Hyponatremia in the 2009 161-km Western States Endurance Run

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Is There Evidence for the Development of Sex-Specific Guidelines for Ultramarathon Coaches and Athletes? A Systematic Review

BACKGROUND

There is evidence of sex differences in the physiology of endurance exercise, yet most of the advice and guidelines on training, racing, nutrition, and recovery for ultramarathons are based on research that has largely excluded female athletes. The objective was therefore to review the current knowledge of sex differences in ultramarathon runners and determine if sufficient evidence exists for providing separate guidelines for males and females.

METHODS

This systematic review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three databases were searched for studies investigating differences in elite and recreational male and female ultramarathon runners. Studies were included if they compared males and females and looked at outcomes relating to the performance or health of ultramarathon runners. The quality of the included studies was determined using the Grading of Recommendations Assessment Development and Evaluation (GRADE) approach.

RESULTS

The search strategy identified 45 studies that met the inclusion criteria. Most studies were observational in design, with only three papers based on randomised controlled trials. The overall quality of the evidence was low. Sex differences in the predictors of ultramarathon performance; physiological responses to training, racing, and recovery; chronic and acute health issues; and pacing strategies were found. There were areas with contradictory findings, and very few studies examined specific interventions.

CONCLUSION

The results from this review suggest that the development of sex-specific guidelines for ultramarathon coaches and athletes could have a significant effect on the performance and health of female runners. At present, there is insufficient high-quality evidence on which to formulate these guidelines, and further research is required.

Exercise-Associated Hyponatremia in Marathon Runners

Exercise-associated hyponatremia (EAH) was first described as water intoxication by Noakes et al. in 1985 and has become an important topic linked to several pathological conditions. However, despite progressive research, neurological disorders and even deaths due to hyponatremic encephalopathy continue to occur. Therefore, and due to the growing popularity of exercise-associated hyponatremia, this topic is of great importance for marathon runners and all professionals involved in runners' training (e.g., coaches, medical staff, nutritionists, and trainers). The present narrative review sought to evaluate the prevalence of EAH among marathon runners and to identify associated etiological and risk factors. Furthermore, the aim was to derive preventive and therapeutic action plans for marathon runners based on current evidence. The search was conducted on PubMed, Scopus and Google Scholar using a predefined search algorithm by aggregating multiple terms (marathon run; exercise; sport; EAH; electrolyte disorder; fluid balance; dehydration; sodium concentration; hyponatremia). By this criterion, 135 articles were considered for the present study. Our results revealed that a complex interaction of different factors could cause EAH, which can be differentiated into event-related (high temperatures) and person-related (female sex) risk factors. There is variation in the reported prevalence of EAH, and two major studies indicated an incidence ranging from 7 to 15% for symptomatic and asymptomatic EAH. Athletes and coaches must be aware of EAH and its related problems and take appropriate measures for both training and competition. Coaches need to educate their athletes about the early symptoms of EAH to intervene at the earliest possible stage. In addition, individual hydration strategies need to be developed for the daily training routine, ideally in regard to sweat rate and salt losses via sweat. Future studies need to investigate the correlation between the risk factors of EAH and specific subgroups of marathon runners.

Effect of a Multi-Strain Probiotic Supplement on Gastrointestinal Symptoms and Serum Biochemical Parameters of Long-Distance Runners: A Randomized Controlled Trial

As many as 70% of athletes who practice endurance sports report experiencing gastrointestinal (GI) symptoms, such as abdominal pain, intestinal gurgling or splashing (borborygmus), diarrhea or the presence of blood in the stool, that occur during or after intense physical exercise. The aim of the study was to evaluate the effect of a multi-strain probiotic on the incidence of gastrointestinal symptoms and selected biochemical parameters in the serum of long-distance runners. After a 3-month intervention with a multi-strain probiotic, a high percentage of runners reported subjective improvement in their general health. Moreover, a lower incidence of constipation was observed. In the group of women using the probiotic, a statistically significant (p = 0.035) increase in serum HDL cholesterol concentration and a favorable lower concentration of LDL cholesterol and triglycerides were observed. These changes were not observed in the group of men using the probiotic. Probiotic therapy may reduce the incidence and severity of selected gastrointestinal symptoms in long-distance runners and improve subjectively assessed health condition.

A review of risk factors and prevention strategies for exercise associated hyponatremia

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 to weight gain during exercise. The primary risk factors include the inappropriate secretion of arginine vasopressin, longer exercise duration, smaller body mass, and to smaller extent ingestion of non-steroidal anti-inflammatory drugs. Accurate tracking of fluid intake and losses to prevent weight gain during exercise, sodium supplementation, and heat acclimatization may help attenuate declines in serum sodium concentration during exercise.

Nutrition-Related Adverse Outcomes in Endurance Sports Competitions: A Review of Incidence and Practical Recommendations

During the last few years, the numbers of competitors in endurance and ultra-endurance sports modalities have increased significantly. This type of competition is an extreme challenge for athletes. Therefore, they have an increased the risk of developing medical and nutritional problems. The aim of the work is to estimate the incidence of nutrition-related adverse outcomes in endurance and ultra-endurance sports, considering the variables that influence them. A critical review was carried out based on the PubMed database, by means of a search strategy based on keywords separated by Boolean connectors. For all the results obtained in a period from 2008 to 2019, a series of inclusion/exclusion criteria was applied to select only the studies that fitted the objective of the present study. Results and discussion: Of the 871 publications identified, 33 met the inclusion criteria. The adverse outcomes found included exercise-associated hyponatremia (EAH), heat stroke by exertion (EHS), gastrointestinal (GI) problems, dehydration, and hypothermia; the provision of misinformation to athletes about nutrient intake and hydration during competition was identified as the main cause. Conclusions: The main adverse outcomes in endurance and ultra-endurance sports modalities are EAH, GI inconveniences, and EHS. These problems can affect the performance and health status of the athlete during and post-competition. Several nutritional guidelines have been suggested that can prevent these adverse outcomes, and it is essential to individualize and adjust the nutritional intake and hydration status according to the characteristics of each competition.

Carbohydrate intake and ketosis in self-sufficient multi-stage ultramarathon runners

Ultra-endurance athletes accumulate an energy deficit throughout their events and those competing in self-sufficient multi-stage races are particularly vulnerable due to load carriage considerations. Whilst urinary ketones have previously been noted in ultra-endurance exercise and attributed to insufficient carbohydrate (CHO) availability, not all studies have reported concomitant CHO intake. Our aim was to determine changes in blood glucose and β-hydroxybutyrate concentrations over five days (240 km) of a self-sufficient multi-stage ultramarathon in combination with quantification of energy and macronutrient intakes, estimated energy expenditure and evaluation of energy balance. Thirteen runners (8 male, 5 female, mean age 40 ± 8 years) participated in the study. Glucose and β-hydroxybutyrate were measured every day immediately post-running, and food diaries completed daily. CHO intakes of 301 ± 106 g·day^-1 (4.3 ± 1.8 g·kg^-1·day^-1) were not sufficient to avoid ketosis (5-day mean β-hydroxybutyrate: 1.1 ± 0.6 mmol.L^-1). Furthermore, ketosis was not attenuated even when CHO intake was high (9 g·kg^-1·day^-1). This suggests that competing in a state of ketosis may be inevitable during multi-stage events where load reduction is prioritised over energy provisions. Attenuating negative impacts associated with such a metabolic shift in athletes unaccustomed to CHO and energy restriction requires further exploration.

Heat Stress Challenges in Marathon vs. Ultra-Endurance Running

Several studies have investigated the effect of hot and humid ambient conditions on running exercise up to the marathon. However, studies on exercise longer than marathon are sparse. Events exceeding 6 h can be defined as ultra-endurance and have variable characteristics (e.g., distance, elevation profile, technical difficulty, altitude, night running) making hazardous the transposition of the current knowledge obtained in marathon to ultra-endurance running. Thus, the aim of this manuscript was to discuss the potential differences between marathon and ultra-endurance running in terms of heat stress challenges. The high running intensity (especially for the fastest runners), the urban context with high albedo effect materials, and the hot self-generated microclimate in mass-participation events (especially for the average to slow runners) are specific risk factors associated with marathon running in hot environments. Uphill running/walking (sometimes with poles), exotic destination with long-haul travel, desert environment and the necessity to sustain thermoregulatory and sweating responses for several days are risk factors more specific to ultra-endurance running. These differences call for specific research on the effect of hot ambient conditions in ultra-endurance disciplines to create appropriate recommendations.

Physiological and Pathophysiological Responses to Ultramarathon Running in Non-elite Runners

Ultramarathon running represents a major physical challenge even for elite athletes. Runners wellbeing may be challenged by fluid and electrolyte disturbances, hemolysis and skeletal muscle damage, decline in hepatic function and kidney injury. We hypothesized that these effects may even be exacerbated in non-elite runners. Physiological, hematological and biochemical parameters of ten males (26–45 years, weekly training time 8.5 h), participating in a mountain ultramarathon (67 km; approximately 4,500 m of total ascent), were determined before (PRE), immediately after finishing the ultramarathon (POST), and 24 h after the individual finish (REC). Race times of the 8 finishers (2 drop-outs due to hot ambient temperature) varied between 10.4 and 16.1 h, which almost represents the range of the entire starter field (8.82 h–17.47 h). The following changes in mean values of selected markers for skeletal muscle damage and kidney injury were observed from PRE to POST: creatine kinase (CK) + 1289%, lactate dehydrogenase (LDH) + 87%, serum creatinine (CR) + 72%, blood urea nitrogen (BUN) + 96%, and estimated glomerular filtration rate (eGFR) – 45%. Values of CK + 1447%, LDH + 56%, and BUN + 71% remained elevated at REC. White blood cells were increased (+ 137%) only POST. In conclusion, CK and LDH levels and leucocytosis may be considered to be relatively harmless “side-effects” of prolonged running in this group of male subjects with rather moderate ultramarathon experience and training status. However, acute kidney injury may become clinically relevant in this population under the certain conditions, which should be considered by responsible race managers and medical advisors.

Exercise-Associated Hyponatremia in Endurance and Ultra-Endurance Performance-Aspects of Sex, Race Location, Ambient Temperature, Sports Discipline, and Length of Performance: A Narrative Review

Exercise-associated hyponatremia (EAH) is defined as a plasma sodium concentration of <135 mmol/L during or after endurance and ultra-endurance performance and was first described by Timothy Noakes when observed in ultra-marathoners competing in the Comrades Marathon in South Africa in the mid-1980s. It is well-established that a decrease in plasma sodium concentration <135 mmol/L occurs with excessive fluid intake. Clinically, a mild hyponatremia will lead to no or very unspecific symptoms. A pronounced hyponatremia (<120 mmol/L) will lead to central nervous symptoms due to cerebral edema, and respiratory failure can lead to death when plasma sodium concentration reaches values of <110–115 mmol/L. The objective of this narrative review is to present new findings about the aspects of sex, race location, sports discipline, and length of performance. The prevalence of EAH depends on the duration of an endurance performance (i.e., low in marathon running, high to very high in ultra-marathon running), the sports discipline (i.e., rather rare in cycling, more frequent in running and triathlon, and very frequent in swimming), sex (i.e., increased in women with several reported deaths), the ambient temperature (i.e., very high in hot temperatures) and the country where competition takes place (i.e., very common in the USA, very little in Europe, practically never in Africa, Asia, and Oceania). A possible explanation for the increased prevalence of EAH in women could be the so-called Varon–Ayus syndrome with severe hyponatremia, lung and cerebral edema, which was first observed in marathon runners. Regarding the race location, races in Europe seemed to be held under rather moderate conditions whereas races held in the USA were often performed under thermally stressing conditions (i.e., greater heat or greater cold).

Ultra-endurance events in tropical environments and countermeasures to optimize performances and health

Physical performance in a tropical environment, combining high heat and humidity, is a difficult physiological challenge that requires specific preparation. The elevated humidity of a tropical climate impairs the thermoregulatory mechanisms by limiting the rate of sweat evaporation. Hence, a proper management of whole-body temperature is required to complete an ultra-endurance event in such an environment. In these long-duration events, which can last from 8 to 20 h, held in hot and humid settings, performance is tightly linked to the ability in maintaining an optimal hydration status. Indeed, the rate of withdrawal in these longer races was associated with lower water intake, and the majority of finishers exhibited alterations in electrolyte balance (e.g., sodium). Hence, this work reviews the effects on performance of high heat and humidity in two representative ultra-endurance sports, ultramarathons and long-distance triathlons, and several countermeasures to counteract the impact of these harsh environmental stresses and maintain a high level of performance, such as hydration, cooling strategies and heat acclimation.

[Exercise-Associated Hyponatremia in Endurance Performance]

Exercise-Associated Hyponatremia in Endurance Performance Abstract. Exercise-associated hyponatremia is defined as a plasma sodium concentration of <135 mmol/l and was first described by Timothy Noakes at the Comrades Marathon in South Africa in the mid-1980s. A decrease in plasma sodium <135 mmol/l occurs with excessive fluid intake. Risk factors include long to very long endurance performance, extreme climatic conditions, female gender and competitions in the USA. Regarding its prevalence by sport, exercise-associated hyponatraemia tends to occur while swimming and running, but rarely when cycling. While mild exercise-associated hyponatremia does not lead to clinical symptoms, severe hyponatremia due to cerebral edema can lead to neurological deficits and even death. The best prevention of exercise-associated hyponatremia is the reduction of fluid intake during exercise.

Nutrition in Ultra-Endurance: State of the Art

Athletes competing in ultra-endurance sports should manage nutritional issues, especially with regards to energy and fluid balance. An ultra-endurance race, considered a duration of at least 6 h, might induce the energy balance (i.e., energy deficit) in levels that could reach up to ~7000 kcal per day. Such a negative energy balance is a major health and performance concern as it leads to a decrease of both fat and skeletal muscle mass in events such as 24-h swimming, 6-day cycling or 17-day running. Sport anemia caused by heavy exercise and gastrointestinal discomfort, under hot or cold environmental conditions also needs to be considered as a major factor for health and performance in ultra-endurance sports. In addition, fluid losses from sweat can reach up to 2 L/h due to increased metabolic work during prolonged exercise and exercise under hot environments that might result in hypohydration. Athletes are at an increased risk for exercise-associated hyponatremia (EAH) and limb swelling when intake of fluids is greater than the volume lost. Optimal pre-race nutritional strategies should aim to increase fat utilization during exercise, and the consumption of fat-rich foods may be considered during the race, as well as carbohydrates, electrolytes, and fluid. Moreover, to reduce the risk of EAH, fluid intake should include sodium in the amounts of 10–25 mmol to reduce the risk of EAH and should be limited to 300–600 mL per hour of the race.

Predicted Risk for Exacerbation of Exercise-Associated Hyponatremia from Indiscriminate Postrace Intravenous Hydration of Ultramarathon Runners

BACKGROUND

Asymptomatic or mildly symptomatic exercise-associated hyponatremia (EAH) can be exacerbated by aggressive hydration.

OBJECTIVE

This work predicts the percentage of athletes at risk for exacerbation of EAH from indiscriminate hydration after an ultramarathon.

METHODS

Postrace serum sodium, creatinine, creatine kinase (CK), and urea nitrogen concentrations were determined for 161-km ultramarathon participants. Body mass was measured prior to and immediately after the race. Incidents when serum CK was > 20,000 U/L or creatinine ≥ 1.5 times estimated baseline were considered to be "at risk for receiving I.V. hydration" if presenting to a hospital. Those with EAH without body mass loss during the race were considered "overhydrated" and "at risk for EAH exacerbation."

RESULTS

Among 627 finishers, 16 (2.6%) were at risk for EAH exacerbation. Considering 421 observations at risk for receiving I.V. hydration, 16 (47.1%) of the 34 observations with EAH were at risk for EAH exacerbation. Among those at risk for receiving I.V. hydration and with EAH, serum urea nitrogen and creatine concentration as a multiple of estimated baseline were lower (p < 0.05) for those at risk for EAH exacerbation, compared with those without overhydration, but there were no clinically useful laboratory findings to distinguish these two groups due to considerable overlap of values.

CONCLUSIONS

Whether in the field or hospital setting, I.V. hydration of an athlete after an ultramarathon carries a notable risk for exacerbating EAH, so clinicians should use caution when hydrating athletes after endurance events.

The role of the nervous system in neuromuscular fatigue induced by ultra-endurance exercise

Ultra-endurance events are not a recent development but they have only become very popular in the last 2 decades, particularly ultramarathons run on trails. The present paper reviews the role of the central nervous system in neuromuscular fatigue induced by ultra-endurance exercise. Large decreases in voluntary activation are systematically found in ultra-endurance running but are attenuated in ultra-endurance cycling for comparable intensity and duration. This indirectly suggests that afferent feedback, rather than neurobiological changes within the central nervous system, is determinant in the amount of central fatigue produced. Whether this is due to inhibition from type III and IV afferent fibres induced by inflammation, disfacilitation of Ia afferent fibers owing to repeated muscle stretching or other mechanisms still needs to be determined. Sleep deprivation per se does not seem to play a significant role in central fatigue although it still affects performance by elevating ratings of perceived exertion. The kinetics of central fatigue and recovery, the influence of muscle group (knee extensors vs plantar flexors) on central deficit as well as the limitations related to studies on central fatigue in ultra-endurance exercise are also discussed in the present article. To date, no study has quantified the contribution of spinal modulations to central fatigue in ultra-endurance events. Future investigations utilizing spinal stimulation (i.e., thoracic stimulation) must be conducted to assess the role of changes in motoneuronal excitability on the observed central fatigue. Recovery after ultra-endurance events and the effect of sex on neuromuscular fatigue must also be studied further.

Physiology and Pathophysiology in Ultra-Marathon Running

In this overview, we summarize the findings of the literature with regards to physiology and pathophysiology of ultra-marathon running. The number of ultra-marathon races and the number of official finishers considerably increased in the last decades especially due to the increased number of female and age-group runners. A typical ultra-marathoner is male, married, well-educated, and ~45 years old. Female ultra-marathoners account for ~20% of the total number of finishers. Ultra-marathoners are older and have a larger weekly training volume, but run more slowly during training compared to marathoners. Previous experience (e.g., number of finishes in ultra-marathon races and personal best marathon time) is the most important predictor variable for a successful ultra-marathon performance followed by specific anthropometric (e.g., low body mass index, BMI, and low body fat) and training (e.g., high volume and running speed during training) characteristics. Women are slower than men, but the sex difference in performance decreased in recent years to ~10–20% depending upon the length of the ultra-marathon. The fastest ultra-marathon race times are generally achieved at the age of 35–45 years or older for both women and men, and the age of peak performance increases with increasing race distance or duration. An ultra-marathon leads to an energy deficit resulting in a reduction of both body fat and skeletal muscle mass. An ultra-marathon in combination with other risk factors, such as extreme weather conditions (either heat or cold) or the country where the race is held, can lead to exercise-associated hyponatremia. An ultra-marathon can also lead to changes in biomarkers indicating a pathological process in specific organs or organ systems such as skeletal muscles, heart, liver, kidney, immune and endocrine system. These changes are usually temporary, depending on intensity and duration of the performance, and usually normalize after the race. In longer ultra-marathons, ~50–60% of the participants experience musculoskeletal problems. The most common injuries in ultra-marathoners involve the lower limb, such as the ankle and the knee. An ultra-marathon can lead to an increase in creatine-kinase to values of 100,000–200,000 U/l depending upon the fitness level of the athlete and the length of the race. Furthermore, an ultra-marathon can lead to changes in the heart as shown by changes in cardiac biomarkers, electro- and echocardiography. Ultra-marathoners often suffer from digestive problems and gastrointestinal bleeding after an ultra-marathon is not uncommon. Liver enzymes can also considerably increase during an ultra-marathon. An ultra-marathon often leads to a temporary reduction in renal function. Ultra-marathoners often suffer from upper respiratory infections after an ultra-marathon. Considering the increased number of participants in ultra-marathons, the findings of the present review would have practical applications for a large number of sports scientists and sports medicine practitioners working in this field.

A Placebo-Controlled Trial of Riboflavin for Enhancement of Ultramarathon Recovery

Background

Riboflavin is known to protect tissue from oxidative damage but, to our knowledge, has not been explored as a means to control exercise-related muscle soreness. This study investigated whether acute ingestion of riboflavin reduces muscle pain and soreness during and after completion of a 161-km ultramarathon and improves functional recovery after the event.

Methods

In this double-blind, placebo-controlled trial, participants of the 2016 161-km Western States Endurance Run were assigned to receive a riboflavin or placebo capsule shortly before the race start and when reaching 90 km. Capsules contained either 100 mg of riboflavin or 95 mg of maltodextrin and 5 mg of 10% ß-carotene. Subjects provided muscle pain and soreness ratings before, during, and immediately after the race and for the 10 subsequent days. Subjects also completed 400-m runs at maximum speed on days 3, 5, and 10 after the race.

Results

For the 32 (18 in the riboflavin group, 14 in the placebo group) race finishers completing the study, muscle pain and soreness ratings during and immediately after the race were found to be significantly lower (p = .043) for the riboflavin group. Analysis of the 400-m run times also showed significantly faster (p < .05) times for the riboflavin group than the placebo group at post-race days 3 and 5. Both groups showed that muscle pain and soreness had returned to pre-race levels by 5 days after the race and that 400-m run times had returned to pre-race performance levels by 10 days after the race.

Conclusions

This preliminary work suggests that riboflavin supplementation before and during prolonged running might reduce muscle pain and soreness during and at the completion of the exercise and may enhance early functional recovery after the exercise.

Is Sodium Supplementation Necessary to Avoid Dehydration During Prolonged Exercise in the Heat?

The primary purpose of this work was to gain further insight into the need for sodium supplementation for maintenance of appropriate hydration during prolonged exercise under hot conditions. Participants of a 161-km ultramarathon (ambient temperature reaching 39° C) underwent body weight measurements immediately before, during, and after the race, and completed a postrace questionnaire about supplemental sodium intake and drinking strategies during 4 race segments. The postrace questionnaire was completed by 233 (78.7%) race finishers. Significant direct relationships were found for percentage weight change during the race with intake rate (r = 0.18, p = 0.0058) and total amount (r = 0.24, p = 0.0002) of sodium in supplements. Comparing those using no sodium supplements throughout the race (n = 15) with those using sodium supplements each race segment (n = 138), body weight change across the course showed significant group (p = 0.022), course location (p < 0.0001), and interaction (p = 0.0098) effects. Posttests revealed greater weight loss at 90 km (p = 0.016, -3.2 ± 1.6% vs. -2.2 ± 1.5%, mean ± SD) and the finish (p = 0.014, -3.2 ± 1.5% vs. -1.9 ± 1.9%) for those using no sodium supplements compared with those using sodium supplements each segment. Six runners who used no sodium supplements, drank to thirst, and only drank water or a mixture of mostly water with some electrolyte-containing drink finished with mean weight change of -3.4%. Although the use of supplemental sodium enhanced body weight maintenance, those not using sodium supplements maintained a more appropriate weight than those consistently using sodium supplements. Therefore, we conclude that the supplemental sodium is unnecessary to maintain appropriate hydration during prolonged exercise in the heat.

Injuries and Health Considerations in Ultramarathon Runners

Ultramarathon runners are a relatively small and unique group of distance runners with somewhat different medical issues than other distance runners. This article outlines some of those differences so that clinicians caring for these runners in the clinic or at competitions might be better prepared.

Does Acute Kidney Injury From an Ultramarathon Increase the Risk for Greater Subsequent Injury?

OBJECTIVE

Examine whether the acute kidney injury (AKI) commonly observed among ultramarathon participants places the individual at risk for subsequent AKI of worse magnitude.

DESIGN

Observational.

SETTING

Western States Endurance Run.

PARTICIPANTS

Race finishers with postrace blood studies.

INDEPENDENT VARIABLE

Acute kidney injury after 1 race.

MAIN OUTCOME MEASURES

Extent of AKI in subsequent race.

RESULTS

Among 627 finishes in which serum creatinine values were known, 36.2% met "risk" or "injury" criterion with this group characterized by having faster finish times, greater body weight loss during the race, and higher postrace serum creatine kinase and urea nitrogen concentrations when compared with those not meeting the criteria. We identified 38 runners who had undergone postrace blood analyses at multiple races among which 16 (42.1%) met the risk or injury criterion at the first race. Of those 16 runners, 12 (75%) met the criteria at a subsequent race, an incidence that was higher (P = 0.0026) than the overall 36.2% incidence. For most (56.2%) of the 16 runners meeting the criteria at the first race, the subsequent race caused less increase in serum creatinine concentration and decrement in estimated glomerular filtration rate than the first race.

CONCLUSIONS

Mild AKI is common in 161-km ultramarathons, but there was no evidence that previous AKI caused greater renal dysfunction from a subsequent exercise stimulus of similar magnitude. This offers some reassurance to runners and their physicians that mild to moderate AKI in the setting of an ultramarathon is not cumulative or without complete recovery of kidney function when stressed.

Medical Coverage of Ultramarathons and Its Unique Challenges

Medical coverage of ultramarathons must take into account unique logistical, environmental, and psychological components in addition to the medical conditions that may arise. Each ultramarathon is unique and carries with it distinct specific challenges with regard to appropriate planning and organizing. The medical issues encountered with ultramarathons can overlap with those seen in other endurance events, but the extreme and protracted nature of ultramarathons also lends itself to various other medical challenges not frequently encountered in other aspects of sports medicine. This article gives an overview of logistical considerations that go into the medical planning, as well as information regarding diagnosis and acute management of some of the most common and most important conditions that one might encounter when covering an ultramarathon.

Sodium Supplementation and Exercise-Associated Hyponatremia during Prolonged Exercise

PURPOSE

This work examines whether sodium supplementation is important in prevention of hyponatremia during continuous exercise up to 30 h and whether any distinguishing characteristics of those developing hyponatremia could be identified.

METHODS

Participants of the 161-km Western States Endurance Run underwent body weight measurements before, during, and after the race, completed a postrace questionnaire about drinking strategies and use of sodium supplementation during four race segments, and underwent analysis of postrace serum sodium concentration.

RESULTS

The postrace questionnaire was completed by 74.5% of the 376 starters, a postrace blood sample was provided by 61.1% of the 296 finishers, and 53.0% of finishers completed the postrace survey and also provided a postrace blood sample. Among this population, the incidence of hyponatremia among finishers was 6.6% and sodium supplements were used by 93.9% of the runners. Postrace serum sodium concentration was found to be directly related to the rate of sodium intake in supplements (r = 0.24, P = 0.0027) and indirectly related to the percentage change in body weight from immediately before the race start (r = -0.19, P = 0.010). There was no difference in rate of sodium intake in supplements between the hyponatremic and normonatremic finishers, and none of the hyponatremic finishers lost >4.3% body weight. Hyponatremic finishers were not distinguished from normonatremic or hypernatremic finishers by other runner characteristics considered, drinking strategies, or gastrointestinal symptoms of nausea and vomiting.

CONCLUSIONS

We conclude that a low sodium intake in supplements has minimal responsibility for development of hyponatremia during continuous exercise up to 30 h, whereas overhydration is the primary characteristic of those developing hyponatremia. Therefore, avoiding overhydration seems to be the most important means for preventing hyponatremia under these conditions.

A Randomized Controlled Trial of Massage and Pneumatic Compression for Ultramarathon Recovery

Study Design Randomized controlled trial. Background Postexercise recovery techniques are widely used, but little research has examined their effectiveness. Objectives To examine the effectiveness of massage and pneumatic compression on recovery from a 161-km ultramarathon. Methods Participants in the 2015 161-km Western States Endurance Run were randomized to a 20-minute postrace intervention of massage, intermittent sequential pneumatic compression, or supine rest. Each subject completed two 400-m runs at maximum speed before the race and on days 3 and 5 after the race, and also provided muscle pain and soreness ratings and overall muscular fatigue scores before and for 7 days after the race. Results Among the 72 runners who finished the race and completed the study, comparison among intervention groups revealed no significant group or interaction effect on 400-m run time, but there was a significant (P<.0001) time effect. Immediately posttreatment, massage resulted in lower muscle pain and soreness ratings compared with the supine-rest control condition (P<.0001), while both massage (P<.0001) and pneumatic compression (P<.01) resulted in lower overall muscular fatigue scores compared with the control group. There were no significant differences between groups in any outcome 1 to 7 days after the race. Conclusion Single 20-minute sessions of postrace massage and intermittent sequential pneumatic compression provide some immediate subjective benefit. There is no evidence, however, that such treatments provide extended subjective or functional benefits of clinical importance. The trial was registered at www.clinicaltrials.gov (NCT02530190). Level of Evidence Therapy, level 1b. J Orthop Sports Phys Ther 2016;46(5):320-326. Epub 23 Mar 2016. doi:10.2519/jospt.2016.6455.

Does oral buffered sodium supplementation reduce nausea and vomiting during an ultramarathon?

This work examines whether nausea or vomiting during an ultramarathon are due to a fluid or electrolyte imbalance, and if these symptoms can be reduced through the use of buffered sodium supplements. Starters (n = 376) of a 161.3-km ultramarathon underwent body weight measurements, 74.5% completed a post-race questionnaire, and 53.0% also underwent a post-race blood draw. The incidence of nausea or vomiting progressively increased during the race, and affected 60% of runners overall. Weight change and rate of sodium intake in supplements or in buffered sodium supplements did not differ between those with and without nausea or vomiting. Post-race serum sodium concentration also did not differ between those with and without symptoms in the last race segment. We conclude that weight change, the rate of sodium intake in supplements or in buffered sodium supplements, and serum sodium concentration are not related to symptoms of nausea or vomiting during a 161-km ultramarathon.

Sodium Intake During an Ultramarathon Does Not Prevent Muscle Cramping, Dehydration, Hyponatremia, or Nausea

BACKGROUND

Ultramarathon runners commonly believe that sodium replacement is important for prevention of muscle cramping, dehydration, hyponatremia, and nausea during prolonged continuous exercise. The purpose of this study was to measure total sodium intake to determine if these beliefs are supported.

METHODS

Participants of a 161-km ultramarathon (air temperature reaching 39 °C) provided full dietary information during the race, underwent body weight measurements before and after the race, completed a post-race questionnaire about muscle cramping and nausea or vomiting during the race, and had post-race plasma sodium concentration measured.

RESULTS

Among 20 finishers providing dietary data, mean (±SD) total sodium intake was 13,651 ± 8444 mg (range 2541-38,338 mg), and sodium in food and drink accounted for 66 % of the sodium when averaged across subjects (range 34-100 %). Sodium intake rates were similar when comparing the 10 % of subjects who were hyponatremic with those who were not hyponatremic, the 39 % with muscle cramping or near cramping with those without cramping, and the 57 % who reported having symptoms of nausea or vomiting with those without these symptoms. Weight change between race start and finish was significantly related to rate of sodium intake (r = 0.49, p = 0.030) and total sodium intake (r = 0.53, p = 0.016), but the maximum weight loss among those taking the least total sodium (<4400 mg total sodium during the race) was 4-5 % below the weight measured immediately pre-race.

CONCLUSIONS

Exercise-associated muscle cramping, dehydration, hyponatremia, and nausea or vomiting during exercise up to 30 h in hot environments are unrelated to total sodium intake, despite a common belief among ultramarathon runners that sodium is important for the prevention of these problems.

Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia: 2014 update

Exercise-associated hyponatremia (EAH) is defined by a serum or plasma sodium concentration below the normal reference range of 135 mmol/L that occurs during or up to 24 hours after prolonged physical activity. It is reported to occur in individual physical activities or during organized endurance events conducted in austere environments in which medical care is limited and often not available, and patient evacuation to definitive care is often greatly delayed. Rapid recognition and appropriate treatment are essential in the severe form to ensure a positive outcome. Failure in this regard is a recognized cause of event-related fatality. In an effort to produce best practice guidelines for EAH in the austere environment, the Wilderness Medical Society convened an expert panel. The panel was charged with the development of evidence-based guidelines for management of EAH. Recommendations are made regarding the situations when sodium concentration can be assessed in the field and when these values are not known. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks/burdens for each parameter according to the methodology stipulated by the American College of Chest Physicians. This is an updated version of the original WMS Practice Guidelines for Treatment of Exercise-Associated Hyponatremia published in Wilderness & Environmental Medicine 2013;24(3):228-240.

Incidence of Exercise-Associated Hyponatremia and Its Association With Nonosmotic Stimuli of Arginine Vasopressin in the GNW100s Ultra-endurance Marathon

OBJECTIVES

(1) To examine the incidence of exercise-associated hyponatremia (EAH) during and after an ultramarathon and (2) to evaluate hypothesized nonosmotic stimuli [interleukin-6 (IL-6), hypoglycemia, ambient temperature] with arginine vasopressin (AVP) concentrations in hyponatremic versus normonatremic runners.

DESIGN

Prospective cohort study.

SETTING

The Great North Walk 100s ultramarathons.

PARTICIPANTS

Fifteen runners participated in either 103.7- or 173.7-km ultramarathons.

MAIN OUTCOME MEASURES

Serum sodium concentration ([Na]) and AVP concentration. Secondary outcome measures included IL-6, blood glucose, ambient temperature, weight change, fluid consumption, and use of nonsteroidal anti-inflammatory drugs (NSAIDs).

RESULTS

Postrace EAH incidence was 4 of 15 runners, whereas EAH incidence at any point during the race was in 10 of 15 runners. A significant positive correlation was noted between AVP and IL-6 (r = 0.31, P < 0.05) but not between AVP and blood glucose (r = 0.09, nonsignificant) or ambient temperature (r = -0.12, NS). Subgroup analysis revealed that the correlation between AVP and IL-6 was significant in hyponatremic (r = 0.37, P < 0.05) but not normonatremic runners (r = 0.31, NS). Hyponatremic runners lost less weight than normonatremic runners (2.5 vs. 3.7 kg, P < 0.05, respectively) despite similar fluid consumption. Seven of 10 hyponatremic runners consumed NSAIDs versus 0 of 5 normonatremic runners.

CONCLUSIONS

Exercise-associated hyponatremia incidence mid-race is higher than postrace, suggesting that 40% of runners are able to self-correct low serum [Na] status during an ultramarathon. Interleukin-6 seems to be the main nonosmotic stimulus associated with AVP in hyponatremic runners. Nonsteroidal anti-inflammatory ingestion is more common in hyponatremic versus normonatremic runners.

CLINICAL RELEVANCE

Exercise-associated hyponatremia associated with nonosmotic AVP secretion may be more common during ultramarathon races without discriminatory clinical symptomatology.

Body Mass Changes Across a Variety of Running Race Distances in the Tropics

BACKGROUND

Current literature evaluating body mass (BM) changes across a variety of running race distances is limited. The primary objective of this study was to profile the range of BM changes across race distances. The secondary objective was to evaluate the prevalence of exercise-associated hyponatremia (EAH) in runners admitted to the on-site medical tent following participation of race events of different distances.

METHODS

A total of 1934 runners across seven footrace categories (10-, 21-, 25-, 42-, 50-, 84-, and 100-km) were included in the study. One thousand eight hundred eighty-seven runners had their BM measured before and after each race. Blood sodium concentrations were measured from the remaining 47 symptomatic runners admitted to the on-site medical tents and did not complete the race.

RESULTS

In terms of hydration status, 106 (6 %) were overhydrated, 1377 (73 %) were euhydrated, and 404 (21 %) were dehydrated. All race distances exhibited similar percentage of overhydrated runners (5 % in 10 km, 3 % in 21 km, 5 % in 25 km, 6 % in 42 km, 8 % in 50 km, 7 % in 84 km, and 6 % in 100 km). Forty-seven runners were admitted to the medical tents. Eight (17 %) were diagnosed with EAH (4 from 42 km, 2 from 84 km, 2 from 100 km), 38 (81 %) were normonatremic, and 1 (2 %) was hypernatremic. The % ΔBM across all races ranged from -8.0 to 4.1 % with a greater decrement noted in the 42-, 50-, 84-, and 100-km categories.

CONCLUSIONS

Approximately 3-8 % runners had increased post-race BM, suggesting overhydration regardless of race distance. Symptomatic EAH was seen at race distances at or above 42 km, where BM changes demonstrated the widest range of values.

Muscle Cramping During a 161-km Ultramarathon: Comparison of Characteristics of Those With and Without Cramping

BACKGROUND

This work sought to identify characteristics differing between those with and without muscle cramping during a 161-km ultramarathon.

METHODS

In this observational study, race participants underwent body weight measurements before, during, and after the race; completed a post-race questionnaire about muscle cramping and "near" cramping (controllable, not reaching full-blown cramping), drinking strategies, and use of sodium supplementation during four race segments; and underwent a post-race blood draw for determination of serum sodium and blood creatine kinase (CK) concentrations.

RESULTS

The post-race questionnaire was completed by 280 (74.5 %) of the 376 starters. A post-race blood sample was provided by 181 (61.1 %) of the 296 finishers, and 157 (53.0 %) of finishers completed the post-race survey and also provided a post-race blood sample. Among those who completed the survey, the prevalence of cramping and near cramping was 14.3 and 26.8 %, respectively, with greatest involvement being in the calf (54 %), quadriceps (44 %), and hamstring (33 %) muscles. Those with cramping or near cramping were more likely to have a prior history of muscle cramping during an ultramarathon (p < 0.0001) and had higher blood CK concentrations (p = 0.001) than those without cramping. Weight change during the race, use of sodium supplements, intake rate of sodium in supplements, and post-race serum sodium concentration did not differ between those with and without cramping.

CONCLUSIONS

Muscle cramping is most common in those with a prior history of cramping and greater muscle damage during an ultramarathon, suggesting an association with relative muscular demand. Impaired fluid and sodium balance did not appear to be an etiology of muscle cramping during an ultramarathon.

Exercise-associated hyponatremic encephalopathy in an endurance open water swimmer

Exercise-associated hyponatremia and its more serious form, known as exercise-associated hyponatremic encephalopathy, are recognized as some of the most important medical problems seen in a variety of different forms of endurance exercise. We describe a case of exercise-associated hyponatremic encephalopathy presenting as altered conscious state and seizures in a woman who had completed a 20-km open ocean swim. Her serum sodium measured approximately 1 hour after her seizure was 119 mmol/L on point-of-care testing. With ongoing critical care support and the use of hypertonic saline, she was able to be extubated the next day, neurologically intact, and ultimately was discharged from hospital without neurological sequelae. This case emphasizes both the importance of considering exercise-associated hyponatremic encephalopathy as a cause of neurological impairment in all athletes and the pivotal role of hypertonic saline in the treatment of this condition.

Analysis of weight change and Borg rating of perceived exertion as measurements of runner health and safety during a 6-day, multistage, remote ultramarathon

OBJECTIVE

To determine the feasibility of using weight change and Borg score as tools for monitoring runner health and safety during a multistage, remote ultramarathon.

DESIGN

Observational cohort study of feasibility on nonblinded event participants.

SETTING

Six-day, multistage, remote ultramarathon in Utah.

PARTICIPANTS

Twenty-seven athletes in the 2012 Desert R.A.T.S. (Race Across the Sand) ultramarathon.

ASSESSMENT OF RISK FACTORS

Participant weight, health conditions that limited race participation, such as fatigue or exhaustion, and Borg score were reviewed.

MAIN OUTCOME MEASURES

Inability to complete a stage of the race (Did Not Finish status) or development of a clinically significant health condition during the race. Potential prognostic risk factors, such as a high Borg score and weight loss, were analyzed.

RESULTS

An overall decrease in weight was observed over the course of the event. Median percent weight changes were losses of 2.96% (day 1), 7.42% (day 2), 2.21% (day 4), and 3.35% (day 6). There was no statistically significant difference in percent weight change between the 14 runners who finished the race and the 13 runners who did not finish the race (U = 73; z = 0.189; P = 0.85). Runners' ability to complete the race was related to the development of adverse health conditions (P = 0.004). Median Borg scores reported were 15 (day 1), 17 (day 2), 13 (day 3), 16 (day 4), and 15 (day 6). Only 2 racers who finished the entire event without adverse events ever gave a Borg score of ≥ 18.

CONCLUSIONS

The feasibility of weight change as a tool for monitoring runner health and safety in this setting is limited, but the Borg rating of perceived exertion warrants further study as a potential field expedient tool for monitoring runner health and safety during a multiday, remote ultramarathon.

The prevalence of exercise-associated hyponatremia in 24-hour ultra-mountain bikers, 24-hour ultra-runners and multi-stage ultra-mountain bikers in the Czech Republic

BACKGROUND

To assess the prevalence of exercise-associated hyponatremia (EAH) in two 24-hour mountain bike (MTB) (R1,R2), one 24-hour running (R3) and one multi-stage MTB (R4) races held in the Czech Republic in a cluster of four cross-sectional studies.

METHODS

In 27 ultra-mountain bikers (ultra-MTBers), 12 ultra-runners, and 14 multi-stage MTBers, fluid intake, changes (Δ) in body mass, hematocrit, plasma volume, plasma [Na+], plasma [K+], plasma osmolality, urine [Na+], urine [K+], urine specific gravity, urine osmolality, K+/Na+ ratio in urine, transtubular potassium gradient and glomerular filtration rate were measured and calculated. The use of non-steroidal anti-inflammatory drugs and symptoms of EAH were recorded using post-race questionnaires.

RESULTS

Of the 53 finishers, three (5.7%) developed post-race EAH, thereof one (3.7%) ultra-MTBer, one (8.3%) ultra-runner and one (7.1%) multi-stage MTBer. Plasma [Na+] decreased significantly (p < 0.001) only in R4. Urine osmolality (R1, R3, R4 p < 0.001; R2 p < 0.05) and glomerular filtration rate (p < 0.001) increased, and body mass decreased in all races (p < 0.05). Δ body mass was inversely related to the number of kilometers achieved (p < 0.001) in R2 where better ultra-MTBers tended to lose more weight. Δ body mass (p < 0.001) and %Δ body mass (p = 0.05) were positively related to lower post-race plasma [Na+] in R3 that was associated with increased loss in body mass. Fluid intake was positively related to race performance in R1 and R2 (R1: p = 0.04; R2: p = 0.01) where ultra-MTBers in R1 and R2 who drank more finished ahead of those who drank less. Post-race plasma [Na+] was negatively associated with race performance in ultra-MTBers in R2 (p < 0.05), similarly ultra-runners in R3 (p < 0.05) where finishers with more kilometres had lower post-race plasma [Na+].

CONCLUSIONS

The prevalence of EAH in the Czech Republic was no higher compared to existing reports on ultra-endurance athletes in other countries. Lower plasma [Na+] and development of EAH may be attributed to overdrinking, a pituitary secretion of vasopressin, an impaired mobilization of osmotically inactive sodium stores, and/or an inappropriate inactivation of osmotically active sodium.

Exercise-associated hyponatremia in an ultra-endurance mountain biker: a case report

Symptomatic exercise-associated hyponatremia (EAH), which is relatively common among marathon runners, is an uncommon event among ultra-endurance athletes. A 44-year-old man presented to the emergency department with increased thirst after successfully completing a 100-mile mountain bike race in Leadville, Colorado. Initial laboratory tests revealed a blood sodium level of 116 mEq/L. The primary etiologic factor in EAH is fluid consumption in excess of fluid losses in prolonged exertion. Early diagnosis and management is crucial to prevent cerebral and pulmonary edema.

Exercise-associated hyponatremia and hydration status in 161-km ultramarathoners

PURPOSE

This work combines and reanalyzes 5 yr of exercise-associated hyponatremia (EAH) research at 161-km ultramarathons in northern California with primary purposes to define the relationship between postrace blood sodium concentration ([Na]) and change in body weight; to examine the interactions among EAH incidence, ambient temperature, and hydration state; and to explore the effect of hydration status on performance.

METHODS

Prerace and postrace body weight and finish time data were obtained on 887 finishers, and postrace [Na] was also obtained on a subset of 669 finishers.

RESULTS

EAH incidence was 15.1% overall (range, 4.6%-51.0% by year) and had a significant positive relationship with ambient temperature. Of the runners with EAH, 23.8% were classified as overhydrated (weight change, ≥0), 40.6% were euhydrated (weight change, <0% to -3%), and 35.6% were dehydrated (weight change, <-3%) at the finish. There was a weak significant relationship (r = 0.17, P < 0.0001) between postrace [Na] and change in body weight such that a lower [Na] was more common with increased weight loss. Considering all finishers examined, 18.5% were dehydrated and 34.9% were overhydrated at the finish. There was a weak significant relationship (r = 0.092, P = 0.006) between change in body weight and performance in that faster runners tended to lose more weight. Top finishers varied in body weight change from ∼1% gain to ∼6% loss.

CONCLUSIONS

EAH incidence can be high in 161-km ultramarathons in northern California. In this environment, EAH is more common with dehydration than overhydration and is more common in hotter ambient temperature conditions. Because weight loss >3% does not seem to have an adverse effect on performance, excessive sodium supplementation and aggressive fluid ingestion beyond the dictates of thirst are ill advised.

The effect of physiology and hydration beliefs on race behavior and postrace sodium in 161-km ultramarathon finishers

PURPOSE

To determine if beliefs about physiology and rehydration affect ultramarathon runners' hydration behaviors or if these beliefs increase the risk for exercise-associated hyponatremia (EAH).

METHODS

Participants of the 2011 161-km Western States Endurance Run completed a prerace questionnaire, prerace and postrace body-mass measurements, and postrace assessment of serum sodium ([Na⁺]).

RESULTS

Of 310 finishers, 309 (99.7%) completed the prerace questionnaire and 207 (67%) underwent postrace blood studies. Twelve (5.8%) finishers had asymptomatic EAH ([Na⁺] range 131-134 mmol/L). The most common hydration plan (43.1%) was drinking according to schedule, and these runners did so to replace fluid lost when sweating (100%) and to avoid dehydration (81.2%). Prerace drinking plan was not associated with postrace [Na⁺] or the development of postrace hyponatremia. There also were no group differences between those with and those without EAH for any other variables including planned energy intake or knowledge of fluid balance. Runners not planning to drink to thirst trended toward more influence from advertisements (P = .056) and were significantly more influenced by scientific organizations (P = .043) than runners with other drinking plans. Finally, runners who believe that EAH is caused by excessive drinking adopted a lower-volume drinking plan (P = .005), while runners who believe that EAH is caused by sodium loss via sweating reported more common use of sodium supplementation during the race (P = .017).

CONCLUSIONS

Beliefs regarding the causes of EAH alter race behaviors including drinking plan and sodium supplementation but do not appear to affect the likelihood of developing EAH during a 161-km ultramarathon.

Urine dipstick analysis for identification of runners susceptible to acute kidney injury following an ultramarathon

This study examined whether urine dipstick testing might be useful to predict the development of acute kidney injury after an ultramarathon. Participants in the 2011 161-km Western States Endurance Run underwent post-race blood and urine dipstick analyses. Of the 310 race finishers, post-race urine dipstick testing was completed on 152 (49%) and post-race blood also was obtained from 150 of those runners. Based on "injury" and "risk" criteria for acute kidney injury of blood creatinine 2.0 and 1.5 times estimated baseline, respectively, 4% met the criteria for injury and an additional 29-30% met the criteria for risk of injury. Those meeting the injury criteria had higher creatine kinase concentrations (P < 0.001) than those not meeting the criteria. Urine dipstick tests that read positive for at least 1+ protein, 3+ blood, and specific gravity ≥ 1.025 predicted those meeting the injury criteria with sensitivity of 1.00 (95% confidence interval [CI] 0.54-1.00), specificity of 0.76 (95% CI 0.69-0.83), positive predictive value of 0.15 (95% CI 0.06-0.30), negative predictive value of 1.00 (95% CI 0.97-1.00), and likelihood ratio for a positive test of 4.2. We conclude that urine dipstick testing was successfully able to identify those individuals meeting injury criteria for acute kidney injury with excellent sensitivity and specificity.

National athletic trainers' association position statement: preventing sudden death in sports

OBJECTIVE

To present recommendations for the prevention and screening, recognition, and treatment of the most common conditions resulting in sudden death in organized sports.

BACKGROUND

Cardiac conditions, head injuries, neck injuries, exertional heat stroke, exertional sickling, asthma, and other factors (eg, lightning, diabetes) are the most common causes of death in athletes.

RECOMMENDATIONS

These guidelines are intended to provide relevant information on preventing sudden death in sports and to give specific recommendations for certified athletic trainers and others participating in athletic health care.