Training with low-load exercise performed under blood flow restriction can augment muscle hypertrophy and maximal strength to a similar extent as the classical high-load strength training method. ...However, the blood flow restriction method elicits only minor neural adaptations. In an attempt to maximize training-related gains, we propose using other protocols that combine high voluntary activation, mechanical tension, and metabolic stress.
Although high intensity physical activities may represent a great proportion of the total energy expenditure in active people, only sparse studies have investigated the accuracy of wearable monitors ...to assess activity related energy expenditure (AEE) during high intensity exercises. Therefore, the purpose of the present study was to investigate the accuracy of the Actiheart, a light portable monitor estimating AEE based on heart rate (HR) and activity counts (ACT), during two popular activities (running and cycling) performed at high intensities. The benefit of an individual calibration of the HR-AEE relationship established during a preliminary maximal test was also evaluated.
AEE was estimated in eighteen active adults (4 women and 14 men; 25 ± 4 yr) with indirect calorimetry using a respiratory gas analysis system (reference method) and the Actiheart during 5-min running and cycling at 60, 75 and 85% of maximal oxygen uptake (VO2max) previously determined during a maximal test performed on a treadmill or cycle ergometer. For the Actiheart, AEE was estimated either using the group or individual calibrated equations available in the dedicated software, and their respective HR, ACT or combined HR/ACT algorithms.
When the HR algorithm was used for cycling and the HR or HR/ACT algorithms for running, AEE measured by the Actiheart increased proportionally to exercise intensity from 60 to 85% VO2max (P<0.001). Compared to indirect calorimetry, the Actiheart group calibrated equations slightly to moderately underestimated (3 to 20%) AEE for the three exercise intensities (P<0.001). Accuracy of AEE estimation was greatly improved by individual calibration of the HR-AEE relationship (underestimation below 5% and intraclass correlation coefficient ICC: 0.79-0.93) compared to group calibration (ICC: 0.64-0.79).
The Actiheart enables to assess AEE during high intensity running and cycling when the appropriate algorithm is applied. Since an underestimation was present for group calibration, an individual and sport-specific calibration should be performed when a high accuracy is required.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The objective of this article is to examine the association between agricultural subsidies and dairy farm technical efficiency in the European Union, and in so doing we make novel contributions to ...the literature. We include in the analysis nine diverse western European Union (EU) countries over an 18-year period (1990–2007) encompassing the various Common Agricultural Policy (CAP) reforms enacted since the inception of the EU. Further, we account for input endogeneity using an original method of moments estimator. Our results show that the effect of subsidies on technical efficiency may be positive, null, or negative, depending on the country. The analysis reveals that the introduction of decoupling with the 2003 CAP reform weakens the effect that subsidies have on technical efficiency.
Background Cell transplantation for the regeneration of ischemic myocardium is limited by poor graft viability and low cell retention. In ischemic cardiomyopathy, the extracellular matrix is deeply ...altered; therefore, it could be important to associate a procedure aiming at regenerating myocardial cells and restoring the extracellular matrix function. We evaluated the feasibility and safety of intrainfarct cell therapy associated with a cell-seeded collagen scaffold grafted onto infarcted ventricles. Methods In 20 consecutive patients presenting with left ventricular postischemic myocardial scars and indication for coronary artery bypass graft surgery, bone marrow cells were implanted during surgery. In the last 10 patients, we added a collagen matrix seeded with bone marrow cells, placed onto the scar. Results There was no mortality and any related adverse events (follow-up 10 ± 3.5 months). New York Heart Association functional class improved in both groups from 2.3 ± 0.5 to 1.3 ± 0.5 (matrix, p = 0.0002) versus 2.4 ± 0.5 to 1.5 ± 0.5 (no matrix, p = 0.001). Left ventricular end-diastolic volume evolved from 142.4 ± 24.5 mL to 112.9 ± 27.3 mL (matrix, p = 0.02) versus 138.9 ± 36.1 mL to 148.7 ± 41 mL (no matrix, p = 0.57), left ventricular filling deceleration time improved significantly in the matrix group from 162 ± 7 ms to 198 ± 9 ms ( p = 0.01) versus the no-matrix group (from 159 ± 5 ms to 167 ± 8 ms, p = 0.07). Scar area thickness progressed from 6 ± 1.4 to 9 mm ± 1.1 mm (matrix, p = 0.005) versus 5 ± 1.5 mm to 6 ± 0.8 mm (no matrix, p = 0.09). Ejection fraction improved in both groups, from 25.3% ± 7.3% to 32% ± 5.4% (matrix, p = 0.03) versus 27.2% ± 6.9% to 34.6% ± 7.3% (no matrix, p = 0.031). Conclusions This tissue-engineered approach is feasible and safe and appears to improve the efficiency of cellular cardiomyoplasty. The cell-seeded collagen matrix increases the thickness of the infarct scar with viable tissue and helps to normalize cardiac wall stress in injured regions, thus limiting ventricular remodeling and improving diastolic function.
Choosing the optimal aortic valve prosthesis for middle-aged patients (late 40s to early 60s) with aortic stenosis presents a challenge. The available options all have substantial drawbacks that must ...be considered in the decision-making process. Current data indicate that there is little or no difference in survival between mechanical and bioprosthetic aortic valve replacement in middle-aged patients at 10-15 years after surgery. Patients who receive a mechanical valve replacement have an annual risk of major hemorrhagic or embolic events of 2-4% per year for life compared with about 1% per year for patients who have a bioprosthetic valve. However, bioprostheses are associated with an increasing risk of structural valve degeneration from 10 years postimplantation, and most patients will require reoperation if they survive much longer than a decade. The mortality risk associated with reoperation is similar to that of primary surgery for most patients, and does not seem to impact on the 15-year survival in this patient group. The Ross procedure, in which the aortic valve is replaced with a pulmonary autograft, can provide improved freedom from morbidity, but operative mortality is probably double that of isolated aortic valve replacement and most patients will require reoperation. Informed patient choice is the most important factor in deciding which valve to use, with biological valves increasingly favored over mechanical valves in middle-aged patients.
Abstract Objective Tricuspid valve repair has been recently advocated in patients undergoing mitral valve surgery who have mild to moderate secondary tricuspid regurgitation. However, the incidence ...of heart conduction disorders after combined mitral valve and tricuspid valve interventions has not been evaluated. We sought to analyze the incidence of permanent pacemaker implantations and heart conduction disorders in patients undergoing mitral valve surgery with and without tricuspid valve annuloplasty. Methods In 2011 and 2012, among 201 consecutive patients referred to the Hôpital Européen Georges Pompidou for isolated nonischemic mitral valve disease, 113 underwent an isolated mitral valve procedure (group 1) and 88 had a concomitant tricuspid valve ring annuloplasty (group 2). Results Patients' mean age was 59.7 ± 16.5 years in group 1 and 60.7 ± 14.9 years in group 2 ( P = .5). Mean crossclamp time and bypass time were 78 ± 35 minutes and 105 ± 47 minutes in group 1 and 92 ± 36 minutes and 128 ± 50 minutes in group 2, respectively ( P = .001 and .005, respectively). Operative mortality was 3% (2.7% in group 1 and 3.2% in group 2, P = .4). Incidence of high-grade heart conduction disorders lasting more than 3 days postoperatively was 14.5% in group 1 and 41.2% in group 2 ( P = .001). At 3 years, freedom from permanent pacemaker implantation was 99% ± 2% in group 1 and 94.1% ± 5% in group 2 ( P = .02). For the entire cohort, longer crossclamp time ( P = .02) and tricuspid ring annuloplasty (hazard ratio, 3.8; P = .001) were independent predictors of heart conduction disorders. Conclusions The need for permanent pacemaker implantation is increased after concomitant tricuspid ring annuloplasty in the setting of mitral valve surgery. A clinical period of observation up to 14 days after postoperative heart conduction disorders should be observed before recommending permanent pacemaker placement.
Summary Background The development of artificial hearts in patients with end-stage heart disease have been confronted with the major issues of thromboembolism or haemorrhage. Since valvular ...bioprostheses are associated with a low incidence of these complications, we decided to use bioprosthetic materials in the construction of a novel artificial heart (C-TAH). We report here the device characteristics and its first clinical applications in two patients with end-stage dilated cardiomyopathy. The aim of the study was to evaluate safety and feasibility of the CARMAT TAH for patients at imminent risk of death from biventricular heart failure and not eligible for transplant. Methods The C-TAH is an implantable electro-hydraulically actuated pulsatile biventricular pump. All components, batteries excepted, are embodied in a single device positioned in the pericardial sac after excision of the native ventricles. We selected patients admitted to hospital who were at imminent risk of death, having irreversible biventricular failure, and not eligible for heart transplantation, from three cardiac surgery centres in France. Findings The C-TAH was implanted in two male patients. Patient 1, aged 76 years, had the C-TAH implantation on Dec 18, 2013; patient 2, aged 68 years, had the implantation on Aug 5, 2014. The cardiopulmonary bypass times for C-TAH implantation were 170 min for patient 1 and 157 min for patient 2. Both patients were extubated within the first 12 postoperative hours and had a rapid recovery of their respiratory and circulatory functions as well as a normal mental status. Patient 1 presented with a tamponade on day 23 requiring re-intervention. Postoperative bleeding disorders prompted anticoagulant discontinuation. The C-TAH functioned well with a cardiac output of 4·8–5·8 L/min. On day 74, the patient died due to a device failure. Autopsy did not detect any relevant thrombus formation within the bioprosthesis nor the different organs, despite a 50-day anticoagulant-free period. Patient 2 experienced a transient period of renal failure and a pericardial effusion requiring drainage, but otherwise uneventful postoperative course. He was discharged from the hospital on day 150 after surgery with a wearable system without technical assistance. After 4 months at home, the patient suffered low cardiac output. A change of C-TAH was attempted but the patient died of multiorgan failure. Interpretation This preliminary experience could represent an important contribution to the development of total artificial hearts using bioprosthetic materials. Funding CARMAT SA.
Background Pigs/bovines share common antigens with humans: α-Gal, present in all pigs/bovines close to the human B-antigen; and AH-histo-blood-group antigen, identical to human AH-antigen and present ...only in some animals. We investigate the possible impact of patients' ABO blood group on bioprosthesis structural valve degeneration (SVD) through calcification/pannus/tears/perforations for patients ≤60 years at implantation. Methods and Results This was a single-center study (Paris, France) that included all degenerative bioprostheses explanted between 1985 and 1998, mostly porcine bioprostheses (Carpentier-Edwards second/third porcine bioprostheses) and some bovine bioprostheses. For the period 1998 to 2014, only porcine bioprostheses with longevity ≥13 years were included (total follow-up ≥29 years). Except for blood groups, important predictive factors for SVD were prospectively collected (age at implantation/longevity/number/site/sex/SVD types) and analyzed using logistic regression. All variables were available for 500 explanted porcine bioprostheses. By multivariate analyses, the A group was associated with an increased risk of: tears (odds ratioOR, 1.61;
=0.026); pannus (OR, 1.5;
=0.054), pannus with tears (OR, 1.73;
=0.037), and tendency for lower risk of: calcifications (OR, 0.63;
=0.087) or isolated calcification (OR, 0.67;
=0.17). A-antigen was associated with lower risk of perforations (OR 0.56;
=0.087). B-group patients had an increased risk of: perforations (OR, 1.73;
=0.043); having a pannus that was calcified (OR, 3.0,
=0.025). B-antigen was associated with a propensity for calcifications in general (OR, 1.34;
=0.25). Conclusions Patient's ABO blood group is associated with specific SVD types. We hypothesize that carbohydrate antigens, which may or may not be common to patient and animal bioprosthetic tissue, will determine a patient's specific immunoreactivity with respect to xenograft tissue and thus bioprosthesis outcome in terms of SVD.
In 67 single motor units, the mechanical properties, the recruitment and derecruitment thresholds, and the discharge rates
were recorded concurrently in the first dorsal interosseus (FDI) of human ...subjects during intermittent fatiguing contractions.
The task consisted of isometric ramp-and-hold contractions performed at 50% of the maximal voluntary contraction (MVC). The
purpose of this study was to examine the influence of fatigue on the behaviour of motor units with a wide range of activation
thresholds.
For low-threshold (< 25% MVC) motor units, the mean twitch force increased with fatigue and the recruitment threshold either
did not change or increased. In contrast, the twitch force and the activation threshold decreased for the high-threshold (>
25% MVC) units. The observation that in low-threshold motor units a quick stretch of the muscle at the end of the test reset
the unit force and recruitment threshold to the prefatigue value suggests a significant role for fatigue-related changes in
muscle stiffness but not twitch potentiation or motor unit synchronization.
Although the central drive intensified during the fatigue test, as indicated by an increase in surface electromyogram (EMG),
the discharge rate of the motor units during the hold phase of each contraction decreased progressively over the course of
the task for motor units that were recruited at the beginning of the test, especially the low-threshold units. In contrast,
the discharge rates of newly activated units first increased and then decreased.
Such divergent behaviour of low- and high-threshold motor units could not be individually controlled by the central drive
to the motoneurone pool. Rather, the different behaviours must be the consequence of variable contributions from motoneurone
adaptation and afferent feedback from the muscle during the fatiguing contraction.
PDF
