EFFECT OF FATIGUE ON DYNAMIC BALANCE AFTER MAXIMUM INTENSITY CROSS-COUNTRY SKIING

Cross-country skiing stresses most of the joints, muscles and tendons in the body giving an overall workout. Skiing requires aerobic and anaerobic power, muscular strength and a variety of complex motor abilities including reaction time, agility, balance, coordination and attention demands (Emily & Arthur, 1989). Muscular fatigue is a key factor which can influence performance via impaired joint proprioception and postural control. Fatigue alters the force generation capacity of the muscle and ultimately leads to task failure (Mahyar et al, 2007). Injury risk increases as time duration of the skiing increases (Smith, Matheson & Meeuwisse, 1996). The maintenance of body posture and balance is an essential requirement for performance of daily tasks and sporting activities. Thus fatigue could affect a skier’s performance through an effect on balance. Fast starts at the beginning of races and short intense efforts required for ascending hills could result in periods of fatigue that could affect balance and performance. Hence fatigue may either result in injury or affect the finish time of the skiers. The main purpose of this study was to evaluate how dynamic balance of the skiers can be influenced by fatigue states following maximum exercis

Exogenous schwann cells migrate, remyelinate and promote clinical recovery in experimental auto-immune encephalomyelitis

Schwann cell (SC) transplantation is currently being discussed as a strategy that may promote functional recovery in patients with multiple sclerosis (MS) and other inflammatory demyelinating diseases of the central nervous system (CNS). However this assumes they will not only survive but also remyelinate demyelinated axons in the chronically inflamed CNS. To address this question we investigated the fate of transplanted SCs in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) in the Dark Agouti rat; an animal model that reproduces the complex inflammatory demyelinating immunopathology of MS. We now report that SCs expressing green fluorescent protein (GFP-SCs) allografted after disease onset not only survive but also migrate to remyelinate lesions in the inflamed CNS. GFP-SCs were detected more frequently in the parenchyma after direct injection into the spinal cord, than via intra-thecal delivery into the cerebrospinal fluid. In both cases the transplanted cells intermingled with astrocytes in demyelinated lesions, aligned with axons and by twenty one days post transplantation had formed Pzero protein immunoreactive internodes. Strikingly, GFP-SCs transplantation was associated with marked decrease in clinical disease severity in terms of mortality; all GFP-SCs transplanted animals survived whilst 80% of controls died within 40 days of disease

Comparing the retinal structures and functions in two species of gulls (Larus delawarensis and Larus modestus) with significant nocturnal behaviours

AbstractRing-billed gulls (Larus delawarensis) and gray gulls (Larus modestus) are two species active both by day and night. We have investigated the retinal adaptations that allow the diurnal and nocturnal behaviours of these two species. Electroretinograms and histological analyses show that both species have a duplex retina in which cones outnumber rods, but the number of rods appears sufficient to provide vision at night. Their retinas respond over the same scotopic dynamic range of 3.4logcdm−2, which encompasses all of the light levels occurring at night in their photic environment. The amplitudes of the scotopic saturated a- and b-wave responses as well as the photopic saturated b-wave response and the photopic sensitivity parameter S are however higher in ring-billed gulls than in gray gulls. Moreover, the process of dark adaptation is about 30min faster in gray gulls than in ring-billed gulls. Our results suggest that both species have acquired in the course of their evolution functional adaptations that can be related to their specific photic environment

American Governors and the Incarceration Epidemic

Throughout the latter part of the twentieth century the United States of America has experienced an incredible boom in the rate of incarceration of its citizens. This increase arguably began in the 1960’s when the Nixon administration oversaw the beginning of the war on drugs in America. The U.S. now has one of the highest rates of incarceration amongst industrialized nations. The increase in incarceration has not impacted all groups of society equally. Citizens who have been incarcerated on drug charges have disproportionately been African American or other racial minorities, even though many studies have concluded that drug use is fairly equal amongst racial groups. In order to remedy this situation it is essential to first understand what causes and has caused rising incarceration rates. In this research I explore gubernatorial rhetoric as a potential explanation for the epidemic of mass incarceration in the United States. Using SAS® Enterprise Content Categorization, SAS® Text Miner, and SAS® Contextual Analysis I gathered data from the state of the state speeches of governors from all 50 states. I find that gubernatorial rhetoric that is tough on crime corresponds strongly and consistently to an increase in the incarceration rate in the states. The political phenomenon that I am trying to understand is how state government employees are affected by the tone that the chief executive of a state uses when discussing crime, and whether the actions of these state employees subsequently lead to higher rates of incarceration. The governor is the top government official in charge of employees of a state, so when this official addresses the state the employees may take the governor’s message as an order for how they should do their jobs. While many political factors may affect legislation and its enforcement, a governor has the ability to set the tone of a state when it comes to policy issues such as crime.Bachelor of Art

RELIABILITY OF A DIGITAL METHOD TO DETERMINE FRONTAL AREA OF A CYCLIST

Eight cyclists were photographed with a digital camera for three trials while positioned on their own bicycle wearing their helmet. The positions were different from each other and described as: hands on the brake hoods; hands below the curve of the brakehoods on the handlebars; and using aerobars. Twenty four trials were digitized by two different individuals three times to estimate the inter- and intra-rater reliability of the method. The Intraclass Correlation Coefficient (p < 0.05) value for the intra-rater (test-retest) reliability was ICC = .993; for inter-rater consistency the ICC = .976. There were significant differences (p < 0.05) between digitizers and between trials apparently due to a learning effect that disappeared by the third trial. Due to small differences between digitizers and trials, caution is recommended when considering use of this method

POWER OUTPUT, MUSCLE ACTIVITY, AND FRONTAL AREA OF A CYCLIST IN DIFFERENT CYCLING POSITIONS

Nine cyclists completed three trials of cycling 25W below lactate threshold (LT) with 1) hands on top of the brake hoods (BH); 2) hands below the dropped, curved, portion of the handlebars (DH); and 3) using clip-on triathlon aerobars (AB). Each trial lasted three minutes and was immediately followed by a 20sec maximal sprint during which power output and muscle EMG were measured. Frontal projection area (FPA) differed across all three positions. EMG did not differ between positions during submax or sprint cycling. Submax power output also did not differ, but during the sprint AB was lower than BH, while DH did not differ from the other conditions. Although power output was 8.1% less while cycling in the AB position than BH, its FPA was 17.4% less, indicating the AB position allows a savings in resistive power greater than that lost in power production

The Discovery of the Most Metal-Rich White Dwarf: Composition of a Tidally Disrupted Extrasolar Dwarf Planet

Cool white dwarf stars are usually found to have an outer atmosphere that is practically pure in hydrogen or helium. However, a small fraction have traces of heavy elements that must originate from the accretion of extrinsic material, most probably circumstellar matter. Upon examining thousands of Sloan Digital Sky Survey spectra, we discovered that the helium-atmosphere white dwarf SDSS J073842.56+183509.6 shows the most severe metal pollution ever seen in the outermost layers of such stars. We present here a quantitative analysis of this exciting star by combining high S/N follow-up spectroscopic and photometric observations with model atmospheres and evolutionary models. We determine the global structural properties of our target star, as well as the abundances of the most significant pollutants in its atmosphere, i.e., H, O, Na, Mg, Si, Ca, and Fe. The relative abundances of these elements imply that the source of the accreted material has a composition similar to that of Bulk Earth. We also report the signature of a circumstellar disk revealed through a large infrared excess in JHK photometry. Combined with our inferred estimate of the mass of the accreted material, this strongly suggests that we are witnessing the remains of a tidally disrupted extrasolar body that was as large as Ceres.Comment: 7 pages in emulateapj, 5 figures, accepted for publication in Ap

A simple mean field model for social interactions: dynamics, fluctuations, criticality

We study the dynamics of a spin-flip model with a mean field interaction. The system is non reversible, spacially inhomogeneous, and it is designed to model social interactions. We obtain the limiting behavior of the empirical averages in the limit of infinitely many interacting individuals, and show that phase transition occurs. Then, after having obtained the dynamics of normal fluctuations around this limit, we analize long time fluctuations for critical values of the parameters. We show that random inhomogeneities produce critical fluctuations at a shorter time scale compared to the homogeneous system.Comment: 37 pages, 2 figure