Hydration advice for athletes has changed dramatically over the last ~100 years.
This has perhaps been most clearly documented in the writing of Prof. Tim Noakes, along with two prominent ex-sports science students from his department the University of Cape Town; Ross Tucker and Jonathan Dugas.
Their research into hydration concluded that, in the early 1900s, it was considered best practice to advise athletes to drink nothing, or as little as possible, during all athletic pursuits.
They highlight a quote from James E. Sullivan, Head of the Amateur Athletic Union, from 1909):
“Don’t get in the habit of drinking and eating in a marathon race; some prominent runners do, but it is not beneficial.”
Fast forward 50 years and the advice hadn’t really changed much.
In the 1960s, Tour de France rider Tommy Simpson’s trainer said...
“Four small bottles for a long stage of the Tour, it is frowned upon to drink more. Avoid drinking when racing, especially in hot weather. Drink as little as possible, and with the liquid not too cold. It is only a question of will power. ”
Then things started to change.
1965 was the year that Dr Robert Cade came up with the first iteration of the sports drink that eventually became known as ‘Gatorade’.
It was developed to combat the fatigue that the University of Florida football team - ‘The Gators’ - suffered in the oppressive heat and humidity that Florida is famous for.
The hypothesis was that this fatigue was often being caused by a combination of carbohydrate depletion, dehydration and electrolyte loss.
So a drink formulated with sugar, salts and water was developed and found to be remarkably effective.
Gatorade got off to a great start commercially, was named a sponsor of the NFL in 1969 and has been used to wash the hair of football coaches ever since...
Rising sales led Gatorade’s marketers to promote the positive benefits of drinking and, increasingly, highlight the dangers of dehydration.
In 1985, the Gatorade Sports Science Institute was set up.
It’s stated mission is to “help athletes optimize their health and performance through research and education in hydration and nutrition science”.
In the 80s and 90s, GSSI conducted studies into the effects of dehydration on performance.
Many of these studies appeared to demonstrate that dehydration was a serious performance limiter, especially during endurance sports in the heat.
And, over time, this message gradually became established as ‘fact’ within the sporting community.
This reached its height in 1996, with the American College of Sports Medicine’s, ‘Position Stand on Exercise and Fluid Replacement’. It included the statement:
“During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating or consume the maximal amount that can be tolerated.”
The movement from ‘nil by mouth’, to ‘consume as much as can be tolerated’ is one of those classic ‘pendulum swings’ in the world of sports science. Other examples include the High Carb vs Low Carb diet debate and Cushioned, Supportive running shoes vs Barefoot Running.
These polarisations tend to occur because human brains love simple answers and ‘either/or, black or white’ debates. We struggle with grey areas, even though that tends to be where the answers to complicated questions often reside!
Prof. Tim Noakes was amongst the first to question whether the ‘drink, drink, drink’
philosophy’ was really a good idea.
He uncovered a growing number of cases of hyponatremia - a sometimes fatal condition characterised by low blood sodium levels - in an increasing number of endurance athletes who had seemingly followed advice to drink as much as they could.
Noakes went on to write a thoroughly researched and emotionally-charged book called ‘Waterlogged. The Serious Problem of Overhydration in Endurance Sports’.
In this he suggests that hyponatremia has become a significant problem largely
because of the marketing efforts of the sports drink industry.
He makes the tragic point that there have been a number of preventable deaths
from over-drinking and that these could have been avoided with more balanced messaging.
It’s impossible to argue that the the sports drink industry, has not been influential in over-emphasising the dangers of dehydration and this counter argument has definitely started to have an impact.
In 2007 the American College of Sports Medicine updating it’s guidelines:
“The goal of drinking during exercise is to prevent excessive Dehydration (>2% body weight loss) and excessive changes in electrolyte balance to avert compromised performance.
Because there is considerable variability in sweating rates and sweat electrolyte content between individuals, customized fluid replacement programs are recommended.
Individual sweat rates can be estimated by measuring body weight before and after exercise.”
This was definitely a significant step away from ‘drink as much as tolerable’,
but it’s correctness and practical usefulness to athletes has still been challenged.
Noakes and his supporters cite numerous examples of world-class performances occurring when dehydration has exceeded 2%, sometimes by a significant amount.
Like when marathon runner Halie Gebraselassie lost almost 10% of his body weight during a 2:05:29 marathon winning performance in Dubai in 2009.
Data collected on large numbers of IRONMAN finishers in New Zealand and South Africa shows that most of the field ended up significantly dehydrated at the finish line and that some of the faster finishers were in fact some of the most dehydrated of all, losing in the region of 2-7% of their bodyweight.
This kind of evidence, along with real world experience from endurance athletes, suggests that an arbitrary, 2% dehydration limit is neither useful, nor correct in all scenarios.
The truth is significantly more complex and seeking a simpler, ‘one-size-fits-all’ solution can be counter-productive.
Noakes’ current theory is that athletes simply need to drink water to the dictates of thirst in order to avoid hyponatremia, whilst maintaining sufficient hydration levels for survival and the maintenance of performance.
This theory has won a lot of support in recent years.
He argues, quite compellingly, that the human body is designed to optimize its own hydration levels so, if you drink to thirst, that is basically all you need to know about hydration. End of story.
This approach has merit in many circumstances. It’s likely to be compatible with the main goal of avoiding over-drinking for most people in normal situations.
But, it’s also yet another oversimplification in the field of hydration ‘marketing’, as it’s unlikely to be true for all athletes, all of the time.
There’s evidence that a pre-planned hydration strategy may be more effective for those engaging in very high intensity, medium duration (i.e. ~1-3 hours) endurance events where maintenance of blood volume is critical to support very high levels of performance.
One reason ‘drinking water to thirst’ might not always work is because sweat contains relatively large, and quite variable, levels of electrolytes, so prolonged sweating can deplete the body of these finite reserves.
This is most likely to be the case during ultra-distance events, where total sweat losses can be significant over a long period of time, especially in the heat.
Maybe because of the human tendency towards tribalism, there are currently two opposing camps in hydration science. There’s those who back the ‘drink water to thirst’ argument and those who are proponents of a ‘drink to a plan’ approach (such as Dr Stavros Kavouras’ group working out of The University of Arkansas in the USA, for example).
As is so often the case when considering two completely opposing ideas, it’s a good idea to look for the middle ground for clues as to where truths are likely to be found.
So, where’s the middle ground?
At the sharp end, it seems that opinion is moving towards a view that, whilst drinking to thirst is a sensible approach for shorter or lighter activities, during very long events in the heat, when total sweat and electrolyte losses are high, replenishment might need to be approached more proactively than would be the case in shorter bouts of activity.
Examples of the efficacy of this approach include this 2015 study by researchers in Spain, which showed faster racing times for athletes given salt supplements during a middle distance triathlon compared to a control group given placebos.
Here’s what 2016 Ironman 70.3 World Champ Tim Reed has to say about drinking to thirst...
“Drinking to thirst is likely to be a good approach in day to day life, or endurance training completed at a very low intensity. But, in my opinion, it’s a terrible approach for those looking to maximize their performance in endurance events.
My thirst response doesn’t really kick in until I’ve already lost 1 liter of fluid or more. While that shouldn’t drastically affect my performance, I still continue to lose
far more than I replace after my thirst response has kicked in, and so inevitably have to slow my speed as my blood volume continues to decline.
When drinking to thirst, I can lose 4-4.5kgs in a 2 hour run, leaving my heart rate very high and my performance very lethargic.
During a race, my thirst response is even more subdued due to my ‘fight or flight’ system running on overdrive.
Perhaps there are athletes whose thirst response provides a more reliable guide, but in my experience with both coaching and racing, drinking to a schedule, particularly in the first half of events, leads to vastly better performance outcomes.”
We also asked Sarah Crowley, who came 3rd at the 2017 IRONMAN World Champs and was the 2018 IRONMAN South America Champion, for her opinion on how best to approach hydration planning based on her own experiences...
"Initially I had no idea what I needed to stay hydrated for long course triathlons, having come from ITU. I raced with one gel and a bottle of sports drink in my first 70.3. It ended badly.
After the race I got some good advice. It was to basically work out my general hydration and fuelling needs based on my weight and expected race times. I was also given some general advice to eat and drink at regular intervals.
I took this advice and repeatedly practiced and refined what and when I ate and drank by systematically testing different things during brick training sessions over a period of two years!
I would write down a list of exactly what I had and the intervals each time which meant I had a record of what went well and what didn’t.
People often asked me what I ate and drank, so I told them. I’d often hear after races that they had followed a very similar hydration and food strategy but that it didn’t go so well. My point being, it’s so individual and also dependant on the course and the weather that you can’t copy a formula, you must work out what works for you. I am constantly refining this."
Together, I think these two examples illustrate very nicely that, whilst drinking to thirst is a sensible guiding principal and basis for how to approach hydration for shorter/low sweat activities, a more proactive and individualised approach is probably what's needed for longer, hotter and sweatier events where drinking water to thirst is unlikely to sufficient to maintain optimal performance and health.
Other scenarios where a pre-planned, but flexible and personalised, approach might be beneficial include...
1) During moderate duration, high intensity activities where the maintenance of blood volume to assist cardiac output, heat dissipation and other metabolic challenges is very important.
2) During days and weeks of back-to-back, hard or high intensity training or competition in hot conditions, where cumulative sweat losses have the potential to cause stepwise depletion in fluid and electrolyte levels in the body.
3) When individuals have exceptionally high sweat sodium losses and need to be more aggressive with replacement protocols to balance those out.
4) When the athlete is inexperienced and so all of the sensations associated with pushing their bodies very hard are relatively new and difficult to interpret accurately.
5) In environments where opportunities to access fluids are limited or constrained.
6) Where drinking at certain times and abstaining at others can be tactically advantageous, such as in bike racing or Long Distance triathlons.
Hopefully this brief summary of a hundred years or so of hydration advice leaves you in an informed position from which you can start understanding your own individual hydration needs and refine your strategy from there.
This blog on sodium's role in hydration and performance is well worth a read if you're starting this journey and, if you need help understanding your own hydration requirements, we've written guides on how to calculate your sweat rate and estimate how salty your sweat is.