123 research outputs found
New fundamental resistance exercise determinants of molecular and cellular muscle adaptations
Physical activity relies on muscular force. In adult skeletal muscle, force results from the contraction of postmitotic, multinucleated myofibres of different contractile and metabolic properties. Myofibres can adapt to (patho-)physiological conditions of altered functional demand by radial growth, longitudinal growth, and regulation of fibre type functional gene modules. The adaptation's specificity depends on the distinct molecular and cellular events triggered by unique combinations of conditional cues. In order to derive effective and tailored exercise prescriptions, it must be determined (1) which mechano-biological condition leads to what molecular/cellular response, and (2) how this molecular/cellular response relates to the structural, contractile, and metabolic adaptation. It follows that a thorough mechano-biological description of the loading condition is imperative. Unfortunately, the definition of (resistance) exercise conditions in the past and present literature is insufficient. It is classically limited to load magnitude, number of repetitions and sets, rest in-between sets, number of interventions/week, and training period. In this review, we show why the current description is insufficient, and identify new determinants of quantitative and/or qualitative effects on skeletal muscle with respect to resistance exercise in healthy, adult humans. These new mandatory determinants comprise the fractional and temporal distribution of the contraction modes per repetition, duration of one repetition, rest in-between repetitions, time under tension, muscular failure, range of motion, recovery time, and anatomical definition. We strongly recommend to standardise the design and description of all future resistance exercise investigations by using the herein proposed set of 13 mechano-biological determinants (classical and new ones
Non-invasive haemodynamic assessments using Innocorâą during standard graded exercise tests
Cardiac output (Q) and stroke volume (V S) represent primary determinants of cardiovascular performance and should therefore be determined for performance diagnostics purposes. Since it is unknown, whether measurements of Q and V S can be performed by means of Innocorâą during standard graded exercise tests (GXTs), and whether current GXT stages are sufficiently long for the measurements to take place, we determined Q and V S at an early and late point in time on submaximal 2min GXT stages. 16 male cyclists (age 25.4±2.9years, body mass 71.2±5.0kg) performed three GXTs and we determined Q and V S after 46 and 103s at 69, 77, and 85% peak power. We found that the rebreathings could easily be incorporated into the GXTs and that Q and V S remained unchanged between the two points in time on the same GXT stage (69% peak power, Q: 18.1±2.1 vs. 18.2±2.3lminâ1, V S: 126±18 vs. 123±21ml; 77% peak power, Q: 20.7±2.6 vs. 21.0±2.3lminâ1, V S: 132±18 vs. 131±18ml; 85% peak power, Q: 21.6±2.4 vs. 21.8±2.7lminâ1, V S: 131±17 vs. 131±22ml). We conclude that Innocorâą may be a useful device for assessing Q and V S during GXTs, and that the adaptation of Q and V S to exercise-to-exercise transitions at moderate to high submaximal power outputs is fast enough for 1 and 2min GXT stage duration
Cardiac output but not stroke volume is similar in a Wingate and test in young men
Wingate test (WT) training programmes lasting 2-3weeks lead to improved peak oxygen consumption. If a single 30s WT was capable of significantly increasing stroke volume and cardiac output, the increase in peak oxygen consumption could possibly be explained by improved oxygen delivery. Thus, we investigated whether a single WT increases stroke volume and cardiac output to similar levels than those obtained at peak exercise during a graded cycling exercise test (GXT) to exhaustion. Fifteen healthy young men (peak oxygen consumption 45.0±5.3mlkgâ1minâ1) performed one WT and one GXT on separate days in randomised order. During the tests, we estimated cardiac output using inert gas rebreathing (nitrous oxide and sulphur hexafluoride) and subsequently calculated stroke volume. We found that cardiac output was similar (18.2±3.3 vs. 17.9±2.6lminâ1; P=0.744), stroke volume was higher (127±37 vs. 94±15ml; P<0.001), and heart rate was lower (149±26 vs. 190±12 beatsminâ1; P<0.001) at the end (27±2s) of a WT as compared to peak exercise during a GXT. Our results suggest that a single WT produces a haemodynamic response which is characterised by similar cardiac output, higher stroke volume and lower heart rate as compared to peak exercise during a GX
Combined whole-body vibration, resistance exercise, and sustained vascular occlusion increases PGC-1α and VEGF mRNA abundances
We previously reported that high load resistance exercise with superimposed whole-body vibration and sustained vascular occlusion (vibroX) markedly improves cycling endurance capacity, increases capillary-to-fibre ratio and skeletal muscle oxidative enzyme activity in untrained young women. These findings are intriguing, since increases in oxidative muscle phenotype and endurance capacity are typically induced by endurance but not heavy resistance exercise. Here, we tested the hypothesis that vibroX activates genes associated with mitochondrial biogenesis and angiogenesis. Eight healthy, recreationally resistance-trained young men performed either vibroX or resistance exercise (RES) in a randomised, cross-over design. Needle biopsies (M. vastus lateralis) were obtained at rest and 3h post-exercise. Changes in relative gene expression levels were assessed by real-time quantitative PCR. After vibroX, vascular endothelial growth factor and peroxisome proliferator-activated receptor-γ coactivator 1α mRNA abundances increased to 2- and 4.4-fold, respectively, but did not significantly change above resting values after RES. Other genes involved in mitochondrial biogenesis were not affected by either exercise modality. While vibroX increased the expression of hexokinase II, xanthine dehydrogenase, and manganese superoxide dismutase mRNA, there were no changes in these transcripts after RES. This study demonstrates that high load resistance exercise with superimposed whole-body vibration and sustained vascular occlusion activates metabolic and angiogenic gene programs, which are usually activated after endurance but not resistance exercise. Thus, targeted modification of high load resistance exercise by vibration and vascular occlusion might represent a novel strategy to induce endurance-type muscle adaptation
Nonlinear quantum model for atomic Josephson junctions with one and two bosonic species
We study atomic Josephson junctions (AJJs) with one and two bosonic species
confined by a double-well potential. Proceeding from the second quantized
Hamiltonian, we show that it is possible to describe the zero-temperature AJJs
microscopic dynamics by means of extended Bose-Hubbard (EBH) models, which
include usually-neglected nonlinear terms. Within the mean-field approximation,
the Heisenberg equations derived from such two-mode models provide a
description of AJJs macroscopic dynamics in terms of ordinary differential
equations (ODEs). We discuss the possibility to distinguish the Rabi,
Josephson, and Fock regimes, in terms of the macroscopic parameters which
appear in the EBH Hamiltonians and, then, in the ODEs. We compare the
predictions for the relative populations of the Bose gases atoms in the two
wells obtained from the numerical solutions of the two-mode ODEs, with those
deriving from the direct numerical integration of the Gross-Pitaevskii
equations (GPEs). Our investigations shows that the nonlinear terms of the ODEs
are crucial to achieve a good agreement between ODEs and GPEs approaches, and
in particular to give quantitative predictions of the self-trapping regime.Comment: Accepted for the publication in J. Phys. B: At. Mol. Opt. Phy
A strategy to identify breakdown location in MITICA test facility: results of high voltage test campaign
The Acceleration Grid Power Supply of the MITICA test facility in Padova
(Italy) is currently under commissioning. The power conversion system, the DC
generator, and the High Voltage equipment have been individually commissioned,
whereas the integration tests are ongoing. It is a challenging process due to
the unconventional application, to the variety of different electrical
technologies involved and to the complexity of the interfaces. During the
integrated tests of the power supplies the achievement of 700kV stable
operation has been demonstrated for the first time in a Neutral Beam Injector,
but an unexpected event occurred, most likely a breakdown in the HV part, which
resulted in a fault of the DC generator. A subsequent test using an auxiliary
power supply was performed to check the voltage withstanding capability of the
HV plant, but another breakdown occurred at around 1MV. This paper describes
the activity performed to identify the location of the breakdowns affecting the
integrated tests. A test campaign has been devised with increased diagnostic
capabilities and specific strategy conceived to trigger intentional breakdowns
in specific locations and collect measurement patterns for different cases. The
results of the campaign will be presented and the current understanding of the
issue will be described, with a view on future tests and further improvements
of diagnostics
Atomic Josephson junction with two bosonic species
We study an atomic Josephson junction (AJJ) in presence of two interacting
Bose-Einstein condensates (BECs) confined in a double well trap. We assume that
bosons of different species interact with each other. The macroscopic wave
functions of the two components obey to a system of two 3D coupled
Gross-Pitaevskii equations (GPE). We write the Lagrangian of the system, and
from this we derive a system of coupled ordinary differential equations (ODE),
for which the coupled pendula represent the mechanic analogous. These
differential equations control the dynamical behavior of the fractional
imbalance and of the relative phase of each bosonic component. We perform the
stability analysis around the points which preserve the symmetry and get an
analytical formula for the oscillation frequency around the stable points. Such
a formula could be used as an indirect measure of the inter-species s-wave
scattering length. We also study the oscillations of each fractional imbalance
around zero and non zero - the macroscopic quantum self-trapping (MQST) - time
averaged values. For different values of the inter-species interaction
amplitude, we carry out this study both by directly solving the two GPE and by
solving the corresponding coupled pendula equations. We show that, under
certain conditions, the predictions of these two approaches are in good
agreement. Moreover, we calculate the crossover value of the inter-species
interaction amplitude which signs the onset of MQST.Comment: Accepted for the publication in J. Phys. B: At. Mol. Opt. Phy
Structural Musculotendinous Parameters That Predict Failed Tendon Healing After Rotator Cuff Repair
BACKGROUND: Healing of the rotator cuff after repair constitutes a major clinical challenge with reported high failure rates. Identifying structural musculotendinous predictors for failed rotator cuff repair could enable improved diagnosis and management of patients with rotator cuff disease.
PURPOSE: To investigate structural predictors of the musculotendinous unit for failed tendon healing after rotator cuff repair.
STUDY DESIGN: Cohort study; Level of evidence, 2.
METHODS: Included were 116 shoulders of 115 consecutive patients with supraspinatus (SSP) tear documented on magnetic resonance imaging (MRI) who were treated with an arthroscopic rotator cuff repair. Preoperative assessment included standardized clinical and imaging (MRI) examinations. Intraoperatively, biopsies of the joint capsule, the SSP tendon, and muscle were harvested for histological assessment. At 3 and 12 months postoperatively, patients were re-examined clinically and with MRI. Structural and clinical predictors of healing were evaluated using logistic and linear regression models.
RESULTS: Structural failure of tendon repair, which was significantly associated with poorer clinical outcome, was associated with older age (ÎČ = 1.12; 95% CI, 1.03 to 1.26; P = .03), shorter SSP tendon length (ÎČ = 0.89; 95% CI, 0.8 to 0.98; P = .02), and increased proportion of slow myosin heavy chain (MHC)-I/fast MHC-II hybrid muscle fibers (ÎČ = 1.23; 95% CI, 1.07 to 1.42; P = .004). Primary clinical outcome (12-month postoperative Constant score) was significantly less favorable for shoulders with fatty infiltration of the infraspinatus muscle (ÎČ = -4.71; 95% CI, -9.30 to -0.12; P = .044). Conversely, a high content of fast MHC-II muscle fibers (ÎČ = 0.24; 95% CI, 0.026 to 0.44; P = .028) was associated with better clinical outcome.
CONCLUSION: Both decreased tendon length and increased hybrid muscle fiber type were independent predictors for retear. Clinical outcome was compromised by tendon retearing and increased fatty infiltration of the infraspinatus muscle. A high content of fast MHC-II SSP muscle fibers was associated with a better clinical outcome
Combined whole-body vibration, resistance exercise, and sustained vascular occlusion increases PGC-1α and VEGF mRNA abundances
We previously reported that high load resistance exercise with superimposed whole-body vibration and sustained vascular occlusion (vibroX) markedly improves cycling endurance capacity, increases capillary-to-fibre ratio and skeletal muscle oxidative enzyme activity in untrained young women. These findings are intriguing, since increases in oxidative muscle phenotype and endurance capacity are typically induced by endurance but not heavy resistance exercise. Here, we tested the hypothesis that vibroX activates genes associated with mitochondrial biogenesis and angiogenesis. Eight healthy, recreationally resistance-trained young men performed either vibroX or resistance exercise (RES) in a randomised, cross-over design. Needle biopsies (M. vastus lateralis) were obtained at rest and 3 h post-exercise. Changes in relative gene expression levels were assessed by real-time quantitative PCR. After vibroX, vascular endothelial growth factor and peroxisome proliferator-activated receptor-γ coactivator 1α mRNA abundances increased to 2- and 4.4-fold, respectively, but did not significantly change above resting values after RES. Other genes involved in mitochondrial biogenesis were not affected by either exercise modality. While vibroX increased the expression of hexokinase II, xanthine dehydrogenase, and manganese superoxide dismutase mRNA, there were no changes in these transcripts after RES. This study demonstrates that high load resistance exercise with superimposed whole-body vibration and sustained vascular occlusion activates metabolic and angiogenic gene programs, which are usually activated after endurance but not resistance exercise. Thus, targeted modification of high load resistance exercise by vibration and vascular occlusion might represent a novel strategy to induce endurance-type muscle adaptations
Partial Discharges detection in 1 MV power supplies in MITICA experiment, the ITER Heating Neutral Beam Injector prototype
MITICA (Megavolt ITER Injector & Concept Advancement), the full scale
prototype of ITER Heating Neutral Beam, is under realization at the Neutral
Beam Test Facility (Padova, Italy). It is designed to deliver 16.5 MW to ITER
plasma, obtained by accelerating negative Deuterium ions up to 1 MeV for a
total ion current of 40 A and then neutralized. MITICA Acceleration Power
Supply is composed of several non-standard equipment, beyond industrial
standard for insulation voltage level (-1 MVdc) and dimensions. Voltage
withstand tests (up to 1.265 MVdc) have been performed in five subsequent steps
(from 2018 to 2019), according to the installation progress, after connecting
equipment belonging to different procurements. During integrated commissioning,
started in 2021, two breakdowns occurred in a position of the HV plant not
still identified, so they could be occurred either in air or in SF6. To
identify the locations of possible weak insulation points, the existing
diagnostics for partial discharge detection (the precursor of breakdowns) as a
first step have been improved on air-insulated parts by consisting in a set of
instrumentation, like capacitive probes and off-the-shelf instruments for AC
application (acoustic and electromagnetic sensors). The paper deals with the
instruments qualification to assess their suitability for DC usage and then
with the investigation performed in MITICA, in particular: 1) sensitivity
assessment campaign, with artificially produced corona effect to identify the
minimum threshold of each diagnostics 2) voltage application to MITICA plant,
moving the instrumentation around equipment and increasing progressively the
voltage looking for corona phenomena to identify possible weak insulation
points.Comment: Nine pages, twelve figures, accepted manuscript of a paper published
in Fusion Engineering and Desig
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