Stavros A Kavouras

• PhD
• Arizona State University

Context The training stress of heat acclimatization optimizing exercise performance in a hot environment can be demanding. Objectives This study evaluated the efficiency of different single heating protocols to elevate core temperature. Design Not randomized controlled trial. Setting Passive heating (PAS), 30-min active heating using a high-inte...

Few previous review articles have focused on the associations between inadequate daily water intake (LOW) or urinary biomarkers of dehydration ( U D; low urine volume or high urine osmolality) and multiple diseases. Accordingly, we conducted manual online searches (47 key words) of the PubMed, Embase, and Google Scholar databases with these inclusi...

Background: Although prior evidence indicates that water intake is important for health, the ability to accurately measure community-dwelling intake is limited. Only a few studies have evaluated self-reported water intake against an objective recovery biomarker. Objectives: The aim was to compare preformed water intakes (all sources including fo...

The purpose of this investigation was to characterize factors that predict tap water mistrust among Phoenix, Arizona Latinx adults. Participants (n = 492, 28 ± 7 years, 37.4% female) completed water security experience-based scales and an Adapted Survey of Water Issues in Arizona. Binary logistic regression determined odds ratios (OR) with 95% conf...

Background/aim: Bone response to exercise depends on the type and size of the mechanical stimulus. In rowing, athletes are exposed to low mechanical but large compression loads mainly on the trunk. Thus, this study aimed to investigate the impact of rowing on total and regional bone quality and bone turnover parameters in elite rowing athletes vs....

Background: Education may improve hiker safety on trails. Aim: To investigate the impact of an educational video on hiker fluid selection and fluid consumption in a hot environment. Methods: Quasi-experimental field study at hiking trails in which the intervention group (INT) viewed a three-minute hydration education video, whereas the control grou...

The ideal lifestyle intervention to battle both obesity and diabetes is currently unknown. The aim of this pilot uncontrolled intervention trial was to assess the effect of a modified Mediterranean diet (MedDiet) on weight loss and glucoregulation among overweight/obese adults. Eleven men and women with overweight/obesity, aged 37 ± 12 years, parti...

Background: Females are prone to urinary tract infections (UTIs) due to estrogen fluctuations affecting vaginal flora. While menstruating, increased fluid consumption to support urination frequency and void volume may be important, as the urethra and urinary tract are more predisposed to bacteria, particularly UTI pathogens. Aim: This study aimed t...

U.S. border colonias are peri-urban settlements along the U.S.–Mexico border. Residents often face substandard housing, inadequate septic and sewer systems, and unsafe or inadequate household water. As of 2015, an estimated 30% of over 5 million U.S. colonia residents lacked access to clean drinking water, suggesting health complications. This scop...

Purpose Recent studies suggest that 24-h urine osmolality (UOsm) for optimal water intake should be maintained < 500 mmol·kg⁻¹. The purpose of this study was to determine the total water intake (TWI) requirement for healthy adults to maintain optimal hydration as indicated by 24-h urine osmolality < 500 mmol·kg⁻¹. Methods Twenty-four-hour UOsm was...

Objective: Physiological systems responsible for water homeostasis and energy metabolism are interconnected. This study hypothesized altered responses to dehydration including thirst, ad libitum water intake, and copeptin in men with obesity. Methods: Forty-two men (22 lean and 20 with obesity) were stimulated by a 2-hour hypertonic saline infus...

There is potential for error when athletes self-assess urine color when attempting to distinguish between high and low urine concentration. This study investigates student athletes’ ability to score artificial urine color samples (Uc) using an 8-color Uc chart. A total of 35 student-athletes (n = 30 women) scored 51 samples on two days 2–5 days apa...

Objectives The purpose of this investigation was to characterize the various factors that predict the perception that tap water is not safe in Latinx adults. Methods 489 Latinx adults (37.2% female, 28 ± 7 y) were recruited from the Phoenix, AZ area. Participants completed an Adapted Survey of Water Issues in Arizona, which evaluates awareness, ap...

The purpose of our study was to determine the responses to an acute water bolus in long-term oral contraception (OCP) users. Seventeen female volunteers (27 ± 5 y, 64.1 ± 13.7 kg, 39.6 ± 5.9 kg/LBM) provided consent and enrolled in our study. All were long-term OCP users and participated in two trials, one during the active pill (High Hormone, HH)...

Background: Arginine vasopressin (AVP), a key hormone in fluid balance, may be a modifiable contributor to hyperglycemia [ 1 ]. Low daily water drinkers often exhibit increased urine concentration and copeptin, a surrogate marker for AVP [ 2 , 3 ]. Objective: The primary purpose was to investigate the acute effect of adequate water intake on dai...

Introduction: Total fluid intake and the type of fluids consumed have been reported by many studies [ 1 - 3 ] and have shown that while an individual may be drinking sufficiently, in terms of volume, to meet or exceed recommendations on fluid intake, there may be a wide variety of combinations of fluids within that total volume [ 4 - 6 ]. Moreover...

[This corrects the article DOI: 10.3389/fspor.2021.722305.].

Background: To determine the physiological, perceptual, and exercise performance responses to breathing cooled air during and following exercise in the heat. Methods: Twelve trained male cyclists (26 ± 4y; 180.5 ± 5.6cm; 56.4 ± 7.5ml/kg/min VO2max) cycled at 60% VO2max for 75min, completed a 5 kilometer (5k) time trial, and recovered for 15min i...

Elevated body mass index (BMI) has been associated with elevated urine osmolality (UOsm), despite having higher total water intake, but it is unclear if overweight/obese individuals have reduced thirst. In this observational study, we found that overweight/obese individuals had higher UOsm compared to normal-weight individuals (749 ± 37 vs. 624 ± 3...

Exercise-associated hyponatremia (EAH) is defined as a serum sodium concentration under 135 mmol·L⁻¹ during or within 24 h of exercise. Increasing interest in endurance events has led to a higher number of athletes presenting with this potentially life-threatening condition. EAH is largely caused by the overconsumption of hypotonic fluids leading t...

The purpose of this study was to investigate the relationship between volume regulatory biomarkers and the estrogen to progesterone ratio (E:P) prior to and following varying methods and degrees of dehydration. Ten women (20 ± 1 year, 56.98 ± 7.25 kg, 164 ± 6 cm, 39.59 ± 2.96 mL•kg•min⁻¹) completed four intermittent exercise trials (1.5 h, 33.8 ± 1...

Our aim was to investigate the validity of osmolality from 24-h urine collection in examining the risk for calcium-oxalate (CaOx) kidney stone formation in patients with recurrent urolithiasis. Three hundred and twelve subjects (males/females: 184/128) from France with a history of recurrent kidney stones from confirmed or putative CaOx origin were...

Hydration is a particular concern for infants and young children due to their greater risk of dehydration. However, studies on their water intakes are scarce. The current survey aimed to analyze total water intake (TWI) in non-breastfed children aged 0.5-35 months compared to the adequate intake (AI) for the same age group set by the EFSA and to ex...

Insufficient water intake is associated with adverse health outcomes, including chronic disease prevalence and mortality. Adherence to Institute of Medicine total water intake (TWI) recommendations has been low in recent decades, and TWI has been consistently lower in Latinx adults compared with non-Hispanic (NH) white adults. While overall plain w...

To test the diagnostic ability of two combined practical markers for elevated urine osmolality (underhydration) in free-living adults and children. One hundred and one healthy adults (females n = 52, 40 ± 14 y, 1.70 ± 0.95 m, 76.7 ± 17.4 kg, 26.5 ± 5.5 kg/m²) and 210 children (females = 105, 1.49 ± 0.13 m, 43.4 ± 12.6 kg, 19.2 ± 3.2 kg m⁻²) collect...

Although it is well established that dehydration has a negative impact on thermoregulation during exercise in the heat, it is unclear whether this effect of dehydration is different between men and women, or across the phases of the menstrual cycle (MC). Twelve men and seven women (men: 20 ± 2 years, 70.13 ± 10.5 kg, 173.4 ± 6.0 cm, 54.2 ± 8.6 ml k...

The purpose of this investigation was to assess the validity and reliability of a seven-day water frequency questionnaire (TWI-FQ) to estimate daily total water intake (TWI) in comparison to a water turnover objective reference value via deuterium oxide (D 2 O). Data collection occurred over 3 weeks, with a wash-out period during week two. Healthy...

PurposeAn increasing body of evidence suggests that excreting a generous volume of diluted urine is associated with short- and long-term beneficial health effects, especially for kidney and metabolic function. However, water intake and hydration remain under-investigated and optimal hydration is poorly and inconsistently defined. This review tests...

Wardenaar, FC, Ortega-Santos, CP, Vento, K, Beaumont, JS, Griffin, SC, Johnston, C, and Kavouras, SA. A 5-day heat acclimation program improves heat stress indicators while maintaining exercise capacity. J Strength Cond Res 35(5): 1279-1286, 2021-This study aimed to evaluate whether a daily 60 minutes isothermic biking protocol during a 5-day perio...

Atkins, WC, McDermott, BP, Kanemura, K, Adams, JD, and Kavouras, S. Effects of Hydration Educational Intervention in High School Football Players. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to assess the effects of a one-time educational intervention (EI) on hydration behaviors, status, and knowledge. In a pre-test, post...

Context: The measurement of urine specific gravity should be performed at room temperature (20 °C) but sample temperature is not always taken in consideration. Objective: Evaluate the effect of sample temperature on the measurement accuracy of a digital (DIG) and optical (MAN) refractometer and a hydrometer (HYD). Design: Quantitative comparison be...

Confusion has persisted for decades in the United States (U.S.) over how much plain water to drink, despite national water intake recommendations which are based on high quality scientific evidence. This editorial summarizes the definition, alignment and coordination of evidence that informs the current U.S. adequate intake (AI) recommendations for...

It is unclear if mild-to-moderate dehydration independently affects mood without confounders like heat exposure or exercise. This study examined the acute effect of cellular dehydration on mood. Forty-nine adults (55 % female, age 39 ( sd 8) years) were assigned to counterbalanced, crossover trials. Intracellular dehydration was induced with 2-h (0...

Reproductive hormones can have significant non-reproductive physiological effects, including altering the regulation of body fluid volume. The purpose of this investigation was to explore the impact of sex and menstrual cycle (MC) phase on volume regulatory responses to 24-hour fluid restriction (24-h FR). Participants (men: n=12, 20±2y; women: n=1...

Dietary patterns provide valuable information for the development of public health policies. Despite increasing interest in the role of fluids in health and disease there are limited data on drinking patterns in adults. The aim of this analysis was to identify and characterize patterns of fluid intake in adults in cross-sectional surveys in China,...

Health care professionals often ask their patients questions about their water intake, or water drinking frequency. The aim of the present analysis was to compare 3 questions (prospective 7-day fluid record, an open question (OQ) and a frequency question (FQ)) used to record the volumes of water drank. 8159 participants (18–65 years) from Argentina...

While daily hydration is best assessed in 24-h urine sample, spot sample is often used by health care professionals and researchers due to its practicality. However, urine output is subject to circadian variation, with urine being more concentrated in the morning. It has been demonstrated that afternoon spot urine samples are most likely to provide...

Objectives To assess the acute effect of adequate water consumption on copeptin, a marker of arginine vasopressin, in low drinkers. Methods Six healthy (5 males, 1 female) low drinkers (age 43 ± 7 y, BMI 30.5 ± 3) were recruited based on self-reported daily water consumption ≤1.5 L·day−1 in males or 1.0 L·day−1 in females (854 ± 432 mL·d−1) and 24...

Objectives Water loss via sweating increases during exercise especially in the heat, however, the evidence is limited as to whether moderate physical activity (PA) and ambient temperature (Ta) influence water intake in daily life. The purpose of this study was to examine the influence of PA and Ta on water intake and hydration state in free-living...

Research on hyponatremia during mountain marathons is scarce. The present study aimed to investigate the prevalence of exercise-associated hyponatremia during a 44-km trail running race that reached an altitude of 2780 m (Olympus Marathon). Sixty-two runners (five women) who completed the race participated in the study (age: 34.4 ± 8.6 years; heigh...

Purpose This study aimed to examine the psychological factors (knowledge, barriers and facilitators) that can contribute to hydration-related behaviors (i.e., fluid intake) in the general population and how these relate to physical health. Methods A structured survey was developed to examine the links between hydration knowledge (29 items), attitu...

Nationally representative data from the National Health and Nutrition Examination Survey (NHANES) indicate that over 65% of adults aged 51–70 years in the U.S. do not meet hydration criteria. They have hyponatremia (serum sodium < 135 mmol/L) and/or underhydration (serum sodium >145 mmol/L, spot urine volume <50 mL, and/or spot urine osmolality ≥50...

The motivation to seek and consume water is an essential component of human fluid–electrolyte homeostasis, optimal function, and health. This review describes the evolution of concepts regarding thirst and drinking behavior, made possible by magnetic resonance imaging, animal models, and novel laboratory techniques. The earliest thirst paradigms fo...

Purpose: The purpose of this observational study was to examine the incidence of exercise-associated hyponatremia (EAH) in a 246-km continuous ultra-marathon. Methods: Over 2 years, 63 male finishers of the annual Spartathlon ultra-marathon foot race from Athens to Sparta, Greece were included in the data analysis. A blood sample was drawn from an...

Background: Epidemiological studies in humans show increased concentrations of copeptin, a surrogate marker of arginine vasopressin (AVP), to be associated with increased risk for type 2 diabetes. Objectives: To examine the acute and independent effect of osmotically stimulated AVP, measured via the surrogate marker copeptin, on glucose regulati...

Background: Proper hydration is vital for both exercise and general health. Although various methods for hydration assessment exist, many are not valid for either use or never tested. Introduction: The purpose of this study was to determine whether the uChek© smart phone application can be used to diagnose underhydration based on elevated urine...

Personalized hydration strategies play a key role in optimizing the performance and safety of athletes during sporting activities. Clinicians should be aware of the many physiological, behavioral, logistical and psychological issues that determine both the athlete’s fluid needs during sport and his/her opportunity to address them; these are often s...

Objectives: Investigators sought to: 1) evaluate the validity of a water frequency questionnaire (WFQ) to estimate mean daily water intake (WI) in adults through comparison to the gold standard, deuterium oxide (D2O) disappearance, and 2) evaluate reliability of WFQ to estimate WI. Methods: Data collection occurred over three weeks, with validit...

Objectives: Mild and moderate dehydration adversely affect mood and cognitive function. During dehydration, hypertonic hypovolemia activates both osmo- and baro-receptors but it is not known which physiological pathway is associated with degraded mood state. This study examined the acute effect of osmoreceptor stimulation on mood. Methods: Sixty...

Objectives: Examine potential sex differences in osmotically stimulated thirst. Methods: 60 healthy adults (30 female - measured in early follicular phase, age: 39 ± 8 y, weight: 78.2 ± 15.2 kg, body mass index: 26.9 ± 4.0 kg·m-2) were infused intravenously with 3% (HYPER) or 0.9% (ISO) NaCl for 120 min (0.1 ml·kg-1·min-1) in a counterbalanced,...

Purpose Although low water intake has been associated with adverse health outcomes, available literature indicated that the majority of children do not meet the water intake guidelines and they are underhydrated based on elevated hydration biomarkers. This review examined the water intake habits and hydration status in children from 32 observationa...

The aim of the present study was to observe the effect of mild hypohydration on exercise performance with subjects blinded to their hydration status. Eleven male cyclists (weight 75.8±6.4 kg, VO2peak: 64.9±5.6 mL·kg⁻¹·min⁻¹, body fat: 12.0±5.8%, Powermax: 409±40 W) performed three sets of criterium‐like cycling, consisting of 20‐min steady‐state cy...

Water is an often-forgotten and understudied nutrient although it composes 55%-80% of the human body and is involved in nearly all physiological processes. However, the literature has begun to shift from investigating hydration and athletic performance to how the process of fluid homeostasis is implicated in health and well-being. Hormonal and mech...

Background: Although plenty of evidence indicates that weight loss maintainers are highly physically active, studies focusing on the sex-specific differences in activity levels between maintainers and regainers are scarce. The authors aimed to investigate sex-specific differences in activity patterns in a cohort of Mediterranean maintainers and re...

Preliminary data from experimental animals have linked dehydration to glucose dysregulation via the action of vasopressin. Also epidemiological data suggest that humans with low water intake or elevated vasopressin are more prone to develop diabetes. PURPOSE Therefore, the purpose of this study was to investigate the effects of cellular dehydratio...

Formation of kidney stone affects approximately 1 in 11 people in the U.S., and it can develop into various adverse renal outcomes. Although American Urological Association guideline recommends having at least 2.5 L of urine daily by having a high fluid intake to reduce 50% of recurrence rate in stone formers, few studies have evaluated the associa...

PURPOSE To evaluate the diagnostic ability of two combined practical markers for elevated urine osmolality in free‐living adults. METHODS One hundred and one healthy adults (females N=52, 1.64±0.06 m, 72.0±16.6 kg, 26.9±6.1 kg/m2; males N=49, 1.77±0.07 m, 81.5±16.0 kg, 26.0±4.7 kg/m2) collected urine for 24 h on two occasions day 1 (D1) and day 2...

Introduction: Obesity and hypohydration independently affect postsynaptic endothelial function, but it is unknown if hypohydration affects lean and obese individuals differently. Purpose: To examine the effect of hypohydration on postsynaptic cutaneous vasodilation and sweating in men with high and low adiposity (HI- and LO-BF, respectively). M...

Purpose: The primary aim of this survey was to report total fluid intake (TFI) and different fluid types for children (4-9 years) and adolescents (10-17 years) in Mexico, Brazil, Argentina and Uruguay. The second aim was to compare TFI with the adequate intake (AI) of water from fluids as recommended by the USA Institute of Medicine. Methods: Da...

Purpose: To report total fluid intake (TFI) and the intake of different fluid types in adults (≥ 18 years old) from Mexico, Argentina, Brazil and Uruguay. To compare intakes between countries and with recommended adequate intake (AI) of water from fluids. Methods: Cross-sectional data were collected using a validated liquid intake 7-day record (...

Purpose: This study aimed to identify and characterize patterns of fluid intake in children and adolescents from six countries: Argentina, Brazil, China, Indonesia, Mexico and Uruguay. Methods: Data on fluid intake volume and type amongst children (4-9 years; N = 1400) and adolescents (10-17 years; N = 1781) were collected using the validated 7-...

Purpose: To assess drinking occasions (volume and type) according to consumption with food in or outside meals, and location, for six countries. Methods: A total of 10,521 participants aged 4-65 years from Argentina, Brazil, China, Indonesia, Mexico and Uruguay completed a validated 7-day fluid intake record. For each drinking event, the volume...

Purpose: To describe total fluid intake (TFI) and types of fluid consumed in urban China by age, gender, regions and city socioeconomic status relative to the adequate intakes (AI) set by the Chinese Nutrition Society. Methods: In 2016, participants aged 4-9, 10-17 and 18-55 years were recruited via a door-to-door approach in 27 cities in China....

Purpose To report daily total fluid intake (TFI) and fluid types in Indonesia according to age, sex, socio-economic status (SES) and geographic region, and compare TFI with the Indonesian adequate fluid intake (AI) recommendations. Methods Data were collected in 32 cities over nine regions from children (4–9 years, n = 388), adolescents, (10–17 ye...

Objective: To assess the diagnostic ability of urine reagent strips to identify hypohydration based on urine specific gravity (USG). Design: This study examined the agreement of USG between strips and refractometry with Bland-Altman, whereas the diagnostic ability of the strips to assess hypohydration was performed by receiver operating characte...

The reference values for daily total water intake from fluids and foods (TWI) from the Institute of Medicine (IOM) are 2.7 and 3.7 liters for females and males, respectively. Recent studies suggest that for optimal water intake 24h urine osmolality should be maintained below 500 mmol·kg ⁻¹ . Purpose To determine the total water intake requirement...

Low water intake and plasma hypertonicity have been independently associated with hyperglycemia and incidence of diabetes mellitus in epidemiological studies. Recent data also suggest that reducing water intake deteriorates glucose regulation in patients with type 2 diabetes. To date, it is unclear whether plasma hypertonicity would also impact gly...

Copeptin, a c‐terminal segment of arginine vasopressin (AVP) prohormone, has equimolar secretion to AVP in response to osmotic, stress‐related, and hemodynamic stimulation. For this reason, and because of the difficulties in measuring AVP directly linked to its short half‐life, copeptin has been used as a stable and sensitive surrogate marker for A...

Background/objectives: Children consume various fluids to meet dietary water intake needs. However, the contribution of different fluid types on hydration is unclear. The purpose of this study was to develop fluid intake patterns and examine their association with hydration, as indicated by 24-h urine osmolality. Subjects/methods: Two hundred te...

Purpose: The aim of the present study was to examine the effect of dehydration on exercise performance independently of thirst with subjects blinded of their hydration status. Methods: Seven male cyclists (weight: 72±9 kg, body fat: 14±6%, VO2peak: 59.4±6 ml[BULLET OPERATOR]kg·min) exercised for 2 hours on a cycle ergometer at 55% VO2peak, in a...

Background: Occult (i.e., non-visible) gastrointestinal (GI) bleeding is a well-recognized complication that can occur during vigorous endurance physical exertion, especially in the heat. Objectives: The purpose of this study was to investigate the incidence of GI bleeding during a non-impact (cycling) prolonged race (161-km) in the heat. Methods:...

This chapter discusses the physiology of hydration, the evidence for how hydration affects performance, and practical applications for individuals who exercise. The body has an amazing ability to detect changes in body fluid, and individuals exercising are constantly losing body fluid through sweat. These losses are sensed by the body, and without...

Aim: To examine the validity of published resting energy expenditure (REE) equations in Greek adults, and if indicated, develop new cohort-specific predictive REE equations. Methods: Indirect calorimetry and anthropometric data were obtained from 226 adult volunteers of diverse age groups and body mass index ranges (18-60 years, 16.6-67.7 kg·m-2...

The purpose of this manuscript is to assess hydration status of elite young sailing athletes during World Championship competition. 12 young elite male Laser Class sailors (age: 15.8±1.1 y, height: 1.74±0.1 m, weight: 65.1±1.5 kg, body fat: 12.5±3.1%, training experience: 7.0±1.2 y) participated in this descriptive study. After three-day baseline b...