Bone: An Acute Buffer of Plasma Sodium during Exhaustive Exercise?

Both hyponatremia and osteopenia separately have been well documented in endurance athletes. Although bone has been shown to act as a “sodium reservoir” to buffer severe plasma sodium derangements in animals, recent data have suggested a similar function in humans. We aimed to explore if acute changes in bone mineral content were associated with changes in plasma sodium concentration in runners participating in a 161 km mountain footrace. Eighteen runners were recruited. Runners were tested immediately pre- and post-race for the following main outcome measures: bone mineral content (BMC) and density (BMD) via dual-energy X-ray absorptiometry (DEXA); plasma sodium concentration ([Na+]p), plasma arginine vasopressin ([AVP]p), serum aldosterone concentration ([aldosterone]s), and total sodium intake. Six subjects finished the race in a mean time of 27.0±2.3 h. All subjects started and finished the race with [Na+]p within the normal range (137.7±2.3 and 136.7±1.6 mEq/l, pre- and post-race, respectively). Positive correlations were noted between change (Δ; post-race minus pre-race) in total BMC (grams) and [Na+]p (mEq/l) (r=0.99;

Association of Gastrointestinal Distress in Ultramarathoners with Race Diet

Context: Gastrointestinal (GI) distress is common during ultrarunning. Purpose: To determine if race diet is related to GI distress in a 161-km ultramarathon. Methods: Fifteen (10 male, 5 female) consenting runners in the Javelina Jundred (6.5 loops on a desert trail) participated. Body mass was measured immediately pre-race and after each loop. Runners reported if they had nausea, vomiting, abdominal cramps, and/or diarrhea after each loop. Subjects were interviewed after each loop to record food, fluid, and electrolyte consumption. Race diets were analyzed using Nutritionist Pro. Results: Nine (8 male, 1 female) of 15 runners experienced GI distress including nausea (89%), abdominal cramps (44%), diarrhea (44%), and vomiting (22%). Fluid consumption rate was higher (p = .001) in runners without GI distress (10.9 ± 3.2 ml · kg–1 · hr–1) than in those with GI distress (5.9 ± 1.6 ml · kg–1 · hr–1). Runners without GI distress consumed a higher percentage fat (p = .03) than runners with GI distress (16.5 ± 2.6 vs. 11.1 ± 5.0). In addition, fat intake rate was higher (p = .01) in runners without GI distress (0.06 ± 0.03 g · kg–1 · hr–1) than in runners with GI distress (0.03 ± 0.01 g · kg–1 · hr–1). Lower fluid and fat intake rates were evident in those developing GI distress before the onset of symptoms. Conclusions: A race diet with higher percentage fat and higher intake rates of fat and fluid may protect ultramarathoners from GI distress. However, these associations do not indicate cause and effect, and factors other than race diet may have contributed to GI distress

Hyponatremia in the 2009 161-km Western States Endurance Run

Purpose:To determine the incidence of exercise-associated hyponatremia (EAH), the associated biochemical measurements and risk factors for EAH, and whether there is an association between postrace blood sodium concentration ([Na+]) and changes in body mass among participants in the 2009 Western States Endurance Run, a 161-km mountain trail run. Methods: Change in body mass, postrace [Na+], and blood creatine phosphokinase (CPK) concentration, and selected runner characteristics were evaluated among consenting competitors. Results: Of the 47 study participants, 14 (30%) had EAH as defined by a postrace [Na+] /L. Postrace [Na+] and percent change in body mass were directly related (r = .30, P = .044), and 50% of those with EAH had body mass losses of 3–6%. EAH was unrelated to age, sex, finish time, or use of nonsteroidal anti-inflammatory drugs during the run, but those with EAH had completed a smaller (P = .03) number of 161-km ultramarathons. The relationship of CPK levels to postrace [Na+] did not reach statistical significance (r = –.25, P = .097). Conclusions: EAH was common (30%) among finishers of this 161-km ultramarathon and it was not unusual for those with EAH to be dehydrated. As such, changes in body mass should not be relied upon in the assessment for EAH during 161-km ultramarathons

Incipient Formation of an Electron Lattice in a Weakly Confined Quantum Wire

We study the low-temperature transport properties of 1D quantum wires as the confinement strength V-conf and the carrier density n(1D) are varied using a combination of split gates and a top gate in GaAs/AlGaAs heterostructures. At intermediate V-conf and n(1D), we observe a jump in conductance to 4e(2)/h, suggesting a double wire. On further reducing n(1D), plateau at 2e(2)/h returns. Our results show beginnings of the formation of an electron lattice in an interacting quasi-1D quantum wire. In the presence of an in-plane magnetic field, mixing of spin-aligned levels of the two wires gives rise to more complex states

Characterisation of spin-incoherent transport in one dimension

Spin-incoherent transport in quantum wires, whereby exchange coupling between neighbouring electrons is overcome by thermal energy, leading to the suppression of spin modes of transport expected in a Luttinger liquid, has been observed in the form of a conductance plateau at e(2)/h in the absence of a magnetic field. We present here further characterisation of this spin-incoherent plateau in a source-drain bias, which causes it to evolves to 0.85 x 2e(2)/h. Laterally shifting the channel and illuminating the sample allows us to verify its origin

On-line case discussion assessment in Ultrasound: The effect on student centred and inter-professional learning

In 2009 an asynchronous on-line case discussion assessment was introduced, to replace an existing traditional case-study assessment, within the Medical Ultrasound Programmes at City University London, to help extend collaborative, interprofessional student-led learning skills. Two clinical modules were used to develop the on-line learning method with associated assessments. Students selected and led a clinical case from their department, uploaded anonymised images and case details with questions, to encourage interaction from other colleagues. Thirty students participated in the on-line case discussions. The assessment was evaluated via informal feedback, end of module feedback and an on-line questionnaire. Some students completed two modules, using the on-line discussion, others were involved in only one module, of which 21 out of 26 students completed end of module feedback for the 1st module and 18 out of 20 students completed feedback from the 2nd module. Twelve students out of 30 completed the on-line questionnaire. Feedback suggested that the on-line case discussions were a good learning tool, providing a wide range of cases for students to participate in or read and learn from each other. All students found the cases interesting, engaging and useful, but time consuming. Despite the small numbers involved, useful feedback was provided to assist further development of the assessment, particularly in relation to the number of cases being assessed and length of availability. On-line case discussions are an innovative, engaging method to encourage self directed, collaborative learning which could be utilised in the health care setting to share interesting cases, promote inter-professional and self-directed learning

Spin-incoherent transport in quantum wires

When a quantum wire is weakly confined, a conductance plateau appears at e(2)/h with decreasing carrier density in zero magnetic field accompanied by a gradual suppression of the 2e(2)/h plateau. Applying an in-plane magnetic field B-parallel to does not alter the value of this quantization; however, the e(2)/h plateau weakens with increasing B-parallel to up to 9 T, and then strengthens on further increasing B-parallel to, which also restores the 2e(2)/h plateau. Our results are consistent with spin-incoherent transport in a one-dimensional wire

Exploring the attitudes of students undertaking sports degrees towards online international learning

Abstract Aims: There is an increased focus on the internationalisation of the learning experiences of university students1. One way this can be achieved is through ‘virtual internationalisation’2, which can be promoted through the use of Online International Learning (OIL) programmes. This article on sport pedagogy investigates the attitudes of sport students to such a programme. Methods: This article uses quantitative and qualitative methods. 63 students completed a survey and wrote reflective reports. Data was collected from a survey of 16 targeted questions addressing the attitudes of students towards the programme. Students also wrote reflective reports on their experiences, allowing for qualitative responses to be analysed. Results: 62% of students surveyed found the internationalised module to have been a worthwhile experience in terms of learning new skills and working with a partner from an institution based in another continent. 65% suggested that they learned skills on the internationalised module they would use again in education and in future employment. Students from European Union countries gave high rates of positive feedback. 100% reported that the module was a worthwhile experience, compared to 60% of UK students and 38% of international students from outside the European Union. Conclusion: 62% of students surveyed stated that they learned new skills, and there was a perceived value to the programme in terms of enhancing employment prospects. Virtual mobilities projects offer a possible method for tutors to give students international experiences, which is important as sport is now a globalised industry

Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devices

Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 x 2e^2/h anomaly. We report on the dependence of the 1D Lande g-factor g* and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g* values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs, and approaching that in InGaAs/InP QPCs. We show that g* is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g* desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature.Comment: 23 pages, 7 figure