Indicators of dehydration and haemoconcentration are associated with Woo S-H, Ranade S, Weyer AD, Dubin AE, Baba Y, Qiu Z, et al. Piezo1 channels sense whole body physical activity to reset cardiovascular homeostasis and enhance performance. Stone AM, Stahl WM. During the 120 min, the load intensity was determined individually based on the RER (0.850.95), ensuring that sufficient intensity was achieved for all participants, while staying in the aerobic range. 65 Therefore, fluid administration is advantageous in patients with CAE, to achieve normovolemia. A review article by Cheuvron and Kenefick also emphasizes that the performance-impairing effects of 2% TBM loss may have negative effects of multiple sports skills. Piezo1: properties of a cation selective mechanical channel. The clinical guidelines state that dehydration after stroke results in a poorer vital and functional prognosis (1-4).Dehydration increases hemoconcentration and blood viscosity and decreases blood pressure, factors that may worsen the effects of brain ischemia (), resulting in greater brain damage, and more severe symptoms.. Dehydration is related also with a higher risk of . Hemoconcentration is defined an increase in the relative number of red blood cells in a unit volume of plasma resulting from either a decrease in plasma volume (due to dehydration for instance) or increased production of erythrocytes (due to polycythemia vera for instance). Regulation of skeletal muscle perfusion during exercise. It's a mouthful. In both cases, a minor extent of hemodilution was observed during the first 5 minutes of the recovery after maximal exercise, and hemoglobin-hematocrit values finally returned to resting values by the 30th minute of the resting period. 1 However, the data substantiating such a correlation are fairly weak, being limited to a small in vitro study and 3 clinical studies comprising 67 patients in total. If you enjoy the site, please support our mission and consider a small gift to help us keep pace with its rapid growth. TBM: total body mass. In the present study, we examined 12 male kayak-canoe athletes. official website and that any information you provide is encrypted The effect of phenylephrine on arterial and venous cerebral blood flow in healthy subjects. Extra- and intracellular water spaces in muscles of man at rest and with dynamic exercise. Operationally defined as > 290 mOsm/kg in patients. A decreasing trend was observed during the recovery period, however, after 30 minutes the core temperature was significantly higher than the resting value (median 37.0 (q1 36.76; q3 37.35)C, p = 0.003). beat, Dehydration (>3.5% body mass loss) enhances. 8600 Rockville Pike sharing sensitive information, make sure youre on a federal McCance RA, Widdowson EM. Our goal was to determine the extent to which dehydration affects the degree of hemoconcentration and to investigate the extent of hemodilution following maximal exercise during hydrated and dehydrated conditions. Changes of hematocrit and hemoglobin concentration in the cold A 35 year-old African-American male with a history of obesity, hypertension, and recently diagnosed diabetes mellitus stopped metformin following an upper respiratory infection. Hemoglobin, hematocrit, ions (Na+, K+, Ca2+, Cl-, anion gap), blood gases (pO2, pCO2, O2-saturation), acid-base parameters (pH, lactate, bicarbonate, base excess), and osmolality were measured (Radiometer ABL 800 Flex). Rest: baseline values, sampling time before exercise. ON DIABETIC ACIDOSIS: A Detailed Study of Electrolyte Balances Following the Withdrawal and Reestablishment of Insulin Therapy. Faculty of Natural Sciences Department of Geometry, Budapest University of Technology and Economics, Budapest, Hungary, 7 Montain SJ, Coyle EF. Only effective osmoles trapped on either side of the cell membrane change cell volume; they obligate the hydration of their respective body space through transmembrane water flow until effective osmolality equalizes across all fluid compartments to establish tonicity. FOIA Careers, Unable to load your collection due to an error. For example, 1L of isotonic saline may be excreted as 2L of hypotonic urine producing a net free water loss of 1L. Maughan et al. Fluid Balance in Team Sport Athletes and the Effect of Hypohydration on Cognitive, Technical, and Physical Performance. During the HS protocol, the resting blood glucose level was 4.85 (q1 4.68; q3 5.05) mmol/l, followed by an increase at the anaerobic threshold and at the maximum load, which became even more pronounced at the 5th minute of the recovery, then decreased values were observed in the 30th minute of the rest. official website and that any information you provide is encrypted This physiological response is a temporary, short-term process, with hemodilution occurring in 710 minutes post-exercise [19]. sharing sensitive information, make sure youre on a federal Riddez L, Hahn RG, Brismar B, Strandberg A, Svensen C, Hedenstierna G. Central and regional hemodynamics during acute hypovolemia and volume substitution in volunteers. Edelman IS, Leibman J. Anatomy of body water and electrolytes. All subjects provided written informed consent to the study. Neuropsychological performance, postural stability, and symptoms after dehydration. New Insights Into the Impact of Dehydration on Blood Flow an National Library of Medicine All Rights Reserved. Regional brain blood flow in man during acute changes in arterial blood gases. Rest: baseline values, sampling time before exercise; 20, 40, , 120: sampling times at 20th, 40th, , 120th minutes of the exercise, respectively. These methods may represent useful improvements in the measurement of hydration status in sports since sampling is non-invasive; their sensitivity and specificity have yet to be clarified [29, 31]. Dehydration and performance on clinical concussion measures in collegiate wrestlers. Dorrington KL. Glucose accounts for about 50-60% of this urine osmolality and combined urinary Na+ + K+ concentration is in the range of 50-100 mEq/L (49-52). Kenefick RW, Mahood NV, Hazzard MP, Quinn TJ, Castellani JW. Hemodynamic responses to. A common misconception is that isotonic saline will correct hypertonicity since infusate tonicity is less than body tonicity. Dehydration induced by physical exercise leads to hypertonic hypovolemia due to plasma water loss [22, 28]. Hyperglycemia-induced hyponatremia--calculation of expected serum sodium depression. Muscle blood flow and muscle metabolism during exercise and. Subjects arrived with the same body composition and hydration levels before the two protocols. A supine blood pressure of 132/88 with a pulse of 90 beats/min changed on standing to a blood pressure of 121/90 with a pulse of 122 beats/min. To better represent visually the changes in the other components, we used an exponential magnification of the values, however, the numbers on the graphs show the actual values. Sthr EJ, Gonzlez-Alonso J, Pearson J, et al. the contents by NLM or the National Institutes of Health. A measure of effective osmoles in a fluid compartment which produces water movement into the given compartment. The highest values of hemoconcentration were measured at the maximum of the load, HS HgbMax median 17.4 (q1 17.03; q3 17.9) g/dl (p<0.01 compared to resting value); HS HctMax 53.50 (q1 52.28; q3 54.8) % (p<0.01 compared to resting value). Cerebral Venous Sinus Density on Noncontrast CT Correlates with Tonicity is different than serum osmolality because measurement of the latter reflects the totality of effective and ineffective osmoles in a liter of body fluid. When net fluid loss is isotonic, it draws completely from the ECF and thus the volume of fluid loss exactly equals the volume deficit. We found that the phenomenon of hemoconcentration up to the average 3.69% TBM loss is not significantly influenced by the extent of hydration, but the intensity of the workload, which can be related to the phenomenon of plasma shift and spleen contraction. Term to denote an ill-defined quality of arterial filling which often but not always parallels ECFV. Pearson J, Low DA, Sthr E, et al. Fatigue is obviously a complex process, but with a normal supply of nutrients and acid-base homeostasis, muscle efficiency has continuously deteriorated in our observation. Nuccio RP, Barnes KA, Carter JM, Baker LB. R5 and R30: sampling times at the 5th and 30th minutes of the recovery period, respectively. See more. A rationale approach to therapy begins with estimation of the volume and water deficits, as these deficits are replenished with rapid isotonic saline administration and slow free water repletion, respectively. Kitabchi AE, Umpierrez GE, Miles JM, Fisher JN. Vascular disease from hypertension or diabetes, cardiac dysfunction, chronic kidney disease, or medications interfering with compensatory angiotensin or prostaglandin systems, will exhibit GFR declines at lower levels of volume depletion (35). Hemoconcentration: causes, consequences and diagnosis But you have to know what you're talking about. Hemoconcentration - wikidoc Spleen Contraction and Hemoconcentration Regarding the Review Hemoconcentration and Hemostasis During Acute Stress: Interacting and Independent Effects by Austin et al. Please try after some time. You could not be signed in, please check and try again. After exercise, hemodilution was observed, reaching the resting value 30 minutes after loading. Polycythemia - Wikipedia Hungarian Canoe Federation, Budapest, Hungary, 4 Brodsky WA, Rapoport S, West CD. Rasmussen P, Nybo L, Volianitis S, Mller K, Secher NH, Gjedde A. Cerebral oxygenation is reduced during hyperthermic exercise in humans. Protein, Total, Serum - Mayo Clinic Laboratories - Test Catalog Hyperosmolar Hyperglycemic Syndrome - StatPearls - NCBI Bookshelf Besides, plasma proteins, primarily albumin fraction, also play an essential role in regulating plasma colloid-oncotic pressure. Synergy between Piezo1 and Piezo2 channels confers high-strain mechanosensitivity to articular cartilage. Cerebral oxygenation and, 3. Samples and data were collected at rest before exercise; at times T20, T40, T60, T80, T100, T120 (indicating the 20th, 40th 120th minutes of the exercise), at the maximum load and at the 5th and 30th minutes of the recovery period. However, rapid correction of chronic, compensated hypertonicity may precipitate cerebral edema when osmotic entry of water into brain cells outstrips their short-term ability to shed accumulated organic osmoles (41). Chiesa ST, Trangmar SJ, Gonzlez-Alonso J. Insulin also inhibits the breakdown of fat in the adipose tissue, known as lipolysis. Haemoconcentration results in increased blood viscosity. The variable hyponatremic response to hyperglycemia. The day before the study, a standard carbohydrate (55%), fat (30%), protein intake (15%), and at least 3000ml of fluid (or the usual amount of fluid consumed by the athlete) were prescribed to the volunteers by a registered dietitian. The clinical term volume is bedside shorthand for ECF volume (ECFV). Erythrocytosisis defined as anincrease in red blood cell (RBC) mass, usuallyabsolute, and is also associated with an increased hematocrit (HCT) and hemoglobin concentration. As the intensity increased (after 120 min), additional significant hemoconcentration occurred. The required 5% dextrose infusion rate is often surprising. The threshold of significance was p<0.05. Ferrannini E, Smith JD, Cobelli C, Toffolo G, Pilo A, DeFronzo RA. As a library, NLM provides access to scientific literature. 44. No conversion is necessary for sodium, potassium, chloride, bicarbonate, and anion gap in mEq/L and mmol/L. The effect of dehydration on a particular sporting skill or task is likely to depend on the structure of the task itself (e.g., endurance, strength, cognitive, and motor skills) [54]. McCance RA. Increased erythrocytes count through hemoconcentration can locally reduce peripheral vascular resistance by directly increasing endothelial vasodilating NO synthesis [6] as well as ATP, which can also stimulate NO formation [7]. 45. An increase in the proportion of red blood cells in blood, usually due to a reduction in the volume of plasma; the absolute number of red blood cells remains unchanged. However, it is also a known fact that, during long term exercises, fluid loss and dehydration can be detrimental to performance [14, 26] or even dangerous to health [913]. 8. Hypohydration and Human Performance: Impact of Environment and Physiological Mechanisms. Li J, Hou B, Tumova S, Muraki K, Bruns A, Ludlow MJ, et al. Nielsen B, Savard G, Richter EA, Hargreaves M, Saltin B. Walsh NP, Montague JC, Callow N, Rowlands AV. Exercise-related hemoconcentration and hemodilution in hydrated and National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894. Nielsen B, Strange S, Christensen NJ, Warberg J, Saltin B. Accessibility Impact of acute versus prolonged exercise and dehydration on kidney function and injury. At the end of the procedure, subjects achieved a 3.69 (q1 3.23; q3 3.90) % TBM loss, corresponding to a fluid loss of 2.80 (q1 2.40; q3 3.1) liters. The sampling break lasted for 1 min while blood sampling, weight, and body temperature measurements were taken. During the short protocol (HS), subjects achieved a maximum power of 301.5W (q1 290.5; q3 312.8), VO2max was 3932 ml/min (q1 3675; q3 4028), relative VO2max 50.1 ml/min/kg (q1 48.0; q3 52.4) at the end of the gradually increasing intensity. Volume Depletion versus Dehydration: How Understanding the Difference Stroke volume decline during prolonged exercise is influenced by the increase in heart rate. Horses with severe non-neoplastic liver disease (e.g. In the euhydrated state, physiological hemoconcentration can increase performance, and fluid replacement can even impair performance during short-term high intense exercise [8]. As volume resuscitation proceeds, GFR will often recover before hyperglycemia, leading to recrudescent polyuria. Tzamaloukas AH, Ing TS, Siamopoulos KC, et al. 28. Ranade SS, Woo S-H, Dubin AE, Moshourab RA, Wetzel C, Petrus M, et al. Given our patients morbid obesity, TBH2O is estimated using anthropomorphic equations (2) rather than weight based rules of thumb: total body water (L) = 2.4470.09516 age (years) + 0.1074 height (cm) + 0.3362 weight (kg) = 70L. Drucker WR, Chadwick CD, Gann DS. The mechanism of glycosuric diuresis in diabetic man. A relatively low fall in serum glucose of 50 mg/dL/hour (55) in our patient requires a 5% dextrose infusion rate of 250-300 mL/hour to simply maintain serum glucose constant. 48. Using a case of hyperglycemic hypertonic nonketosis we examine the changing composition of body fluid spaces to explore the distinction between dehydration with hypertonicity and volume depletion. Stamler JS, Jia L, Eu JP, McMahon TJ, Demchenko IT, Bonaventura J, et al. Erythrocytosis and Polycythemia in Animals - Circulatory System - Merck 20, 40, , 120: averages of VO2 and heart rate parameters measured over 20-minute workout periods, respectively. Berl T. Impact of solute intake on urine flow and water excretion. . ati chapter 57 Fluid imbalances Flashcards | Quizlet The distinction between these two conditions is important as the type of fluids used for therapy and their rate of administration differs for each. An increase in RBC number (whether relative to changes in body water or an absolute increase in RBC mass) is more precisely called erythrocythemia, but this term is not in general use and we are currently using the term erythrocytosis instead of polycythemia for a general increase in RBCs (whether relative orabsolute), even if not completely correct. Zeitler P, Haqq A, Rosenbloom A, Glaser N. Hyperglycemic Hyperosmolar Syndrome in Children: Pathophysiological Considerations and Suggested Guidelines for Treatment. ), HS HctR30 48.15 (q1 46.5; q3 49.2) % vs. DHS HctR30 48.25 (q1 47.48; q3 49.45) % (n.s. Atchley DW, Loeb RF, Richards DW, Benedict EM, Driscoll ME. Most nucleated cells acclimate to hypertonicity by accumulating electrolyte osmoles initially followed by organic osmoles chronically. ), HctR30 48.15 (q1 46.5; q3 49.2) % (p = 0.43 n.s.)]. Using a case of hyperglycemic hypertonic nonketosis we examine the changing composition of body fluid spaces to explore the distinction between dehydration with hypertonicity and volume depletion. 20. Plasma volume, osmolality, vasopressin, and renin activity during graded exercise in man. It occurs in dehydrated patients, in large burns, in dengue hemorrhagic fever or in patients with systemic capillary leak syndrome. All relevant data are within the manuscript and its Supporting Information files. Bone marrow aspiration is usually not worthwhile as the marrow shows an erythroid hyperplasia in all causes of erythrocytosis. and transmitted securely. Hemoconcentration: Big word, big problem A decrease in plasma volume resulting from dehydration affects renal function and interferes with diagnostics, since it leads to hemoconcentration, changing the concentration of substances diluted in water. Seldin DW, Tarail R. The metabolism of glucose and electrolytes in diabetic acidosis. Conversely, an equivalent pure water deficit does not measurably alter blood volume or GFR, while hypernatremia and hypertonicity are prominent (30-34). The height of the columns and the numbers at the top indicate the changes in osmolality values. The aim of our study was to better understand the changes in fluid spaces and blood components in hydrated and dehydrated states in athletes under dynamic (cyclic type) loading. VM: sampling time at the maximum power after 120 min preload. As blood volume and ECBV fall, initial intrarenal events maintain renal blood flow (RBF) and GFR primarily through prostaglandin effects on afferent arteriolar tone despite systemic vasoconstriction. This drives erythropoiesis, either independently of erythropoietin or because RBC precursors become hypersensitive to normal concentrations of erythropoietin. The W/VO2 and W/HR ratios decrease during exercise, ie. Gennari FJ. Theoretically, the concept of isotonic or pure water loss is attractive, but such losses rarely occur in isolation. Sum of ICF and ECF and accounts for all body water. RER 1.0: median value 1.0 of the Respiratory Exchange Ratio (the anaerobic threshold of the exercise). Delp MD, Laughlin MH. Biomarkers in Sports and Exercise: Tracking Health, Performance, and Recovery in Athletes. The concept of "hemoconcentration" or elevated levels of HGB or HCT leading to increased x-ray attenuation within the vasculature is widely accepted. 19. RER 0.9: median value 0.9 of the Respiratory Exchange Ratio (the aerobic range of the exercise). Several research groups have shown that the concentrated hemoglobin and hematocrit return to resting levels 30 minutes after a single acute anaerobic exercise [1719]. The Effects of Acute High-Intensity Interval Training on Hematological Parameters in Sedentary Subjects. Our calculations were performed in the Python programming language (version 3.7.3) using the SciPy (1.5.0) package for the statistical tests, Numpy (1.19.1) for the numerical computations, Pandas (1.1.3) for data transformation, and Plotly (5.3.1) for visualization. Hemoconcentration is defined as hematocrit level >44% in men and >40% in women. At the 30th minute of the recovery period, the hemoglobin and hematocrit levels returned to baseline values [HgbR30 15.7 (q1 15.15; q3 16.05) g/dl (p = 0.42 n.s. Reduced urine output insufficient to eliminate metabolic by-products. The defense of ECBV classically involves vasoconstriction, tachycardia, and improved myocardial contractility to maintain circulatory pressure and flow to vital organs. Chumlea WC, Guo SS, Zeller CM, et al. Judelson DA, Maresh CM, Anderson JM, Armstrong LE, Casa DJ, Kraemer WJ, et al. Management of HHNK typically occurs in three overlapping phases: ECBV restoration, repletion of ECF deficits and correction of hyperglycemia, and correction of free water deficits (Figure 2). Assuming TBH2O = 40L, blood volume = 5L, baseline % Hct = 40 & serum Na+ = 140 mEq/L. Uses and limitations. New approach to disturbances in the plasma sodium concentration. DKA occurs predominantly in patients with type 1 (insulin-dependent) diabetes mellitus, but 10% to 30% of cases occur in newly diagnosed type 2 (non-insulin-dependent) diabetes mellitus, especially in African Americans and Hispanics. erythrocytosis). Blood glucose was between 4 and 5 mmol/l and lactate was below 2 mmol/l during the 120-minute preload (Table 4). Free water administration of about 150-200 mL/hour in excess of on-going urinary (about urinary volume) and insensible losses (30-50 mL/hour) will be required. Gonzlez-Alonso J, Calbet JA, Nielsen B. Although the power output was constant during the 120-min preload, the same RER, glucose, and lactate values were recorded, but VO2 and heart rate increased steadily. Max: sampling time at the maximum exercise. White MD, Cabanac M. Exercise hyperpnea and. FOIA Furthermore, failures to obtain repeated measurements needed to calculate the degree of hemoconcentration often . Refers essentially to total body content of potassium. Dehydration is one cause of renal hypoperfusion associated with exercise. Hemoconcentration: a major risk factor for neurological - Springer Haemodynamic responses to dehydration in the resting and exercising human leg. Hyperproteinemia may be seen in dehydration due to inadequate water intake or to excessive water loss (eg, severe vomiting, diarrhea, Addison disease, and diabetic acidosis) or as a result of . His pure water deficit is calculated using hyperglycemia corrected serum Na+G in the oft cited formula: Water Deficit = TBH2O [(serum Na+G 140) 1] (6) where the corrected serum Na+G is 158 mEq/L (139 mEq/L + 1.7 11.1) with a water deficit of 9L. Biochemical Markers of Renal Hypoperfusion, Hemoconcentration, and According to the literature, blood osmolality is a more sensitive marker compared to serum sodium, so it can be used to monitor the level of hydration in athletes [2931]. Effect of exercise. The experiments were performed under air-conditioned laboratory conditions at a temperature of 2223C and a humidity of 3040% at an altitude of 145m above sea level. Whittlesey MJ, Maresh CM, Armstrong LE, Morocco TS, Hannon DR, Gabaree CLV, et al. Koomans HA, Geers AB, Mees EJ. Breath by breath VO2, VCO2, Respiratory Exchange Ratio (RER), ventilation, and beat-to-beat heart rate were recorded continuously. However, several working groups have reported that much of the lost fluid is missing from the muscle [38, 39], but further investigation is needed to clarify this. Am J Kidney Dis. Dehydration: Background, Pathophysiology, Etiology - Medscape 15. Lee EC, Fragala MS, Kavouras SA, Queen RM, Pryor JL, Casa DJ. Pollock AS, Arieff AI. The rate of correction is always a point of contention, but a rational approach is to replenish plasma volume quickly and then slowly replace the interstitial fluid as transcapillary refill reverses direction over the next 24 hours. On the second test day (long protocol, dehydrated state, DHS), one week later, an aerobic 120-minute preload was performed on a Lode bicycle ergometer to achieve a dehydrated state at a constant pedal speed of 70-80/min individually setting the intensity with respiratory exchange ratio (RER) between 0.85 and 0.95. Jacquez JA. Project no.TKP2021-EGA-37 has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-EGA funding scheme. 24. Hemoglobin and hematocrit parameters increased immediately after HIIT and their values began to return to resting levels 3 h after exercise, and completely returned to resting levels 6 h after exercise, moreover overcompensation can occur [20]. VM: sampling time at the maximum of the long protocol exercise. After exercise, we observed a modest decrease in hemoglobin-hematocrit values from the 5th minute of the recovery period, but still significantly higher values were confirmed than the resting parameters (HgbR5 p = 0.0018 and HctR5 p = 0.0021 compared to resting value). Lee W, Leddy HA, Chen Y, Lee SH, Zelenski NA, McNulty AL, et al. Since transcapillary refill replenishes 75-80% of lost vascular volume, the plasma volume deficit is about 20-25% (100% minus 75-80%) of the total ECF deficit or around 1-1.5L. Federal government websites often end in .gov or .mil. You can donate securely via PayPal or credit card. Therefore, further studies are needed for a more accurate understanding. We have analyzed the role of hemoconcentration in disease severity. Your current browser may not support copying via this button. On the first test day (short protocol, hydrated state, HS), an exercise ramp protocol was performed with a Schiller ERG 911 recumbent bicycle ergometer at a constant pedal speed of 70-80/min with a 50Watt power increase every 3 minutes until maximum exhaustion (vita maxima type protocol). The load was continuous during sampling and was not interrupted for the duration of blood taking. )], however, plasma osmolality did not follow a corresponding decrease in hemoglobin and hematocrit in the dehydrated group. The .gov means its official. Hemoconcentration. 6. Our results can contribute to optimizing the training program of not only elite sports but also recreational athletes. Most non-hemorrhagic fluid losses are hypotonic, but can be partitioned into isotonic and pure water components to apply the theoretical framework. The sites of fluid loss during dehydration have not been sufficiently clarified. Dehydration refers to a loss of total body water producing hypertonicity. Experimental Human Salt Deficiency. Lapides J, Bourne RB, Maclean LR. Villiger M, Stoop R, Vetsch T, Hohenauer E, Pini M, Clarys P, et al. Roh J, Hwang S-M, Lee S-H, Lee K, Kim YH, Park C-K. Functional Expression of Piezo1 in Dorsal Root Ganglion (DRG) Neurons. Serum osmolality. Human circulatory and thermoregulatory adaptations with heat acclimation and exercise in a hot, dry environment. Normally, JAK2 is only activated (by phosphorylation of tyrosine residues) when erythropoietin binds to its receptor. Eventually the mechanisms combating afferent arteriolar vasoconstriction fail leading to a precipitous fall in RBF and GFR (35). Synonym(s): haemoconcentration . Not to mention, that Piezo1 of striated muscle membranes could contribute in an analogous way, but more actively to the aforementioned enormous muscle fluid loss. The median body weight of the athletes was 74.3 (q1 72.88; q3 79.0) kg after exercise, corresponding to total body mass (TBM) loss of 1.18% (q1 1.05; q3 1.50; p = 0.23 n.s.). The Effects of Hemorrhage on Body Composition. Worldwide, dehydration secondary to diarrheal illness is the leading cause of infant and child mortality. The authors sought to determine the acute effects of mild to moderate dehydration on thyroid hormo Hydration and muscular performance: does fluid balance affect strength, power and high-intensity endurance? An official website of the United States government. RER 0.9: median value 0.9 of the Respiratory Exchange Ratio (the aerobic range of the exercise).