We aimed to investigate haemodynamics during active and passive recovery following repeated bouts of supramaximal exercise. Seven male athletes underwent two sessions of supramaximal exercise which consisted of a warm-up and of five bouts of cycling at the maximum speed possible for 30 s against a resistance equivalent to 150% of the maximum workload achieved in a previous incremental test. Bouts were separated by 1 min of recovery and followed by 10 min of recovery which was either active (pedalling at 40 W) or passive (completely rest seated on the cycle). Haemodynamic variables were evaluated by means of impedance cardiography. Heart rate (HR), stroke volume (SV), cardiac output (CO), mean blood pressure (MBP), thoracic electrical impedance (Z 0 ) as an inverse index of central blood volume, and systemic vascular resistance (SVR) were assessed. The main findings were that active recovery, with respect to passive recovery, induced higher changes from baseline in HR (+29.1 ± 4.5 versus +15.6 ± 2.9 beats min −1 at the 10th minute of recovery, P < 0.05), SV (+19.9 ± 5.6 versus -6.4 ± 3.3 ml, P < 0.01) and CO (+3.8 ± 1.2 versus +0.4 ± 0.2 l min −1 , P < 0.01). Furthermore, MBP was similar between the two kinds of recovery despite an increase in Z 0 during passive compared to active recovery. These results suggest that the faster haemodynamic recovery towards baseline and the decrease in cardiac preload during passive recovery may be successfully prevented by cardiovascular regulatory mechanisms which include an increase in SVR, thus avoiding a drop in blood pressure.

No abstract

There is some evidence that, above anaerobic threshold (AT), the arteriovenous oxygen difference may increase due to a reduced hemoglobin affinity for oxygen. Thus, it should be expected that above AT, the oxygen consumption to cardiac output (VO 2 /CO) relationship would become steeper compared to below AT since, if a larger amount of O 2 could be extracted from blood, a lower CO would be required for carrying the same O 2 quantity. We tested the possibility that the VO 2 /CO relationship shows a break point after AT, becoming steeper. Cardiodynamics and expired gases were measured with an impedance cardiograph and a mass spectrometer in ten healthy male subjects during an incremental test on a cycle ergometer. We performed three linear regressions for each subject's VO 2 /CO ratio: one for the entire exercise dataset, one for data below AT, and one for data above AT. Statistical comparisons of linear regressions obtained from VO 2 and CO for below and above AT data failed to find any significant difference between these data. This study demonstrates that the slope of the VO 2 /CO relationship does not exhibit a break point at AT. Therefore, it seems that AT does not play a key role in affecting this relationship during incremental exercise.

No abstract

The aim of this work was to evaluate silica nanocomposites as topical drug delivery systems for the model drug, caffeine. Preparation, characterization, and skin permeation properties of caffeine-silica nanocomposites are described. Caffeine was loaded into the nanocomposites by grinding the drug with mesoporous silica in a ball mill up to 10 h and the efficiency of the process was studied by XRPD. Formulations were characterized by several methods that include FTIR, XRPD, SEM and TEM. The successful loading of caffeine was demonstrated by XRPD and FTIR. Morphology was studied by SEM that showed particle size reduction while TEM demonstrated formation of both core-shell and multilayered caffeine-silica structures. Solid-state NMR spectra excluded chemical interactions between caffeine and silica matrix, thus confirming that no solid state reactions occurred during the grinding process. Influence of drug inclusion in silica nanocomposite on the in vitro caffeine diffusion into and through the skin was investigated in comparison with a caffeine gel formulation (reference), using newborn pig skin and vertical Franz diffusion cells. Results from the in vitro skin permeation experiments showed that inclusion into the nanocomposite reduced and delayed caffeine permeation from the silica nanocomposite in comparison with the reference, independently from the amount of the tested formulation.