Cardiovascular responses during recovery from exercise and thermal stress.

Although the central cardiovascular adjustments to exercise in the heat have been identified, little is known about the post-exercise hemodynamics during recovery from exercise and heat stress. This study examined heart rate (HR), stroke index (SI), cardiac index (CI), systemic vascular resistance (SVR), systolic (SBP) and diastolic (DBP) blood pressure in 8 males during 15 min of passive seated recovery preceded by 30 min of cycle ergometry (60% VO2max) on two separate occasions: under control (C) and heat stress (HS) conditions. During both recovery conditions, SI significantly declined (p < 0.05) to below pre-exercise values. No differences were observed between groups with respect to SI. The decrease in recovery HR was slower (p < 0.05) in HS than C. The greater elevation in HR during HS accounted for the relative increase in CI above that observed prior to exercise. The estimated SVR measured immediately following exercise in both groups was lower (p < 0.05) than pre-exercise values. By 5 min of C recovery, SVR returned to baseline values but remained significantly depressed (p < 0.05) for the entire HS condition. These results indicate that the pressor responses were attenuated during HS; however, CI was maintained above pre-exercise levels due to higher HR responses compensating for the reduction in SI. Stimulation of the baroreceptor reflex and increased myocardial contractility could possibly explain the maintenance of output at a time when preload and afterload were reduced.

Facial cooling does not benefit cardiac dynamics during recovery from exercise hyperthermia.

Cardiovascular responses during passive recovery following exercise-induced hyperthermia were investigated in male subjects (n = 8) on two separate occasions; once with facial cooling (FC; 2 degrees C, 2.5 m/s) and once without (NC). Recovery heart rate (HR) responses were significantly (p less than 0.05) lower during the FC than NC condition. No statistical differences were observed between groups with respect to stroke volume (SV), cardiac output (CO), systemic vascular resistance (SVR), and mean arterial blood pressure (MAP). After 5 min of recovery, FC caused a significant (p less than 0.05) reduction in HR however, the NC group response remained unchanged. The decline in HR with FC was moderately associated with the decrease in forehead temperature (r = 0.69; p less than 0.05) but poorly correlated with rectal temperature (r = 0.09; p greater than 0.05). As expected, SV, CO, and MAP significantly declined (p less than 0.05) while the estimated SVR progressively increased (p less than 0.05) over time. The results suggest that FC is not beneficial in terms of improving central and peripheral cardiovascular dynamics during recovery from exercise-induced hyperthermia.

[Description and performance of a flow cytometry apparatus: the EPICS]. / Description et performances d'un appareil de cytométrie de flux: l'EPICS.

This is a report on our experience with the EPICS C (Coultronics) cytometric flux apparatus, a screening cell analyzer, employing a laser ray (2 or 5 watts); we obtained good results to analyze immunologically-tagged mononuclear blood cells with or without prior separation: for rhythm, repeatability, and contamination. The EPICS C machine proved to be effective to study the cell cycle using lymphoblastic cells, epithelial cells and cells from a breast cancer. Several screening trials were carried out with fluorescent ball bearings of various sizes; the quality of screening (purity and yield) appear optimal at a speed ranging from 500 to 1,000 bearings per second, using three parameters: the logarithm of green fluorescence, the integral function of green fluorescence, the diffraction of light to small angles. Thus, if results obtained for this analysis are entirely satisfactory, the screening function remains limited because it is slow.