This year I helped pace a friend at the Nike Melbourne Marathon festival, and honestly, I was more concerned about when and what drinks to have than I was about how far I had to run. Most of my worrying stems from Sian Welch in the ’97 Iron Man world championships and not wanting to end up like that as I enter the MCG.

Some of the grim realities of a marathon, such as cramps, fainting, and loss of muscle strength, can be caused by a severe type of dehydration called hyponatremia. As with standard dehydration, it can result from significant body fluid loss through sweating. However, hyponatremia can also be caused by overhydration. Essentially, it occurs because your body’s electrolytes become unbalanced. When you overhydrate, especially on plain water, no new electrolytes enter the body to replace those lost through sweat. Accordingly, your cells become more dilute, leading to an imbalance. 

The dangers of hyponatremia are real. Severe cases can result in seizures, comas and even death. Less severe symptoms are still not ideal, including cramps, vomiting, fatigue and confusion.

Excluding the possibility of hyponatremia, maintaining good hydration practice is still paramount to you crushing that PB out there on the course. A decline in body weight by just 2% due to sweating is enough to cause drastically decreased performances due to a range of physiological and psychological issues. 2% body weight for a person who weighs 65kg is about 1.3kg. Trained marathon runners lose on average 1.5L/hour in 20°C, so taking on some drinks is probably not a bad idea. In the 1984 Los Angeles Olympic marathon they measured one runner who lost a staggering 3.7L/hour. 

I won’t over drink, don’t even worry!

Research that was conducted on London Marathon participants highlighted a concerning fact. Despite the organisers providing advice on strategies to avoid hyponatremia, 12% of participants still planned to consume fluid levels that would put them at risk. This is considering that 93% of runners acknowledged they had read and understood the provided hydration information package. 

If not water, what should I drink then?

A better idea is to use some sort of sports drink. Typically, sports drinks contain electrolytes at a similar concentration to your body, thus not diluting your cells. Another bonus with sports drinks over plain water is the sugar. We all know we use carbs as our primary fuel source, even when running at marathon intensity. Our muscles can hold, at the most, about 90-120 minutes worth of glycogen (how sugar is stored). 

The evidence on mid-race carbohydrate consumption is solid. Individuals who consumed regular high GI carbs while running showed decreased fatigue relative to those who didn’t. This was independent of whether they had some sugars in a gel or something pre-race. It’s not all peaches and lollipops though, too much sugar, as with too much water, negatively impacts performance while racing.

It’s called a sugar crash, something I’m sure we can all relate to. It’ll leave you buggered, feeling nauseous, and lacking motivation in no time. So, to avoid ending up like a kid 20 minutes after drinking too much red cordial, keep a lid on your mid-race sugar consumption.

There is a recommended amount of carbohydrates to consume hourly to avoid a sugar crash. The typical stance is around 90g/hour. Despite this, athletes consuming 120g/hour displayed better recovery than those on lesser amounts but, race day performance didn’t significantly improve.

What brands are good?

Looking at all the options, SIS, Winners, Powerbar, Maurten and so on, it can be pretty overwhelming. I asked a few elite marathon runners what they reckon, they almost unanimously said Maurten. They also mentioned that it tastes terrible, and without practice in training, it can cause some GI issues, including vomiting.

Generally, the way to go is to just choose what you know. If you’ve been using a particular brand during your training sessions, it’s probably best to stick to it. If you haven’t used anything, go for something safe like Powerade or Gatorade. While it may not be on the top shelf, it’s going to work fine, and it’s better than getting to 30km, tucking into a gel, and feeling sick. That far in, there’s enough to worry about.

Additionally, given there are only three personal drink stations in Melbourne, you aren’t going to have much access to your own formula anyway. Potentially some practice with the SIS stuff that they have out on the course is not such a bad idea given how abundant it will be. It’s also a good idea to avoid anything with fructose in it. Fructose is more likely to cause GI problems than other sugars. However, if you have trained with it, it will be fine.

A somewhat new idea that has begun gaining some traction is adding amino acids (building blocks of protein) to your drinks as part of a rehydration strategy. It sounds kind of weird but has got evidence to back it up. Athletes who consumed the protein added drinks outperformed their peers in an endurance test. Another massive benefit was the reported 83% reduction in muscle damage the next day compared to a more traditional sports drink.

So when should I drink these drinks?

As always, the internet forums had some pretty mixed responses, so I once more enlisted the help of our elite marathoners.

Again, almost unanimously, they said they had planned drinks every 5km and gels at around the 10-15km and 25-30km marks. 

Their plans for the last 10km of the race, where your legs are rooted, varied slightly. However, generally, a source of caffeine was advised, whether that be from a gel or from some flattened Coke.

The research I read typically agreed with this approach but added a caveat. Drinking every 5km is a relatively aggressive hydration strategy, so fluid quantity needs to be monitored carefully to avoid hyponatremia. The American College of Sports Medicine and the International Marathon Medical Directors Association recommends keeping fluid intake below 700ml per hour to prevent overhydration. Clearly, how much you drink at each station will depend on your speed if you adhere to this guideline. If you are going to consume gels, accompany them with some water. This will help you digest them and prevent disruptions to the nutrient concentrations in your blood and cells.

Another strategy that I know people consider is consuming some gel-infused water or other forms of high GI carbs before the race, beyond standard meals. Studies into this highlighted that it works effectively. 

However, it isn’t sufficient to replace mid-race carb consumption. The two approaches can be combined, although there is little evidence to suggest this enhances performances compared to mid-race consumption alone. A standard breakfast a few hours before racing would be just as effective.

Am I ready to go now?

It’s integral to acknowledge the vast degree of individual variability when considering all these factors. The only way to know what will work best for you is to try various strategies until you find one that works. Even scientifically, they acknowledge heaps of variation within their participants.

Trying to organise a hydration strategy can be difficult and feel pretty daunting. But the benefits don’t stop at just your health, you’ll see the results carry over to your completion time too. Good luck to everyone racing this weekend, and I look forward to seeing you out there.

Disclaimer 

I am not a doctor or health professional and therefore my advice should be taken with a grain of salt. You are responsible for your own decisions regarding the nutrition you use while racing or during your general life.

Further Reading

These are a couple of reviews that have some great info in you would like to know more.

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2575187/
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8001428/

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