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A research report submitted to the Faculty of Medicine, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Medicine in Applied Physiology. Johannesburg, 1997. / A post-exercise reduction in blood pressure (BP) may be the primary reason that athletes suffer from exerclse-assoclated collapse (EAC) at the end ot ultra-endurance running ever.s. Plasma volume decreases, possibly caused by dehydration, may be the cause of the decrease til blood pressure, In order to determine whether there is a correlation between plasma volume changes and the post-exercise BP drop, this study evaluated alterations in pre- and post-race blood pressures and changes in blood and plasma volumes, It found that compared to resting values, systolic, dlastollc and mean arterial blood pressures (mmHg) fell significantly from 119 ± 4, mean ± standard deviation, 74 ± 8, and 88 ± 5 respectively to '106 ± 14, 62 ± 12 and 77 ± 10 (ps 0,05), whereas pulse pressure failed to change, Compared to pre-race values, plasma and blood volume were found not to have changed significantly, During the race plasma urea (U) and creatinine (C) concentrations increased significantly, whereas body mass and body mass index both fell significantly. Haernatocrlt, haemoglobin, mean cell volume, red blood cell number, mean cell haemoglobin concentration, the mean cell haemoglobin, plasma sodium, potassium, chloride and protein concentrations, the U:C ratio and osmolality remained constant. There were no significClnt correlations between changes in plasma or blood volume and changes in blood pressure, These data support the Idea that a post-race decrease in blood pressure does not result primarily from an intravascular fluid loss, It is likely therefore that athletes who collapse at the end of ultraendurance races due to EAC do so as a result of 'post-exercise hypotension' secondary to venous pooling, and not as a result of a reduction in plasma volume, / MT2017

The supine posture has been shown to limit exercise-induced plasma volume expansion. Differences in hydrostatic pressure gradients between the standing and seated position indicate that treadmill exercise might promote a greater plasma volume expansion than cycle ergometer exercise. To test this hypothesis ten subjects performed intermittent high intensity exercise (4 min at 85% VO2max, 5 min at 40% VO2max repeated 8 times) on separate days on the treadmill and cycle ergometer. Changes in plasma volume expansion were calculated from changes in hematocrit and hemoglobin. Stroke volume (SV), trans-thoracic impedance (Z0), HR, and arterial blood pressure (non-invasive arm cuff, SBP & DBP) were assessed in the seated position before and postexercise. Zo increased (p<0.05) as subjects started exercise (both treadmill and cycling), indicating a reduction in central blood volume (CBV), which returned to baseline towards the end of exercise. Postexercise Zo returned to control levels within 30 min regardless of the previous exercise mode. A significant post-exercise hypotension was observed following cycle ergometer exercise (p<0.05) but not following treadmill exercise. Plasma volume increased 6.1±1.0% and 7.0 ± 1.1% (p<0.05) following treadmill and cycle ergometer exercise, respectively. The increase in PV was similar for both exercise modes. Initial differences in central blood volume disappeared over the course of the exercise protocol and during recovery, possibly indicating that there is a postural threshold and moving beyond it yields no further effect. The lack of differences between modes of exercise on plasma albumin content and Z0 indicate that the upright postures were not different from each other. As such, PV expansion following high intensity intermittent exercise appears to be independent of upright exercise mode.

Yes / Introduction: Investigate the effectiveness of short-term heat acclimation (STHA), over 5-days (permissive dehydration), on an intermittent sprint exercise protocol (HST) with females. Controlling for menstrual cycle phase. Materials and Methods: Ten, moderately trained, females (Mean [SD]; age 22.6 [2.7] y; stature 165.3 [6.2] cm; body mass 61.5 [8.7] kg; VO˙ 2 peak 43.9 [8.6] mL·kg−1 ·min−1 ) participated. The HST (31.0◦C; 50%RH) was 9 × 5 min (45-min) of intermittent exercise, based on exercise intensities of female soccer players, using a motorized treadmill and Wattbike. Participants completed HST1 vs. HST2 as a control (C) trial. Followed by 90 min, STHA (no fluid intake), for five consecutive days in 39.5◦C; 60%RH, using controlled-hyperthermia (∼rectal temperature [Tre] 38.5◦C). The HST3 occurred within 1 week after STHA. The HST2 vs HST3 trials were in the luteal phase, using self-reported menstrual questionnaire and plasma 17β-estradiol. Results: Pre (HST2) vs post (HST3) STHA there was a reduction at 45-min in Tre by 0.20◦C (95%CI −0.30 to −0.10◦C; d = 0.77); Tsk (−0.50; −0.90 to −0.10◦C; d = 0.80); and Tb (−0.25; −0.35 to −0.15◦C; d = 0.92). Cardiac frequency reduced at 45-min (−8; −16 to −1 b·min−1 ; d = 1.11) and %PV increased (7.0; −0.4 to 14.5%: d = 1.27). Mean power output increased across all nine maximal sprints by 56W (−26 to 139W; d = 0.69; n = 9). There was limited difference (P > 0.05) for these measures in HST1 vs HST2 C trial. Discussion: Short-term heat acclimation (5-days) using controlled-hyperthermia, leads to physiological adaptation during intermittent exercise in the heat, in moderately trained females when controlling for menstrual cycle phase.

This thesis investigated whether highly concentrated sodium solutions ([HS] 126-164 mmol.L-1 NaCl) could provide viable strategies before during and after exercise in the heat to improve cardiovascular and thermoregulatory functioning and exercise performance. To do this it also examined the gustatory responses to HS drinks before, during and after exercise. All studies compared HS with a low sodium control ([LS] 10-27 mmol.L-1). Chapter 4 found that during 3 h recovery from dehydration, ingestion of 120 % body mass losses of HS restored fluid balance to a greater extent (121 vs. 84 %) than LS. Chapter 7 was the first to investigate the effects of ingesting HS during exercise in the heat and in an untrained population. HS attenuated the decline in stroke volume [SVDrift] and increase in heart rate [HRDrift], but did not affect rectal temperature [TRec], cardiac output, or oxygen uptake during the second of two consecutive 45 min bouts at 55% . In Chapters 8 and 9 untrained participants ingested either HS or LS during 30-45 min pre-exercise rest. HS reduced HRDrift and SVDrift but did not affect TRec during 45-60 min exercise at 10% of the difference between and gas exchange threshold [∆]. HS also increased both time to exhaustion and exercise toleranceduring subsequent exercise bouts at 60-70% ∆. Chapters 5 and 6 found that taste perceptions act as physiological regulators, in this case, one reflecting the priority to restore hyperosmolality over hypovolemia. Exercise-induced dehydration increased the palatability of water, and decreased the palatability HS, when measured before, immediately after and during 3 h recovery. The changes were highly correlated with physiological indicators of fluid balance. The ingestion of highly concentrated sodium solutions can be both an efficient and acceptable means to improve hydration, reduce cardiovascular stress, and improve exercise performance in the heat. Whilst highly effective, caution should apply since the unpleasant taste evoked by these solutions persists for at least three hours post exercise.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.

Background: A negative fluid balance during bed rest (BR) is accompanied by decreased plasma volume (PV) which contributes to cardiovascular deconditioning. Hypothesis: We hypothesized that increasing dietary sodium while controlling fluid intake would increase plasma osmolality (POSM), stimulate fluid conserving hormones, and reduce fluid/electrolyte (F/E) losses during BR; conversely, decreasing dietary sodium would decrease POSM, suppress fluid conserving hormones, and increase F/E losses. Methods: We controlled fluid intake (30 ml · kg-1 · d-1) in 17 men who consumed either a 4.0 ± 0.06 g · d-1 (174 mmol · d-1) (CONT; n = 6), 1.0 ± 0.02 g · d-1 (43 mmol · d-1) (LS; n = 6), or 10.0 ± 0.04 g · d-1 (430 mmol · d-1) (HS; n = 5) sodium diet before, during, and after 21 d of 6° head-down BR. PV, total body water, urine volume and osmolality, POSM, and F/E controlling hormone concentrations were measured. Results: In HS subjects, plasma renin activity (-92%), plasma/urinary aldosterone (-59%; -64%), and PV (-15.0%; 6.0 ml · kg-1; p < 0.05) decreased while plasma atrial natriuretic peptide (+34%) and urine antidiuretic hormone (+24%) increased during BR (p < 0.05) compared with CONT. In LS, plasma renin activity (+166%), plasma aldosterone (+167%), plasma antidiuretic hormone (+19%), and urinary aldosterone (+335%) increased with no change in PV compared with CONT (p < 0.05). Total body water did not change in any of the subjects. Conclusions: Contrary to our hypothesis, increasing dietary sodium while controlling fluid intake during BR resulted in a greater loss of PV compared with the CONT subjects. Reducing dietary sodium while controlling fluid intake did not alter the PV response during BR compared with CONT subjects.

Introduction- Exercise-induced plasma volume (PV) expansion is typically associated with an increase in plasma albumin content. Increased hepatic albumin synthesis, a transcriptionally regulated process, is thought to contribute to the increase in albumin content. Objective- We tested the hypothesis that exercise training induces an increase in albumin gene expression in relationship to the increase in PV. Methods and Results- 40 adult male Sprague-Dawley rats weighing between 245-350 grams were randomly assigned to one of four groups: cage control (CC); sham exercise 10 min/day at 48% VO2max (NE); continuous exercise training, 60 min /day at 72% VO2max (LI); and high intensity, intermittent exercise training, 8 bouts of 4 min at 98% VO2max followed by 5 min at 48% VO2max (HI). The training period lasted for two weeks with 12 training sessions with equalized training volumes in the exercise groups. 24 hours after the last training session the rats were anesthetized and a jugular catheter was placed for collecting blood samples during PV determination by a dilution of a labeled-albumin molecule (Texas Red albumin). The liver and red quadriceps (RQ) muscle tissue was then removed, flash frozen, and stored for later analysis. The training protocol produced a significant increase in RQ citrate synthase activity (p < 0.05). PV increased in proportion to the exercise intensity (p < 0.05) averaging 23.6 ± 2.7 ml•kg-1 body weight in the CC group and 26.6 ± 1.3 ml•kg-1 body weight in the HI group. Albumin mRNA expression determined by real time polymerase chain reaction (PCR) increased 2.2 ± 0.1 and 2.9 ± 0.2 fold following LI and HI exercise training, respectively. Conclusion- These data support the hypothesis that, during exercise-induced PV expansion, albumin gene expression is increased and contributes to an increase in plasma albumin content and PV.

Previous data have shown that the most prevalent, indirect plasma volume (PV) measurement technique, which utilises changes in haematocrit (Hct) and haemoglobin concentration ([Hb]), underestimates actual PV changes during immersion, when compared to a direct tracer-dilution method. An increase in the F-cell ratio (whole-body haematocrit (Hctw) to large-vessel haematocrit (Hctv) ratio) has been purported as a possible explanation, probably due to hydrostatic and thermally-mediated changes during water immersion. Previous investigators have not quantified the F-cell ratio during immersion. Therefore, this study sought to determine the effect of the F-cell ratio on the indirect method during both, thermoneutral and cold-water immersions. Seven healthy males were tested three times, seated upright in air (control: 21.2°C SD ±1.1), and during thermoneutral (34.5oC SD ±0.2) and cold-water immersion (18.6oC SD ±0.2), immersed to the third intercostal space for 60 min. Measurements during the immersion tests included PV (Evans blue dye column elution, Evans blue dye computer programme, and Hct [Hb]), red cell volume (RCV; sodium radiochromate), cardiac frequency (fc) and rectal temperature (Tre). Plasma volume during the control trial remained stable, and equivalent across the three tests. There was a hydrostatically-induced increase in PV during thermoneutral immersion, when determined by the Evans blue dye method (16.2%). However, the Hct/[Hb] calculation did not adequately reflect this change, and underestimated the relative PV change by 43%. In contrast, PV decreased during cold immersion when determined using the Evans blue dye method by 17.9% and the Hct/[Hb] calculation by 8.0%, respectively, representing a 52% underestimation by the latter method. There was a non-significant decline in RCV during both immersions. Furthermore, an increase (8.6%) and decrease (-14.4%) in blood volume (BV) was observed during thermoneutral and cold-water immersions, respectively. The decline in RCV during thermoneutral immersion attenuated the BV expansion. Despite the disparity between the PV methods, there was no increase in the F-cell ratio during either immersion. In contrast, there was a significant decline in the F-cell ratio during the control: air and thermoneutral immersion, which may indicate that other, undefined variables may impact on the stability of the red cell compartment. The current study is the first to show that the Hct/[Hb] method clearly underestimates PV changes during both thermoneutral and cold-water immersion. Furthermore, RCV was shown, for the first time, to decline during both immersions. However, the changes in the F-cell ratio during this study, did not account for the underestimation of PV change using the Hct/[Hb] method.

The routines for blood testing were changed during 2010 at the blood bank in UAS. At first, the blood test was taken before the donation and now it is taken after donation. Along with this, the blood bank increased the lowest level for allowance of blood donation with 10 g/L both for men and women. The level is now on 125 g/L and 135 g/L for women respectively men. After the increase, it was noticed that the amount of blood donors were deferred due to low Hb levels in creased. A study made in year 2013, investigated how much the Hb-levels actually was changed during a blood donation. It showed that it was lowered in means by 6 g/L and not 10 g/L as previously thought.The aim of this study was to see if the sitting position of the blood donor during waiting time and the supine position during the time of blood donation may had any effect on the difference of the Hb-level during the blood donation.Data from the 120 blood donors in the earlier study was collected. Hb values, before and after blood donation, were taken from the earlier study and registered times were taken from the database Prosang. The waiting time, time of blood donation and the difference of Hb-levels were calculated and correlated with Spearmanns correlation coefficient.The results did not show any correlation between the times and the difference in Hb-levels. One of the reasons may be that the blood donor physiology differ and thus the change in Hb-level can vary.