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Food intake and electrolyte status of ultramarathoners competing in extreme heat.
J Am Coll Nutr 2002; 21(6):553-9JA

Abstract

OBJECTIVE

To relate changes in laboratory indices to dietary intake during extremely prolonged running and to determine if dietary intake influences the ability of runners to finish an 160 km trail race.

METHODS

We monitored intake and serum chemistries of 26 runners competing in an 160 km foot race in temperatures which peaked at 38 degrees C. Blood was drawn pre-, mid- and post-race. Dietary intake and incidence of gastrointestinal distress or changes in mental status were determined by interview with runners approximately every 13 km. Twenty-three runners completed at least 88 kms and, of these 23 runners, 13 finished 160 km in a mean time of 26.2 +/- 3.6 hours.

RESULTS

Finishers ingested nearly 30,000 J, 19.4 +/- 8.1 L of fluid and 16.4 +/- 9.5 g of sodium (Na). Sodium and fluid intake per hour was estimated to be 0.6 g/hour and 0.7 L/hour, respectively. Electrolyte intake during the first half of the race was similar between those that finished the race and those that did not. Finishers ingested fluid at a greater rate than non-finishers (p = 0.01) and tended to meet their caloric needs more closely than did non-finishers (p = 0.09). Body weight was unchanged over time (ANOVA, p = 0.52). Serum Na concentration tended to fall from 143 to 140 mEq/L during the race (p = 0.06), and was inversely correlated with weight loss (p = 0.009). Serum Na concentration was lower mid-race in runners experiencing changes in mental status than in runners without changes (p = 0.04). Fluid intake was inversely correlated with serum Na concentrations (p = 0.04). Most of the runners experienced nausea or vomiting; these symptoms were not related to serum sodium concentration. Hyponatremia (<135 mEq/L) was seen in one runner at 88 kms, but resolved by 160 km. Urinary sodium excretion decreased (p = 0.002) as serum aldosterone concentration increased pre- to post-race (p < 0.001). From start to finish of the race plasma volume increased by 12%.

CONCLUSIONS

Food and fluid was ingested at a greater rate than described previously. Runners consumed adequate fluid to maintain body weight although dietary sodium fell far short of the recommended 1 g/hour. The rate of fluid intake was greater in finishers than in non-finishers, and finishers tended to more nearly meet their energy needs. Maintenance of body mass despite large exercise energy expenditures in extreme heat is consistent with fluid overload during a running event lasting more than 24 hours in hot and humid conditions.

Authors+Show Affiliations

Nicholas Institute of Sports Medicine and Athletic Trauma, New York, New York 10021, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

12480801

Citation

Glace, Beth W., et al. "Food Intake and Electrolyte Status of Ultramarathoners Competing in Extreme Heat." Journal of the American College of Nutrition, vol. 21, no. 6, 2002, pp. 553-9.
Glace BW, Murphy CA, McHugh MP. Food intake and electrolyte status of ultramarathoners competing in extreme heat. J Am Coll Nutr. 2002;21(6):553-9.
Glace, B. W., Murphy, C. A., & McHugh, M. P. (2002). Food intake and electrolyte status of ultramarathoners competing in extreme heat. Journal of the American College of Nutrition, 21(6), pp. 553-9.
Glace BW, Murphy CA, McHugh MP. Food Intake and Electrolyte Status of Ultramarathoners Competing in Extreme Heat. J Am Coll Nutr. 2002;21(6):553-9. PubMed PMID: 12480801.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Food intake and electrolyte status of ultramarathoners competing in extreme heat. AU - Glace,Beth W, AU - Murphy,Christine A, AU - McHugh,Malachy P, PY - 2002/12/14/pubmed PY - 2003/5/7/medline PY - 2002/12/14/entrez SP - 553 EP - 9 JF - Journal of the American College of Nutrition JO - J Am Coll Nutr VL - 21 IS - 6 N2 - OBJECTIVE: To relate changes in laboratory indices to dietary intake during extremely prolonged running and to determine if dietary intake influences the ability of runners to finish an 160 km trail race. METHODS: We monitored intake and serum chemistries of 26 runners competing in an 160 km foot race in temperatures which peaked at 38 degrees C. Blood was drawn pre-, mid- and post-race. Dietary intake and incidence of gastrointestinal distress or changes in mental status were determined by interview with runners approximately every 13 km. Twenty-three runners completed at least 88 kms and, of these 23 runners, 13 finished 160 km in a mean time of 26.2 +/- 3.6 hours. RESULTS: Finishers ingested nearly 30,000 J, 19.4 +/- 8.1 L of fluid and 16.4 +/- 9.5 g of sodium (Na). Sodium and fluid intake per hour was estimated to be 0.6 g/hour and 0.7 L/hour, respectively. Electrolyte intake during the first half of the race was similar between those that finished the race and those that did not. Finishers ingested fluid at a greater rate than non-finishers (p = 0.01) and tended to meet their caloric needs more closely than did non-finishers (p = 0.09). Body weight was unchanged over time (ANOVA, p = 0.52). Serum Na concentration tended to fall from 143 to 140 mEq/L during the race (p = 0.06), and was inversely correlated with weight loss (p = 0.009). Serum Na concentration was lower mid-race in runners experiencing changes in mental status than in runners without changes (p = 0.04). Fluid intake was inversely correlated with serum Na concentrations (p = 0.04). Most of the runners experienced nausea or vomiting; these symptoms were not related to serum sodium concentration. Hyponatremia (<135 mEq/L) was seen in one runner at 88 kms, but resolved by 160 km. Urinary sodium excretion decreased (p = 0.002) as serum aldosterone concentration increased pre- to post-race (p < 0.001). From start to finish of the race plasma volume increased by 12%. CONCLUSIONS: Food and fluid was ingested at a greater rate than described previously. Runners consumed adequate fluid to maintain body weight although dietary sodium fell far short of the recommended 1 g/hour. The rate of fluid intake was greater in finishers than in non-finishers, and finishers tended to more nearly meet their energy needs. Maintenance of body mass despite large exercise energy expenditures in extreme heat is consistent with fluid overload during a running event lasting more than 24 hours in hot and humid conditions. SN - 0731-5724 UR - https://www.unboundmedicine.com/medline/citation/12480801/Food_intake_and_electrolyte_status_of_ultramarathoners_competing_in_extreme_heat_ L2 - http://www.tandfonline.com/doi/full/10.1080/07315724.2002.10719254 DB - PRIME DP - Unbound Medicine ER -