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Implications of moderate altitude training for sea level endurance in elite distance runners
Elite distance runners participated in one of
two studies designed to investigate the e ects of mod-
erate altitude training (inspiratory partial pressure of
oxygen »115±125 mmHg) on submaximal, maximal and
supramaximal exercise performance following return to
sea-level. Study 1 (New Mexico, USA) involved 14
subjects who were assigned to a 4-week altitude training
camp (1500±2000 m) whilst 9 performance-matched
subjects continued with an identical training programme
at sea-level (CON). Ten EXP subjects who trained at
1640 m and 19 CON subjects also participated in study 2
(Krugersdorp, South Africa). Selected metabolic and
cardiorespiratory parameters were determined with the
subjects at rest and during exercise 21 days prior to
(PRE) and 10 and 20 days following their return to sea-
level (POST). Whole blood lactate decreased by 23%
(P < 0.05 vs PRE) during submaximal exercise in the
EXP group only after 20 days at sea-level (study 1).
However, the lactate threshold and other measures of
running economy remained unchanged. Similarly, su-
pramaximal performance during a standardised track
session did not change. Study 2 demonstrated that
hypoxia per se did not alter performance. In contrast, in
the EXP group supramaximal running velocity de-
creased by 2% (P < 0.05) after 20 days at sea-level.
Both studies were characterised by a 50% increase in the
frequency of upper respiratory and gastrointestinal tract
infections during the altitude sojourns, and two male
subjects were diagnosed with infectious mononucleosis
following their return to sea-level (study 1). Group mean
plasma glutamine concentrations at rest decreased by
19% or 143 (74) lM (P < 0.001) after 3 weeks at alti-
tude, which may have been implicated in the increased
incidence of infectious illness
Apparent and actual galaxy cluster temperatures
The redshift evolution of the galaxy cluster temperature function is a
powerful probe of cosmology. However, its determination requires the
measurement of redshifts for all clusters in a catalogue, which is likely to
prove challenging for large catalogues expected from XMM--Newton, which may
contain of order 2000 clusters with measurable temperatures distributed around
the sky. In this paper we study the apparent cluster temperature, which can be
obtained without cluster redshifts. We show that the apparent temperature
function itself is of limited use in constraining cosmology, and so concentrate
our focus on studying how apparent temperatures can be combined with other
X-ray information to constrain the redshift. We also briefly study the
circumstances in which non-thermal spectral features can give redshift
information.Comment: 7 pages LaTeX file with 13 figures incorporated (uses mn.sty and
epsf). Minor changes to match MNRAS accepted versio
Influence of upper-body exercise on the fatigability of human respiratory muscles
PURPOSE: Diaphragm and abdominal muscles are susceptible to contractile fatigue in response to high-intensity, whole-body exercise. This study assessed whether the ventilatory and mechanical loads imposed by high-intensity, upper-body exercise would be sufficient to elicit respiratory muscle fatigue. METHODS: Seven healthy men (mean±SD: age 24±4 y; peak O2 uptake [V[Combining Dot Above]O2 peak] 31.9±5.3 ml/kg/min) performed asynchronous arm-crank exercise to exhaustion at work rates equivalent to 30% (heavy) and 60% (severe) of the difference between gas-exchange threshold and V[Combining Dot Above]O2 peak. Contractile fatigue of the diaphragm and abdominal muscles was assessed by measuring pre- to post-exercise changes in potentiated transdiaphragmatic and gastric twitch pressures (Pdi,tw and Pga,tw) evoked by supramaximal magnetic stimulation of the cervical and thoracic nerves, respectively. RESULTS: Exercise time was 24.5±5.8 min for heavy exercise and 9.8±1.8 min for severe exercise. Ventilation over the final minute of heavy exercise was 73±20 L/min (39±11% maximum voluntary ventilation [MVV]) and 99±19 L/min (53±11% MVV) for severe exercise. Mean Pdi,tw did not differ pre- to post-exercise at either intensity (p>0.05). Immediately (5-15 min) after severe exercise, mean Pga,tw was significantly lower than pre-exercise values (41±13 vs. 53±15 cmH2O, p<0.05), with the difference no longer significant after 25-35 min. Abdominal muscle fatigue (defined as â„15% reduction in Pga,tw) occurred in 1/7 subjects after heavy exercise and 5/7 subjects after severe exercise. CONCLUSIONS: High-intensity, upper-body exercise elicits significant abdominal, but not diaphragm, muscle fatigue in healthy men. The increased magnitude and prevalence of fatigue during severe-intensity exercise is likely due to additional (non-respiratory) loading of the thorax.This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 American College of Sports Medicin
Multispeckle diffusing-wave spectroscopy: a tool to study slow relaxation and time-dependent dynamics
A multispeckle technique for efficiently measuring correctly
ensemble-averaged intensity autocorrelation functions of scattered light from
non-ergodic and/or non-stationary systems is described.
The method employs a CCD camera as a multispeckle light detector and a
computer-based correlator, and permits the simultaneous calculation of up to
500 correlation functions, where each correlation function is started at a
different time.
The correlation functions are calculated in real time and are referenced to a
unique starting time.
The multispeckle nature of the CCD camera detector means that a true ensemble
average is calculated; no time averaging is necessary.
The technique thus provides a "snapshot" of the dynamics, making it
particularly useful for non-stationary systems where the dynamics are changing
with time.
Delay times spanning the range from 1 ms to 1000 s are readily achieved with
this method.
The technique is demonstrated in the multiple scattering limit where
diffusing-wave spectroscopy theory applies.
The technique can also be combined with a recently-developed two-cell
technique that can measure faster decay times.
The combined technique can measure delay times from 10 ns to 1000 s.
The method is peculiarly well suited for studying aging processes in soft
glassy materials, which exhibit both short and long relaxation times,
non-ergodic dynamics, and slowly-evolving transient behavior.Comment: 11 pages 13 figures Accepted in Review of Scientific Instrument (june
02
An extension of the SHARC survey
We report on our search for distant clusters of galaxies based on optical and
X-ray follow up observations of X-ray candidates from the SHARC survey. Based
on the assumption that the absence of bright optical or radio counterparts to
possibly extended X-ray sources could be distant clusters. We have obtained
deep optical images and redshifts for several of these objects and analyzed
archive XMM-Newton or Chandra data where applicable. In our list of candidate
clusters, two are probably galaxy structures at redshifts of z0.51 and
0.28. Seven other structures are possibly galaxy clusters between z0.3
and 1. Three sources are identified with QSOs and are thus likely to be X-ray
point sources, and six more also probably fall in this category. One X-ray
source is spurious or variable. For 17 other sources, the data are too sparse
at this time to put forward any hypothesis on their nature. We also
serendipitously detected a cluster at z=0.53 and another galaxy concentration
which is probably a structure with a redshift in the [0.15-0.6] range. We
discuss these results within the context of future space missions to
demonstrate the necessity of a wide field of view telescope optimized for the
0.5-2 keV range.Comment: Accepted in A&
Effect of abdominal binding on respiratory mechanics during exercise in athletes with cervical spinal cord injury
West CR, Goosey-Tolfrey VL, Campbell IG, Romer LM. Effect of
abdominal binding on respiratory mechanics during exercise in athletes
with cervical spinal cord injury. J Appl Physiol 117: 36â45, 2014. First
published May 22, 2014; doi:10.1152/japplphysiol.00218.2014.âWe
asked whether elastic binding of the abdomen influences respiratory
mechanics during wheelchair propulsion in athletes with cervical
spinal cord injury (SCI). Eight Paralympic wheelchair rugby players
with motor-complete SCI (C5-C7) performed submaximal and maximal
incremental exercise tests on a treadmill, both with and without
abdominal binding. Measurements included pulmonary function,
pressure-derived indices of respiratory mechanics, operating lung
volumes, tidal flow-volume data, gas exchange, blood lactate, and
symptoms. Residual volume and functional residual capacity were
reduced with binding (77 18 and 81 11% of unbound, P 0.05),
vital capacity was increased (114 9%, P 0.05), whereas total lung
capacity was relatively well preserved (99 5%). During exercise,
binding introduced a passive increase in transdiaphragmatic pressure,
due primarily to an increase in gastric pressure. Active pressures
during inspiration were similar across conditions. A sudden, sustained
rise in operating lung volumes was evident in the unbound condition,
and these volumes were shifted downward with binding.
Expiratory flow limitation did not occur in any subject and there
was substantial reserve to increase flow and volume in both
conditions. V Ë O2 was elevated with binding during the final stages
of exercise (8 â12%, P 0.05), whereas blood lactate concentration
was reduced (16 â19%, P 0.05). V Ë O2/heart rate slopes were
less steep with binding (62 35 vs. 47 24 ml/beat, P 0.05).
Ventilation, symptoms, and work rates were similar across conditions.
The results suggest that abdominal binding shifts tidal
breathing to lower lung volumes without influencing flow limitation,
symptoms, or exercise tolerance. Changes in respiratory
mechanics with binding may benefit O2 transport capacity by an
improvement in central circulatory function.This article has been made available through the Brunel Open Access Publishing Fund
A COMPARISON OF PEDALING MECHANICS IN EXPERIENCED POSE AND TRADITIONAL CYCLISTS
The purpose of this study was to describe the mechanical differences between two experienced male Pose cyclists and traditional cyclists. Pose cycling requires a specific set-up that attempts to place the centre of mass over the pedal to increase the non-muscular force/power component during the downstroke. Results revealed that for the Pose cyclists the centre of mass was closer to vertically above the pedal when in the horizontal forward position. Non-muscular contributions to pedal power tended to be greater in the Pose cyclists compared to the traditional cyclists. In addition, we found joint differences in the power contribution to pedal power in the traditional cyclists who relied more heavily on contributions from the muscles spanning the knee joint, whereas Pose cyclists had greater ankle and hip power contributions
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