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

Research in Sports Medicine (Impact Factor: 1.7). 07/2014; 22(3):213-225. DOI: 10.1080/15438627.2014.915838
Source: PubMed


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.

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    ABSTRACT: This work examines whether sodium supplementation is important in prevention of hyponatremia during continuous exercise up to 30 hours, and if any distinguishing characteristics of those developing hyponatremia could be identified. Participants of the 161-km Western States Endurance Run underwent body weight measurements before, during and after the race, completed a post-race questionnaire about drinking strategies and use of sodium supplementation during four race segments, and underwent analysis of post-race serum sodium concentration. The post-race questionnaire was completed by 74.5% of the 376 starters, a post-race blood sample was provided by 61.1% of the 296 finishers, and 53.0% of finishers completed the post-race survey and also provided a post-race 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. Post-race 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=0.10). 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. We conclude that a low sodium intake in supplements has minimal responsibility for development of hyponatremia during continuous exercise up to 30 hours, whereas overhydration is the primary characteristic of those developing hyponatremia. Therefore, avoiding overhydration appears to be the most important means for preventing hyponatremia under these conditions.
    No preview · Article · Dec 2014 · Medicine & Science in Sports & Exercise
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Questions & Answers about this publication

  • Martin Hofmeister added an answer in Dehydration:
    What are the effects of dehydration in ultra-endurance runners?

    If anyone knows the answer or know of any related article please answer me

    Thank you

    Martin Hofmeister

    Dear Marcos,

    maybe you can use the following studies:

    Knechtle B, Duff B, Schulze I, Kohler G. A multi-stage ultra-endurance run over 1,200 KM leads to a continuous accumulation of total body water. J Sports Sci Med. 2008;7(3):357-64.

    Winger JM, Hoffman MD, Hew-Butler TD, Stuempfle KJ, Dugas JP, Fogard K, Dugas LR. The effect of physiology and hydration beliefs on race behavior and postrace sodium in 161-km ultramarathon finishers. Int J Sports Physiol Perform. 2013;8(5):536-41.

    Hoffman MD, Hew-Butler T, Stuempfle KJ. Exercise-associated hyponatremia and hydration status in 161-km ultramarathoners. Med Sci Sports Exerc. 2013 Apr;45(4):784-91. doi: 10.1249/MSS.0b013e31827985a8.

    Hoffman MD, Stuempfle KJ. Hydration strategies, weight change and performance in a 161 km ultramarathon. Res Sports Med. 2014;22(3):213-25. doi: 10.1080/15438627.2014.915838.

    Kao WF, Hou SK, Chiu YH, Chou SL, Kuo FC, Wang SH, Chen JJ. Effects of 100-km ultramarathon on acute kidney injury. Clin J Sport Med. 2015;25(1):49-54. doi: 10.1097/JSM.0000000000000116.

    Best wishes from Germany

    • [Show abstract] [Hide abstract]
      ABSTRACT: 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.
      No preview · Article · Feb 2013 · International journal of sports physiology and performance

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