The relationship between blood potassium, blood lactate, and electromyography signals related to fatigue in a progressive cycling exercise test

Local muscle fatigue may be related to potassium efflux from the muscle cell and lactate accumulation within the muscle. However, this has not been verified. The primary purpose of this investigation was to determine if there was a relationship between fatigue related changes in median power frequency (MPF) of EMG signals from the vastus lateralis and blood lactate (LAC) or potassium (K) during a progressive cycling test. This was tested in eight trained cyclists and triathletes under normal and glycogen reduced conditions to modify the LAC environment. No significant relationships were found between LAC (p>0.27) or K (p>0.16) in either condition during exercise or recovery. Though both lactate and potassium have been implicated as factors relating to neuromuscular fatigue, neither is significantly related to changes in MPF during or after progressive exercise on a cycle ergometer

Maximal force and tremor changes across the menstrual cycle

PURPOSE: Sex hormones have profound effects on the nervous system in vitro and in vivo. The present study examines the effect of the menstrual cycle on maximal isometric force (MVC) and tremor during an endurance task. METHODS: Nine eumenorrheic females participated in five study visits across their menstrual cycle. In each menstrual phase, an MVC and an endurance task to failure were performed. Tremor across the endurance task was quantified as the coefficient of variation in force and was assessed in absolute time and relative percent time to task failure. RESULTS: MVC decreases 23% from ovulation to the mid luteal phase of the menstrual cycle. In absolute time, the mid luteal phase has the highest initial tremor, though the early follicular phase has substantially higher tremor than other phases after 150 s of task performance. In relative time, the mid luteal phase has the highest level of tremor throughout the endurance task. CONCLUSIONS: Both MVC and tremor during an endurance task are modified by the menstrual cycle. Performance of tasks and sports which require high force and steadiness to exhaustion may be decreased in the mid luteal phase compared to other menstrual phases

Exercise-Induced Glycogen Reduction Increases Muscle Activity

International Journal of Exercise Science 9(3): 336-346, 2016. Intramuscular glycogen stores are an important energy source during extended bouts of strenuous exercise. A substantial reduction in glycogen could influence neural muscular drive and result in a decreasing quality of exercise performance and potentially increased injury rates. The aim of this study was to examine the effect of glycogen reduction on motor drive as determined by the surface electromyogram (EMG) amplitude and median frequency during a cycling graded exercise test. Eight trained cyclists performed a discontinuous cycling graded exercise test to exhaustion under both normal and glycogen reduced conditions. EMG was collected from the vastus lateralis. Repeated measures regression models indicated that EMG amplitudes were elevated at cycling workloads higher than 196 Watts and metabolic workloads higher than 40.8 ml/kg/min, corresponding to 77% VO2max. There was no effect of increases in workload or glycogen reduction on EMG median frequency. Changes in mechanical and metabolic workload had a substantial effect on EMG amplitude (Cohen’s f2 = 0.227 and 0.247, respectively), but not median frequency (Cohen’s f2 = 0.026 and 0.033, respectively). Thus, EMG amplitude is a more effective and reliable measure to examine changes in motor drive during variable workload conditions and metabolic perturbations. The results suggest that healthy glycogen reduced humans require higher levels of muscle activity in order to attain a given mechanical and metabolic workload. This may affect the long term performance of professional and military athletes who need to be able to perform at a high level for extended periods of activity

Effects of Cognitive Fatigue on High Intensity Circuit Exercise: Preliminary study

Please refer to the pdf version of the abstract located adjacent to the title

Cognitive Fatigue Influences Time-On-Task during Bodyweight Resistance Training Exercise

Prior investigations have shown measurable performance impairments on continuous physical performance tasks when preceded by a cognitively fatiguing task. However, the effect of cognitive fatigue on bodyweight resistance training exercise task performance is unknown. In the current investigation 18 amateur athletes completed a full body exercise task preceded by either a cognitive fatiguing or control intervention. In a randomized repeated measure design, each participant completed the same exercise task preceded by a 52 minute cognitively fatiguing intervention (vigilance) or control intervention (video). Data collection sessions were separated by 1 week. Participants rated the fatigue intervention as being significantly more mentally demanding than the control intervention (p .05). There was no statistical difference for heart rate or metabolic expenditure as a function of fatigue intervention during exercise. Cognitively fatigued athletes have decreased time-on-task in bodyweight resistance training exercise tasks

Estimating abundance and habitat suitability in a micro-endemic snake: the Walser viper

Recently described species suffer lack of information that hampers setting up appropriate conservation strategies. The situation is particularly complex with micro-endemic snakes, for which detection and monitoring are particularly challenging. The Walser viper Vipera walser is a recently described snake inhabiting a small area of the SW Italian alps. We combined information on species distribution with repeated monitoring to identify the areas most suitable for the species, and to obtain estimates of species abundance. Species distribution models were used to identify the topographical, climatic, and land-cover features related to the occurrence of vipers. Furthermore, repeated transects and N-mixture models were used to estimate abundance and to identify factors related to the variation of abundance. The available data suggested that the species has a disjunct range, with a Northern range of ~45 km2 , and a southern range of ~225 km2. Distribution models suggested that vipers are associated with areas with open egetation,altitude between 1300 and 2300 m, high precipitation, low forest cover, low slope, and southern aspect. N-mixture models confirmed very low detection probability of these vipers, and suggested that the species has a low abundance,with the highest abundance in south-facing plots. We provide the first quantitative information on habitats and abundance variation for Walser vipers. The broad confidence intervals of abundance estimates exemplify the complexity of providing range-wide measures of abundance for secretive species. Given the narrow range of these vipers, continuous monitoring is required to understand how they respond to ongoing environmental changes in mountainous areas

Information theory in the study of anisotropic radiation

Information theory is used to perform a thermodynamic study of non equilibrium anisotropic radiation. We limit our analysis to a second-order truncation of the moments, obtaining a distribution function which leads to a natural closure of the hierarchy of radiative transfer equations in the so-called variable Eddington factor scheme. Some Eddington factors appearing in the literature can be recovered as particular cases of our two-parameter Eddington factor. We focus our attention in the study of the thermodynamic properties of such systems and relate it to recent nonequilibrium thermodynamic theories. Finally we comment the possibility of introducing a nonequilibrium chemical potential for photons.Comment: 1 eps figure upon request by e-mail, to appear in Journal of Physics

Vaccine derived human-bovine double reassortant rotavirus in infants with acute gastroenteritis

Rotavirukset ovat maailmanlaajuisesti yleisin pienten lasten vakavien ripulitautien aiheuttaja. Ennen rotavirusrokotuksia lasten rotavirusinfektiot aiheuttivat vuosittain kymmeniätuhansia sairaala- ja poliklinikkakäyntejä pienillä lapsilla. RotaTeq® rokote lisättiin Suomen kansalliseen rokotusohjelmaan syyskuussa 2009, kun se oli massiivisten tutkimusten jälkeen todettu turvalliseksi ja tehokkaaksi rokotteeksi rotavirus tautia vastaan. RotaTeq® on elävä, heikennetty rokote, joka sisältää viittä ihmisen ja naudan yhdistelmävirusta. Yhdistelmäviruksissa toinen ulommista pintaproteiineista, VP7 tai VP4, on ihmisperäinen ja toinen nautaperäinen. Suomessa immunisointi tapahtuu 2, 3 ja 5 kuukauden ikäisenä. Tutkimuksen tarkoituksena oli selvittää Tampereen yliopistollisessa sairaalassa (TAYS) syyskuun 2009 ja elokuun 2011 välillä hoidettujen oksennus- ja/tai ripulitautia sairastavien lasten pääasiallisia taudinaiheuttajia. Tutkimukseen osallistuneilta lapsilta kerättiin ulostenäyte, josta tutkittiin rotaviruksen lisäksi norovirus, adenovirus, coronavirus sekä bocavirus PCR- menetelmillä. Rotavirus positiivisista näytteistä selvitettiin lisäksi viruksen uloimman kerroksen kahden pintaproteiinin, VP7 ja VP4 genomi viruksen tyypitystä varten, sekä keskikerroksen proteiinin VP6 sekvenssi mahdollisen rokoteviruksen tunnistamiseksi. Tutkimuksessa löydettiin 3 lasta, joilla oksennus-ja/tai ripulitaudin aiheuttaja oli rokotteesta peräisin oleva uusi yhdistelmävirus. Uudessa rokoteperäisessä viruksessa kaksi RotaTeq® rokotteen virusta ovat yhdistyneet siten, että muodostuneen uuden yhdistelmäviruksen uloimman kerroksen kumpikin proteiini, VP7 ja VP4, ovat ihmisperäisiä. Merkittävänä tutkimustuloksena selvisi, että uusi rokoteperäinen yhdistelmävirus on infektiivinen ja stabiili. Se voi aiheuttaa oksennus-ja/tai ripulitaudin oireita rokotetuilla lapsilla, jotka voivat erittää virusta edelleen ympäristöönsä

Early-succession secondary forests following agropastoral abandonment are key winter habitats for the conservation of a priority bird in the European Alps

In contrast to old-growth forests, early-successional stands remain understudied despite potentially harbouring species of conservation interest. With this work, focused on hazel grouse Tetrastes bonasia, a cryptic and indicator species known to select for close-to-natural forests, we evaluated winter densities, home range, microhabitat selection and diet, combining DNA-based mark-recapture and metabarcoding from faecal samples. In total, 216 droppings, collected over 2 years along forest transects in the Italian Alps, were successfully genotyped and 43 individuals were identified. Density estimates were similar to values reported by other studies in the Alps with an average of 4.5 and 2.4 individuals/km2 in the first and second study year, respectively, and mean home ranges estimated at 0.95 km2. According to habitat selection models and eDNA-based diet analysis, hazel grouse selected early-succession secondary-growth forests formed after the abandonment of traditional agropastoral activities. These forests, mostly composed of hazel Corylus avellana, Norway spruce Picea abies and Sorbus spp., provided winter food resources and shelter. The diet analysis also highlighted forest arthropods as a non-negligible source of food. Birds avoided areas subject to intensive browsing by ungulates; small forest roads seasonally closed to traffic had positive influence on hazel grouse (i.e. higher abundance of droppings), while roads open to traffic had no effect. Importantly, despite the high coverage of mature forest habitats of Community Interest (53% of our study area), droppings were more abundant in non-listed early-succession secondary forests with similar plant composition. Our results suggest that forest succession after agropastoral abandonment may be beneficial for some forest birds of conservation interest, while acknowledging its negative effects on the previous grassland biodiversity. Graphical abstract: [Figure not available: see fulltext.