Lawrence Armstrong

Hampton VA

Exertional heat stroke is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers should be...

Background: Athletes training in heat experience physiological and perceptual symptoms that risk their safety and performance without adaptation. Purpose: We examined the changes in environmental symptoms, assessed with the Environmental Symptoms Questionnaire (ESQ), during heat acclimatization (HAz), heat acclimation (HA), and intermittent heat...

We sought to examine the effectiveness of an acute prolonged exercise session on post-exercise executive function in physically active adults and to assess if age or pre-exercise cognitive performance was predictive of the magnitude of change in executive task performance. Self-registered cyclists were recruited prior to participating in a 161-km m...

The purpose of this study was to examine the changes in metabolic heat production (Hprod), evaporative heat loss (Hevap), and dry heat loss (Hdry), following heat acclimatization (HAz) and heat acclimation (HA). Twenty-two male endurance athletes (mean ± standard deviation; age, 37 ± 12 y; body mass, 73.4 ± 8.7 kg; height, 178.7 ± 6.8 cm; and VO2ma...

Purpose: The purpose was to determine the effect of a single-dose prophylactic ibuprofen use before a 164-km road cycling event in high ambient temperature on the circulating cytokine and leukocyte responses. Methods: Twenty-three men (53 ± 8 y, 172.0 ± 22.0 cm, 85.1 ± 12.8 kg, 19.6 ± 4.4% body fat) completed a 164-km self-paced recreational road c...

The phenomenon of reduced athletic performance following sustained, intense training (Overtraining Syndrome, and OTS) was first recognized more than 90 years ago. Although hundreds of scientific publications have focused on OTS, a definitive diagnosis, reliable biomarkers, and effective treatments remain unknown. The present review considers existi...

Objectives To examine the efficacy of weekly and bi-weekly heat training to maintain heat acclimatization (HAz) and heat acclimation (HA) for 8 weeks in aerobically trained athletes. Design Randomized, between-group. Methods Twenty-four males (mean [m ± standard deviation [sd]; (age, 34 ± 12 y; body mass, 72.6 ± 8.8 kg, VO2peak, 57.7±6.8 ml·kg⁻¹·...

Exertional heat stroke (EHS) is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers sho...

The purpose of this study was to assess the effectiveness of heat acclimatization (HAz) followed by heat acclimation (HA) on physiological adaptations. 25 male endurance athletes (age 36 ± 12 y, height 178.8 ± 6.39 cm, body mass 73.03 ± 8.97 kg, and VO2peak 57.5 ± 7.0 mL·kg−1·min−1) completed HAz and HA. HAz was 3 months of self-directed summer tra...

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...

Objectives Determine whether five days of heat acclimation reduces cardiovascular and thermoregulatory strain during consecutive exercise-heat exposures on the sixth day in the heat. Design Pair-matched randomized control trial. Methods Twenty-four males completed two, 120 min exercise sessions (Session 1, Session 2) in a single day before (Day 1...

During endurance exercise, two problems arise from disturbed fluid–electrolyte balance: dehydration and overhydration. The former involves water and sodium losses in sweat and urine that are incompletely replaced, whereas the latter involves excessive consumption and retention of dilute fluids. When experienced at low levels, both dehydration and o...

Context Hypohydration has been shown to alter neuromuscular function. However, the longevity of these impairments remains unclear. Objective To examine the effects of graded exercise-induced dehydration on neuromuscular control 24 hours after exercise-induced hypohydration. Design Crossover study. Setting Laboratory. Patients or Other Participa...

Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising...

Thirst motivates consumption of water necessary for optimal health and cognitive-physiological functions. Other than thirst, little is known about coexisting perceptions and moods that provide information to the brain and participate in body water homeostasis. The purpose of this investigation was to observe perceptions, somatic sensations, and moo...

Current models of afferent inputs to the brain, which influence body water volume and concentration via thirst and drinking behavior, have not adequately described the interactions of subconscious homeostatic regulatory responses with conscious perceptions. The purpose of this investigation was to observe the interactions of hydration change indice...

Purpose This investigation had three purposes: (a) to evaluate changes in hydration biomarkers in response to a graded rehydration intervention (GRHI) following 3 days of water restriction (WR), (b) assess within-day variation in urine concentrations, and (c) quantify the volume of fluid needed to return to euhydration as demonstrated by change in...

The effects of mode of rehydration on stress hormone response to subsequent maximal intensity exercise in the heat. Linda M. Yamamoto1,2, Elaine C. Lee1, Brendon P. McDermott1, Kathleen N. Beasley1, Holly Emmanuel1, Jeff S. Volek1, Douglas J. Casa1, FACSM, Lawrence E. Armstrong1, FACSM, William J. Kraemer1, FACSM, and Carl M. Maresh1, FACSM. 1U...

We investigated the impact of nutrient intake on hydration biomarkers in cyclists before and after a 161 km ride, including one hour after a 650 mL water bolus consumed post-ride. To control for multicollinearity, we chose a clustering-based, machine learning statistical approach. Five hydration biomarkers (urine color, urine specific gravity, plas...

A long-standing body of clinical observations associates low 24-h total water intake (TWI = water + beverages + food moisture) with acute renal disorders such as kidney stones and urinary tract infections. These findings prompted observational studies and experimental interventions comparing habitual low volume (LOW) and high volume (HIGH) drinkers...

Background Individuals of all ages are encouraged to monitor their hydration status daily to prevent clinically severe fluid imbalances such as hyponatremia or dehydration. However, acute oral nutritional supplementation may alter urinary hydration assessments and potentially increase the likelihood of inappropriate clinical decisions or diagnosis....

The combination of hyperthermia, dehydration, and strenuous exercise can result in severe reductions in kidney function, potentially leading to acute kidney injury (AKI). We sought to determine whether six days of heat acclimation (HA) mitigates the rise in clinical biomarkers of AKI during strenuous exercise in the heat. Twenty men completed two c...

Exertional heat exhaustion (HEX) is the most prevalent form of heat illness in athletic, industrial, and military settings. The common etiological features include dehydration, high ambient temperature/humidity/solar radiation with slow air movement, and strenuous/prolonged exercise. The fundamental pathophysiology of HEX involves total body water...

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...

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...

The micro-organisms which inhabit the human gut (i.e. the intestinal microbiota) influence numerous human biochemical pathways and physiological functions. The present review focuses on two questions, ‘Are intestinal microbiota effects measurable and meaningful?’ and ‘What research methods and variables are influenced by intestinal microbiota effec...

Objectives: An exercise session in a hot environment may increase thermal strain during subsequent exercise sessions on the same and consecutive days. Therefore, this study was conducted to determine lasting physiological strain from moderate-high intensity, intermittent exercise in heat on subsequent exercise. Design: Repeated measures laborato...

The effects of mode of rehydration on subsequent exercise-heat challenge performance. Linda M. Yamamoto1,2, Elaine C. Lee1, Brendon P. McDermott1, Kathleen N. Beasley1, Holly Emmanuel1, Jeff S. Volek1, Douglas J. Casa1, FACSM, Lawrence E. Armstrong1, FACSM, William J. Kraemer1, FACSM, and Carl M. Maresh1, FACSM. 1University of Connecticut, 2Central...

See https://books.google.com/books/about/Exertional_Heat_Illnesses.html?id=vQZVECNmJeUC

Water is essential for metabolism, substrate transport across membranes, cellular homeostasis, temperature regulation, and circulatory function. Although nutritional and physiological research teams and professional organizations have described the daily total water intakes (TWI, L/24h) and Adequate Intakes (AI) of children, women, and men, there i...

Objective To test the hypothesis that prescribed fluid replacement is more effective at replacing fluid losses than ad libitum replacement following exercise‐induced dehydration. Methods Eleven healthy, recreationally active males (mean±SD; age, 22±3 y; height, 178±6 cm; VO 2max , 54.3±5.4 ml•kg ⁻¹ •min ⁻¹ ; body fat, 11.6±3.9%) completed three ex...

Obesity affects approximately one‐third of American adults. Recent evidence suggests that weight bias may be pervasive among both exercise and nutrition professionals working with adults who have obesity. However, the published literature on this topic is limited. This review aimed to (i) systematically review existing literature examining weight b...

Hypertension (high blood pressure [BP]) is the most common, costly, and preventable cardiovascular disease risk factor in the world. Regular aerobic exercise is universally recommended as a lifestyle therapeutic intervention for the prevention, treatment, and control of high blood pressure. However, the stressor response to exercise in extreme but...

Objectives: To observe the effects of endurance cycling in the heat on renal function. Secondarily, we investigated the effect of ibuprofen ingestion on kidney stress. Design: Randomized, placebo controlled and observational methods were utilized. Methods: Forty cyclists (52±9y, 21.7±6.5% body fat) volunteered and completed an endurance cyclin...

Exertional heatstroke (EHS) is a medical emergency that cannot be predicted, requires immediate whole-body cooling to reduce elevated internal body temperature, and is influenced by numerous host and environmental factors. Widely accepted predisposing factors (PDF) include prolonged or intense exercise, lack of heat acclimatization, sleep deprivati...

Dehydration attenuates exercise and cognitive function performance in younger adults, but less is known about the impact of dehydration on the aging population. Regular exercise serves as a robust prophylactic treatment to prevent age‐related decline in physical and cognitive function. However, middle‐age and older adults often display a blunted th...

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:...

Human thermoregulatory responses represent one point on the spectrum of physiological and behavioral adaptations across the animal kingdom. By examining the wide variety of mechanisms and behaviors that animals employ to cope with changing ambient conditions, we can better understand our own responses to environmental stressors. The examples presen...

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...

IntroductionPrevious research established significant relationships between total fluid intake (TFI) and urinary biomarkers of the hydration process in free-living males and females; however, the nature of this relationship is not known for pregnant (PREG) and lactating (LACT) women. PurposeTo determine the relationship between urinary and hematolo...

Objective: To present evidence-based recommendations that promote optimized fluid-maintenance practices for physically active individuals. Background: Both a lack of adequate fluid replacement (hypohydration) and excessive intake (hyperhydration) can compromise athletic performance and increase health risks. Athletes need access to water to prev...

Participation in organized sport and recreational activities presents an innate risk for serious morbidity and mortality. Although death during sport or physical activity has many causes, advancements in sports medicine and evidence-based standards of care have allowed clinicians to prevent, recognize, and treat potentially fatal injuries more effe...

Objective: This study aims to examine blood hemostatic responses to completing a 164-km road cycling event in a hot environment. Methods: Thirty-seven subjects (28 men and 9 women; 51.8±9.5 [mean±SD] y) completed the ride in 6.6±1.1 hours. Anthropometrics (height, body mass [taken also during morning of the ride], percent body fat [%]) were coll...

Background: Urine osmolality (UOSM) reflects the renal regulation of excess fluid or deficit fluid, and therefore, serves as a marker of hydration status. Little is known about monitoring hydration in pregnant and lactating women despite significant physiological challenges to body water balance during that time. Therefore, we designed a study to...

Lipopolysaccharide (LPS) is a gram‐negative bacterial marker that might be released into circulation during exercise‐heat stress. LPS induces an innate immune response by binding LPS‐binding protein (LBP) and its cognate receptor, TLR4 (toll‐like receptor 4), expressed on CD16+CD14+ circulating immune cells. LPS‐induced TLR4 activation results in r...

Objectives Water is an essential nutrient for thermoregulation, metabolism, cognition, and overall physiological homeostatic function. However, aging adults display a blunted thirst mechanism and subsequently have an increased risk for dehydration or hyponatremia. Fluid consumption behaviors are modifiable and the importance of practicing adequate...

Aim: Urine concentration measured via osmolality (U OSM) and specific gravity (U SG) reflects the adequacy of daily fluid intake, which has important relationships to health in pregnant (PREG) and lactating (LACT) women. Urine color (U COL) may be a practical, surrogate marker for whole-body hydration status. Purpose: To determine whether U COL...

Heat exposure and hypohydration induce physiological and psychological strain during exercise; however, it is unknown if the separate effects of heat exposure and hypohydration are synergistic when co-occurring during loaded exercise. This study compared separate and combined effects of heat exposure and hypohydration on physiological strain, mood...

Background Heat acclimation (HA) reduces the risk of exertional heat illnesses (EHI). However, HA adaptations are temporary and must be sustained to safely perform physical activity in hot environments. Objective To determine if intermittent exercise-heat exposures every fifth day mitigates HA decay, 25 days after initial HA (+25 d). Design Rando...

Introduction: Exertional hyponatremia (EH) during prolonged exercise involves all avenues of fluid-electrolyte gain and loss. Although previous research implicates retention of excess fluid, EH may involve either loss, gain, or no change of body mass. Thus, the etiology, predisposing factors, and recommendations for prevention are vague-except for...

PurposeThe purpose of this study was to examine the circulating cytokine response to a recreational 164-km road cycling event in a high ambient temperature and to determine if this response was affected by self-paced exercise time to completion. Methods Thirty-five men and five women were divided into tertiles based on time to complete the cycling...

Purpose: To assess the impact of completing a 164 km road cycling event performed in a hot environment (Wichita Falls, Texas in August), on endothelial biomarkers and resultant risk of blood clots in men and women. Methods: 37 event participants (28 men and 9 women; 51.8 ± 9.5 y) completed the ride. Plasma samples were collected in the morning befo...

Caffeine can reduce muscle pain during exercise; however the efficacy of caffeine in improving muscle soreness and recovery from a demanding long-duration exercise bout has not been established. The purpose of this study was to investigate the effects of caffeine intake on ratings of perceived muscle soreness (RPMS) and perceived lower extremity fu...

Purpose of review: The purpose of the review is to provide recommendations to improve clinical decision-making based on the strengths and weaknesses of commonly used hydration biomarkers and clinical assessment methods. Recent findings: There is widespread consensus regarding treatment, but not the diagnosis of dehydration. Even though it is gen...

The purpose of this investigation was to compare run-prescription by HR versus RPE during six weeks to determine which is superior for consistent achievement of target intensities and improved performance. 40 untrained males participated in this laboratory and field controlled trial. Participants were divided into heart rate (HRTG) and rating of pe...

Background: Surprisingly little is known about the physiological and perceptual differences of women who consume different volumes of water each day. The purposes of this investigation were to (a) analyze blood osmolality, arginine vasopressin (AVP), and aldosterone; (b) assess the responses of physiological, thirst, and hydration indices; and (c)...

Exercise and environmental stressors shift genome‐wide, transcript‐level expression in a tissue‐specific manner to upregulate stress‐specific protective genes and downregulate genes required for normal growth and function. The dynamic transcriptional landscape can inform us of the effect that whole body stress (e.g., exercise, environmental heat/hu...

Main outcome variables: Time, heart rate (HR), gastrointestinal temperature (TGI), fluid consumed, percent body mass loss (BML), and urine osmolality (Uosm). Race times between groups were similar. There was a significant condition x time interaction (P= 0.048) for HR, but TGI was similar between conditions. Subjects drank 30 ± 14% of their water...