In 2007, the ACSM updated its position stand on “exercise and fluid replacement” under lead author Michael Sawka. In the decade prior, documented cases of athletes dying from exercise-associated hyponatremic encephalopathy (EAHE) were linked to the ACSM’s 1996 position stand which encouraged athletes to drink “as much as tolerable” as well as to Gatorade advertisements like this one, which encouraged drinking potentially fatal quantities of fluid.
Yet the ACSM and Gatorade Sports Science Institute’s current hydration guidelines do not encourage athletes to limit fluid consumption by drinking based on thirst. The justification for this appears to be the belief that dehydration is a causal factor in heat stroke. Gatorade itself has perpetuated this misconception, but case studies of heat-stroke victims suggests this assumption is questionable at best. (source 1, 2)
Instead, the ACSM and GSSI are promoting the idea that electrolyte-enhanced fluids can help prevent hyponatremia. The ACSM’s 1996 position stand speculated that
“Inclusion of sodium (0.5–0.7 g ⋅ l–1 of water) in the rehydration solution ingested during exercise lasting longer than 1 h is recommended since it may be advantageous in enhancing palatability, promoting fluid retention, and possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid.” (my emphasis)
Rather than working to limit the quantity of fluid ingested to prevent EAHE deaths, the ACSM seems principally concerned with speculating, without research citation, about the possible benefits of drinking Gatorade, the product of their platinum sponsor.
ACSM’s 2007 position stand abandons this language, and instead states that:
“Consumption of beverages containing electrolytes and carbohydrates can help sustain fluid-electrolyte balance and exercise performance.”
Note that the ACSM now presents this concept as established fact, yet they don’t present a citation. The message is clear: consuming electrolyte-enhanced fluids can prevent serum sodium (Na) deficiencies associated with EAHE.
This message becomes even more transparent as the position stand attempts to exclusively link hyponatremia to the ingestion of hypotonic solutions. Tonicity is a term that describes the concentration of a solution on both sides of a semipermeable membrane. When this concept is extended to beverages, plain water is considered hypotonic because it has a lesser concentration of solutes than would be expected inside normal human cells. Gatorade, because it contains electrolytes and CHO, is considered isotonic.
The ACSM’s 2007 position stand states:
“In marathoners, symptomatic hyponatremia is more likely to occur in smaller and less lean individuals who run slowly, sweat less, and drink heavily-water and other hypotonic fluids before, during, and after the race (4,46,71).” (my emphasis)
Gatorade is marketed as an isotonic beverage (source). In other words, this statement is implying that excess water consumption is the cause of hyponatremia, not excess Gatorade consumption.
Yet a careful analysis of the citations provided shows that they do not support the conclusion that hyponatremia is caused by excess “hypotonic” fluid at the exclusion of “isotonic” fluid.
1. Citation “4” is a study titled Hyponatremia among Runners in the Boston Marathon. This study found that 13% of finishers of the 2002 Boston Marathon were hyponatremic, and concludes quite clearly that “Considerable weight gain while running, a long racing time, and body-mass-index extremes were associated with hyponatremia, whereas female sex, composition of fluids ingested… were not.” (my emphasis)
2. Citation “46” is a study titled Exercise-associated hyponatremia in marathon runners: a two-year experience. It doesn’t support the ACSM’s claim either. It reads: “It is concluded that the development of exercise-associated hyponatremia is associated with excessive fluid consumption during and after extreme athletic events.” (my emphasis)
3. Citation “71” is a study titled The incidence, risk factors, and clinical manifestations of hyponatremia in marathon runners. It also fails to support the ACSM’s “hypotonic” claim, stating that “The hyponatremic group drank significantly more total cups of water (p=.004), electrolyte/carbohydrate solution (p=.005), and total amount of fluid (p <.001) than the control group.” The study goes on to conclude that “Excessive fluid consumption and longer finishing times were the primary risk factors for developing this condition.”(my emphasis)
In every one of these citations, excess fluid consumption, regardless of electrolyte content or composition is found to cause hyponatremia. But that’s not all, the ACSM uses one more citation:
“Contributing factors to exercise-associated hyponatremia include overdrinking of hypotonic fluids and excessive loss of total body sodium (95).”
Citation “95” is a 2006 study, also authored by M. Sawka. It states that, “Sports beverages can help to delay the development of hyponatraemia in these situations. Fluid replacement strategies designed to prevent symptomatic hyponatraemia should target both fluid and electrolyte intake.”
The problem with this conclusion is that it is based solely on a mathematical model developed to predict the effect of drinking behavior on sodium plasma concentrations. The study itself rightly acknowledges the limitations of drawing any real conclusions from such a model, noting that
“Central to acceptance of the outcomes of these simulations is the validity of the assumptions used in producing the model. Specifically, it was assumed that sweat rates and sweat electrolyte composition would remain constant over time … It is likely that running pace and sweat rate and composition would vary during a race.”
In the same year (well before the publication of the 2007 position stand) two other studies were published in the British Journal of Sports medicine. Rather than rely on conclusions drawn from mathematical models, these researchers used data collected from controlled experiments with real human beings. They found exactly the opposite of what Sawka predicted.
1. Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon – T D Hew‐Butler, K Sharwood, M Collins, D Speedy, and T Noakes.
In short, the ACSM authors seem to have completely ignored published empirical evidence contradicting their own conclusions, and instead chose to publish their weaker mathematical prediction as objective fact.
Sawka’s 2006 paper also claims that “The use of sports drinks instead of water or electrolyte‐free drinks is one strategy for slowing down the development of hyponatraemia. This approach is recommended by the American College of Sports Medicine for ultra endurance races (31).”
But this citation isn’t evidence that the claim is true, it is simply mentioning that someone else has listed this as a strategy to avoid hyponatremia. Who do the authors of this study cite? Amazingly, citation 31 is the ACSM’s 1996 position stand on hydration, which states that “Inclusion of sodium (0.5–0.7 g ⋅ l–1 of water) in the rehydration solution ingested during exercise lasting longer than 1 h is recommended since it may be advantageous in … possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid.” (my emphasis)
In other words this 1996 speculation regarding the protective benefits of electrolyte-enhanced fluid has been slipped into the 2007 position statement as fact. On what basis, I can’t say.
The 2007 position stand also states that “If not appropriately replaced, water and electrolytes imbalances (dehydration and hyponatremia) can develop and adversely impact on the individuals exercise performance and perhaps health.” The implicit suggestion here is that hyponatremia is caused by the failure to appropriately replace fluids, not the failure to appropriately restrict fluids. This again clearly suggests the unsupported belief that drinking sports drinks will prevent hyponatremia.
To summarize, the authors of the ACSM’s 2007 position statement mischaracterized the cause of hyponatremia, supported that mischaracterization with three invalid citations, failed to account for published experimental research that contradicted their predicted model, and transformed speculation on the imagined benefits of electrolyte-enhanced beverages in preventing hyponatremia into fact via a fourth inappropriate citation.
These errors wouldn’t be tolerated on a Wikipedia entry, yet the ACSM continues to use them. Is it an accident that every one of these issues directly benefits or protects the sale of Gatorade, the ACSM’s biggest sponsor?