. To assess current and future developments, it is crucial to understand past environmental dynamics in these landscapes. Causes and interactions of environmental variability can hardly be resolved by instrumental records covering modern time scales. However, long-term environmental variability is recorded in paleoenvironmental archives. Lake sediments are important archives that allow reconstruction of local limnogeological processes as well as past environmental changes driven directly or indirectly by climate dynamics. This study aims at reconstructing Late Quaternary permafrost and thermokarst dynamics in central-eastern Beringia, the terrestrial land mass connecting Eurasia and North America during glacial sea-level low stands. In order to investigate development, processes and influence of thermokarst dynamics, several sediment cores from extant lakes and drained lake basins were analyzed to answer the following research questions: 1. When did permafrost degradation and thermokarst lake development take place and what were enhancing and inhibiting environmental factors? 2. What are the dominant processes during thermokarst lake development and how are they reflected in proxy records? 3. How did, and still do, thermokarst dynamics contribute to the inventory and properties of organic matter in sediments and the carbon cycle? Methods applied in this study are based upon a multi-proxy approach combining sedimentological, geochemical, geochronological, and micropaleontological analyses, as well as analyses of stable isotopes and hydrochemistry of pore-water and ice. Modern field observations of water quality and basin morphometrics complete the environmental investigations. The investigated sediment cores reveal permafrost degradation and thermokarst dynamics on different time scales. The analysis of a sediment core from GG basin on the northern Seward Peninsula (Alaska) shows prevalent terrestrial accumulation of yedoma throughout the Early to Mid Wisconsin with intermediate wet conditions at around 44.5 to 41.5 ka BP. This first wetland development was terminated by the accumulation of a 1-meter-thick airfall tephra most likely originating from the South Killeak Maar eruption at 42 ka BP. A depositional hiatus between 22.5 and 0.23 ka BP may indicate thermokarst lake formation in the surrounding of the site which forms a yedoma upland till today. The thermokarst lake forming GG basin initiated 230 ± 30 cal a BP and drained in Spring 2005 AD. Four years after drainage the lake talik was still unfrozen below 268 cm depth. A permafrost core from Mama Rhonda basin on the northern Seward Peninsula preserved a full lacustrine record including several lake phases. The first lake generation developed at 11.8 cal ka BP during the Lateglacial-Early Holocene transition; its old basin (Grandma Rhonda) is still partially preserved at the southern margin of the study basin. Around 9.0 cal ka BP a shallow and more dynamic thermokarst lake developed with actively eroding shorelines and potentially intermediate shallow water or wetland phases (Mama Rhonda). Mama Rhonda lake drainage at 1.1 cal ka BP was followed by gradual accumulation of terrestrial peat and top-down refreezing of the lake talik. A significant lower organic carbon content was measured in Grandma Rhonda deposits (mean TOC of 2.5 wt%) than in Mama Rhonda deposits (mean TOC of 7.9 wt%) highlighting the impact of thermokarst dynamics on biogeochemical cycling in different lake generations by thawing and mobilization of organic carbon into the lake system. Proximal and distal sediment cores from Peatball Lake on the Arctic Coastal Plain of Alaska revealed young thermokarst dynamics since about 1,400 years along a depositional gradient based on reconstructions from shoreline expansion rates and absolute dating results. After its initiation as a remnant pond of a previous drained lake basin, a rapidly deepening lake with increasing oxygenation of the water column is evident from laminated sediments, and higher Fe/Ti and Fe/S ratios in the sediment. The sediment record archived characterizing shifts in depositional regimes and sediment sources from upland deposits and re-deposited sediments from drained thaw lake basins depending on the gradually changing shoreline configuration. These changes are evident from alternating organic inputs into the lake system which highlights the potential for thermokarst lakes to recycle old carbon from degrading permafrost deposits of its catchment. The lake sediment record from Herschel Island in the Yukon (Canada) covers the full Holocene period. After its initiation as a thermokarst lake at 11.7 cal ka BP and intense thermokarst activity until 10.0 cal ka BP, the steady sedimentation was interrupted by a depositional hiatus at 1.6 cal ka BP which likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines. The specific setting of the lake on a push moraine composed of marine deposits is reflected in the sedimentary record. Freshening of the maturing lake is indicated by decreasing electrical conductivity in pore-water. Alternation of marine to freshwater ostracods and foraminifera confirms decreasing salinity as well but also reflects episodical re-deposition of allochthonous marine sediments. Based on permafrost and lacustrine sediment records, this thesis shows examples of the Late Quaternary evolution of typical Arctic permafrost landscapes in central-eastern Beringia and the complex interaction of local disturbance processes, regional environmental dynamics and global climate patterns. This study confirms that thermokarst lakes are important agents of organic matter recycling in complex and continuously changing landscapes. N2 - Derzeit werden deutliche Landschaftsveränderungen in der Arktis beobachtet, welche sich höchstwahrscheinlich zukünftig v.a. in den Permafrostregionen verstärken, da diese besonders empfindlich auf Klimaveränderungen reagieren. Um derzeitige und zukünftige Entwicklungen einschätzen zu können, ist es wichtig vergangene Umweltprozesse zu verstehen. Ursachen und Wechselwirkungen von Umweltveränderungen können nur bedingt durch instrumentelle Aufzeichnungen erklärt werden, doch Paleo-Umweltarchive können weit in die Vergangenheit reichende Umweltdynamiken aufzeichnen. Seesedimente sind wichtige Archive, die lokale limnogeologische Prozesse, aber auch direkt oder indirekt klimatisch gesteuerte Umweltveränderungen der Vergangenheit aufzeichnen. Ziel der vorliegenden Arbeit ist es, spätquartäre Permafrost- und Thermokarstdynamik im zentral-östlichen Beringia zu rekonstruieren. Beringia umfasst jene terrestrische Landmasse, welche Eurasien und Nord-Amerika zu Zeiten von Meeresspiegeltiefständen verband. Um die Entwicklung, die Prozesse und den Einfluss von Thermokarstdynamik zu untersuchen, wurden mehrere Sedimentkerne von rezenten Seen und ausgelaufenen Seebecken analysiert, um folgende Forschungsfragen zu beantworten: 1. Zu welcher Zeit degradierte Permafrost und wann entwickelten sich Thermokarstseen? Was waren hemmende oder verstärkende Faktoren? 2. Was sind dominierende Prozesse während der Entwicklung von Thermokarstseen und wie spiegeln sich diese in Proxy-Aufzeichnungen wieder? 3. Wie hat Thermokarstdynamik damals und heute zur Bedeutung von organischer Substanz in Sedimenten und im Kohlenstoffkreislauf beigetragen? Die in dieser Arbeit angewandten Methoden basieren auf einem sogenannten „multi-proxy“ Ansatz, der sedimentologische, geochemische, geochronologische und mikropaläontologische Analysen, sowie die Untersuchung von stabilen Isotopen und die Hydrochemie von Porenwasser und -eis, verbindet. Feldmessungen der modernen Wasserqualität und Beckenmorphometrie komplettieren die Umweltuntersuchungen. Auf Grundlage der untersuchten Sedimentkerne lässt sich die Degradation von Permafrost und die Dynamik von Thermokarst auf zeitlich verschiedenen Skalen rekonstruieren. Die Analyse eines Sedimentkerns vom GG-Becken auf der nördlichen Seward-Halbinsel (Alaska) zeigt eine vorwiegend terrestrische Akkumulation von Yedoma während des Früh- und Mittel-Wisconsin mit zwischenzeitlich feuchteren Verhältnissen zwischen 44,5 und 41,5 ka BP. Diese frühe Feuchtgebietsphase wurde durch die Akkumulation einer 1 m dicken Tephra-Lage beendet, welche sehr wahrscheinlich von der Eruption des heutigen South Killeak Maar vor etwa 42.000 Jahren stammt. Eine Schichtlücke im Sedimentkern von etwa 22,5 und 0,23 ka BP gibt einen Hinweis auf Thermokarstentwicklung in der Umgebung der Kernlokation, welche bis heute ein Yedoma-Rudiment bildet. Der Thermokarstsee, der GG-Becken formte, entstand 230 ± 30 cal a BP und drainierte im Frühling 2005 AD. Vier Jahre nach der Drainage war der Talik des Sees in einer Tiefe von 268 cm noch ungefroren. Ein Permafrostkern vom Mama Rhonda-Becken auf der nördlichen Seward-Halbinsel archivierte eine vollständige limnische Fazies mit mehreren Seephasen. Die erste Seegeneration entstand am Übergang vom Spätglazial zum Frühholozän um etwa 11,8 cal ka BP; das alte Seebecken (Grandma Rhonda) ist bis heute südlich der Kernlokation erhalten. Etwa um 9,0 cal ka BP entwickelte sich ein eher flaches und dynamisches Seesystem mit aktiv erodierenden Ufern und potenziell zwischengeschalteten Flachwasser- oder Feuchtgebietsphasen (Mama Rhonda). Die Drainage vom Mama Rhonda-See etwa 1,1 cal ka BP wurde gefolgt von gradueller Torfakkumulation und einem von oben zurückfrierenden See-Talik Es wurde ein deutlich geringerer organischer Kohlenstoff-Gehalt in Grandma Rhonda-Ablagerungen (TOC im Mittel 2,5 Gew.-%) festgestellt, als in Mama Rhonda Ablagerungen (TOC im Mittel 7,9 Gew.-%). Dies zeigt den bedeutenden Einfluss von Thermokarst auf biogeochemische Kreisläufe, da in verschiedenen Seegenerationen organischen Kohlenstoff durch Permafrost-Tauen im Seesystem mobilisiert wird. Seesedimentkerne aus der Uferzone und dem zentralen Bereich von Peatball Lake auf der Arktischen Küstenebene von Alaska, ergaben eine junge Thermokarstdynamik von 1.400 Jahren, welche auf der Basis von absoluten Datierungen und Uferexpansionsraten rekonstruiert wurde. Nach der Seeinitiierung als Rest-See eines zuvor ausgelaufenen Seebeckens, vertiefte sich Peatball Lake verhältnismäßig schnell mit zunehmender Sauerstoffanreicherung der Wassersäule, wie aus laminierten Sedimenten und hohen Fe/Ti- und Fe/S-Verhältnissen im Sediment ersichtlich ist. Die Sedimente von Peatball Lake archivierten einen Wechsel des Ablagerungsregimes bei Ausdehnung der Seefläche und einen Wechsel der Sedimentquelle von ursprünglichen, rein terrestrischen Ablagerungen und bereits umgelagerten Sedimenten aus drainierten Seebecken. Angezeigt wird dieser Wechsel durch eine Veränderung im Eintrag organischen Materials in das Seesystem, was wiederum das Potential von Thermokarstseen bei der Aufarbeitung alten Kohlenstoffs aus degradierendem Permafrost im Einzugsgebiet verdeutlicht. Der Seesedimentkern von der Herschel Insel im Yukon (Kanada) deckt das gesamte Holozän ab. Nach der Seeentstehung um 11,7 cal ka BP und einer Zeit intensiver Thermokarstaktivität bis 11,0 cal ka BP, wird die Phase einer eher kontinuierlichen Sedimentation von einer Schichtlücke um 1,6 cal ka BP unterbrochen. Diese wurde entweder durch die Drainage des Sees oder einer allochthonen Rutschung instabiler Uferlinien verursacht. Die spezielle Situation des Sees auf einer Stauchendmoräne aus marinem Material spiegelt sich auch in dem Seesedimentarchiv wieder. Das Aussüßen des wachsenden Sees wird durch die abnehmende elektrische Leitfähigkeit im Porenwasser angezeigt. Der Wechsel von marinen und Süßwasserostrakoden- und Foraminiferengemeinschaften bestätigt zum einen die abnehmende Salinität des Sees, aber zeigt zum anderen auch episodische Umlagerung von allochthonem, marinem Sediment. Auf der Grundlange von Permafrost- und Seesedimentkernen zeigt diese Arbeit Beispiele spätquartärer Entwicklungsgeschichte typischer Arktischer Permafrostlandschaften im zentral-östlichen Beringia. Es werden komplexe Zusammenhänge zwischen lokalen Störungsprozessen, regionaler Umweltdynamik und globalen Klimaveränderungen aufgezeigt. Thermokarstseen spielen dabei eine wichtige Rolle im sich kontinuierlich verändernden Landschaftsbild der hohen Breiten und im Stoffkreislauf bei der Aufarbeitung organischer Substanz. KW - paleolimnology KW - permafrost degradation KW - periglacial landscape evolution KW - thermokarst processes KW - carbon cycling KW - central-eastern Beringia KW - Paläolimnologie KW - Permafrostdegradation KW - periglaziale Landschaftsentwicklung KW - Thermokarstprozesse KW - Kohlenstoffkreislauf KW - zentral-östliches Beringia Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-101364 ER - TY - THES A1 - Morgenstern, Anne T1 - Thermokarst and thermal erosion : degradation of Siberian ice-rich permafrost T1 - Thermokarst und Thermoerosion : Degradation von sibirischem eisreichem Permafrost N2 - Current climate warming is affecting arctic regions at a faster rate than the rest of the world. This has profound effects on permafrost that underlies most of the arctic land area. Permafrost thawing can lead to the liberation of considerable amounts of greenhouse gases as well as to significant changes in the geomorphology, hydrology, and ecology of the corresponding landscapes, which may in turn act as a positive feedback to the climate system. Vast areas of the east Siberian lowlands, which are underlain by permafrost of the Yedoma-type Ice Complex, are particularly sensitive to climate warming because of the high ice content of these permafrost deposits. Thermokarst and thermal erosion are two major types of permafrost degradation in periglacial landscapes. The associated landforms are prominent indicators of climate-induced environmental variations on the regional scale. Thermokarst lakes and basins (alasses) as well as thermo-erosional valleys are widely distributed in the coastal lowlands adjacent to the Laptev Sea. This thesis investigates the spatial distribution and morphometric properties of these degradational features to reconstruct their evolutionary conditions during the Holocene and to deduce information on the potential impact of future permafrost degradation under the projected climate warming. The methodological approach is a combination of remote sensing, geoinformation, and field investigations, which integrates analyses on local to regional spatial scales. Thermokarst and thermal erosion have affected the study region to a great extent. In the Ice Complex area of the Lena River Delta, thermokarst basins cover a much larger area than do present thermokarst lakes on Yedoma uplands (20.0 and 2.2 %, respectively), which indicates that the conditions for large-area thermokarst development were more suitable in the past. This is supported by the reconstruction of the development of an individual alas in the Lena River Delta, which reveals a prolonged phase of high thermokarst activity since the Pleistocene/Holocene transition that created a large and deep basin. After the drainage of the primary thermokarst lake during the mid-Holocene, permafrost aggradation and degradation have occurred in parallel and in shorter alternating stages within the alas, resulting in a complex thermokarst landscape. Though more dynamic than during the first phase, late Holocene thermokarst activity in the alas was not capable of degrading large portions of Pleistocene Ice Complex deposits and substantially altering the Yedoma relief. Further thermokarst development in existing alasses is restricted to thin layers of Holocene ice-rich alas sediments, because the Ice Complex deposits underneath the large primary thermokarst lakes have thawed completely and the underlying deposits are ice-poor fluvial sands. Thermokarst processes on undisturbed Yedoma uplands have the highest impact on the alteration of Ice Complex deposits, but will be limited to smaller areal extents in the future because of the reduced availability of large undisturbed upland surfaces with poor drainage. On Kurungnakh Island in the central Lena River Delta, the area of Yedoma uplands available for future thermokarst development amounts to only 33.7 %. The increasing proximity of newly developing thermokarst lakes on Yedoma uplands to existing degradational features and other topographic lows decreases the possibility for thermokarst lakes to reach large sizes before drainage occurs. Drainage of thermokarst lakes due to thermal erosion is common in the study region, but thermo-erosional valleys also provide water to thermokarst lakes and alasses. Besides these direct hydrological interactions between thermokarst and thermal erosion on the local scale, an interdependence between both processes exists on the regional scale. A regional analysis of extensive networks of thermo-erosional valleys in three lowland regions of the Laptev Sea with a total study area of 5,800 km² found that these features are more common in areas with higher slopes and relief gradients, whereas thermokarst development is more pronounced in flat lowlands with lower relief gradients. The combined results of this thesis highlight the need for comprehensive analyses of both, thermokarst and thermal erosion, in order to assess past and future impacts and feedbacks of the degradation of ice-rich permafrost on hydrology and climate of a certain region. N2 - Die gegenwärtige Klimaerwärmung wirkt sich auf arktische Regionen stärker aus als auf andere Gebiete der Erde. Das hat weitreichende Konsequenzen für Permafrost, der weite Teile der terrestrischen Arktis unterlagert. Das Tauen von Permafrost kann zur Freisetzung erheblicher Mengen an Treibhausgasen sowie zu gravierenden Änderungen in der Geomorphologie, Hydrologie und Ökologie betroffener Landschaften führen, was wiederum als positive Rückkopplung auf das Klimasystem wirken kann. Ausgedehnte Gebiete der ostsibirischen Tiefländer, die mit Permafrost des Yedoma Eiskomplex unterlagert sind, gelten aufgrund des hohen Eisgehalts dieser Permafrostablagerungen als besonders empfindlich gegenüber Klimaerwärmungen. Thermokarst und Thermoerosion sind zwei Hauptformen der Permafrostdegradation in periglazialen Landschaften. Die zugehörigen Landschaftsformen sind auf der regionalen Skala bedeutende Indikatoren klimainduzierter Umweltvariationen. Thermokarstseen und senken (Alasse) sowie Thermoerosionstäler sind in den Küstentiefländern der Laptewsee weit verbreitet. Die vorliegende Dissertation untersucht die räumliche Verbreitung und die morphometrischen Eigenschaften dieser Degradationsformen mit dem Ziel, ihre Entwicklungsbedingungen während des Holozäns zu rekonstruieren und Hinweise auf potenzielle Auswirkungen zukünftiger Permafrostdegradation im Zuge der erwarteten Klimaerwärmung abzuleiten. Der methodische Ansatz ist eine Kombination aus Fernerkundungs-, Geoinformations- und Geländeuntersuchungen, die Analysen auf lokalen bis regionalen räumlichen Skalen integriert. Thermokarst und Thermoerosion haben die Untersuchungsregion tiefgreifend geprägt. Im Eiskomplexgebiet des Lena-Deltas nehmen Thermokarstsenken eine weitaus größere Fläche ein als Thermokarstseen auf Yedoma-Hochflächen (20,0 bzw. 2,2 %), was darauf hin deutet, dass die Bedingungen für die Entwicklung von großflächigem Thermokarst in der Vergangenheit wesentlich günstiger waren als heute. Die Rekonstruktion der Entwicklung eines einzelnen Alas im Lena-Delta belegt eine andauernde Phase hoher Thermokarstaktivität seit dem Übergang vom Pleistozän zum Holozän, die zur Entstehung einer großen und tiefen Senke führte. Nach der Drainage des primären Thermokarstsees im mittleren Holozän erfolgten Permafrostaggradation und degradation parallel und in kürzeren abwechselnden Etappen innerhalb des Alas und führten zu einer komplexen Thermokarstlandschaft. Trotzdem die spätholozäne Thermokarstentwicklung im Alas dynamischer ablief als die erste Entwicklungsphase, resultierte sie nicht in der Degradation großer Teile pleistozäner Eiskomplexablagerungen und einer wesentlichen Veränderung des Yedoma-Reliefs. Weitere Thermokarstentwicklung in bestehenden Alassen ist begrenzt auf geringmächtige Lagen holozäner eisreicher Alas-Sedimente, da die Eiskomplexablagerungen unter den großen primären Thermokarstseen vollständig getaut waren und die unterlagernden Sedimente aus eisarmen, fluvialen Sanden bestehen. Thermokarstprozesse auf ungestörten Yedoma-Hochflächen wirken am stärksten verändernd auf Eiskomplexablagerungen, werden aber in Zukunft auf geringere Ausmaße begrenzt sein, da die Verfügbarkeit großer ungestörter, schwach drainierter Yedoma-Hochflächen abnimmt. Auf der Insel Kurungnakh im zentralen Lena-Delta beträgt der für zukünftige Thermokarstentwicklung verfügbare Anteil an Yedoma-Hochflächen nur 33,7 %. Die zunehmende Nähe von sich entwickelnden Thermokarstseen auf Yedoma-Hochflächen zu bestehenden Degradationsstrukturen und anderen negativen Reliefformen verringert die Möglichkeit der Thermokarstseen, große Ausmaße zu erreichen bevor sie drainieren. Die Drainage von Thermokarstseen durch Thermoerosion ist in der Untersuchungsregion weit verbreitet, aber Thermoerosionstäler versorgen Thermokarstseen und –senken auch mit Wasser. Neben diesen direkten hydrologischen Wechselwirkungen zwischen Thermokarst und Thermoerosion auf der lokalen Ebene existiert auch eine Interdependenz zwischen beiden Prozessen auf der regionalen Ebene. Eine regionale Analyse weitreichender Netze von Thermoerosionstälern in drei Tieflandgebieten der Laptewsee mit einer Fläche von insgesamt 5800 km² zeigte, dass diese Formen häufiger in Gebieten mit höheren Geländeneigungen und Reliefgradienten auftreten, während Thermokarstentwicklung stärker in flachen Tiefländern mit geringeren Reliefgradienten ausgeprägt ist. Die kombinierten Ergebnisse dieser Dissertation zeigen die Notwendigkeit von umfassenden Analysen beider Prozesse und Landschaftsformen, Thermokarst und Thermoerosion, im Hinblick auf die Abschätzung vergangener und zukünftiger Auswirkungen der Degradation eisreichen Permafrosts auf Hydrologie und Klima der betrachteten Region und deren Rückkopplungen. KW - Fernerkundung KW - GIS KW - räumliche Analyse KW - periglaziale Landschaften KW - Arktis KW - remote sensing KW - GIS KW - spatial analyses KW - periglacial landscapes KW - Arctic Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-62079 ER - TY - THES A1 - Jongejans, Loeka Laura T1 - Organic matter stored in ice-rich permafrost T1 - Ablagerung von organischem Kohlenstoff in eisreichem Permafrost BT - future permafrost thaw and greenhouse gas release BT - zukünftige Permafrosttauen und Treibhausgasemissionen N2 - The Arctic is changing rapidly and permafrost is thawing. Especially ice-rich permafrost, such as the late Pleistocene Yedoma, is vulnerable to rapid and deep thaw processes such as surface subsidence after the melting of ground ice. Due to permafrost thaw, the permafrost carbon pool is becoming increasingly accessible to microbes, leading to increased greenhouse gas emissions, which enhances the climate warming. The assessment of the molecular structure and biodegradability of permafrost organic matter (OM) is highly needed. My research revolves around the question “how does permafrost thaw affect its OM storage?” More specifically, I assessed (1) how molecular biomarkers can be applied to characterize permafrost OM, (2) greenhouse gas production rates from thawing permafrost, and (3) the quality of OM of frozen and (previously) thawed sediments. I studied deep (max. 55 m) Yedoma and thawed Yedoma permafrost sediments from Yakutia (Sakha Republic). I analyzed sediment cores taken below thermokarst lakes on the Bykovsky Peninsula (southeast of the Lena Delta) and in the Yukechi Alas (Central Yakutia), and headwall samples from the permafrost cliff Sobo-Sise (Lena Delta) and the retrogressive thaw slump Batagay (Yana Uplands). I measured biomarker concentrations of all sediment samples. Furthermore, I carried out incubation experiments to quantify greenhouse gas production in thawing permafrost. I showed that the biomarker proxies are useful to assess the source of the OM and to distinguish between OM derived from terrestrial higher plants, aquatic plants and microbial activity. In addition, I showed that some proxies help to assess the degree of degradation of permafrost OM, especially when combined with sedimentological data in a multi-proxy approach. The OM of Yedoma is generally better preserved than that of thawed Yedoma sediments. The greenhouse gas production was highest in the permafrost sediments that thawed for the first time, meaning that the frozen Yedoma sediments contained most labile OM. Furthermore, I showed that the methanogenic communities had established in the recently thawed sediments, but not yet in the still-frozen sediments. My research provided the first molecular biomarker distributions and organic carbon turnover data as well as insights in the state and processes in deep frozen and thawed Yedoma sediments. These findings show the relevance of studying OM in deep permafrost sediments. N2 - Die Arktis ist eine der sich am schnellsten verändernden Regionen der Erde, was zum tauen des dortigen Permafrosts führt. Eisreicher Permafrost, wie der spätpleistozäne Yedoma, ist besonders anfällig für schnelle und tiefe Auftauprozesse infolge von Absenkungen der Oberfläche nach dem Schmelzen des Grundeises. Durch das Auftauen des Permafrosts wird der im Permafrost gespeicherte Kohlenstoff für Mikroben zunehmend zugänglich, was zu erhöhten Treibhausgasemissionen führt und die Klimaerwärmung verstärkt. Die Untersuchung der molekularen Struktur und der biologischen Abbaubarkeit von organischem Material (OM) im Permafrost ist dringend erforderlich. In meiner Forschung geht es um die zentrale Frage inwieweit das Auftauen des Permafrost die Speicherfähigkeit von OM beeinflusst. Insbesondere untersuchte ich (1) wie molekulare Biomarker bei der Charakterisierung von Permafrost-OM verwendet werden können, (2) Treibhausgasproduktionsraten in auftauendem Permafrost und (3) die Qualität von OM in gefrorenen und (vorher) aufgetauten Sedimenten. Dazu habe ich tiefe (bis zu 55 m) Yedoma und aufgetaute Yedoma Permafrostsedimente aus Jakutien (Republik Sacha) untersucht. Es wurden Sedimentkerne unter Thermokarstseen auf der Bykovsky-Halbinsel (südöstlich des Lenadeltas) und im Yukechi-Alas (Zentraljakutien) entnommen, und deren Biomarkerkonzentrationen gemessen. Desweiteren wurden Bodenproben von der Permafrostklippe Sobo-Sise (Lenadelta) und der Taurutschung Batagai (Jana-Hochland) genommen und untersucht. Darüber hinaus habe ich Inkubationsexperimente durchgeführt, um die Treibhausgasproduktion in auftauenden Permafrost zu quantifizieren. Ich habe gezeigt, dass Biomarker-Proxies nützlich sind, um die Quelle des OM zu ermitteln und zwischen OM aus Landpflanzen, Wasserpflanzen und mikrobieller Aktivität zu unterscheiden. Außerdem sind einige Proxies hilfreich, den Abbaugrad von Permafrost-OM zu beurteilen. Dies trifft insbesondere in Kombination mit sedimentologischen Daten in einem Multi-Proxy-Ansatz. Ich zeigte dass der OM von Yedoma im Allgemeinen besser erhalten ist als der von aufgetauten Yedoma-Sedimenten. Die Treibhausgasproduktion in den erstmalig auftauenden Permafrostsedimenten war am höchsten. Dies bedeutet, dass die gefrorenen Yedoma-Sedimente das meiste labile OM enthielten. Außerdem zeigte ich, dass sich die methanproduzierenden Gemeinschaften in den frisch aufgetauten Sedimenten etabliert hatten, jedoch nicht in den noch gefrorenen Sedimenten. Meiner Forschung hat die ersten molekularen Biomarkerverteilungen und Kohlenstoffumsatzdaten geliefert und Einsichten in den Zustand und Prozesse von gefrorenen und aufgetauten Yedoma-Sedimenten geschaffen. Diese Ergebnisse demonstrieren die Relevanz der Untersuchung von OM in tiefen Permafrostsedimenten. N2 - Het Noordpoolgebied verandert snel en permafrost ontdooit. Met name ijsrijke permafrost, zoals Yedoma uit het laat Pleistoceen, is gevoelig voor snelle en diepe dooiprocessen als gevolg van bodemdaling na het smelten van bodemijs. Door het ontdooien van permafrost wordt het permafrostkoolstofreservoir beter toegankelijk voor microben, wat tot verhoogde broeikasgasemissies leidt en de klimaatopwarming versterkt. Het is van groot belang om de moleculaire structuur en de biologische afbreekbaarheid van organisch materiaal (OM) in permafrost vast te leggen. Mijn onderzoek draait om de vraag "hoe beinvloedt permafrostdooi de OM-opslag?" Specifiek heb ik onderzocht (1) hoe moleculaire biomarkers kunnen worden gebruikt om permafrost-OM te karakteriseren, (2) wat broeikasgasproductiesnelheden in ontdooiende permafrost zijn en (3) wat de kwaliteit is van het OM in bevroren en (eerder) ontdooide sedimenten. Ik heb diepe (max. 55 m) Yedoma en ontdooide Yedoma permafrostsedimenten uit Jakoetië (republiek Sacha) onderzocht. Sedimentkernen zijn genomen onder thermokarstmeren op het Bykovsky schiereiland (ten zuidoosten van de Lenadelta) en in de Yukechi Alas (centraal Jakoetië). Ook zijn bodemmonsters genomen van de permafrostklif Sobo-Sise (Lenadelta) en de zogenaamde thaw slump Batagai (Jana-hoogvlakte). In alle monsters heb ik de biomarkerconcentraties gemeten. Ook heb ik incubatie-experimenten uitgevoerd om de broeikasgasproductie in ontdooiende permafrost te kwantificeren. Mijn onderzoek wijst uit dat de biomarkerproxies nuttig zijn bij het vaststellen van de bron van het OM en om onderscheid te kunnen maken tussen OM van landplanten, waterplanten en OM afkomstig van microbiële activiteit. Daarnaast heb ik aangetoond dat sommige proxies nuttig zijn om de mate van degradatie van het OM vast te stellen, vooral in combinatie met sedimentologische data in een multi-proxy-benadering. Het blijkt dat het OM in Yedoma over het algemeen beter bewaard gebleven is dan het OM in ontdooide Yedoma-sedimenten. De broeikasgasproductie bleek het hoogst in de voor het eerst ontdooide permafrostsedimenten, wat betekent dat de bevroren Yedoma-sedimenten het meeste labiele OM bevatten. Bovendien heb ik aangetoond dat de methaan-producerende gemeenschappen zich wel in de recentelijk ontdooide sedimenten hebben gevestigd, maar nog niet in de nog bevroren sedimenten. Mijn onderzoek heeft de eerste moleculaire biomarker- en koolstofomzetdata en inzichten opgeleverd in de toestand en processen van diepe, bevroren en ontdooide Yedoma-sedimenten. Deze resultaten tonen de relevantie van het bestuderen van OM in diepe permafrostsedimenten. KW - permafrost sediments KW - organic matter KW - molecular biomarkers KW - anaerobic incubation experiments KW - Russian Arctic KW - Permafrostsedimente KW - organisches Material KW - molekulare Biomarker KW - anaerobe Inkubationensexperimente KW - russische Arktis Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-564911 ER - TY - JOUR A1 - Fühner, Thea Heidi A1 - Granacher, Urs A1 - Golle, Kathleen A1 - Kliegl, Reinhold T1 - Age and sex effects in physical fitness components of 108,295 third graders including 515 primary schools and 9 cohorts JF - Scientific Reports N2 - Children’s physical fitness development and related moderating effects of age and sex are well documented, especially boys’ and girls’ divergence during puberty. The situation might be different during prepuberty. As girls mature approximately two years earlier than boys, we tested a possible convergence of performance with five tests representing four components of physical fitness in a large sample of 108,295 eight-year old third-graders. Within this single prepubertal year of life and irrespective of the test, performance increased linearly with chronological age, and boys outperformed girls to a larger extent in tests requiring muscle mass for successful performance. Tests differed in the magnitude of age effects (gains), but there was no evidence for an interaction between age and sex. Moreover, “physical fitness” of schools correlated at r = 0.48 with their age effect which might imply that "fit schools” promote larger gains; expected secular trends from 2011 to 2019 were replicated. Y1 - 2021 U6 - https://doi.org/10.1038/s41598-021-97000-4 SN - 2045-2322 VL - 11 SP - 1 EP - 13 PB - Nature Portfolio CY - Berlin ER - TY - JOUR A1 - Gäbler, Martijn A1 - Berberyan, Hermine S. A1 - Prieske, Olaf A1 - Elferink-Gemser, Marije Titia A1 - Hortobágyi, Tibor A1 - Warnke, Torsten A1 - Granacher, Urs T1 - Strength Training Intensity and Volume Affect Performance of Young Kayakers/Canoeists JF - Frontiers in physiology N2 - Purpose: The aim of this study was to compare the effects of moderate intensity, low volume (MILV) vs. low intensity, high volume (LIHV) strength training on sport-specific performance, measures of muscular fitness, and skeletal muscle mass in young kayakers and canoeists. Methods: Semi-elite young kayakers and canoeists (N = 40, 13 ± 0.8 years, 11 girls) performed either MILV (70–80% 1-RM, 6–12 repetitions per set) or LIHV (30–40% 1-RM, 60–120 repetitions per set) strength training for one season. Linear mixed-effects models were used to compare effects of training condition on changes over time in 250 and 2,000 m time trials, handgrip strength, underhand shot throw, average bench pull power over 2 min, and skeletal muscle mass. Both between- and within-subject designs were used for analysis. An alpha of 0.05 was used to determine statistical significance. Results: Between- and within-subject analyses showed that monthly changes were greater in LIHV vs. MILV for the 2,000 m time trial (between: 9.16 s, SE = 2.70, p < 0.01; within: 2,000 m: 13.90 s, SE = 5.02, p = 0.01) and bench pull average power (between: 0.021 W⋅kg–1, SE = 0.008, p = 0.02; within: 0.010 W⋅kg–1, SE = 0.009, p > 0.05). Training conditions did not affect other outcomes. Conclusion: Young sprint kayakers and canoeists benefit from LIHV more than MILV strength training in terms of 2,000 m performance and muscular endurance (i.e., 2 min bench pull power). KW - youth sports KW - water sports KW - exercise test KW - athletic performance KW - anthropometry Y1 - 2021 U6 - https://doi.org/10.3389/fphys.2021.686744 SN - 1664-042X VL - 12 SP - 1 EP - 10 PB - Frontiers Research Foundation CY - Lausanne, Schweiz ER - TY - JOUR A1 - Nobari, Hadi A1 - Mahmoudzadeh Khalili, Sara A1 - Denche Zamorano, Angel Manuel A1 - Bowman, ‪Thomas G. A1 - Granacher, Urs T1 - Workload is associated with the occurrence of non-contact injuries in professional male soccer players: A pilot study JF - Frontiers in Psychology N2 - Injuries in professional soccer are a significant concern for teams, and they are caused amongst others by high training load. This cohort study describes the relationship between workload parameters and the occurrence of non-contact injuries, during weeks with high and low workload in professional soccer players throughout the season. Twenty-one professional soccer players aged 28.3 ± 3.9 yrs. who competed in the Iranian Persian Gulf Pro League participated in this 48-week study. The external load was monitored using global positioning system (GPS, GPSPORTS Systems Pty Ltd) and the type of injury was documented daily by the team's medical staff. Odds ratio (OR) and relative risk (RR) were calculated for non-contact injuries for high- and low-load weeks according to acute (AW), chronic (CW), acute to chronic workload ratio (ACWR), and AW variation (Δ-Acute) values. By using Poisson distribution, the interval between previous and new injuries were estimated. Overall, 12 non-contact injuries occurred during high load and 9 during low load weeks. Based on the variables ACWR and Δ-AW, there was a significantly increased risk of sustaining non-contact injuries (p < 0.05) during high-load weeks for ACWR (OR: 4.67), and Δ-AW (OR: 4.07). Finally, the expected time between injuries was significantly shorter in high load weeks for ACWR [1.25 vs. 3.33, rate ratio time (RRT)] and Δ-AW (1.33 vs. 3.45, RRT) respectively, compared to low load weeks. The risk of sustaining injuries was significantly larger during high workload weeks for ACWR, and Δ-AW compared with low workload weeks. The observed high OR in high load weeks indicate that there is a significant relationship between workload and occurrence of non-contact injuries. The predicted time to new injuries is shorter in high load weeks compared to low load weeks. Therefore, the frequency of injuries is higher during high load weeks for ACWR and Δ-AW. ACWR and Δ-AW appear to be good indicators for estimating the injury risk, and the time interval between injuries. KW - ACWR KW - external load KW - football KW - prevention KW - performance KW - injury risk Y1 - 2022 U6 - https://doi.org/10.3389/fpsyg.2022.925722 SN - 1664-1078 SP - 1 EP - 9 PB - Frontiers CY - Lausanne, Schweiz ER - TY - JOUR A1 - Gebel, Arnd A1 - Busch, Aglaja A1 - Stelzel, Christine A1 - Hortobágyi, Tibor A1 - Granacher, Urs T1 - Effects of Physical and Mental Fatigue on Postural Sway and Cortical Activity in Healthy Young Adults JF - Frontiers in Human Neuroscience N2 - Physical fatigue (PF) negatively affects postural control, resulting in impaired balance performance in young and older adults. Similar effects on postural control can be observed for mental fatigue (MF) mainly in older adults. Controversial results exist for young adults. There is a void in the literature on the effects of fatigue on balance and cortical activity. Therefore, this study aimed to examine the acute effects of PF and MF on postural sway and cortical activity. Fifteen healthy young adults aged 28 ± 3 years participated in this study. MF and PF protocols comprising of an all-out repeated sit-to-stand task and a computer-based attention network test, respectively, were applied in random order. Pre and post fatigue, cortical activity and postural sway (i.e., center of pressure displacements [CoPd], velocity [CoPv], and CoP variability [CV CoPd, CV CoPv]) were tested during a challenging bipedal balance board task. Absolute spectral power was calculated for theta (4–7.5 Hz), alpha-2 (10.5–12.5 Hz), beta-1 (13–18 Hz), and beta-2 (18.5–25 Hz) in frontal, central, and parietal regions of interest (ROI) and baseline-normalized. Inference statistics revealed a significant time-by-fatigue interaction for CoPd (p = 0.009, d = 0.39, Δ 9.2%) and CoPv (p = 0.009, d = 0.36, Δ 9.2%), and a significant main effect of time for CoP variability (CV CoPd: p = 0.001, d = 0.84; CV CoPv: p = 0.05, d = 0.62). Post hoc analyses showed a significant increase in CoPd (p = 0.002, d = 1.03) and CoPv (p = 0.003, d = 1.03) following PF but not MF. For cortical activity, a significant time-by-fatigue interaction was found for relative alpha-2 power in parietal (p < 0.001, d = 0.06) areas. Post hoc tests indicated larger alpha-2 power increases after PF (p < 0.001, d = 1.69, Δ 3.9%) compared to MF (p = 0.001, d = 1.03, Δ 2.5%). In addition, changes in parietal alpha-2 power and measures of postural sway did not correlate significantly, irrespective of the applied fatigue protocol. No significant changes were found for the other frequency bands, irrespective of the fatigue protocol and ROI under investigation. Thus, the applied PF protocol resulted in increased postural sway (CoPd and CoPv) and CoP variability accompanied by enhanced alpha-2 power in the parietal ROI while MF led to increased CoP variability and alpha-2 power in our sample of young adults. Potential underlying cortical mechanisms responsible for the greater increase in parietal alpha-2 power after PF were discussed but could not be clearly identified as cause. Therefore, further future research is needed to decipher alternative interpretations. KW - balance KW - cognitive/muscular fatigue KW - EEG KW - theta KW - alpha-2 Y1 - 2022 U6 - https://doi.org/10.3389/fnhum.2022.871930 SN - 1662-5161 VL - 16 SP - 1 EP - 14 PB - Frontiers Media S.A. CY - Lausanne, Schweiz ER - TY - JOUR A1 - Ramirez-Campillo, Rodrigo A1 - Moran, Jason A1 - Oliver, Jonathan L. A1 - Pedley, Jason S. A1 - Lloyd, Rhodri S. A1 - Granacher, Urs T1 - Programming Plyometric-Jump Training in Soccer: A Review JF - Sports N2 - The aim of this review was to describe and summarize the scientific literature on programming parameters related to jump or plyometric training in male and female soccer players of different ages and fitness levels. A literature search was conducted in the electronic databases PubMed, Web of Science and Scopus using keywords related to the main topic of this study (e.g., “ballistic” and “plyometric”). According to the PICOS framework, the population for the review was restricted to soccer players, involved in jump or plyometric training. Among 7556 identified studies, 90 were eligible for inclusion. Only 12 studies were found for females. Most studies (n = 52) were conducted with youth male players. Moreover, only 35 studies determined the effectiveness of a given jump training programming factor. Based on the limited available research, it seems that a dose of 7 weeks (1–2 sessions per week), with ~80 jumps (specific of combined types) per session, using near-maximal or maximal intensity, with adequate recovery between repetitions (<15 s), sets (≥30 s) and sessions (≥24–48 h), using progressive overload and taper strategies, using appropriate surfaces (e.g., grass), and applied in a well-rested state, when combined with other training methods, would increase the outcome of effective and safe plyometric-jump training interventions aimed at improving soccer players physical fitness. In conclusion, jump training is an effective and easy-to-administer training approach for youth, adult, male and female soccer players. However, optimal programming for plyometric-jump training in soccer is yet to be determined in future research. KW - human physical conditioning KW - exercise KW - resistance training KW - muscle strength KW - plyometric exercise KW - musculoskeletal and neural physiological phenomena KW - movement KW - sports KW - football KW - youth sport Y1 - 2022 U6 - https://doi.org/10.3390/sports10060094 SN - 2075-4663 VL - 10 SP - 1 EP - 20 PB - MDPI CY - Basel, Schweiz ET - 6 ER - TY - JOUR A1 - Granacher, Urs A1 - Nobari, Hadi A1 - Ruivo Alves, Ana A1 - Clemente, Filipe Manuel A1 - Pérez-Gómez, Jorge A1 - Clark, Cain Craig Truman A1 - Zouhal, Hassane T1 - Associations Between Variations in Accumulated Workload and Physiological Variables in Young Male Soccer Players Over the Course of a Season JF - Frontiers in physiology N2 - This study sought to analyze the relationship between in-season training workload with changes in aerobic power (VO2max), maximum and resting heart rate (HRmax and HRrest), linear sprint medium (LSM), and short test (LSS), in soccer players younger than 16 years (under-16 soccer players). We additionally aimed to explain changes in fitness levels during the in-season through regression models, considering accumulated load, baseline levels, and peak height velocity (PHV) as predictors. Twenty-three male sub-elite soccer players aged 15.5 ± 0.2 years (PHV: 13.6 ± 0.4 years; body height: 172.7 ± 4.2 cm; body mass: 61.3 ± 5.6 kg; body fat: 13.7% ± 3.9%; VO2max: 48.4 ± 2.6 mL⋅kg–1⋅min–1), were tested three times across the season (i.e., early-season (EaS), mid-season (MiS), and end-season (EnS) for VO2max, HRmax, LSM, and LSS. Aerobic and speed variables gradually improved over the season and had a strong association with PHV. Moreover, the HRmax demonstrated improvements from EaS to EnS; however, this was more evident in the intermediate period (from EaS to MiS) and had a strong association with VO2max. Regression analysis showed significant predictions for VO2max [F(2, 20) = 8.18, p ≤ 0.001] with an R2 of 0.45. In conclusion, the meaningful variation of youth players’ fitness levels can be observed across the season, and such changes can be partially explained by the load imposed. KW - internal load KW - heart rate KW - linear sprint KW - aerobic power KW - football Y1 - 2021 U6 - https://doi.org/10.3389/fphys.2021.638180 SN - 1664-042X VL - 12 SP - 1 EP - 12 PB - Frontiers Research Foundation CY - Lausanne, Schweiz ER - TY - JOUR A1 - Jafarnezhadgero, Amir Ali A1 - Noroozi, Raha A1 - Fakhri Mirzanag, Ehsan A1 - Granacher, Urs A1 - de Souza Castelo Oliveira, Anderson T1 - The Impact of COVID-19 and Muscle Fatigue on Cardiorespiratory Fitness and Running Kinetics in Female Recreational Runners JF - Frontiers in Physiology N2 - Background: There is evidence that fully recovered COVID-19 patients usually resume physical exercise, but do not perform at the same intensity level performed prior to infection. The aim of this study was to evaluate the impact of COVID-19 infection and recovery as well as muscle fatigue on cardiorespiratory fitness and running biomechanics in female recreational runners. Methods: Twenty-eight females were divided into a group of hospitalized and recovered COVID-19 patients (COV, n = 14, at least 14 days following recovery) and a group of healthy age-matched controls (CTR, n = 14). Ground reaction forces from stepping on a force plate while barefoot overground running at 3.3 m/s was measured before and after a fatiguing protocol. The fatigue protocol consisted of incrementally increasing running speed until reaching a score of 13 on the 6–20 Borg scale, followed by steady-state running until exhaustion. The effects of group and fatigue were assessed for steady-state running duration, steady-state running speed, ground contact time, vertical instantaneous loading rate and peak propulsion force. Results: COV runners completed only 56% of the running time achieved by the CTR (p < 0.0001), and at a 26% slower steady-state running speed (p < 0.0001). There were fatigue-related reductions in loading rate (p = 0.004) without group differences. Increased ground contact time (p = 0.002) and reduced peak propulsion force (p = 0.005) were found for COV when compared to CTR. Conclusion: Our results suggest that female runners who recovered from COVID-19 showed compromised running endurance and altered running kinetics in the form of longer stance periods and weaker propulsion forces. More research is needed in this area using larger sample sizes to confirm our study findings. KW - hospitalization KW - running mechanics KW - ground reaction forces KW - virus infection KW - COVID-19 Y1 - 2022 U6 - https://doi.org/10.3389/fphys.2022.942589 SN - 1664-042X VL - 13 SP - 1 EP - 10 PB - Frontiers CY - Lausanne, Schweiz ER - TY - JOUR A1 - Jararnezhadgero, AmirAli A1 - Mamashli, Elaheh A1 - Granacher, Urs T1 - An Endurance-Dominated Exercise Program Improves Maximum Oxygen Consumption, Ground Reaction Forces, and Muscle Activities in Patients With Moderate Diabetic Neuropathy JF - Frontiers in physiology / Frontiers Research Foundation N2 - Background: The prevalence of diabetes worldwide is predicted to increase from 2.8% in 2000 to 4.4% in 2030. Diabetic neuropathy (DN) is associated with damage to nerve glial cells, their axons, and endothelial cells leading to impaired function and mobility. Objective: We aimed to examine the effects of an endurance-dominated exercise program on maximum oxygen consumption (VO2max), ground reaction forces, and muscle activities during walking in patients with moderate DN. Methods: Sixty male and female individuals aged 45–65 years with DN were randomly assigned to an intervention (IG, n = 30) or a waiting control (CON, n = 30) group. The research protocol of this study was registered with the Local Clinical Trial Organization (IRCT20200201046326N1). IG conducted an endurance-dominated exercise program including exercises on a bike ergometer and gait therapy. The progressive intervention program lasted 12 weeks with three sessions per week, each 40–55 min. CON received the same treatment as IG after the post-tests. Pre- and post-training, VO2max was tested during a graded exercise test using spiroergometry. In addition, ground reaction forces and lower limbs muscle activities were recorded while walking at a constant speed of ∼1 m/s. Results: No statistically significant baseline between group differences was observed for all analyzed variables. Significant group-by-time interactions were found for VO2max (p < 0.001; d = 1.22). The post-hoc test revealed a significant increase in IG (p < 0.001; d = 1.88) but not CON. Significant group-by-time interactions were observed for peak lateral and vertical ground reaction forces during heel contact and peak vertical ground reaction force during push-off (p = 0.001–0.037; d = 0.56–1.53). For IG, post-hoc analyses showed decreases in peak lateral (p < 0.001; d = 1.33) and vertical (p = 0.004; d = 0.55) ground reaction forces during heel contact and increases in peak vertical ground reaction force during push-off (p < 0.001; d = 0.92). In terms of muscle activity, significant group-by-time interactions were found for vastus lateralis and gluteus medius during the loading phase and for vastus medialis during the mid-stance phase, and gastrocnemius medialis during the push-off phase (p = 0.001–0.044; d = 0.54–0.81). Post-hoc tests indicated significant intervention-related increases in vastus lateralis (p = 0.001; d = 1.08) and gluteus medius (p = 0.008; d = 0.67) during the loading phase and vastus medialis activity during mid-stance (p = 0.001; d = 0.86). In addition, post-hoc tests showed decreases in gastrocnemius medialis during the push-off phase in IG only (p < 0.001; d = 1.28). Conclusions: This study demonstrated that an endurance-dominated exercise program has the potential to improve VO2max and diabetes-related abnormal gait in patients with DN. The observed decreases in peak vertical ground reaction force during the heel contact of walking could be due to increased vastus lateralis and gluteus medius activities during the loading phase. Accordingly, we recommend to implement endurance-dominated exercise programs in type 2 diabetic patients because it is feasible, safe and effective by improving aerobic capacity and gait characteristics. KW - oxygen consumption KW - kinetics KW - electromyography KW - diabetic KW - gait Y1 - 2021 U6 - https://doi.org/10.3389/fphys.2021.654755 SN - 1664-042X VL - 12 SP - 1 EP - 15 PB - Frontiers Research Foundation CY - Lausanne, Schweiz ER - TY - JOUR A1 - Fernandez-Fernandez, Jaime A1 - Granacher, Urs A1 - Martinez-Martin, Isidoro A1 - Garcia-Tormo, José Vicente A1 - Herrero-Molleda, Alba A1 - Barbado, David A1 - García López, Juan T1 - Physical fitness and throwing speed in U13 versus U15 male handball players JF - BMC Sports Science, Medicine and Rehabilitation N2 - Background The aim of this study was to analyze the shoulder functional profile (rotation range of motion [ROM] and strength), upper and lower body performance, and throwing speed of U13 versus U15 male handball players, and to establish the relationship between these measures of physical fitness and throwing speed. Methods One-hundred and nineteen young male handball players (under (U)-13 (U13) [n = 85]) and U15 [n = 34]) volunteered to participate in this study. The participating athletes had a mean background of sytematic handball training of 5.5 ± 2.8 years and they exercised on average 540 ± 10.1 min per week including sport-specific team handball training and strength and conditioning programs. Players were tested for passive shoulder range-of-motion (ROM) for both internal (IR) and external rotation (ER) and isometric strength (i.e., IR and ER) of the dominant/non-dominant shoulders, overhead medicine ball throw (OMB), hip isometric abductor (ABD) and adductor (ADD) strength, hip ROM, jumps (countermovement jump [CMJ] and triple leg-hop [3H] for distance), linear sprint test, modified 505 change-of-direction (COD) test and handball throwing speed (7 m [HT7] and 9 m [HT9]). Results U15 players outperformed U13 in upper (i.e., HT7 and HT9 speed, OMB, absolute IR and ER strength of the dominant and non-dominant sides; Cohen’s d: 0.76–2.13) and lower body (i.e., CMJ, 3H, 20-m sprint and COD, hip ABD and ADD; d: 0.70–2.33) performance measures. Regarding shoulder ROM outcomes, a lower IR ROM was found of the dominant side in the U15 group compared to the U13 and a higher ER ROM on both sides in U15 (d: 0.76–1.04). It seems that primarily anthropometric characteristics (i.e., body height, body mass) and upper body strength/power (OMB distance) are the most important factors that explain the throw speed variance in male handball players, particularly in U13. Conclusions Findings from this study imply that regular performance monitoring is important for performance development and for minimizing injury risk of the shoulder in both age categories of young male handball players. Besides measures of physical fitness, anthropometric data should be recorded because handball throwing performance is related to these measures. KW - Overhead athletes KW - Shoulder KW - Injury risk KW - Sport-specific performance Y1 - 2022 U6 - https://doi.org/10.1186/s13102-022-00507-0 SN - 1758-2555 VL - 14 PB - Springer CY - London ER - TY - JOUR A1 - Brahms, Markus A1 - Heinzel, Stephan A1 - Rapp, Michael A. A1 - Mückstein, Marie A1 - Hortobágyi, Tibor A1 - Stelzel, Christine A1 - Granacher, Urs T1 - The acute effects of mental fatigue on balance performance in healthy young and older adults – A systematic review and meta-analysis JF - Acta Psychologica N2 - Cognitive resources contribute to balance control. There is evidence that mental fatigue reduces cognitive resources and impairs balance performance, particularly in older adults and when balance tasks are complex, for example when trying to walk or stand while concurrently performing a secondary cognitive task. We conducted a systematic literature search in PubMed (MEDLINE), Web of Science and Google Scholar to identify eligible studies and performed a random effects meta-analysis to quantify the effects of experimentally induced mental fatigue on balance performance in healthy adults. Subgroup analyses were computed for age (healthy young vs. healthy older adults) and balance task complexity (balance tasks with high complexity vs. balance tasks with low complexity) to examine the moderating effects of these factors on fatigue-mediated balance performance. We identified 7 eligible studies with 9 study groups and 206 participants. Analysis revealed that performing a prolonged cognitive task had a small but significant effect (SMDwm = −0.38) on subsequent balance performance in healthy young and older adults. However, age- and task-related differences in balance responses to fatigue could not be confirmed statistically. Overall, aggregation of the available literature indicates that mental fatigue generally reduces balance in healthy adults. However, interactions between cognitive resource reduction, aging and balance task complexity remain elusive. KW - Cognitive fatigue KW - Exertion KW - Tiredness KW - Postural control KW - Gait KW - Sway Y1 - 2022 U6 - https://doi.org/10.1016/j.actpsy.2022.103540 SN - 1873-6297 VL - 225 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Aloui, Ali A1 - Tayech, Amel A1 - Arbi Mejri, Mohamed A1 - Makhlouf, Issam A1 - Clark, Cain C. T. A1 - Granacher, Urs A1 - Zouhal, Hassane A1 - Ben Abderrahman, Abderraouf T1 - Reliability and Validity of a New Taekwondo-Specific Change-of-Direction Speed Test With Striking Techniques in Elite Taekwondo Athletes: A Pilot Study JF - Frontiers in Physiology N2 - The purpose of this study was to examine the test-retest reliability, and convergent and discriminative validity of a new taekwondo-specific change-of-direction (COD) speed test with striking techniques (TST) in elite taekwondo athletes. Twenty (10 males and 10 females) elite (athletes who compete at national level) and top-elite (athletes who compete at national and international level) taekwondo athletes with an average training background of 8.9 ± 1.3 years of systematic taekwondo training participated in this study. During the two-week test-retest period, various generic performance tests measuring COD speed, balance, speed, and jump performance were carried out during the first week and as a retest during the second week. Three TST trials were conducted with each athlete and the best trial was used for further analyses. The relevant performance measure derived from the TST was the time with striking penalty (TST-TSP). TST-TSP performances amounted to 10.57 ± 1.08 s for males and 11.74 ± 1.34 s for females. The reliability analysis of the TST performance was conducted after logarithmic transformation, in order to address the problem of heteroscedasticity. In both groups, the TST demonstrated a high relative test-retest reliability (intraclass correlation coefficients and 90% compatibility limits were 0.80 and 0.47 to 0.93, respectively). For absolute reliability, the TST’s typical error of measurement (TEM), 90% compatibility limits, and magnitudes were 4.6%, 3.4 to 7.7, for males, and 5.4%, 3.9 to 9.0, for females. The homogeneous sample of taekwondo athletes meant that the TST’s TEM exceeded the usual smallest important change (SIC) with 0.2 effect size in the two groups. The new test showed mostly very large correlations with linear sprint speed (r = 0.71 to 0.85) and dynamic balance (r = −0.71 and −0.74), large correlations with COD speed (r = 0.57 to 0.60) and vertical jump performance (r = −0.50 to −0.65), and moderate correlations with horizontal jump performance (r = −0.34 to −0.45) and static balance (r = −0.39 to −0.44). Top-elite athletes showed better TST performances than elite counterparts. Receiver operating characteristic analysis indicated that the TST effectively discriminated between top-elite and elite taekwondo athletes. In conclusion, the TST is a valid, and sensitive test to evaluate the COD speed with taekwondo specific skills, and reliable when considering ICC and TEM. Although the usefulness of the TST is questioned to detect small performance changes in the present population, the TST can detect moderate changes in taekwondo-specific COD speed. KW - taekwondo-specific testing KW - sport-specific performance KW - striking combat sports KW - sensitivity KW - taekwondo electronic scoring system Y1 - 2022 U6 - https://doi.org/10.3389/fphys.2022.774546 SN - 1664-042X VL - 13 SP - 1 EP - 15 PB - Frontiers CY - Lausanne, Schweiz ER - TY - JOUR A1 - Delfan, Maryam A1 - Vahed, Alieh A1 - Bishop, David A1 - Juybari, Raheleh Amadeh A1 - Laher, Ismail A1 - Saeidi, Ayoub A1 - Granacher, Urs A1 - Zouhal, Hassane T1 - Effects of two workload-matched high-intensity interval training protocols on regulatory factors associated with mitochondrial biogenesis in the soleus muscle of diabetic rats JF - Frontiers in Physiology N2 - Aims: High intensity interval training (HIIT) improves mitochondrial characteristics. This study compared the impact of two workload-matched high intensity interval training (HIIT) protocols with different work:recovery ratios on regulatory factors related to mitochondrial biogenesis in the soleus muscle of diabetic rats. Materials and methods: Twenty-four Wistar rats were randomly divided into four equal-sized groups: non-diabetic control, diabetic control (DC), diabetic with long recovery exercise [4–5 × 2-min running at 80%–90% of the maximum speed reached with 2-min of recovery at 40% of the maximum speed reached (DHIIT1:1)], and diabetic with short recovery exercise (5–6 × 2-min running at 80%–90% of the maximum speed reached with 1-min of recovery at 30% of the maximum speed reached [DHIIT2:1]). Both HIIT protocols were completed five times/week for 4 weeks while maintaining equal running distances in each session. Results: Gene and protein expressions of PGC-1α, p53, and citrate synthase of the muscles increased significantly following DHIIT1:1 and DHIIT2:1 compared to DC (p ˂ 0.05). Most parameters, except for PGC-1α protein (p = 0.597), were significantly higher in DHIIT2:1 than in DHIIT1:1 (p ˂ 0.05). Both DHIIT groups showed significant increases in maximum speed with larger increases in DHIIT2:1 compared with DHIIT1:1. Conclusion: Our findings indicate that both HIIT protocols can potently up-regulate gene and protein expression of PGC-1α, p53, and CS. However, DHIIT2:1 has superior effects compared with DHIIT1:1 in improving mitochondrial adaptive responses in diabetic rats. KW - diabetes mellitus KW - muscle metabolism KW - time-efficient exercise KW - mitochondrial adaptation KW - exercise training Y1 - 2022 U6 - https://doi.org/10.3389/fphys.2022.927969 SN - 1664-042X SP - 1 EP - 12 PB - Frontiers CY - Lausanne, Schweiz ER - TY - JOUR A1 - EL-Ashker, Said A1 - Chaabene, Helmi A1 - Prieske, Olaf T1 - Maximal isokinetic elbow and knee flexor–extensor strength measures in combat sports athletes: the role of movement velocity and limb side JF - BMC Sports Science, Medicine and Rehabilitation N2 - Background Maximal isokinetic strength ratios of joint flexors and extensors are important parameters to indicate the level of muscular balance at the joint. Further, in combat sports athletes, upper and lower limb muscle strength is affected by the type of sport. Thus, this study aimed to examine the differences in maximal isokinetic strength of the flexors and extensors and the corresponding flexor–extensor strength ratios of the elbows and knees in combat sports athletes. Method Forty male participants (age = 22.3 ± 2.5 years) from four different combat sports (amateur boxing, taekwondo, karate, and judo; n = 10 per sport) were tested for eccentric peak torque of the elbow/knee flexors (EF/KF) and concentric peak torque of the elbow/knee extensors (EE/KE) at three different angular velocities (60, 120, and 180°/s) on the dominant and non-dominant side using an isokinetic device. Results Analyses revealed significant, large-sized group × velocity × limb interactions for EF, EE, and EF–EE ratio, KF, KE, and KF–KE ratio (p ≤ 0.03; 0.91 ≤ d ≤ 1.75). Post-hoc analyses indicated that amateur boxers displayed the largest EE strength values on the non-dominant side at ≤ 120°/s and the dominant side at ≥ 120°/s (p < 0.03; 1.21 ≤ d ≤ 1.59). The largest EF–EE strength ratios were observed on amateur boxers’ and judokas’ non-dominant side at ≥ 120°/s (p < 0.04; 1.36 ≤ d ≤ 2.44). Further, we found lower KF–KE strength measures in karate (p < 0.04; 1.12 ≤ d ≤ 6.22) and judo athletes (p ≤ 0.03; 1.60 ≤ d ≤ 5.31) particularly on the non-dominant side. Conclusions The present findings indicated combat sport-specific differences in maximal isokinetic strength measures of EF, EE, KF, and KE particularly in favor of amateur boxers on the non-dominant side. KW - Dynamometry KW - Martial arts KW - Hamstring-quadriceps ratio KW - Eccentric muscle action KW - Injury Y1 - 2022 U6 - https://doi.org/10.1186/s13102-022-00432-2 SN - 1758-2555 VL - 13 PB - Springer Nature CY - London ER - TY - JOUR A1 - Schubarth, Wilfried A1 - Mauermeister, Sylvi A1 - Schulze-Reichelt, Friederike A1 - Erdmann, Melinda T1 - Alles auf (Studien-)Anfang? Faktoren für den Studienerfolg in der Eingangsphase und zur Studienmitte BT - Befunde und Empfehlungen des StuFo-Projekts JF - Potsdamer Beiträge zur Hochschulforschung N2 - Die hohen Abbruchquoten, insbesondere in der Studieneingangsphase, haben die Hochschulen in Deutschland veranlasst, eine Vielzahl von Maßnahmen zu ergreifen, über deren Wirkungen bisher allerdings wenig bekannt ist. Im vorliegenden Beitrag werden Befunde eines Forschungsprojekts speziell zur Studieneingangsphase sowie ergänzend zur Studienmitte vorgestellt, dessen Ziel es war, Bedingungen eines erfolgreichen Studieneinstiegs zu identifizieren und Empfehlungen für eine Optimierung des Studieneingangs abzuleiten. Das Forschungsdesign umfasste neben qualitativen Studien vor allem eine quantitative Längsschnittbefragung an fünf Universitäten (Potsdam, Mainz, Magdeburg, Kiel und Greifswald). Im Ergebnis der Analysen konnte die forschungsleitende Hypothese, dass Maßnahmen zum Studieneingang vor allem dann zur Erhöhung des Studienerfolgs einen Beitrag leisten, wenn sie zur akademischen und sozialen Integration in die Hochschule beitragen, bestätigt werden. Bedeutsam für den Studienerfolg sind demnach insbesondere solche Faktoren wie die Identifikation mit dem Studienfach, die Selbstwirksamkeit, die berufliche bzw. erfolgsorientierte Lernmotivation und die akademische Integration. Daneben konnte ein positiver Einfluss des sozialen Klimas sowie des Forschungs- und Praxisbezugs auf die Studienzufriedenheit nachgewiesen werden. Weiterführende Analysen zur Studienmitte verdeutlichen zudem, dass für die beiden Studienphasen (Eingang und Studienmitte) gleiche Faktoren bei zum Teil unterschiedlicher Gewichtung eine Rolle spielen. So ist die soziale Integration ein wesentlicher Prädiktor in beiden Phasen – in der Eingangsphase eher in die Studierendenschaft und im weiteren Studienverlauf (Studienmitte) eher in die akademische Gemeinschaft (in Form von Lehrenden). Insofern muss die Eingangsfrage wie folgt beantwortet werden: Ja, alles auf Anfang, aber dann mit den Bemühungen, soziale und akademische Integration aller Studierenden voll und ganz zu gewährleisten. Zudem machen die Befunde auf die bisher offenbar unterschätzte Rolle von Verwertungsmotiven aufmerksam. KW - Studienabbruch KW - Studieneingang KW - Studienerfolg KW - Wirkungsforschung Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-492623 SN - 978-3-86956-498-2 SN - 2192-1075 SN - 2192-1083 IS - 6 SP - 27 EP - 54 PB - Universitätsverlag Potsdam CY - Potsdam ER -