Dogma-shattering: an idea integral to the creation and evolution of ultrarunning – a sport created out of the notion that we could run longer and farther, beyond road and track, than anyone believed was possible.
Modern trail ultrarunning was borne from the notion of refusing to accept the belief that no one could run a hundred miles through the mountains in a single day. Done.
Then, no one could run all the uphills in that fabled Sierra Nevada foot race. Done again.
Ultramarathon running has pushed the limits of conventional wisdom on all things in human performance: distance and speed, nutrition, and even footwear. Indeed, it was the tales of the rubber tire-shod indigenous ultrarunners of the Copper Canyons that fueled the mainstream adoption of minimalist running, smashing the dogmatic belief in the necessity of hyper-engineered shoes.
It is fitting, then, that the sport of ultramarathoning be ground zero for more dogma-shattering in another area: hydration in endurance exercise.
A new book by renowned sport medicine expert, Tim Noakes, MD, aims to change our beliefs – many of them longstanding, many of them inaccurate – on what it means to fuel optimally in endurance sports:
- Drink only to thirst, not on a schedule.
- Drinking does not prevent heat illness.
- Ingesting salt is unnecessary in ultras.
- Urine frequency or color has nothing to do with hydration or kidney function.
Say what? Them’s fightin’ words!
Noakes knows it, but he’s ready for the fight. And, with his background, there’s no one better armed. Dr. Noakes has been studying running and endurances sports for nearly fifty years. He has authored or co-authored over 250 scientific studies, including over fifty that examine the role of hydration and electrolytes in sports performance. In addition to sitting on the boards of the American College of Sports Medicine and the International Olympic Committee’s Science Academy, he’s also an experienced ultrarunner: having raced over seventy marathons and ultras, including the famed Comrades Marathon in his native South Africa. One could argue that he wrote the book on distance running: his Lore of Running is one of the most thorough, expansive scientific work on running, and, in its fourth edition, it is standing the test of time.
It was his work with Comrades that first sparked his interest in fluid replacement science. In 1981, Noakes received a letter from a Comrades participant describing her acute illness and hospitalization after that race, the result of drinking too much.
This perplexed and troubled Noakes: he subscribed to the early studies showing relationships between body temperature and weight loss, and was an early proponent of the “drink as much as you can” movement, pervasive to the sport in the 1980s and ‘90s. However, this letter – and mounting cases of Exercise-Associated Hyponatremia (EAH) – caused him to re-evaluate, not only his own beliefs, but also the existing research.
Combining empirical research, fundamentals of human physiology, and numerous performance studies, Waterlogged is an exhaustive look at the research, past and present, the origins of the “dehydration myth” and the role of industry in its propagation, and what athletes really need for optimal performance and safety.
An Argument for Self-Regulation
At its core, Waterlogged is a work that sets out to defend the fundamental biological quality of self-regulation – the idea that the body possesses mechanisms to self-regulate its own physiology to survive any physical challenge, no matter how extreme.
For various reasons – flawed or misinterpreted research, personal beliefs, or outright fear – many people – scientists, physicians, and athletes, alike – began to adopt the “catastrophe model.” Dr. Noakes describes it herein:
“According to this catastrophe model, the body cannot accommodate even small increases in body temperature during exercise, nor can it adjust to the fluid and sodium deficits that develop as it loses both in sweat during exercise. Instead, when exposed to exercise under demanding conditions, the body will simply continue without control until eventually a catastrophic physiological failure must inevitably develop.”
Based on this belief system, the sports medicine community – ranging from doctors to coaches and athletes – has recommended that all exercisers must avoid deficits of fluid – as well as salt and glucose –at all costs. Moreover, this belief system insists that our built-in controls are “hopelessly inadequate,” and that only by overriding these controls can we as athletes avoid catastrophic failure – ranging from DNF to death.
Indeed, this belief system – pushed powerfully by a burgeoning sports drink industry – fueled radical changes in how we fuel for endurance exercise. Within a few years, our drinking habits changed from “not a drop” to “drink as much as you can.” And not without consequence.
The Emergence of Hyponatremia in Endurance Sports
Exercise-Associated Hyponatremia (EAH, or simply hyponatremia) is a condition of decreased blood sodium concentration. Once exceedingly rare if not unheard of during endurance exercise, EAH has exploded in incidence across all events, ranging from marathons to triathlons, to even shorter sub-marathon events.
Its symptoms – weight gain, swelling, nausea and vomiting, headache, muscle cell breakdown, altered consciousness and seizure – were, for years, erroneously attributed to either heat exhaustion or dehydration. As such, EAH was incorrectly treated with the exactly the thing that caused it – more water!
The results can be dangerous and deadly. Excess water causes muscle cells to balloon and burst. It drowns nerve cells. But left unabated, the water accumulates in the confined space of the skull, causing brain tissue to herniate – the brain stem pushes its way out the base of skull, causing death.
Recreational athletes – running easy, in cool temperatures, minding recommendations to “drink as much as you can, to drink before you’re thirsty!” – began showing up in the hospital instead of the finish line.
Some of them were dying.
Hyponatremia was nearly non-existent before the 1970s. Where did it come from?
The Florida Panhandle: Where Dogma – and The Sports Drink Industry – Was Born
Waterlogged tells the story of the creation of Gatorade, the world’s first electrolyte drink. In August of 1965, an assistant football coach for the University of Florida, Dewayne Douglass, shared lunch with a renal scientist, Dr. Dana Shires, at the university, where the coach described his team’s struggles with “heat exhaustion and dehydration.” In that meeting, he implored the scientist and her team – which included renowned renal scientist Robert Cade – to develop “something to negate the strain of the brutal summer heat.” She returned to the lab, conferred with Dr. Cade and within two months, an experimental electrolyte solution was field tested: first with a freshman and varsity B-team scrimmage, and then in a real contest between the Gators and Louisiana State. Based on those two outcomes – second-half “rallies” by both the downtrodden freshman and the underdog Gators – the Legend of Gatorade – was born. The drink was adopted by college and pro teams, alike, and a new industry developed.
It doesn’t take a PhD or a background in research to determine the flaws in this experiment: the lack of any controls and the inability to control placebo effect: the players were given a drink that, coaches insisted, would help.
(It’s worth noting by Dr. Noakes that the success of the ’65 and ’66 Gators also included stellar play from legendary quarterback and future coach, Steve Spurrier, who won the Heisman Trophy in ’66. More notable is that Spurrier drank Coca-Cola, not Gatorade, during games!)
Later studies of Gatorade – performed years after the drink was successfully marketed and sold to masses – demonstrated only that ingesting glucose during competition was beneficial. Every subsequent study of Gatorade failed to demonstrate any significant benefit from the ingestion of either water or low-concentration sodium on core body temperature, blood sodium concentration, and performance.
In some cases, of the opposite was found.
The Tipping Point of Overhydration & Endurance Running: the Wyndham and Strydom Studies
One of the early studies examining hydration, core temperature and weight loss was conducted two South African researchers, Cyril Wyndham and Nic Strydom. Pre-eminent researchers in thermoregulation, they decided to study the role of hydration and marathon running. Their 1969 study found a loose correlation between rising core temperature and percent weight loss during marathon running. Based on those findings, they concluded that dehydration caused core temperature increases, and that, allowed to continue unabated (read: catastrophe model), runners are at high risk for heatstroke unless they drink.
Based on their study, they inferred that the optimal fluid for marathoners to be nearly a liter per hour – roughly two to three times that of previous studies, and an order of magnitude greater than what the elite marathoners of ‘60s were ingesting – in order to prevent the “dangers” of heatstroke.
Initially, the study was tough to argue: it showed a neat, linear relationship between water deficit and core temperature, indicating that any level of dehydration equated to core temperature rise.
But their study was flawed:
- The runners they examined were not allowed to drink any water – rather than compare multiple levels of hydration, they studied only a group that disallowed any fluid.
- The runners were advised to run as hard as they could; their efforts were not controlled.
- There was no correlation of race performance with dehydration and core temperature. This is notable, because the winners of these race studies also happened to have the highest core temperature and weight loss.
Perhaps pressured to release this data and save the masses from impending danger, Wyndham and Strydom failed to execute a thorough study. That, coupled with the emergence of an industry giant replete with anecdotes of athletic prowess, was enough to spin the cogs of hydration dogma for decades: “Drink before you get thirsty! Replace all fluid and electrolytes lost during exercise!”
Noakes began to review the literature pre-Wyndham and Strydom, as well as studies that occurred in its aftermath. Moreover, he conducted his own work. Waterlogged lays out this work dissecting the bad from the good, and presents it to the reader in plain view. Studying events ranging from the standard marathon to hundred-mile and 24-hour endurance competitions, Noakes determined the following:
The Role of Hydration and Performance
- Dogma: In order to ensure optimal performance and/or survive endurance events, one must replace all lost fluids by drinking during the event.
- Science: Fluid (and weight) loss during endurance exercise is normal, if not optimal.
Noakes notes that studies of top performers in endurance events (marathon, triathlon and long-ultras) typically demonstrate weight losses ranging from 2% to upwards of 8% or higher. More notable, weight loss was correlated to performance in these studies. Conversely, weight gain is correlated to impaired performance and – in most cases – a clinical sign of EAH.
The explanation of these findings is two-fold: first, that sugar (in the form of blood glucose and liver and muscle glycogen) is stored with surrounding water, and that when we burn that sugar, the water leaves with it. Therefore, a significant degree of weight loss due to burned glucose and freed water is normal. This value is now accepted to be in the 2% range.
Second, a significant volume of fluid lost during exercise – through vapor, sweat, or urine – comes from extracellular fluid (ECF). This fluid lies in between cells, as opposed to water found within cells (intracellular) or within blood volume (previous studies have shown that upwards of 70-80% of fluid losses are from ECF and glucose storage, not cellular or plasma water).
Therefore, we stand to lose significant volumes of water weight via sugar storage and ECF without physiological – or performance – consequence.
He argues that only when weight loss is coupled with uncorrected thirst, does performance impair due to dehydration.
Hydration and Thermoregulation
- Dogma: We must drink water in order to prevent heat illness during exercise in hot conditions.
- Science: There is no relationship between fluid intake and hydration, and the incidence of heat exhaustion or heatstroke. The only correlate to core temperature is running pace.
Noakes cites volumes of research studies athletes across all sports and events: American football players, marathoners, ultrarunners, and recreational walkers. There is not a single study that demonstrated a difference in core temperature between athletes who drink and those who do not. Nor has there been any evidence – empirical or case study – that links heat exhaustion or stroke to high levels of fluid loss, sodium loss, or the cessation of sweating.
Instead, the only behavioral factor that influences core body temperature during exercise is effort. Again citing the physiological theory of self-regulation and empirical study, Noakes points out that the body will automatically adjust pace in order to ensure that core temperature does not exceed normal thermoregulation (deemed to be <40-42⁰C).
Only pace – dictated by the degree to which our muscles work, burning energy and generating heat – determines core temperature. As such, the athletes who ran the fastest – and won – had the highest core body temperatures, with correlational fluid losses.
It is notable, however, that additional evaporative and external cooling measures – such as ice packs and water dousing – do result in changes in tissue temperature. Indeed, the only acceptable medical treatment for acute heat illness is external cooling via ice packs – not the administration of intravenous fluids, as some may believe.
Heat illness, namely heatstroke, is extraordinarily rare in endurance sports, Noakes points out. Using the clinical definition – a core temperature above 42⁰C, he identifies only six documented cases of heat stroke during endurance (marathon or above) since 1905.
Heat exhaustion or heat stroke is far more common in shorter running events, in large part because the intense efforts and short durations of these events merge to create temperature increases before the body can self-regulate pace. In the vast majority of cases, the heat illness quickly resolves with rest and, when necessary, cooling measures.
Dr. Noakes points out that in most cases of fatal heat illness, there exists an abnormal mechanism of heat build-up – excessive endogenous heat production – whereby the body goes haywire, producing heat, regardless of external temperature or duration of effort. Says Noakes, “this is the only explanation for the large number of cases of heatstroke that occur in cool conditions, or in athletes exercising at a low intensity, or those who have been physically active for only a short time, or in those who have been actively cooled for many hours.” Moreover, some cases have shown insidious spikes in core temp, hours – if not days – after cessation of exercise and onset of treatment.
The high incidence of heat stroke in short distance events – versus virtually none marathons and ultras – also shines light on the lack of connection between hydration and core body temperature. That heat illness is so prevalent in short-lasting events – where very little fluid is lost, yet there is next to no incidence in multi-hour efforts, even with profound water loss – is telling.
Sodium Balance and Performance
- Dogma: We need to supplement with sodium to complete long-distance endurance events.
- Science: The body self-regulates blood sodium concentration via several mechanisms, including sodium sparing in sweat and urine. When one “drinks to thirst,” blood sodium concentration invariably rises during prolonged exercise; it never falls.
One of the most persistent beliefs in ultrarunning is that we must ingest sodium for optimal performance, if not survival. Not so, claims Noakes. He points out several studies, including sodium deprivation studies involving prolonged exercise over several days, that demonstrates that the body will maintain blood sodium levels in a deprivation state.
In explaining this phenomenon, Noakes points out our biological mechanisms to preserve sodium in both sweat and urine – pointing out that these studies measured sodium concentrations next to nothing during prolonged exercise and sodium deprivation. Moreover, blood sodium concentrations stayed within normal ranges – so long as athletes and subjects drank only to thirst.
- Dogma: Heavy sodium concentrations in sweat – evidenced by salt-staining on skin and clothing – identifies a person as a “salty sweater”, and that these people need even more sodium supplementation.
- Science: The self-regulation of sodium concentration results in sodium excesses being secreted; salty secretions will cease when sodium balance is achieved.
Simply put, the presence of salt deposits on skin and clothing are due to the body ridding of excesses, and when sodium balance is achieved – or if a blood sodium deficit is perceived – the body will conserve it from sweat and urine.
- Dogma: Sodium supplementation stops and prevents Exercise-Associated Muscle Cramping (EAMC)
- Science: There is no scientific evidence that shows sodium (or other electrolyte) deficits in those with muscle cramping.
This is another interesting dogma that has thrived, pre-dating even Gatorade. The original belief of salt deficits and cramps was based, according to Noakes’ review of research, on studies of a single miner in the 1920s, who showed salt and fluid losses in association with cramps.
Noakes points out many studies that not only fail to show an association, but demonstrate normal – if not mildly elevated – blood sodium concentrations in those with muscle cramps. Conversely, it is well accepted that those suffering from hyponatremia do not suffer from muscle cramps – the very patient population that would, in theory suffer the most cramping, should a sodium deficit truly cause cramping. Internal or external temperatures also do not play a role, as EAMC occur in cool conditions (including extreme cold water swimmers).
Interestingly, more recent studies have even shown that ingesting electrolyte drinks actually increase cramping incidence: a 2005 study found a 68% incidence of those drinking Gatorade, versus a 54% drinking water, or nothing. And there may be a reason for that.
The current leading theory on muscle cramping is that neuromuscular fatigue – and the loss of inhibitory reflexes – causes excessive muscle activity, resulting in cramping. Moreover, a 2011 study has identified those two risk factors for developing cramping: previous cramping experiences, and faster finishing times; not body weight losses or blood sodium levels. This could explain the greater incidence of cramps amongst Gatorade drinkers: if an athlete perceives protection from drinking it – along with the ergogenic aid of glucose solution – they will run more intensely, possibly resulting in more cramps.
Anti-Diuretic Hormone – the Lynch Pin in Hyponatremic Illness and Death
- Dogma: The frequency and color of my urine will tell me whether or not I am adequately hydrated; I should continue to drink after exercise until I am able to urinate – to ensure optimal hydration and kidney function.
- Science: The presence of excessive anti-diuretic hormone during exercises – referred to as Syndrome of Inappropriate ADH (SIADH) secretion – can cause overt fluid retention and resulting in concentrated or complete lack of urine, despite severe overhydration and hyponatremia.
Antidiuretic Hormone (ADH) is secreted during exercise to conserve water from urine, when the brain determines that blood sodium levels are increasing. When sodium levels are balanced, ADH secretion stops. This is the principal reason that, for most of us, we urinate less (or not at all) during prolonged exercise, or that we urinate a lot when well-hydrated.
For reason unclear to scientists, in a significant population of runners (measures as high as 13% of Boston Marathon runners in a 2002 study) exhibit excessive levels of ADH. This condition, referred to as Syndrome of Inappropriate ADH secretion (SIADH), causes athletes to retain water beyond physiologically need, despite potentially severe overhydration and hyponatremia.
These are the runners that may exhibit symptoms of EAH – swelling, weight gain, impaired performance and brain function – yet report either dark urine or none at all. Yet this has nothing to do with the integrity of the kidneys; it is the presence of high levels of ADH that result in the body holding onto this water.
The presence of SIADH – measured in blood lab tests – has been a common finding in the most severe cases of hyponatremia, including deaths. In short, ADH prevented any passage of urine.
To reiterate: there is zero correlation between frequency or color of urination and hydration, or kidney function. ADH controls whether or not the kidney produces urine. Therefore, runners attempting to ensure hydration or kidney function with copious fluids might be endangering their race, if not their health, if there is excessive ADH in their bloodstream, blocking urine production. Indeed, given that hyponatremia leads to muscles cell lysis (explosion due to swelling), one might be endangering his kidneys with excessive drinking during or after endurance events.
The only things we can trust to ensure adequate fluid intake, according to Noakes, is our thirst and, to a lesser extent, the scale. The absence of thirst and an increasing weight (either absolute, or relative) is evidence that additional fluid is unnecessary and potentially dangerous.
Treatment and Prevention of Exercise-Associated Hyponatremia
As dangerous and deadly as EAH can be, the treatment – if initiated promptly and correctly – is quite simple. Research and clinical application has shown that a simple 100-mL “mini-IV” of high-concentration saline solution (3.0% of greater) produces rapid recovery of even the severely hyponatremic – within minutes.
Notable are studies that found a simple ingestion of the same volume and concentration of sodium solution does not have the same restorative effect. It is not known at this time why simply ingesting sodium is less effective.
Either treatment is far cry from what many hyponatremic runners receive – both at medical aid stations and local hospitals, which is typically more fluid, or intravenous solutions with inadequate sodium concentrations – typically 0.9% or less. Noakes implores sports medicine officials – and public health officials, alike – to make a thorough and accurate diagnosis of a hospitalized runner before initiating any IV fluids.
Given this reality, it is even more shocking that a major ultramarathon, at one point, was offering default intravenous solutions, post-race, without any medical justification. It could’ve killed someone.
Evidence-Based Fueling Recommendations for Optimal Performance and Safety
Drink only to thirst.
According to Noakes and the body of research on hydration and performance, individual differences are too great to make blanket recommendations. The only gauge for fluid need is thirst; the only symptom of dehydration is thirst.
Having said that, Noakes goes on to recommend fluid intake in the range of 400-800ml per hour for athletes across all endurance events, ranging from marathon to 24-hour+ events. This value is determined from observational studies of hydration, performance, and incidence of hyponatremia. The low range is for slower, lighter runners; the high end for heavier, faster runners.
It might be worthy to define “thirst.” Clearly, severe dehydration will cause severe thirst. However, those athletes looking to stay ahead of fluid need might consider a similar notion: “If it tastes good, you need it.” Simply put: does water taste good? If so, this subjective assessment might be a more nuanced assessment of fluid need. Whether the converse (an overt absence of thirst, accompanied by a dissatisfying taste and appeal of fluid) indicates fluid satiation or excess, was not addressed by Noakes or his book.
Consumption of roughly 60g of glucose per hour during competition will improve performance.
Noakes has separately researched and reviewed studies on glucose supplementation and determined this value for greatest performance and gastrointestinal acceptance. Values upwards of 100 grams per hour have shown even greater benefit; however, this increasing sugar invites GI disturbance.
Supplemental sodium is unnecessary in endurance competition.
This conclusion, based on his work and literature review, will undoubtedly result in controversy in the ultra community. Noakes is careful to point out numerous studies demonstrating that blood sodium levels are maintained in absence of supplementation and outright deprivation, with prolonged exercise over many days. Moreover, he points out the absence of any study that identifies performance benefit from sodium supplementation; in fact, he points out two studies in the past decade that contradict the notion.
For the sports medicine community, he recommends the following:
Be very careful to make accurate diagnoses of troubled runners.
Runners who come into medical checkpoints, feeling dizzy while standing still on a scale, are more likely to be experiencing Exercise-Associated Postural Hypotension than any other ailment, says Noakes. It is the simple notion that – in that brief moment of pause – a runner’s blood pressure drops due to the cessation of running. The simple treatment is to elevate the feet over the heart, wherein recovery is rapid. There is no evidence that postural hypotension is due to dehydration.
More important is an accurate diagnosis of the hyponatremic runner. An athlete exhibiting the signs and symptoms of hyponatremia – weight gain, swelling, nausea and vomiting, headache, muscle cell breakdown, altered consciousness and seizure – must be accurately diagnosed. Administering a 100mL bolus of 3.0% sodium solution results in rapid recovery in nearly every hyponatremic runner.
Erroneously determining these athletes as “heat exhausted” or “dehydrated” may result in forcing fluid consumption, or the administration of hypotonic IVs. This “treatment” will only worsen the condition, prolong the suffering and recovery time, and in worst case, may even result in death.
* * * * *
For a text so replete with cold facts, Dr. Noakes’ passion for the message permeates the text. Certainly, he is passionate for the sport, being a veteran of the marathon and ultra distance. But elements of personal frustration, and even guilt over having pushed the “drink” message in his early days, are also felt by the reader. Personal accounts of death from overhydration are included in Waterlogged, not to sensationalize, but to better understand how something as innocuous as water, and the good intentions to avoid suffering, can result in deadly consequences.
For this reader, given what has been known – yet ignored – about hydration science for so long, justifies the strength of message. In the very least, hyponatremia can ruin the race day for runners and families. Worse yet, it could end a running career. Or a life.
It is fitting, therefore, that Noakes finishes his text by putting the hard data away and appealing to our common sense, by saying, simply: “Your body will tell you what it needs, if you just listen.”
Trust your body, and it’ll take you places. Just as it has always done for ultrarunners.
If 4,500 words aren’t enough for you, stay tuned to part two of our discussion on hydration and ultramarathons: “Hyponatremia & Western States.” There, I will share additional insights, including:
- A Q&A with author Tim Noakes, MD
- My personal account (a “n=1 case study”) of applying Noakes’ recommendations to the 2012 Western States Endurance Run
- Insights from Marty Hoffman, MD, lead research director for the WS100, and from Kerry Sullivan, MD, medical director
- What the impact of Waterlogged may have on Western States and other ultramarathons in North America
Until then, here’s to happier, healthier running.
Call for Questions
- Have you ever experienced symptoms of hyponatremia during a race? Have you ever been diagnosed and held at an aid station – or forced to DNF – by medical personnel?
- What is your experience with fueling (either water, salt or calories) “by feel” versus “by a schedule?”
[Disclaimer: The contents of this column as well as the author’s comments are provided for general informational purposes only and are not intended as a substitute for professional medical advice. Do not use the information on this website for diagnosing or treating any medical or health condition.]