Bend sprinting performance : new insights into the effect of running lane

Athletes in inner lanes may be disadvantaged during athletic sprint races containing a bend portion because of the tightness of the bend. We empirically investigated the veracity of modelled estimates of this disadvantage and the effect of running lane on selected kinematic variables. Three-dimensional video analysis was conducted on nine male athletes in lanes 8, 5 and 2 of the bend of an outdoor track (radii: 45.10, 41.41 and 37.72 m, respectively). There was over 2% (p < 0.05) reduction in mean race velocity from lane 8 (left step 9.56 ± 0.43 m/s, right step: 9.49 ± 0.41 m/s) to lane 5 (left step: 9.36 ± 0.51 m/s, right step: 9.30 ± 0.51 m/s), with only slight further reductions from lane 5 to lane 2 (left step: 9.34 ± 0.61 m/s, right step: 9.30 ± 0.63 m/s). Race velocity decreased mainly because of reductions in step frequency as radius decreased. These unique data demonstrate the extent of the disadvantage of inner lane allocation during competition may be greater than previously suspected. Variations in race velocity changes might indicate some athletes are better able to accommodate running at tighter radii than others, which should have implications for athletes' training

THE EFFECT OF THE BEND ON TECHNIQUE AND PERFORMANCE DURING MAXIMAL SPEED SPRINTING

For 200 and 400 m races half of the race is run around the bend. This study aimed to understand the changes in kinematics that occur during maximal effort bend sprinting. Velocity reduction (5%) on the bend compared to the straight was, for the left step, mainly due to increased (20%) touchdown distance and some angular kinematics changes which led to increased contact time and reduced step frequency. During the right step, performance dropped mainly due to a reduction in step length. It is likely that changes caused by inward lean, to counteract moments caused by centripetal forces, on the bend contributed to detrimental changes in sagittal plane kinematics (e.g. knee flexion at touchdown) normally associated with superior performance in sprinting. Similar to straight sprinting, reduced touchdown distance could hold the key to improve bend performance

BEND SPRINTING AT DIFFERENT RADII OF AN OUTDOOR ATHLETICS TRACK

Athletes in the inners lanes may be at a disadvantage during sprint races that contain a bend portion. This study investigated the effect on performance when sprinting on the different radii of an outdoor track. There was an approximately 2% reduction in mean race velocity from lane 8 (left step: 9.56 m/s, right step: 9.49 m/s) to lane 5 (left step: 9.36 m/s, right step: 9.30 m/s), with only slight further reductions from lane 5 to lane 2 (left step: 9.34 m/s, right step: 9.30 m/s). This was mainly due to reductions in step frequency as radius decreased. The disadvantage of the inner lane compared to the outer lane may be greater than previously suspected. Larger race velocity standard deviations as radius decreased may be indicative of athletes being differently able to accommodate running at tighter radii than others. This may have implications for training and competition

TPC2 is a novel NAADP-sensitive Ca2+ release channel, operating as a dual sensor of luminal pH and Ca2+

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a molecule capable of initiating the release of intracellular Ca2+ required for many essential cellular processes. Recent evidence links two-pore channels (TPCs) with NAADP-induced release of Ca2+ from lysosome-like acidic organelles; however, there has been no direct demonstration that TPCs can act as NAADP-sensitive Ca2+-release channels. Controversial evidence also proposes ryanodine receptors as the primary target of NAADP. We show that TPC2, the major lysosomal targeted isoform, is a cation channel with selectivity for Ca2+ that will enable it to act as a Ca2+ release channel in the cellular environment. NAADP opens TPC2 channels in a concentration-dependent manner, binding to high affinity activation and low affinity inhibition sites. At the core of this process is the luminal environment of the channel. The sensitivity of TPC2 to NAADP is steeply dependent on the luminal [Ca2+] allowing extremely low levels of NAADP to open the channel. In parallel, luminal pH controls NAADP affinity for TPC2 by switching from reversible activation of TPC2 at low pH to irreversible activation at neutral pH. Further evidence earmarking TPCs as the likely pathway for NAADP-induced intracellular Ca2+ release is obtained from the use of Ned-19, the selective blocker of cellular NAADP-induced Ca2+ release. Ned-19 antagonizes NAADP-activation of TPC2 in a non-competitive manner at 1 μM but potentiates NAADP activation at nanomolar concentrations. This single-channel study provides a long awaited molecular basis for the peculiar mechanistic features of NAADP signaling and a framework for understanding how NAADP can mediate key physiological events.Publisher PDFPeer reviewe

Examining the alcohol-related consequences of adult drinkers who self-report medicating low mood with alcohol: an analysis of the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions survey data.

The aim of this paper is to examine the alcohol-related consequences experienced by adults who experienced a two-week period of low mood and identify as a 'self-mediator' compared to those who do not. Our focus is on assessing whether the conceptualization of alcohol use disorder severity differs across adult drinkers who self-medicate with alcohol during a period of low mood, compared to those who do not. This study used secondary data from the NESARC survey. The analytic sample consisted of 5945 participants who answered questions from the alcohol abuse/dependence (alcohol experiences) section, in the last 12 months. The sample was split into four groups by whether they self-medicated with alcohol or not, and drank alcohol in the last year and their drinking class. The findings indicated that a one factor model was the best fit and all items were a strong indicator of alcohol use disorder. The two-parameter model had the best fit, indicating that the diagnostic criteria were placed as a good fit along a continuum of severity. It was revealed that the hazardous drinking group who self-medicated, experienced more consequences even at low levels of severity. As the self-medicating hazardous drinking group also showed the highest estimates for alcohol use disorder severity, this may indicate that this group are high functioning self-medicators who are trying to regulate their drinking, and may not be as clinically high risk as expected, due to their drinking patterns

Examination of betahistine bioavailability in combination with the monoamine oxidase B inhibitor, selegiline, in humans—a non-randomized, single-sequence, two-period titration, open label single-center phase 1 study (PK-BeST)

Background: Betahistine was registered in Europe in the 1970s and approved in more than 80 countries as a first-line treatment for Menière's disease. It has been administered to more than 150 million patients. However, according to a Cochrane systematic review of betahistine and recent meta-analyses, there is insufficient evidence to say whether betahistine has any effect in the currently approved dosages of up to 48 mg/d. A combination with the monoamine oxidase B (MAO-B) inhibitor, selegiline, may increase the bioavailability of betahistine to levels similar to the well-established combination of L-DOPA with carbidopa or benserazide in the treatment of Parkinson's disease. We investigated the effect of selegiline on betahistine pharmacokinetics and the safety of the combination in humans. Methods: In an investigator-initiated prospective, non-randomized, single-sequence, two-period titration, open label single-center phase 1 study, 15 healthy volunteers received three single oral dosages of betahistine (24, 48, and 96 mg in this sequence with at least 2 days' washout period) without and with selegiline (5 mg/d with a loading period of 7 days). Betahistine serum concentrations were measured over a period of 240 min at eight time points (area under the curve, AUC0-240 min). This trial is registered with EudraCT (2019-002610-39) and ClinicalTrials.gov. Findings: In all three single betahistine dosages, selegiline increased the betahistine bioavailability about 80- to 100-fold. For instance, the mean (±SD) of the area under curve for betahistine 48 mg alone was 0.64 (+/-0.47) h*ng/mL and for betahistine plus selegiline 53.28 (+/-37.49) h*ng/mL. The half-life time of around 30 min was largely unaffected, except for the 24 mg betahistine dosage. In total, 14 mild adverse events were documented. Interpretation: This phase 1 trial shows that the MAO-B inhibitor selegiline increases betahistine bioavailability by a factor of about 80 to 100. No safety concerns were detected. Whether the increased bioavailability has an impact on the preventive treatment of Menière's disease, acute vestibular syndrome, or post-BPPV residual dizziness has to be evaluated in placebo-controlled trials

Force production during maximal effort sprinting on the bend

The force requirements of bend sprinting are not well understood. This study determined the forces produced and performance characteristics of seven male athletes during maximal effort sprinting on the bend and straight. There were asymmetrical changes in force production. Resultant force was reduced on the bend compared to the straight for the left step, but remained similar for the right step. Additionally, more mediolateral force was produced by the left step than the right step on the bend. Overall, we speculate that strength training should aim to meet the demands of bend running, although care should be taken to avoid introducing undesirable asymmetries into straight line sprinting

Bottom stress generation and sediment transport over the shelf and slope off of Lake Superior's Keweenaw peninsula

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C10S04, doi:10.1029/2003JC001997.Data from near-bottom instruments reveal that the mechanisms responsible for generating bottom stresses and resuspending sediment over the shelf and slope off of Lake Superior's Keweenaw peninsula exhibit distinct seasonal variations. Notably, near-bottom flows over the slope are persistently weak (<10 cm s−1) during summer but frequently attain high speeds, in excess of 20 cm s−1, in autumn and winter. During the intense storms of autumn and winter the generation of bottom stress is enhanced by the action of near-bottom orbital velocities due to surface waves. Even at 90-m depth, orbital velocities can increase bottom stress by a factor of up to 20% during storms. Where the seasonal thermocline intersects the lake floor, bottom stress is also considerably enhanced, often by more than a factor of 2, by high-frequency motions in the internal wave band. Over the Keweenaw slope, sediment resuspension is largely confined to autumn and winter episodes of high bottom stress. Our analysis indicates that this resuspended material tends to be carried offshore, a phenomenon that is partly due to the coincidence of the direction of the buoyancy-driven component of the Keweenaw Current with downwelling favorable alongshore winds. As a result of this coincidence, currents and bottom stresses tend to be greater during periods of downwelling, as opposed to upwelling, circulation. A potential challenge to modeling storm-driven resuspension in the study region is indicated by observations that the minimum stress required for resuspension may vary significantly with time over the autumn and winter.The work described was part of the Keweenaw Interdisciplinary Transport Experiment in Superior funded by the National Science Foundation through grants 9712889 to J. Churchill and A.Williams and 9712871 to E. Ralph