Effect of Ischemic Preconditioning on the Recovery of Cardiac Autonomic Control From Repeated Sprint Exercise

Repeated sprint exercise (RSE) acutely impairs post-exercise heart rate (HR) recovery (HRR) and time-domain heart rate variability (i. e., RMSSD), likely in part, due to lactic acidosis-induced reduction of cardiac vagal reactivation. In contrast, ischemic preconditioning (IPC) mediates cardiac vagal activation and augments energy metabolism efficiency during prolonged ischemia followed by reperfusion. Therefore, we investigated whether IPC could improve recovery of cardiac autonomic control from RSE partially via improved energy metabolism responses to RSE. Fifteen men team-sport practitioners (mean ± SD: 25 ± 5 years) were randomly exposed to IPC in the legs (3 × 5 min at 220 mmHg) or control (CT; 3 × 5 min at 20 mmHg) 48 h, 24 h, and 35 min before performing 3 sets of 6 shuttle running sprints (15 + 15 m with 180° change of direction and 20 s of active recovery). Sets 1 and 2 were followed by 180 s and set 3 by 360 s of inactive recovery. Short-term HRR was analyzed after all sets via linear regression of HR decay within the first 30 s of recovery (T30) and delta from peak HR to 60 s of recovery (HRR60s). Long-term HRR was analyzed throughout recovery from set 3 via first-order exponential regression of HR decay. Moreover, RMSSD was calculated using 30-s data segments throughout recovery from set 3. Energy metabolism responses were inferred via peak pulmonary oxygen uptake (V˙O2peak), peak carbon dioxide output (V˙O2peak), peak respiratory exchange ratio (RERpeak), first-order exponential regression of V˙O2 decay within 360 s of recovery and blood lactate concentration ([Lac-]). IPC did not change T30, but increased HRR60s after all sets (condition main effect: P = 0.03; partial eta square (η2p) = 0.27, i.e., large effect size). IPC did not change long-term HRR and RMSSD throughout recovery, nor did IPC change any energy metabolism parameter. In conclusion, IPC accelerated to some extent the short-term recovery, but did not change the long-term recovery of cardiac autonomic control from RSE, and such accelerator effect was not accompanied by any IPC effect on surrogates of energy metabolism responses to RSE

Ischemic Preconditioning and Repeated Sprint Swimming: A Placebo and Nocebo Study

Purpose Ischemic preconditioning (IPC) has been shown to improve performance of exercises lasting 10-90 s (anaerobic) and more than 90 s (aerobic). However, its effect on repeated sprint performance has been controversial, placebo effect has not been adequately controlled, and nocebo effect has not been avoided. Thus, the IPC effect on repeated sprint performance was investigated using a swimming task and controlling placebo/nocebo effects. Methods Short-distance university swimmers were randomized to two groups. One group (n = 15, 24 1 yr [mean SEM]) was exposed to IPC (ischemia cycles lasted 5 min) and control (CT) (no ischemia)another (n = 15, 24 +/- 1 yr) to a placebo intervention (SHAM) (ischemia cycles lasted 1 min) and CT. Seven subjects crossed over groups. Subjects were informed IPC and SHAM would improve performance compared with CT and would be harmless despite circulatory occlusion sensations. The swimming task consisted of six 50-m all-out efforts repeated every 3 min. Results IPC, in contrast with SHAM, reduced worst sprint time (IPC, 35.21 +/- 0.73 vs CT, 36.53 +/- 0.72 sP = 0.04) and total sprints time (IPC, 203.7 +/- 4.60 vs CT, 206.03 +/- 4.57 sP = 0.02), moreover augmented swimming velocity (IPC, 1.45 +/- 0.03 vs CT, 1.44 +/- 0.03 ms(-1)P = 0.049). Six of seven subjects who crossed over groups reduced total sprints time with IPC versus SHAM (delta = -3.95 +/- 1.49 s, P = 0.09). Both IPC and SHAM did not change blood lactate concentration (P = 0.20) and perceived effort (P = 0.22). Conclusion IPC enhanced repeated sprint swimming performance in university swimmers, whereas a placebo intervention did not.Sao Paulo Research Foundation (FAPESP) [14/15877-8]FAPESP [15/03186-3]Univ Fed Sao Paulo, Dept Med, Grad Program Translat Med, Sao Paulo, SP, BrazilC. Olymp Ctr Training & Res, Lab Exercise Physiol, Sao Paulo, SP, BrazilSao Paulo Assoc Med Dev, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Physiol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Surg, Sao Paulo, SP, BrazilGraduate Program in Translational Medicine, Department of Medicine, Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, BRAZILSão Paulo Association for Medicine Development (SPDM) Universidade Federal de São Paulo (UNIFESP), São Paulo, BRAZILDepartment of Physiology, Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, BRAZILDepartment of Surgery, Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, BRAZILWeb of Scienc

Revealing the Perovskite Film Formation Using the Gas Quenching Method by In Situ GIWAXS: Morphology, Properties, and Device Performance

The optoelectronic properties, morphology, and consequently the performance of metal halide perovskite solar cells are directly related to the crystalline phases and intermediates formed during film preparation. The gas quenching method is compatible with large-area deposition, but an understanding of how this method influences these properties and performance is scarce in the literature. Here, in situ grazing incidence wide angle X-ray scattering is employed during spin coating deposition to gain insights on the formation of MAPbI(3)and Cs(x)FA(1-)(x)Pb(I0.83Br0.17)(3)perovskites, comparing the use of dimethyl sulfoxide (DMSO) and 2-methyl-n-pyrrolidone (NMP) as coordinative solvents. Intermediates formed using DMSO depend on the perovskite composition (e.g., Cs content), while for NMP the same intermediate [PbI2(NMP)] is formed independently on the composition. For MAPbI(3)and Cs(x)FA(1-)(x)Pb(I0.83Br0.17)(3)with a small amount of Cs (10% and 20%), the best efficiencies are achieved using NMP, while the use of DMSO is preferred for higher (30% and 40%) amount of Cs. The inhibition of the 2H/4H hexagonal phase when using NMP is crucial for the final performance. These findings provide a deep understanding about the formation mechanism in multication perovskites and assist the community to choose the best solvent for the desired perovskite composition aiming to perovskite-on-silicon tandem solar cells

Self-assembled organic–inorganic magnetic hybrid adsorbent ferrite based on cyclodextrin nanoparticles

Organic–inorganic magnetic hybrid materials (MHMs) combine a nonmagnetic and a magnetic component by means of electrostatic interactions or covalent bonds, and notable features can be achieved. Herein, we describe an application of a self-assembled material based on ferrite associated with β-cyclodextrin (Fe-Ni/Zn/βCD) at the nanoscale level. This MHM and pure ferrite (Fe-Ni/Zn) were used as an adsorbent system for Cr3+ and Cr2O72− ions in aqueous solutions. Prior to the adsorption studies, both ferrites were characterized in order to determine the particle size distribution, morphology and available binding sites on the surface of the materials. Microscopy analysis demonstrated that both ferrites present two different size domains, at the micro- and nanoscale level, with the latter being able to self-assemble into larger particles. Fe-Ni/Zn/βCD presented smaller particles and a more homogeneous particle size distribution. Higher porosity for this MHM compared to Fe-Ni/Zn was observed by Brunauer–Emmett–Teller isotherms and positron-annihilation-lifetime spectroscopy. Based on the pKa values, potentiometric titrations demonstrated the presence of βCD in the inorganic matrix, indicating that the lamellar structures verified by transmission electronic microscopy can be associated with βCD assembled structures. Colloidal stability was inferred as a function of time at different pH values, indicating the sedimentation rate as a function of pH. Zeta potential measurements identified an amphoteric behavior for the Fe-Ni/Zn/βCD, suggesting its better capability to remove ions (cations and anions) from aqueous solutions compared to that of Fe-Ni/Zn