Influence of menstrual phase on ventilatory response to submaximal exercise

Objectives. To determine whether an increase in respiratory drive, due to elevated progesterone and oestrogen concentration during various menstrual phases, persists throughout prolonged submaximal exercise and potentially contributes to fatigue. Furthermore, to determine whether the difference in the ventilatory response to exercise from one menstrual phase to another is correlated to the ovarian hormone concentrations. Design. We compared the change in ventilatory parameters during 90 min exercise at 60%VO2max between the early follicular (EF) and mid-luteal (ML) phase (N = 9) and between the EF and late follicular (LF) phase (N = 5) in eumenorrhoeic women. Main outcome measures. Menstrual phase comparisons and correlations between the change in ventilatory parameters (minute ventilation (VE), respiratory rate (RR), tidal volume) from the EF to ML or from the EF to LF phase and ovarian hormone concentration. Results. The difference in RR between EF and ML phases correlated to progesterone concentration in the ML phase (r = 0.7, p = 0.04). In addition, RR was higher during exercise in the ML compared with EF phase for the full duration of exercise by on average 2.3 ± 2.1 breaths/min (p < 0.05). However, no difference in submaximal VO2 between menstrual phases was evident. No significant difference in exercising-VE was observed between menstrual phases, but the change in VE from EF to ML correlated to oestrogen (r = 0.8, p = 0.02) and progesterone (r = 0.7, p = 0.04) concentration in the ML phase. South African Journal of Sports Medicine Vol. 18 (2) 2006: pp. 31-3

Efficacy of a modified tapering protocol on swimming performance

Objective. The aim of this study was to determine any difference in performance following two different tapering protocols after a period of heavy training. Design. Twelve swimmers who regularly trained at a high volume and intensity were recruited and trained together for 3 weeks. They were then randomly split into two groups (N=6 per group). One group underwent a standard taper protocol, while the second followed a modified taper in which training load was gradually resumed for 1 week following a standard taper. Performance assessment following tapering consisted of 2 swims over a distance of 200 m, with a recovery period of 5 hours between swims. After resuming normal training, subjects tapered a second time, each group following the alternate protocol. Outcome measures. Total time and split times for each length, stroke rate, distance per stroke, and stroke index in a performance swim were determined as well as heart rate (HR), profile of mood state (POMS), rating of perceived exertion (RPE) and muscle pain during each taper. Results. Mean swim times for the modified and conventional tapers were 134.7±9.1 and 134.7±9.3 seconds, respectively (mean ±SD). There was also no difference in the split times between groups, although both became slower in the final three laps. Stroke rate, distance per stroke, and stroke index were also not different between protocols. There were no differences between protocols in HR, RPE or rating of muscle pain over the duration of the tapering period. However, there was a significant reduction in HR on day 5 of both tapers and a lower POMS on days 3, 4 and 5 on the standard taper protocol. At the time of the performance swim, however, there was no difference in POMS. Conclusion. There were no performance or physiological advantages from the modified tapering protocol. South African Journal of Sports Medicine Vol. 20 (2) 2008: pp. 49-5

Metabolic consequences of exercise-induced muscle damage.

Exercise-induced muscle damage (EIMD) is commonly experienced following either a bout of unaccustomed physical activity or following physical activity of greater than normal duration or intensity. The mechanistic factor responsible for the initiation of EIMD is not known; however, it is hypothesised to be either mechanical or metabolic in nature. The mechanical stress hypothesis states that EIMD is the result of physical stress upon the muscle fibre. In contrast, the metabolic stress model predicts that EIMD is the result of metabolic deficiencies, possibly through the decreased action of Ca(2+)-adenosine triphosphatase. Irrespective of the cause of the damage, EIMD has a number of profound metabolic effects. The most notable metabolic effects of EIMD are decreased insulin sensitivity, prolonged glycogen depletion and an increase in metabolic rate both at rest and during exercise. Based on current knowledge regarding the effects that various types of damaging exercise have on muscle metabolism, a new model for the initiation of EIMD is proposed. This model states that damage initiation may be either metabolic or mechanical, or a combination of both, depending on the mode, intensity and duration of exercise and the training status of the individual

Influence of menstrual phase on ventilatory response to submaximal exercise

Objectives. To determine whether an increase in respiratory drive, due to elevated progesterone and oestrogen concentration during various menstrual phases, persists throughout prolonged submaximal exercise and potentially contributes to fatigue. Furthermore, to determine whether the difference in the ventilatory response to exercise from one menstrual phase to another is correlated to the ovarian hormone concentrations. Design. We compared the change in ventilatory parameters during 90 min exercise at 60%VO2max between the early follicular (EF) and mid-luteal (ML) phase (N = 9) and between the EF and late follicular (LF) phase (N = 5) in eumenorrhoeic women. Main outcome measures. Menstrual phase comparisons and correlations between the change in ventilatory parameters (minute ventilation (VE), respiratory rate (RR), tidal volume) from the EF to ML or from the EF to LF phase and ovarian hormone concentration. Results. The difference in RR between EF and ML phases correlated to progesterone concentration in the ML phase (r = 0.7, p = 0.04). In addition, RR was higher during exercise in the ML compared with EF phase for the full duration of exercise by on average 2.3 ± 2.1 breaths/min (p < 0.05). However, no difference in submaximal VO2 between menstrual phases was evident. No significant difference in exercising-VE was observed between menstrual phases, but the change in VE from EF to ML correlated to oestrogen (r = 0.8, p = 0.02) and progesterone (r = 0.7, p = 0.04) concentration in the ML phase. South African Journal of Sports Medicine Vol. 18 (2) 2006: pp. 31-3

Tris(2-pyridylmethyl)amine (TPA) as a membrane-permeable chelator for interception of biological mobile zinc

We report the characterization of tris(2-pyridylmethyl)amine (TPA) as a membrane-permeable zinc chelator for intercepting biological mobile zinc. Compared to N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), TPA chelates zinc with faster kinetics in cuvettes, live cells, and brain slices. TPA also is generally less toxic than TPEN in cell culture. Mechanistic analysis indicates that these improvements arise from both the electronic and steric properties of TPA including weaker metal-binding affinity, lower pK[subscript a], and smaller size. These results demonstrate that TPA chelation is a valuable addition to the methodologies available for investigating mobile zinc in biology.National Institute of General Medical Sciences (U.S.) (Grant GM065519)FRAXA Research Foundation (Fellowship

What influences the speed of prototyping? An empirical investigation of twenty software startups

It is essential for startups to quickly experiment business ideas by building tangible prototypes and collecting user feedback on them. As prototyping is an inevitable part of learning for early stage software startups, how fast startups can learn depends on how fast they can prototype. Despite of the importance, there is a lack of research about prototyping in software startups. In this study, we aimed at understanding what are factors influencing different types of prototyping activities. We conducted a multiple case study on twenty European software startups. The results are two folds, firstly we propose a prototype-centric learning model in early stage software startups. Secondly, we identify factors occur as barriers but also facilitators for prototyping in early stage software startups. The factors are grouped into (1) artifacts, (2) team competence, (3) collaboration, (4) customer and (5) process dimensions. To speed up a startups progress at the early stage, it is important to incorporate the learning objective into a well-defined collaborative approach of prototypingComment: This is the author's version of the work. Copyright owner's version can be accessed at doi.org/10.1007/978-3-319-57633-6_2, XP2017, Cologne, German

Sex‐biased disease dynamics increase extinction risk by impairing population recovery

The periodicity of life‐cycle events (phenology) modulates host availability to pathogens in a repeatable pattern. The effects of sexual differences in host phenology have been little explored in wildlife epidemiological studies. A recent series of ranavirosis outbreaks led to serious declines of Boscas’ newt populations at Serra da Estrela (Portugal). The peculiar phenology of this species, in which a large number of females remain in the aquatic habitat after the breeding season, turns it into a suitable model to test how sex‐biased mortality can affect host population persistence in the context of infectious diseases. We investigated how the phenology of Bosca's newt (i.e. biased number of females) mediated the impact of Ranavirus. We then evaluated the risk of extinction of the population under different scenarios of sex‐biased mortality using a population viability analysis. Two newt populations (one subject to yearly outbreaks and a comparative site where outbreaks have not been recorded) were tracked for trends over time following emergence of ranaviral disease, allowing us to assess the differential impact of the disease on both sexes. In addition to a significant decline in abundance of adult newts, our data suggest that phenology can affect disease dynamics indirectly, leading to reduction in females and a reversal of the sex ratio of the breeding population. Our models suggest that female‐biased mortality does not exacerbate Ranavirus‐driven population declines in the short‐term, but is likely to have a deleterious impact during the recovery process once the lethal effect of disease is removed from the system

Better Guidance Is Welcome, but without Blinders

David Peters and Sara Bennett provide a critical perspective on a three-part series on health systems guidance that examines how evidence should be used to strengthen health systems and improve the delivery of global health interventions

Physical properties underlying observed kinematics of satellite galaxies

We study the kinematics of satellites around isolated galaxies selected from the Sloan Digital Sky Survey (SDSS) spectroscopic catalog. Using a model of the phase-space density previously measured for the halos of LCDM dark matter cosmological simulations, we determine the properties of the halo mass distribution and the orbital anisotropy of the satellites as a function of the colour-based morphological type and the stellar mass of the central host galaxy. We place constraints on the halo mass and the concentration parameter of dark matter and the satellite number density profiles. We obtain a concentration-mass relation for galactic dark matter haloes that is consistent with predictions of a standard LCDM cosmological model. At given halo or stellar mass, red galaxies have more concentrated halos than their blue counterparts. The fraction of dark matter within a few effective radii is minimal for 11.25<log M_star<11.5. The number density profile of the satellites appears to be shallower than of dark matter, with the scale radius typically 60 per cent larger than of dark matter. The orbital anisotropy around red hosts exhibits a mild excess of radial motions, in agreement with the typical anisotropy profiles found in cosmological simulations, whereas blue galaxies are found to be consistent with an isotropic velocity distribution. Our new constraints on the halo masses of galaxies are used to provide analytic approximations of the halo-to-stellar mass relation for red and blue galaxies.Comment: 12 pages, 11 figures; accepted for publication in MNRAS (updated references

General CP Violation in Minimal Left-Right Symmetric Model and Constraints on the Right-Handed Scale

In minimal left-right symmetric theories, the requirement of parity invariance allows only one complex phase in the Higgs potential and one in the Yukawa couplings, leading to a two-phase theory with both spontaneous and explicit CP violations. We present a systematic way to solve the right-handed quark mixing matrix analytically in this model and find that the leading order solution has the same hierarchical structure as the left-handed CKM matrix with one more CP-violating phase coming from the complex Higgs vev. Armed with this explicit right-handed mixing matrix, we explore its implications for flavor changing and conserving processes in detail, low-energy CP-violating observables in particular. We report an improved lower bound on the $W_R$ mass of 2.5 TeV from $\Delta M_K$ and $\Delta M_{B}$, and a somewhat higher bound (4 TeV) from kaon decay parameters $\epsilon$, $\epsilon'$, and neutron electric dipole moment. The new bound on the flavor-changing neutral Higgs mass is 25 TeV.Comment: 35 pages, 14 figure