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Noakes TD. Is Drinking to Thirst Optimum? ANNALS OF NUTRITION AND METABOLISM 2010; 57 Suppl 2:9-17. [DOI: 10.1159/000322697] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Fluid Intake and Changes in Blood Biochemistry, Running Speed and Body Mass During an 80 km Mountain Trail Race. ACTA ACUST UNITED AC 2009. [DOI: 10.2478/v10036-009-0017-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Knechtle B, Duff B, Welzel U, Kohler G. Body mass and circumference of upper arm are associated with race performance in ultraendurance runners in a multistage race--the Isarrun 2006. RESEARCH QUARTERLY FOR EXERCISE AND SPORT 2009; 80:262-268. [PMID: 19650392 DOI: 10.1080/02701367.2009.10599561] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In the present study, we investigated the association of anthropometric parameters with race performance in ultraendurance runners in a multistage ultraendurance run, in which athletes had to run 338 km within 5 consectitive days. In 17 male successful finishers, calculations of body mass, body height, skinfold thicknesses, extremity circumference, skeletal muscle mass (SM), and percentage body fat (%BF) were performed before the race to correlate anthropometric parameters with race performance. A positive association was shown between total running time and both body mass (r2 = .29, p < .05) and upper arm circumference (r = .23, p < .05). In contrast, body height, skinfold thicknesses, extremity circumference, SM, and %BF showed no association with race performance (p > .05). We concluded that in a multistage ultraendurance run, body mass and upper arm circumference were nega tively associated with race performance in well experienced ultraendurance runners. In contrast, body height, skinfold thicknesses, circumferences of the other extremities, SM, and %BF showed no association with race performance.
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Affiliation(s)
- Beat Knechtle
- St. Gallen Health Center, Vadianstrasse, Switzerland.
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Fluid and food intake during professional men's and women's road-cycling tours. Int J Sports Physiol Perform 2009; 2:58-71. [PMID: 19255455 DOI: 10.1123/ijspp.2.1.58] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
PURPOSE To quantify the fluid and food consumed during a men's and women's professional road-cycling tour. METHODS Eight men (age 25 +/- 5 y, body mass 71.4 +/- 7.4 kg, and height 177.4 +/- 4.5 cm) and 6 women (age 26 +/- 4 y, body mass 62.5 +/- 5.6 kg, and height 170.4 +/- 5.2 cm) of the Australian Institute of Sport Road Cycling squads participated in the study. The men competed in the 6-d Tour Down Under (Adelaide, Australia), and the women, in the 10-d Tour De L'Aude (Aude, France). Body mass was recorded before and immediately after the race. Cyclists recalled the number of water bottles and amount of food they had consumed. RESULTS Men and women recorded body-mass losses of approximately 2 kg (2.8% body mass) and 1.5 kg (2.6% body mass), respectively, per stage during the long road races. Men had an average fluid intake of 1.0 L/h, whereas women only consumed on average 0.4 L/h. In addition, men consumed CHO at the rate suggested by dietitians (average CHO intake of 48 g/h), but again the women failed to reach recommendations, with an average intake of approximately 21 g/h during a road stage. CONCLUSIONS Men appeared to drink and eat during racing in accordance with current nutritional recommendations, but women failed to reach these guidelines. Both men and women finished their races with a body-mass loss of approximately 2.6% to 2.8%. Further research is required to determine the impact of this loss on road-cycling performance and thermoregulation.
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Knechtle B, Knechtle P, Kaul R, Kohler G. No change of body mass, fat mass, and skeletal muscle mass in ultraendurance swimmers after 12 hours of swimming. RESEARCH QUARTERLY FOR EXERCISE AND SPORT 2009; 80:62-70. [PMID: 19408468 DOI: 10.1080/02701367.2009.10599530] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We evaluated whether ultraendurance swimmers suffer a change of body mass, fat mass, skeletal muscle mass, total body water and specific gravity of urine during a 12-hr swim in 12 male Caucasian ultraswimmers. Proton nuclear magnetic resonance of urine samples before and after the race was performed to detect alanine, lactate, and 3-hydroxybutyrate. The 12 swimmers achieved an average distance of 29.4 km (SD = 5.1). No statistically significant changes in body mass, fat mass, skeletal muscle mass, and total body water could be determined (p > .05), but urine gravity decreased significantly (p < .001). Two participants showed increased signals of ketone bodies after the race. In these samples, the hydroxybutyrate-creatinine ratio increased more than tenfold.
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Abstract
OBJECTIVE To understand the urination pattern and to determine the relationships between urine output and performance of ultramarathon runners. DESIGN Prospective observational study. SETTING The 2005 Soochow University international ultramarathon, in which each athlete ran for 12 hours. PARTICIPANTS All entrants in the 12-hour race were invited to participate in the study. INTERVENTIONS None. MAIN OUTCOME MEASURES Athletes were weighed immediately before and after the race. Urine samples were collected during the race and immediately after the race. RESULTS There was a trend toward better performance of the group with less urination (LU), although the difference was not statistically significant. Further analysis of hourly running distances between groups showed better performance in the group with LU during the first 11 hours of the competition. Comparison of athletes in 3 levels of running distance (tertiles) showed statistically significant differences between groups in total urine output. The fastest tertile had lower prerace body weight and greater body weight change than the slowest and intermediate tertiles, but the differences were not statistically significant. Linear regression analysis using the stepwise method showed that total urine output and prerace body weight were negatively associated with performance. CONCLUSIONS Runners with LU had better performance during the first 11 hours of the competition. Linear regression analysis showed that total urine output and prerace body weight were negatively associated with performance.
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Abstract
UNLABELLED Disorders of serum sodium concentration occur commonly in athletes participating in endurance sports. While hypernatremia is the most commonly seen disorder, hyponatremia can occur in 2% to 7% of participants. Hyponatremia is due to a combination of excessive water or hypotonic fluid intake as well as high levels of arginine vasopressin (or anti diuretic hormone), which limits the ability of the kidney to excrete water. Most of these cases are associated with either no or minimal side effects and do not require specific therapy other than close monitoring and fluid restriction. However, a small number of athletes may present with severe and life-threatening hyponatremia associated with cerebral edema and possibly noncardiogenic pulmonary edema. Rapid diagnosis and appropriate therapy of these symptomatic athletes with hypertonic saline is required to prevent severe complications or death. The ability to have rapid on-site measurement of serum sodium concentration greatly facilitates accurate diagnosis and therapy. Prevention is based on widespread education regarding the risks of overhydration and judicious intake of fluids during endurance events. KEYWORDS hyponatremia; cerebral edema; therapy; hypertonic saline.
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Affiliation(s)
- Mitchell H Rosner
- Department of Medicine, University of Virginia Health System, Charlottesville, VA, 22908, USA.
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Knechtle B, Duff B, Amtmann G, Kohler G. An Ultratriathlon Leads to a Decrease of Body Fat and Skeletal Muscle Mass—The Triple Iron Triathlon Austria 2006. Res Sports Med 2008; 16:97-110. [DOI: 10.1080/15438620701878881] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Beat Knechtle
- a Gesundheitszentrum St. Gallen , St. Gallen, Switzerland
- b Department of General Practice , University Hospital Zurich , Zurich, Switzerland
| | - Brida Duff
- a Gesundheitszentrum St. Gallen , St. Gallen, Switzerland
- b Department of General Practice , University Hospital Zurich , Zurich, Switzerland
| | - Gerhard Amtmann
- c Sport Project, Triple Iron Triathlon Moosburg , Kärnten, Austria
| | - Götz Kohler
- d Division of Biophysical Chemistry, Biozentrum, University of Basel , Basel, Switzerland
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Knechtle B, Knechtle P, Schulze I, Kohler G. Upper arm circumference is associated with race performance in ultra-endurance runners. Br J Sports Med 2008; 42:295-9; discussion 299. [PMID: 17599951 DOI: 10.1136/bjsm.2007.038570] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To investigate the association of anthropometric parameters to race performance in ultra-endurance runners in a multistage ultra-endurance run. DESIGN Descriptive field study. SETTING The Deutschlandlauf 2006 race in Germany, where athletes had to run 1200 km within 17 consecutive days. There were no interventions. SUBJECTS In total, there were 19 male Caucasian ultra-endurance runners (mean (SD) 46.2 (9.6) years, 71.8 (5.2) kg, 179 (6) cm, BMI 22.5 (1.9) kg/m(2)). MAIN OUTCOME MEASUREMENTS Determination of body mass, body height, length of lower limbs, skin-fold thicknesses, circumference of limbs, body mass index (BMI), percentage skeletal muscle mass (%SM), and percentage body fat (%BF) in 19 successful finishers in order to correlate anthropometric parameters with running performance. RESULTS A significant association of upper arm circumference with the total running time was found (p<0.05, r2 = 0.26). No significant association was found with the directly measured anthropometric properties body height, body mass, average skin-fold thickness and the circumference of thigh and calf (p>0.05). Furthermore, no significant association was observed between the running time and the calculated parameters BMI, %BF, and %SM (p>0.05). CONCLUSIONS In an ultra-endurance run over 1200 km within 17 consecutive days, circumference of the upper arm was the only factor associated with performance in well-experienced ultra-endurance runners. Body mass, BMI, body height, length of limbs, skin-fold thicknesses, circumference of limbs and the calculated percentage body composition of skeletal muscle mass and body fat showed no association with running performance.
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Affiliation(s)
- B Knechtle
- Gesundheitszentrum St Gallen, St Gallen, Switzerland.
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Abstract
OBJECTIVE The principal objective of this study was to evaluate serial weight changes in athletes during 12- and 24-hour ultra-marathons and to correlate these changes with athletic performance, namely the distance covered. DESIGN This was a prospective study. SETTING The 2003 Soochow University international ultra-marathon. PARTICIPANTS Fifty-two race participants. INTERVENTIONS 12- or 24-hour ultra-marathon. MAIN OUTCOME MEASUREMENTS Body weight changes were measured before, at 4-hour intervals during, and immediately after the 12- and 24-hour races. RESULTS Significant overall decreases in body weight were apparent at the conclusion of both races. The mean relative body weight change after the 12-hour race was -2.89 +/- 1.56%, ranging from 0 to 6.5%. The mean relative body weight change after the 24-hour race was -5.05 +/- 2.28%, ranging from -0.77% to -11.40%. Of runners in the 24-hour race, 26% lost greater than 7% of baseline body weight during the race. During both the 12- and 24-hour races, the greatest weight change (decrease) occurred during the first 4 hours. Weight remained relatively stable after 8 hours, although a further decrease was apparent between 16 and 20 hours in the 24-hour participants. Weight change had no bearing on performance in the 12-hour race, whereas weight loss was positively associated with performance in the 24-hour race. CONCLUSIONS Our findings demonstrate that the majority of weight decrease/dehydration in both the 12- and 24-hour races occurred during the first 8 hours. Hence, to maintain body weight, fluid intake should be optimized in the first 8 hours for both 12- and 24-hour runners and in 16 to 20 hours for 24-hour marathon runners.
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Knechtle B, Duff B, Amtmann G, Kohler G. Cycling and Running Performance, Not Anthropometric Factors, are Associated with Race Performance in a Triple Iron Triathlon. Res Sports Med 2007; 15:257-69. [DOI: 10.1080/15438620701693264] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- B. Knechtle
- a Gesundheitszentrum St. Gallen , St. Gallen, Switzerland
| | - B. Duff
- a Gesundheitszentrum St. Gallen , St. Gallen, Switzerland
| | | | - G. Kohler
- c Division of Biophysical Chemistry, Biozentrum , University of Basel , Basel, Switzerland
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Noakes TD. Drinking guidelines for exercise: what evidence is there that athletes should drink "as much as tolerable", "to replace the weight lost during exercise" or "ad libitum"? J Sports Sci 2007; 25:781-96. [PMID: 17454546 DOI: 10.1080/02640410600875036] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The most recent (1996) drinking guidelines of the American College of Sports Medicine (ACSM) propose that athletes should drink "as much as tolerable" during exercise. Since some individuals can tolerate rates of free water ingestion that exceed their rates of free water loss during exercise, this advice has caused some to overdrink leading to water retention, weight gain and, in a few, death from exercise-associated hyponatraemic encephalopathy. The new drinking guidelines of the International Olympic Committee (IOC), recently re-published in this Journal, continue to argue that athletes must drink enough to replace all their weight lost during exercise and to ingest sodium chloride since sodium is "the electrolyte most critical to performance and health". In this rebuttal to that Consensus Document, I argue that these new guidelines, like their predecessors, lack an adequate, scientifically proven evidence base. Nor have they been properly evaluated in appropriately controlled, randomized, prospective clinical trials. In particular, these new guidelines provide erroneous recommendations on five topics. If novel universal guidelines for fluid ingestion during exercise are to be promulgated by important international bodies including the IOC, they should first be properly evaluated in appropriately controlled, randomized, prospective clinical trials conducted under environmental and other conditions that match those found in "out-of-doors" exercise. This, and the potential influence of commercial interests on scientific independence and objectivity, are the two most important lessons to be learned from the premature adoption of those 1996 ACSM drinking guidelines that are not evidence-based. These concerns need to be addressed before the novel IOC guidelines are accepted uncritically. Otherwise the predictable consequences of the premature adoption of the 1996 ACSM guidelines will be repeated.
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Affiliation(s)
- T D Noakes
- UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Cape Town, South Africa.
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Knechtle B, Knechtle P, Andonie JL, Kohler G. Influence of anthropometry on race performance in extreme endurance triathletes: World Challenge Deca Iron Triathlon 2006. Br J Sports Med 2007; 41:644-8; discussion 648. [PMID: 17556527 PMCID: PMC2465179 DOI: 10.1136/bjsm.2006.035014] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVE To investigate the influence of anthropometric variables on race performance in ultra-endurance triathletes in an ultra-triathlon. DESIGN Descriptive field study. SETTING The "World Challenge Deca Iron Triathlon 2006" in Monterrey, Mexico, in which everyday for 10 consecutive days athletes had to perform the distance of one Ironman triathlon of 3.8 km swimming, 180 km cycling and 42.195 km running. SUBJECTS Eight male ultra-endurance athletes (mean (SD) age 40.6 (10.7) years, weight 76.4 (8.4) kg, height 175 (4) cm and body mass index (BMI) 24.7 (2.2) kg/m2). INTERVENTIONS None. MAIN OUTCOME MEASURES Direct measurement of body mass, height, leg length, skinfold thicknesses, limb circumference and calculation of BMI, skeletal muscle mass (SM), percentage SM (%SM) and percentage body fat (%BF) in order to correlate measured and calculated anthropometric variables with race performance. RESULTS Race time was not significantly (p>0.05) influenced by the directly measured variables, height, leg length, body mass, average skinfold thicknesses, or circumference of thigh, calf or upper arm. Furthermore, no significant (p>0.05) correlation was observed between race time and the calculated variables, BMI, %SM and %BF. CONCLUSIONS In a multistage ultra-triathlon over 10 Ironman triathlon distances in 10 consecutive days, there was no effect of body mass, height, leg length, skinfold thicknesses, limb circumference, BMI, %SM or %BF on race performance in the only eight finishers.
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Hew-Butler T, Collins M, Bosch A, Sharwood K, Wilson G, Armstrong M, Jennings C, Swart J, Noakes T. Maintenance of plasma volume and serum sodium concentration despite body weight loss in ironman triathletes. Clin J Sport Med 2007; 17:116-22. [PMID: 17414479 DOI: 10.1097/jsm.0b013e3180326836] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To examine the relationship between body weight, plasma volume, and serum sodium concentration ([Na]) during prolonged endurance exercise. DESIGN Observational field study. SETTINGS 2000 South African Ironman Triathlon. PARTICIPANTS 181 male triathletes competing in an Ironman triathlon. MAIN OUTCOME MEASURES Body weight, plasma volume, and serum ([Na]) change from pre- to postrace. RESULTS Significant body weight loss occurred (-4.9 +/- 1.7%; P < 0.0001), while both plasma volume (1.0 +/- 11.2%; P = 0.4: NS) and serum [Na] (0.6 +/- 2.4%; P < 0.001) increased from pre- to postrace. Blood volume (-0.6 +/- 6.6%) and red cell volume (-2.6 +/- 5.5%; P < 0.001) decreased in conjunction with the body weight loss. There was a strong correlation between blood and plasma volume change, both as a percentage, and absolute change in fluid volume (r = 0.9; P < 0.001). Body weight change was positively correlated with plasma volume change (r = -0.4; P < 0.001), but inversely correlated with serum [Na] change (r = -0.4; P < 0.001). Plasma volume change was not significantly correlated with serum [Na] change (r = 0.0; NS). Serum [Na] change was inversely correlated with both percentage of red cell volume change (r = -0.2; P < 0.05) and percentage body weight change (r = -0.4; P < 0.001). CONCLUSION Plasma volume and serum [Na] were maintained in male Ironman triathletes, despite significant (5%) body weight loss during the course of the race. Body weight was not an accurate "absolute" surrogate of fluid balance homeostasis during prolonged endurance exercise. Clinicians should be warned against viewing these three regulatory parameters as interchangeable during an Ironman triathlon.
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Affiliation(s)
- Tamara Hew-Butler
- University of Capetown/Medical Research Council Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, South Africa.
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Dumke CL, Nieman DC, Oley K, Lind RH. Ibuprofen does not affect serum electrolyte concentrations after an ultradistance run. Br J Sports Med 2007; 41:492-6; discussion 496. [PMID: 17331976 PMCID: PMC2465418 DOI: 10.1136/bjsm.2006.033597] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To determine the effects of ibuprofen on serum electrolyte concentrations after a 160 km running race. METHODS Twenty nine subjects (mean (SD) age 47.9 (7.4) years) ingested 600 mg ibuprofen the day before, and 1200 mg ibuprofen during, a 160 km competitive trail running race (approximately every 4 h in 200 mg doses). Twenty five control subjects (mean (SD) age 46.8 (10.3) years) avoided ingestion of ibuprofen before or during the race. Blood was drawn on the day before the race and immediately after the race. Serum biochemical profiles were analysed by a clinical laboratory. Significant effects of treatment and time were determined with a general linear model with repeated measures. RESULTS Subjects in the two groups did not differ by age, training volume, race experience, body mass index, body fat, or finishing time (25.8 (3.3) vs 25.6 (3.9) h). Body weight did not change significantly over the race (measured before, mid-race (90 km), and after). Ibuprofen ingestion did not significantly affect any of the serum markers including creatine kinase (p = 0.16). A significant decrease in serum sodium (p = 0.006), potassium (p = 0.001), chloride (p<0.001), calcium (p<0.001), albumin (p<0.001) and globulin (p<0.001) was observed after the race. Increases were seen in creatine kinase (p<0.001), creatinine (p<0.001), blood urea nitrogen (p<0.001), uric acid (p<0.001) and glucose (p<0.001) as the result of the race. CONCLUSIONS These data suggest that the non-specific cyclo-oxygenase inhibitor, ibuprofen, does not alter serum electrolyte concentrations during ultradistance running. However, the stress of ultradistance running appears to be related to significant changes in certain serum markers.
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Affiliation(s)
- Charles L Dumke
- Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone, NC 28608, USA.
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Abstract
Exercise-associated hyponatremia has been described after sustained physical exertion during marathons, triathlons, and other endurance athletic events. As these events have become more popular, the incidence of serious hyponatremia has increased and associated fatalities have occurred. The pathogenesis of this condition remains incompletely understood but largely depends on excessive water intake. Furthermore, hormonal (especially abnormalities in arginine vasopressin secretion) and renal abnormalities in water handling that predispose individuals to the development of severe, life-threatening hyponatremia may be present. This review focuses on the epidemiology, pathogenesis, and therapy of exercise-associated hyponatremia.
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Affiliation(s)
- Mitchell H Rosner
- Division of Nephrology, Department of Internal Medicine, University of Virginia Health System, Charlottesville, VA 22908, USA.
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Sanchez LD, Corwell B, Berkoff D. Medical problems of marathon runners. Am J Emerg Med 2006; 24:608-15. [PMID: 16938602 DOI: 10.1016/j.ajem.2006.01.023] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2006] [Accepted: 01/22/2006] [Indexed: 11/22/2022] Open
Abstract
Several organ systems can be affected by marathon running. Acute musculoskeletal injuries are common, but running does not result in increased rates of musculoskeletal disability. Gastrointestinal complaints are also common among runners; some of these complaints are explained by the decreased mesenteric blood flow during exercise. Although cardiac events are rare, they can be devastating. Symptomatic hyponatremia is another serious but mostly preventable problem.
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Affiliation(s)
- Leon D Sanchez
- Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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Saunders CJ, de Milander L, Hew-Butler T, Xenophontos SL, Cariolou MA, Anastassiades LC, Noakes TD, Collins M. Dipsogenic genes associated with weight changes during Ironman Triathlons. Hum Mol Genet 2006; 15:2980-7. [PMID: 16950802 DOI: 10.1093/hmg/ddl240] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Thirst is regulated by a complex interaction of signalling pathways within the central nervous system, including components of the renin-angiotensin and kalikrein kinin systems, as well as the serotonergic pathways. The aim of this study was to determine whether there were any associations between polymorphisms within the ACE, BDKRB2, NOS3 and/or 5-HTT genes with weight changes during the 2000 and 2001 226 km South African Ironman Triathlons. Pre- and post-race serum [Na(+)] and body weights, as well as genotype data, were collected from 428 (61.1%) Caucasian male triathletes who were divided into three groups according to their relative weight loss during the triathlon (0-3, 3-5 and >5%). There was a significant linear trend for the distribution of both the BDKRB2 +9/+9 genotype and the 5-HTT SS genotype between the three weight loss groups, with the >5% group having the highest percentage of athletes with the +9/+9 genotype (chi(2)=5.3, P=0.021) and the highest percentage of athletes with the SS genotype (chi(2)=5.8, P=0.016). Likewise, the >5% group had the highest percentage of athletes with the combined SS 5-HTT and/or +9/+9 BDKRB2 genotypes (chi(2)=7.4, P=0.007). In conclusion, the functional SS genotype of the serotonin transporter-linked polymorphic region (5-HTTLPR) within the 5-HTT gene and the functional +9/+9 genotype of the BDKBR2 gene were associated with larger weight losses during the Ironman Triathlons. These findings suggest the involvement of the serotonergic pathways in the control of thirst and drinking behaviour and provide further evidence for the dipsogenic effect of circulating bradykinin.
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Affiliation(s)
- Colleen J Saunders
- Medical Research Council of South Africa, MRC/UCT Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Newlands 7725, South Africa
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71
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Noakes TD, Speedy DB. Case proven: exercise associated hyponatraemia is due to overdrinking. So why did it take 20 years before the original evidence was accepted? Br J Sports Med 2006; 40:567-72. [PMID: 16799109 PMCID: PMC2564296 DOI: 10.1136/bjsm.2005.020354] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- T D Noakes
- Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Newlands, South Africa.
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72
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Laursen PB, Suriano R, Quod MJ, Lee H, Abbiss CR, Nosaka K, Martin DT, Bishop D. Core temperature and hydration status during an Ironman triathlon. Br J Sports Med 2006; 40:320-5; discussion 325. [PMID: 16556786 PMCID: PMC2577528 DOI: 10.1136/bjsm.2005.022426] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Numerous laboratory based studies have documented that aggressive hydration strategies (approximately 1-2 litres/h) are required to minimise a rise in core temperature and minimise the deleterious effects of hyperthermia on performance. However, field data on the relations between hydration level, core body temperature, and performance are rare. OBJECTIVE To measure core temperature (Tcore) in triathletes during a 226 km Ironman triathlon, and to compare Tcore with markers of hydration status after the event. METHOD Before and immediately after the 2004 Ironman Western Australia event (mean (SD) ambient temperature 23.3 (1.9) degrees C (range 19-26 degrees C) and 60 (14)% relative humidity (44-87%)) body mass, plasma concentrations of sodium ([Na+]), potassium ([K+]), and chloride ([Cl-]), and urine specific gravity were measured in 10 well trained triathletes. Tcore was measured intermittently during the event using an ingestible pill telemetry system, and heart rate was measured throughout. RESULTS Mean (SD) performance time in the Ironman triathlon was 611 (49) minutes; heart rate was 143 (9) beats/min (83 (6)% of maximum) and Tcore was 38.1 (0.3) degrees C. Body mass significantly declined during the race by 2.3 (1.2) kg (-3.0 (1.5)%; p < 0.05), whereas urine specific gravity significantly increased (1.011 (0.005) to 1.0170 (0.008) g/ml; p < 0.05) and plasma [Na+], [K+], and [Cl-] did not change. Changes in body mass were not related to finishing Tcore (r = -0.16), plasma [Na+] (r = 0.31), or urine specific gravity (r = -0.37). CONCLUSION In contrast with previous laboratory based studies examining the influence of hypohydration on performance, a body mass loss of up to 3% was found to be tolerated by well trained triathletes during an Ironman competition in warm conditions without any evidence of thermoregulatory failure.
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Affiliation(s)
- P B Laursen
- School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.
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Walpole B, Noakes TD, Collins M. Growth hormone 1 (GH1) gene and performance and post-race rectal temperature during the South African Ironman triathlon. Br J Sports Med 2006; 40:145-50; discussion 145-50. [PMID: 16432002 PMCID: PMC2492039 DOI: 10.1136/bjsm.2005.020669] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Some studies have suggested that the insertion allele of the ACE gene is associated with endurance performance, including the Ironman triathlon. It is possible that this association is due to genetic linkage between the ACE I/D locus and the T/A variant in intron 4 of the neighbouring GH1 gene. The A variant is associated with lower levels of growth hormone production. Growth hormone has multiple effects, especially on metabolism during exercise and recovery from exercise. Its production during exercise has also been shown to stimulate sweat rate and heat loss. OBJECTIVE To determine whether the GH1 gene is associated with the performance and/or post-race rectal temperatures of competitors in the South African Ironman triathlon. METHODS A total of 169 of the fastest finishing white male triathletes who completed the 2000 and/or 2001 South African Ironman triathlon and 155 control subjects were genotyped for the T/A variant in the GH1 gene. Post-race rectal temperature was also determined in 103 of these triathletes. RESULTS There was no significant difference in the frequency of this polymorphism in the GH1 gene when the fastest finishing triathletes were compared with the control subjects. Post-race rectal temperatures were, however, significantly higher in those triathletes with an AA genotype (mean (SD) 37.7 (0.8) degrees C) compared with those with a TT genotype (37.2 (0.8) degrees C) (p = 0.019). CONCLUSIONS The T/A polymorphism in intron 4 of the GH1 gene was not associated with performance of the fastest finishers of the South African Ironman triathlon. Post-race rectal temperatures were, however, significantly higher in the fastest finishing athletes, who were homozygous for a GH1 genotype associated with lower growth hormone production.
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Affiliation(s)
- B Walpole
- UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Cape Town, South Africa
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74
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Noakes TD, Sharwood K, Speedy D, Hew T, Reid S, Dugas J, Almond C, Wharam P, Weschler L. Three independent biological mechanisms cause exercise-associated hyponatremia: evidence from 2,135 weighed competitive athletic performances. Proc Natl Acad Sci U S A 2005; 102:18550-5. [PMID: 16344476 PMCID: PMC1311740 DOI: 10.1073/pnas.0509096102] [Citation(s) in RCA: 236] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Indexed: 11/18/2022] Open
Abstract
To evaluate the role of fluid and Na+ balance in the development of exercise-associated hyponatremia (EAH), changes in serum Na+ concentrations ([Na+]) and in body weight were analyzed in 2,135 athletes in endurance events. Eighty-nine percent of athletes completed these events either euhydrated (39%) or with weight loss (50%) and with normal (80%) or elevated (13%) serum [Na+]. Of 231 (11%) athletes who gained weight during exercise, 70% were normonatremic or hypernatremic, 19% had a serum [Na+] between 129-135 mmol/liter, and 11% a serum [Na+] of <129 mmol/liter. Serum [Na+] after racing was a linear function with a negative slope of the body weight change during exercise. The final serum [Na+] in a subset of 18 subjects was predicted from the amount of Na+ that remained osmotically inactive at the completion of the trial. Weight gain consequent to excessive fluid consumption was the principal cause of a reduced serum [Na+] after exercise, yet most (70%) subjects who gained weight maintained or increased serum [Na+], requiring the addition of significant amounts of Na+ (>500 mmol) into an expanded volume of total body water. This Na+ likely originated from osmotically inactive, exchangeable stores. Thus, EAH occurs in athletes who (i) drink to excess during exercise, (ii) retain excess fluid because of inadequate suppression of antidiuretic hormone secretion, and (iii) osmotically inactivate circulating Na+ or fail to mobilize osmotically inactive sodium from internal stores. EAH can be prevented by insuring that athletes do not drink to excess during exercise, which has been known since 1985.
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Affiliation(s)
- T D Noakes
- University of Cape Town/Medical Research Council Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town/Sports Science Institute of South Africa, Newlands, 7700, South Africa.
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75
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Gratze G, Rudnicki R, Urban W, Mayer H, Schlögl A, Skrabal F. Hemodynamic and autonomic changes induced by Ironman: prediction of competition time by blood pressure variability. J Appl Physiol (1985) 2005; 99:1728-35. [PMID: 16002770 DOI: 10.1152/japplphysiol.00487.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that the extreme endurance exercise of an Ironman competition would lead to long-standing hemodynamic and autonomic changes. We investigated also the possibility of predicting competition performance from baseline hemodynamic and autonomic parameters. We have investigated 27 male athletes before competition, 1 h after, and then for the following week after the competition. The Task Force monitor was used to measure beat-to-beat hemodynamic and autonomic parameters during supine rest and active standing. Heart rate ( P < 0.001) was increased, and stroke index ( P = 0.011), systolic blood pressure ( P = 0.004), diastolic blood pressure ( P < 0.001), total peripheral resistance index ( P < 0.001), and baroreceptor reflex sensitivity ( P < 0.001) were decreased after the competition. The 0.05- to 0.17-Hz band of heart rate and blood pressure variability was increased ( P < 0.001 and P < 0.001, respectively), the 0.17- to 0.40-Hz band of heart rate interval variability was decreased after the competition ( P < 0.001). All parameters returned to baseline values 3 days after the competition. After the competition, the autonomic response to orthostasis was significantly impaired. The 0.05- to 0.17-Hz band of diastolic blood pressure variability before competition and weekly net exercise training, but not the other hemodynamic and autonomic parameters, were related to competition time in multivariate regression analysis (multiple r = 0.70, P < 0.001). The marked hemodynamic and autonomic changes after an ultraendurance race, which are compatible with myocardial depression in the face of sympathetic activation and reduction of afterload, return to baseline after only 1–3 days. Because the 0.05- to 0.17-Hz band of diastolic blood pressure variability contributes to the prediction of competition time, the analysis of blood pressure variability in the frequency domain deserves further study for the prediction of endurance capacity.
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Affiliation(s)
- Gerfried Gratze
- Department of Internal Medicine, Krankenhaus Barmherzige Brüder, Marschallgasse, Teaching Hospital, Medical University, Graz, Austria
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76
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Sulzer NU, Schwellnus MP, Noakes TD. Serum Electrolytes in Ironman Triathletes with Exercise-Associated Muscle Cramping. Med Sci Sports Exerc 2005; 37:1081-5. [PMID: 16015122 DOI: 10.1249/01.mss.0000169723.79558.cf] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE To compare serum electrolyte concentrations of cramping and control Ironman triathletes. METHODS Triathletes suffering from acute exercise-associated muscle cramping (EAMC) after the 2000 South African Ironman Triathlon formed the cramping group (CR, N = 11). Non-cramping triathletes matched for race finishing time and body mass formed the control group (CON, N = 9). All subjects were weighed at race start and immediately post-race. Blood samples were drawn from both groups during recovery for the analysis of serum magnesium, glucose, sodium, potassium and chloride concentrations. Hemoglobin concentration and hematocrit were also measured. Surface electromyography (EMG) (mV) was recorded from a non-cramping control muscle (triceps) and the most severely cramping lower limb muscle of the CR group. EMG was recorded at the beginning of every minute for a 10-min period during recovery. RESULTS There were no significant differences between the groups for body mass or percent body mass loss during the race. Post-race sodium concentration was significantly lower (P = 0.01) in the CR group than the CON group (140 +/- 2 vs 143 +/- 3 mmol.L) but was within the normal clinical range of post-race serum sodium concentrations. There were no significant differences between the two groups for post-race serum electrolytes, glucose, hemoglobin concentrations or hematocrit. Surface EMG (mV) was significantly higher (P < 0.05) in the cramping muscles than the control muscle of the CR group at 0, 3, 4, and 5 min of the 10-min recording period. CONCLUSION Acute EAMC in ironman triathletes is not associated with a greater percent body mass loss or clinically significant differences in serum electrolyte concentrations. The increased EMG activity of cramping muscles may reflect increased neuromuscular activity.
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Affiliation(s)
- Nicole U Sulzer
- UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, South Africa
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77
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Abstract
Ultra-endurance competition is defined as events that exceed than 6 hours in duration. The longer events rely on long-term preparation, sufficient nutrition, accommodation of environmental stressors, and psychologic toughness. Successful ultra-endurance performance is characterized by the ability to sustain a higher absolute speed for a given distance than other competitors. This can be achieved through a periodized training plan and by following key principles of training. Periodization is an organization of training into large, medium and small training blocks which are referred to as macro-, meso-, and microcycles, respectively. When the sequencing of training is correctly applied, athletes can achieve a high state of competition readiness and during the months of hard training, avoid the overtraining syndrome. A plan is executed in accordance with the following principles of training: all-around development, overload, specificity, individualization, consistent training, and structural tolerance. Training relies heavily on the athlete's tolerance to repetitive strain. Today's ultra-endurance athlete must also follow appropriate nutritional practices in order to recover and prepare for daily training and remain injury free and healthy. Rehydration after exercise, together with the timing and method of increased food intake to cope with heavy training, are essential for optimal performance. Furthermore, the treatment of soft tissue after training or racing is necessary to control inflammation.
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Affiliation(s)
- Calvin Zaryski
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 2N4, Canada
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78
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Saunders AG, Dugas JP, Tucker R, Lambert MI, Noakes TD. The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment. ACTA ACUST UNITED AC 2005; 183:241-55. [PMID: 15743384 DOI: 10.1111/j.1365-201x.2004.01400.x] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The purposes of this study were to determine (i) the effects of different facing air velocities on body temperature and heat storage during exercise in hot environmental conditions and (ii) the effects of ingesting fluids at two different rates on thermoregulation during exercise in hot conditions with higher air velocities. METHODS On five occasions nine subjects cycled for 2 h at 33.0 +/- 0.4 degrees C with a relative humidity of 59 +/- 3%. Air velocity was maintained at 0.2 km h(-1) (0 WS), 9.9 +/- 0.3 km h(-1) (10 WS), 33.3 +/-2.2 km h(-1) (100 WS) and 50.1 +/- 3.2 km h(-1) (150 WS) while subjects replaced 58.8 +/- 6.8% of sweat losses. In the fifth condition, air velocity was maintained at 33.7 +/- 2.2 km h(-1) and subjects replaced 80.0 +/- 6.8% of sweat losses (100.80 WS). RESULTS Heat storage, body temperature and rating of perceived exertion were higher in 0 and 10 WS compared with all other conditions. There were no differences in any measured variable between 100 and 150 WS, or between 100 and 100.80 WS. Thus, the evaporative capacity of the environment is increased with higher air velocities, reducing heat storage and body temperature. At higher air velocities, a higher rate of fluid ingestion did not influence heat storage, body temperature or sweat rate. CONCLUSION The finding of previous laboratory studies showing a beneficial effect of high rates of fluid ingestion on thermoregulation during exercise in hot, humid, windstill conditions cannot be extrapolated to out-of-doors exercise in which facing air velocities are seldom lower than the athlete's rate of forward progression.
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Affiliation(s)
- A G Saunders
- Department of Human Biology, UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Sports Science Institute of South Africa, Newlands 7725, South Africa
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Sharwood KA, Collins M, Goedecke JH, Wilson G, Noakes TD. Weight changes, medical complications, and performance during an Ironman triathlon. Br J Sports Med 2005; 38:718-24. [PMID: 15562165 PMCID: PMC1724978 DOI: 10.1136/bjsm.2003.007187] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Subjects exercising without fluid ingestion in desert heat terminated exercise when the total loss in body weight exceeded 7%. It is not known if athletes competing in cooler conditions with free access to fluid terminate exercise at similar levels of weight loss. OBJECTIVES To determine any associations between percentage weight losses during a 224 km Ironman triathlon, serum sodium concentrations and rectal temperatures after the race, and prevalence of medical diagnoses. METHODS Athletes competing in the 2000 and 2001 South African Ironman triathlon were weighed on the day of registration and again immediately before and immediately after the race. Blood pressure and serum sodium concentrations were measured at registration and immediately after the race. Rectal temperatures were also measured after the race, at which time all athletes were medically examined. Athletes were assigned to one of three groups according to percentage weight loss during the race. RESULTS Body weight was significantly (p<0.0001) reduced after the race in all three groups. Serum sodium concentrations were significantly (p<0.001) higher in athletes with the greatest percentage weight loss. Rectal temperatures were the same in all groups, with only a weak inverse association between temperature and percentage weight loss. There were no significant differences in diagnostic indices of high weight loss or incidence of medical diagnoses between groups. CONCLUSIONS Large changes in body weight during a triathlon were not associated with a greater prevalence of medical complications or higher rectal temperatures but were associated with higher serum sodium concentrations.
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Affiliation(s)
- K A Sharwood
- UCT/MRC Research Unit for Exercise Science and Sports Medicine, P O Box 115, Newlands 7725, Cape Town, South Africa.
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80
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Abstract
In 1958, Edelman and colleagues empirically showed plasma sodium concentration ([Na+]p) to be primarily a function of the sum of exchangeable sodium and potassium (E) divided by total body water (TBW). Based on Edelman's equation, Nguyen and Kurtz derived an equation to show how [Na+]p changes as a function of TBW, change in TBW (DeltaTBW), and change in the sum of exchangeable sodium and potassium (DeltaE). Using the Nguyen-Kurtz equation, the present study examines the sensitivity of [Na+]p to these parameters: [Na+]p is very sensitive to DeltaTBW and moderately sensitive to DeltaE, and is modulated by TBW. For example, for a person with 50 L TBW, a net increase of 1L water lowers [Na+]p by 3.2 mEq/L, but for a person with 25 L TBW it lowers [Na+]p by 6.3 mEq/L (assuming initial [Na+]p is 140 mEq/L). In each case, a loss of 159 mEq of sodium plus potassium (roughly equivalent to 1.5 teaspoons of table salt) would be required to produce the same effect as the net increase of 1 L water. The present review demonstrates why fluid overload predominates over electrolyte loss in the aetiology of exercise-associated hyponatraemia (EAH), and why the excretion of electrolyte-dilute urine is highly effective in correcting EAH (nonetheless, loss of sodium and potassium is significant in long events in warm weather). Sports drinks will, if overconsumed, result in hyponatraemia. Administration of a sports drink to an athlete with fluid overload hyponatraemia further lowers [Na+]p and increases fluid overload. Administration of either a sports drink or normal (0.9%) saline increases fluid overload.
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81
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Reid SA, Speedy DB, Thompson JMD, Noakes TD, Mulligan G, Page T, Campbell RGD, Milne C. Study of hematological and biochemical parameters in runners completing a standard marathon. Clin J Sport Med 2004; 14:344-53. [PMID: 15523206 DOI: 10.1097/00042752-200411000-00004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To study hematological and biochemical parameters prospectively in runners completing a standard 42.2-km marathon run. To determine the incidence of hyponatremia in runners, and whether consumption of nonsteroidal anti-inflammatory medications (NSAIDs) was associated with alterations in serum biochemical parameters. DESIGN Observational cohort study. SETTING City of Christchurch (New Zealand) Marathon, June 2002. PARTICIPANTS One hundred fifty-five of the 296 athletes entered in the 2002 City of Christchurch Marathon were enrolled in the study. MAIN OUTCOME MEASURES Athletes were weighed at race registration and immediately after the race. Blood was drawn postrace for measurement of serum sodium, potassium, creatinine, and urea concentrations and for hematological analysis (hemoglobin concentration, hematocrit, leukocyte distribution). RESULTS Complete data sets including prerace and postrace weights, and postrace hematological and biochemical analyses were collected on 134 marathon finishers. Postrace serum sodium concentrations were directly related to changes in body weight (P < 0.0001). There were no cases of biochemical or symptomatic hyponatremia. Thirteen percent of runners had taken an NSAID in the 24 hours prior to the race. Mean values for serum creatinine (P = 0.03) and serum potassium (P = 0.007) concentrations were significantly higher in runners who had taken an NSAID. No athlete who had taken an NSAID had a postrace serum creatinine concentration less than 0.09 mmol/L. Ninety-eight percent of runners had a postrace leukocytosis (mean white cell count, 18.97 b/L), of which the major component was a raised neutrophil count (mean neutrophil count, 15.69 b/L). CONCLUSIONS This study found no cases of hyponatremia in runners completing a standard distance marathon. This finding relates to a marathon run under ideal conditions (minimal climatic stress) and in which there were fewer aid stations (every 5 km) than is common in North American marathons (every 1.6 km). Also, aggressive hydration practices were not promoted. Consumption of NSAIDs in the 24 hours prior to distance running was associated with altered renal function.
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82
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Collins M, Xenophontos SL, Cariolou MA, Mokone GG, Hudson DE, Anastasiades L, Noakes TD. The ACE Gene and Endurance Performance during the South African Ironman Triathlons. Med Sci Sports Exerc 2004; 36:1314-20. [PMID: 15292738 DOI: 10.1249/01.mss.0000135779.41475.42] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE Several studies have suggested that the insertion (I) variant rather than the deletion (D) variant of the human angiotensin-converting enzyme (ACE) gene is associated with elite endurance performance. The aim of this study was to determine whether the ID polymorphism is associated with the performance of the fastest finishers of the South African Ironman Triathlons. METHODS A total of 447 Caucasian male triathletes of a variety of nationalities and athletic ability who completed either the 2000 or 2001 South African Ironman Triathlons and 199 Caucasian male control subjects were genotyped for the ACE ID polymorphism. RESULTS There was a significantly higher frequency of the I allele in the fastest 100 South African-born finishers (103 I, 51.5% and 97 D, 48.5%) compared with the 166 South African-born control subjects (140 I, 42.2% and 192 D, 57.8%) (P = 0.036). There was also a significant linear trend for the allele distribution among the fastest 100 finishers (I allele = 51.5%), slowest 100 finishers (I allele = 47.5%), and control (I allele = 42.2%) South African-born subjects (P = 0.033). There was, however, no significant difference in the ACE genotype or allele frequencies when athletes born outside South Africa were analyzed. CONCLUSION To our knowledge this is the first study that has examined the effect of an athlete's ACE genotype on their actual performance during an ultra-endurance race. The I allele of the ACE gene was associated with the endurance performance of the fastest 100 South African-born finishers in these triathlons.
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Affiliation(s)
- Malcolm Collins
- UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, South Africa.
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83
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Abstract
During endurance exercise, about 75% of the energy produced from metabolism is in the form of heat, which cannot accumulate. The remaining 25% of energy available can be used for movement. As running pace increases, the rate of heat production increases. Also, the larger one's body mass, the greater the heat production at a particular pace. Sweat evaporation provides the primary cooling mechanism for the body, and for this reason athletes are encouraged to drink fluids to ensure continued fluid availability for evaporation and circulatory flow to the tissues. Elite level runners could be in danger of heat illness if they race too quickly in hot/humid conditions and may collapse at the end of their event. Most marathon races are scheduled at cooler times of the year or day, however, so that heat loss to the environment is adequate. Typically, this postrace collapse is due simply to postural hypotension from decreased skeletal muscle massage of the venous return circulation to the heart on stopping. Elite athletes manage adequate hydration by ingesting about 200-800 mL/hour, and such collapse is rare. Athletes "back in the pack" are moving at a much slower pace, however, with heat accumulation unlikely and drinking much easier to manage. They are often urged to drink "as much as tolerable," ostensibly to prevent dehydration from their hours out on the race course. Excessive drinking among these participants can lead to hyponatremia severe enough to cause fatalities. A more reasonable approach is to urge these participants not to drink as much as possible but to drink ad libitum (according to the dictates of thirst) no more than 400-800 mL/hour.
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Affiliation(s)
- Tim Noakes
- The MRC/UCT Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, South Africa
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84
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Abstract
PURPOSE OF REVIEW Despite much current debate regarding central and peripheral neural mechanisms which may be responsible for the onset of fatigue during prolonged exercise, maintenance of nutritional and hydration status remains critical for successful participation in ultra-endurance exercise. This review focuses on substrate and fluid homeostasis during ultra-endurance exercise and the use of nutritional supplementation both as ergogenic aid and to attenuate exercise-induced immunosuppression. RECENT FINDINGS Current evidence continues to support mandatory high carbohydrate intakes (1). before the event to maximize muscle glycogen stores, (2). during the event to prevent hypoglycaemia and (3). after the event to optimize post-event repletion of endogenous carbohydrate stores. No consistent performance benefit has yet been shown following a high-fat diet. Greater utilization of intrafascicular triglyceride stores appears to account for additional fat utilization in females. Recent trends towards excessive fluid intake have resulted in frequent reports of hyponatraemic hyperhydration in ultra-distance athletes, with greater incidence in women than in men. Carbohydrate supplementation during the event attenuates immunosuppressive hormonal and cytokine responses to ultra-endurance exercise, but may impair vitamin C absorption, while the ergogenic value of caffeine supplementation in ultra-endurance performance is currently being questioned. SUMMARY Meeting macronutrient and fluid intake demands remains an important priority for ultra-endurance athletes. Yet these athletes are reported to present with a high incidence of disordered eating patterns during periods of training, and excessive fluid replacement strategies have resulted in an increased incidence of water intoxication with resultant central nervous system dysfunction.
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Affiliation(s)
- Edith M Peters
- Department of Physiology, Nelson Mandela Faculty of Health Sciences, University of Natal, Durban, South Africa.
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85
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Puddu P, Ventrice C, Pennasilico G, Guarnaccia G, Ruffelli M, Di Pietro A, De Pità O. An Open Randomized Controlled Study on the Efficacy of Low-Sodium Water Intake Evaluated by Non-Invasive Methods in Patients with Cellulite. EUR J INFLAMM 2003. [DOI: 10.1177/1721727x0300100109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Cellulite is the result of complex physiological changes of the subcutaneous fat layer and of microcirculation, clinically manifesting as orange peel skin especially in women and involving thighs, buttocks, and abdomen. An adequate water intake has been suggested to be helpful in controlling the development and worsening of the disease. An open randomized controlled study has been performed to evaluate modification induced by an adequate diet associated to low-sodium or high-sodium water intake on some clinical features of patients affected with mild to moderate cellulite. Non-invasive instrumental investigations (Bioelectrical Impedance Analysis (BIA), thermography and skin echography) were used before and after dietary treatment. A significant improvement of the disease, in terms of weight loss, cutaneous microcirculation and reduction of subcutaneous fat layer, was observed in the group of patients who underwent low-sodium water intake. An adequate dietary treatment associated to a low-sodium water intake is able to efficiently controll some biological and clinical parameters of mild to moderate cellulite.
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Affiliation(s)
| | | | - G. Pennasilico
- Division of Radiology, Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Rome
| | - G. Guarnaccia
- Division of Internal Medicine, Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Rome
| | | | - A. Di Pietro
- Dermatology Service, L. Marchesi Hospital, Inzago, Italy
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