Oral Salt Supplementation During Ultradistance Exercise

Speedy, Dale B.; Thompson, John M. D.; Rodgers, Ian; Collins, Malcolm; Sharwood, Karen; Noakes, Timothy D.

doi:10.1097/00042752-200209000-00004

Cited by 88 publications

(83 citation statements)

References 33 publications

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“…7,18,27 In all these studies, drinking sodium-free solutions caused a marked decrease in plasma volume that was possibly more profound than sodium losses, resulting in normal blood sodium during exercise. When sodium was also provided, the conservation of plasma volume prevented an increase in blood sodium.…”

Section: Discussionmentioning

confidence: 94%

“…Vrijens and Rehrer 17 found that sodium-free fluid intake during 3 hours of low-intensity exercise at a rate to match fluid loss decreased plasma sodium compared with ingestion of a carbohydrate-electrolyte drink. However, Speedy et al 18 and Hew-Butler et al 19 reported that large amounts of sodium supplemented in the form of tablets (700 mg/h and 40 tablets that each contained 620 mg of table salt) during the Ironman triathlon did not confer any advantage in the preservation of serum sodium. It is important to note that in these studies, participants had a weight loss of about 4% at the end of the race.…”

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confidence: 99%

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Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss

Anastasiou

Kavouras

Arnaoutis

et al. 2009

Journal of Athletic Training

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Context: Sodium replacement during prolonged exercise in the heat may be critically important to maintaining fluid and electrolyte balance and muscle contractility.Objective: To examine the effectiveness of sodium-containing sports drinks in preventing hyponatremia and muscle cramping during prolonged exercise in the heat.Design: Randomized crossover study.Patients or Other Participants: Thirteen active men. Intervention(s): Participants completed 4 trials of an exercise protocol in the heat (306C) consisting of 3 hours of exercise (alternating 30 minutes of walking and cycling at a heart rate of 130 and 140 beats per minute, respectively); a set of standing calf raises (8 sets of 30 repetitions); and 45 minutes of steep, brisk walking (5.5 km?h 21 on a 12% grade). During exercise, participants consumed fluids to match body mass loss. A different drink was consumed for each trial: carbohydrateelectrolyte drink containing 36.2 mmol/L sodium (HNa), carbohydrate-electrolyte drink containing 19.9 mmol/L sodium (LNa), mineral water (W), and colored and flavored distilled water (PL).Main Outcome Measure(s): Serum sodium, plasma osmolality, plasma volume changes, and muscle cramping frequency.Results: During both HNa and LNa trials, serum sodium remained relatively constant (serum sodium concentration at the end of the protocol was 137.3 mmol/L and 136.7 mmol/L, respectively). However, a clear decrease was observed in W (134.5 6 0.8 mmol/L) and PL (134.4 6 0.8 mmol/L) trials compared with HNa and LNa trials (P , .05). The same trends were observed for plasma osmolality (P , .05). Albeit not significant, plasma volume was preserved during the HNa and LNa trials, but a reduction of 2.5% was observed in the W and PL trials. None of the volunteers experienced cramping.Conclusions: The data suggest that sodium intake during prolonged exercise in the heat plays a significant role in preventing sodium losses that may lead to hyponatremia when fluid intake matches sweat losses.Key Words: endurance, fluid replacement, hydration, hyponatremia, plasma volume, sports drinks Key Points: N Under environmental conditions in which fluid intake matched body mass loss, relatively moderate amounts of sodium added to the hydration solution attenuated the decline in sodium concentration of plasma and preserved plasma volume at pre-exercise levels.N Sodium supplementation did not increase serum sodium even when participants consumed a carbohydrate-electrolyte drink containing 36.2 mmol/L sodium.N A relationship between sodium supplementation and the prevention of exercise-associated muscle cramps cannot be established from the environmental and exercise factors of this study.N Further research using appropriate exercise protocols is needed to clarify the effect of sodium supplementation on the propensity to cramp during exercise.

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Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 99%

Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss

Anastasiou

Kavouras

Arnaoutis

et al. 2009

Journal of Athletic Training

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“…(Hew-Butler et al 2006) or to prevent EAH (Speedy et al 2002). A further limitation was that we did not determine plasma [Na ? ]…”

Section: Limitationsmentioning

confidence: 99%

No case of exercise-associated hyponatraemia in top male ultra-endurance cyclists: the ‘Swiss Cycling Marathon’

Rüst

Knechtle

et al. 2011

Eur J Appl Physiol

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The prevalence of exercise-associated hyponatraemia (EAH) has been investigated in endurance athletes such as runners and Ironman triathletes, but not in ultra-endurance road cyclists. We assessed fluid intake and changes in body mass, urine specific gravity and plasma sodium concentration ([Na(+)]) in 65 ultra-endurance road cyclists in a 720-km ultra-cycling marathon, the 'Swiss Cycling Marathon'. The cyclists lost 1.5 (1.7)% body mass (P < 0.01). No athlete developed EAH. Fluid intake was associated with the change in plasma [Na(+)] (r = -0.32, P < 0.05) and the change in body mass (r = -0.30, P < 0.05). The change in plasma [Na(+)] was related to post-race plasma [Na(+)] (r = 0.63, P < 0.0001). To conclude, ad libitum fluid intake in ultra-endurance cyclists in a single-stage ultra-endurance road cycling race showed no case of EAH. Future studies regarding drinking behaviour in different ultra-endurance disciplines might give insights into why the prevalence of EAH is different in the different disciplines. Abstract The prevalence of exercise-associated hyponatraemia (EAH) has been investigated in endurance athletes such as runners and Ironman triathletes, but not in ultraendurance road cyclists. We assessed fluid intake and changes in body mass, urine specific gravity and plasma sodium concentration ([Na ? ]) in 65 ultra-endurance road cyclists in a 720-km ultra-cycling marathon, the 'Swiss Cycling Marathon'. The cyclists lost 1.5 (1.7)% body mass (P \ 0.01). No athlete developed EAH. Fluid intake was associated with the change in plasma [Na ? ] (r = -0.32, P \ 0.05) and the change in body mass (r = -0.30, P \ 0.05). The change in plasma [Na ? ] was related to post-race plasma [Na ? ] (r = 0.63, P \ 0.0001). To conclude, ad libitum fluid intake in ultra-endurance cyclists in a single-stage ultra-endurance road cycling race showed no case of EAH. Future studies regarding drinking behaviour in different ultra-endurance disciplines might give insights into why the prevalence of EAH is different in the different disciplines.

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“…Currently, there is insufficient evidence to support the suggestion that ingestion of sodium prevents or decreases the risk for EAH; neither is there any evidence that consumption of sports drinks (electrolyte-containing hypotonic fluids) can prevent the development of EAH (1,(35)(36)(37)(38)42,100,101). Again, most commercial sports drinks are hypotonic with a sodium content of 10 to 20 mmol/L (230 to 460 mg/L).…”

Section: Prevention Of Eahmentioning

confidence: 99%

Exercise-Associated Hyponatremia

Rosner

Kirven

2007

Clinical Journal of the American Society of Nephrology

168

165

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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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Oral Salt Supplementation During Ultradistance Exercise

Cited by 88 publications

References 33 publications

Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss

Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss

No case of exercise-associated hyponatraemia in top male ultra-endurance cyclists: the ‘Swiss Cycling Marathon’

Exercise-Associated Hyponatremia

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