Kristin J. Stuempfle

Consensus statement of the 1st International Exercise-Associated Hyponatremia Consensus Development Conference, Cape Town, South Africa 2005.

Over the past decade, exercise-associated hyponatremia (EAH) has emerged as an important complication of prolonged endurance activity. Prior to 1985, this condition was not reported, and runners generally finished marathons with weight loss but without serious medical complications. Abnormalities of serum sodium concentrations ([Na]), when measured, were confined to elevated levels consistent with varying degrees of volume depletion. In March 2005, a panel of twelve international experts on exercise physiology, sport medicine, water metabolism and body fluid homeostasis convened in Cape Town, South Africa, for the 1st International Exercise-Associated Hyponatremia Consensus Development Conference. The primary goal of this panel was to review all of the existing data on EAH and formulate an evidence-based analysis that would define the current understanding of the pathophysiology of EAH. In particular, the panel was constituted to facilitate integration of existing medical and scientific knowledge of other forms of hyponatremia with the occurrence of this homeostatic imbalance during endurance exercise. A secondary goal of the EAH Consensus Development Conference was to prepare a statement that would serve to curtail the growing problem of EAH by disseminating the most current information to both medical personnel and the greater public on the prevalence, nature and treatment of this disorder. The panel strived to clearly articulate what we agreed upon, debate issues that we did not agree upon, and describe in detail what we did and did not know, including minority viewpoints that were supported by clinical and experimental data. The following statement reflects a concise summary of the data deliberated and synthesized by the panel and provides a ‘‘snapshot in time’’ of the current state of knowledge on EAH. New knowledge will continue to advance regarding our understanding of EAH, and will mandate future updates to this consensus statement.

Effect of load position on physiological and perceptual responses during load carriage with an internal frame backpack

The purpose of this study was to determine the effect of load position in an internal frame backpack on physiological and perceptual variables. Ten female participants walked on a level treadmill for 10 min carrying 25% of their body weight in a high, central, or low position. The variables measured included oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (R), respiratory rate (RR), minute ventilation (VE), and rating of perceived exertion (RPE). VO2, VE, and RPE were significantly lower in the high position (18.6 ± 2.3 ml/kg/min, 31.7 ± 5.0 l/min, 2.8 ± 0.8, respectively) compared to the low position (22.2 ± 3.0 ml/kg/min, 38.6 ± 7.5 l/min, 3.7 ± 1.0, respectively). HR, R, and RR did not change significantly as the load was moved from the high (129.8 ± 16.8, 0.89 ± 0.06, 30.3 ± 4.2, respectively) to the low position (136.0 ± 25.3, 0.92 ± 0.04, 33.8 ± 5.2, respectively). The results of this study suggest that load placement is an important factor in the physiological and perceptual responses to load carriage, and that packing heavy items high in the backpack may be the most energy efficient method of carrying a load on the back.

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.

Change in serum sodium concentration during a cold weather ultradistance race.

ObjectiveTo investigate change in serum sodium concentration and its potential causes during a cold weather ultradistance race. DesignDescriptive research. SettingA 100-mile (161-km) race over a snow-packed course in the Alaskan wilderness. Athletes competed in 1 of 3 divisions: foot, bike, or ski. ParticipantsTwenty athletes (11 runners, 6 cyclists, 3 skiers) volunteered for the study. InterventionsNone. Main Outcome MeasuresSubjects were weighed and had blood drawn for hematocrit, serum sodium, serum aldosterone, and plasma arginine vasopressin concentrations pre- and postrace. Fluid and sodium intake were determined by race dietary analysis. ResultsSerum sodium concentration decreased significantly prerace (140.8 ± 1.2 mmol/L) to postrace (138.4 ± 2.2 mmol/L), although no athletes were classified as hyponatremic. Mean weight loss was significant during the race (−1.2 kg), although 1 athlete maintained his weight, and 3 athletes gained small amounts of weight (0.2 kg, 0.2 kg, and 0.5 kg, respectively). Hematocrit decreased significantly prerace (42.2 ± 3.5) to postrace (40.3 ± 4.1). Plasma arginine vasopressin and serum aldosterone increased significantly during the race (2.6 ± 0.7 to 6.0 ± 4.6 pg/mL and 5.1 ± 2.6 to 40.8 ± 25.1 ng/dL, respectively). Fluid consumption was 300 ± 100 mL/h, and sodium intake was 310 ± 187 mg/h. ConclusionsDecreased serum sodium concentration after a cold weather ultradistance race was due to fluid overload caused by excessive fluid consumption. Current recommendations that ultradistance athletes consume 500 to 1000 mL/h may be too high for athletes competing in the extreme cold.

Increasing Creatine Kinase Concentrations at the 161-km Western States Endurance Run

OBJECTIVE Very high blood creatine kinase (CK) concentrations have been observed among recent finishers of the 161-km Western States Endurance Run (WSER), and it has been suggested that there is a link between rhabdomyolysis and hyponatremia. Therefore, the purpose of this study was to compare CK concentrations of finishers in the 2010 WSER with past values, and to determine whether there was an association between blood CK and sodium concentrations. METHODS Consenting 2010 WSER finishers provided blood samples at the finish for determination of blood CK and sodium concentrations. Finish time, age, and gender were obtained from official race results, and running experience was determined from our database as number of prior 161-km ultramarathon finishes. RESULTS From 216 (66%) of the 328 finishers, median and mean CK concentrations were found to be 20 850 IU/L and 32 956 IU/L, respectively (range 1500-264 300 IU/L), and 13 (6%) had values greater than 100 000 IU/L. These values were statistically higher (P < .0001) than those reported from the 1995 WSER. The CK concentration was not significantly associated with finish time, age, gender, or running experience. Blood sodium concentrations were obtained from a subgroup of 159 runners, and the relationship between blood CK and sodium concentrations did not reach statistical significance (P = .06, r = -0.12). CONCLUSIONS Creatine kinase concentrations of 2010 WSER finishers are higher than values previously reported. More research should focus on explaining this observation and on whether there is a possible link between higher CK concentrations and hyponatremia.

An intervention study of oral versus intravenous hypertonic saline administration in ultramarathon runners with exercise-associated hyponatremia: a preliminary randomized trial.

Objective:To determine whether asymptomatic exercise-associated hyponatremia (EAH) in ultramarathon runners can be corrected with either oral or intravenous (IV) 3% hypertonic saline (HTS). Design:Prospective with randomization into 1 of 2 intervention arms. Setting:Western States (161 km) Endurance Run, California. Participants:Forty-seven finishers in the event consented to be screened to identify those with EAH, defined as plasma sodium ([Na+]p) <135 mmol/L at race end. Interventions:Participants with EAH but without symptoms were randomized to receive a single 100 mL dose of either oral or IV 3% HTS. Blood was drawn before intervention and at 60 minutes postintervention to measure [Na+]p, and concentrations of plasma potassium, proteins, and arginine vasopressin (AVP). Body mass, percent total body water, and percent body fat were measured prerace and postrace using impedance scales. Main Outcome Measures:Change in [Na+]p. Results:Fourteen of 47 consenting finishers (30%) had EAH. Eight agreed to be randomized into the intervention protocol. Only in the IV group did [Na+]p change significantly (from 130.8 to 134.6 mmol/L) over the 60 minutes post-HTS administration. Elevated AVP concentrations were seen at race finish in both the groups and remained so after HTS treatment. Conclusions:In this preliminary trial, prompt administration of a 100 mL bolus of IV 3% HTS was associated with normalization of [Na+]p in asymptomatic EAH, but a similar effect was not demonstrated for the same dose orally. Elevated AVP levels were observed and may play a part in the development of EAH but were not suppressed significantly by either intervention.

Gastrointestinal distress is common during a 161-km ultramarathon

Abstract This study examined the incidence, severity, and timing of gastrointestinal (GI) symptoms in finishers and non-finishers of the 161-km Western States Endurance Run. A total of 272 runners (71.0% of starters) completed a post-race questionnaire that assessed the incidence and severity (none = 0, mild = 1, moderate = 2, severe = 3, very severe = 4) of 12 upper (reflux/heartburn, belching, stomach bloating, stomach cramps/pain, nausea, vomiting) and lower (intestinal cramps/pain, flatulence, side ache/stitch, urge to defecate, loose stool/diarrhoea, intestinal bleeding/bloody faeces) GI symptoms experienced during each of four race segments. GI symptoms were experienced by most runners (96.0%). Flatulence (65.9% frequency, mean value 1.0, s = 0.6 severity), belching (61.3% frequency, mean value 1.0, s = 0.6 severity), and nausea (60.3% frequency, mean value 1.0, s = 0.7 severity) were the most common symptoms. Among race finishers, 43.9% reported that GI symptoms affected their race performance, with nausea being the most common symptom (86.0%). Among race non-finishers, 35.6% reported that GI symptoms were a reason for dropping out of the race, with nausea being the most common symptom (90.5%). For both finishers and non-finishers, nausea was greatest during the most challenging and hottest part of the race. GI symptoms are very common during ultramarathon running, and in particular, nausea is the most common complaint for finishers and non-finishers.

Race Diet of Finishers and Non-Finishers in a 100 Mile (161 km) Mountain Footrace

Objective: To determine if food and fluid intake is related to completion of a 161-km ultramarathon. Methods: Sixteen consenting runners in the Western States Endurance Run participated in the study. Race diets were analyzed using Nutritionist Pro software. Both total intake and intake by race segment (3 total) were evaluated. Results: Six of 16 subjects completed the race (finishers) in 27.0 ± 2.3 hours (mean ± SD). Non-finishers completed 96.5 ± 20.5 km in 17.0 ± 3.9 h. Overall consumption rates of kilocalories, carbohydrate, fat, and sodium were significantly greater (P < 0.05) in finishers (4.6 ± 1.7 kcal/kg/h, 0.98 ± 0.43 g carbohydrate/kg/h, 0.06 ± 0.03 g fat/kg/h, 10.2 ± 6.0 mg sodium/kg/h) versus non-finishers (2.5 ± 1.3 kcal/kg/h, 0.56 ± 0.32 g carbohydrate/kg/h, 0.02 ± 0.02 g fat/kg/h, 5.2 ± 3.0 mg sodium/kg/h). Kilocalorie, fat, fluid, and sodium consumption rates during segment 1 (first 48 km) were significantly greater in finishers than in non-finishers. Conclusions: Completion of this 161-km race was related to greater fuel, fluid, and sodium consumption rates. However, intake ranges for the finishers were large, so factors other than race diet may have contributed to the successful completion of the race.

Hydration Strategies, Weight Change and Performance in a 161 km Ultramarathon

To examine controversies about hydration strategies, participants (383 starters) of a 161 km ultramarathon (maximum temperature 39.0°C) underwent body weight measurements before, during and after the race; and completed a post-race questionnaire on drinking strategies and sodium supplementation use during 4 race segments. Drinking to thirst was the most common (p < 0.01) drinking strategy (used by 67.0% during at least one segment) and most runners (95.6%) used sodium supplementation during at least one segment. There was no difference in the extent of weight loss (mean 2.0–3.1%) or the weight change pattern when comparing groups using different hydration strategies. Among top-10 finishers, half had lost more than 2% of starting body weight by 90 km. We conclude that weight loss greater than 2% does not necessarily have adverse consequences on performance, and use of sodium supplements or drinking beyond thirst is not required to maintain hydration during ultra-endurance events with high thermal stress.

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

Abstract 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.