Photo: Marcel Hilger
Hydration, cooling, and energy supply are key to marathon success.
Sebastian Reinwand was one of Germany's best professional marathon runners. With a personal best of 2:15:27, he competed at an international level. After the 2018 European Championships in Berlin, the father of two ended his running career and immediately dedicated himself to his next project: triathlon. He also shares his knowledge and experience from 15 years of competitive sports as a running expert and coach. On our blog, he provides you with tips and tricks.
As a marathon runner and coach, I'm often asked how to improve. Naturally, people think specifically about things like long runs, threshold power, or specific intervals. These are all important for a marathon personal best, but many athletes neglect their homework in another area: hydration, cooling, and energy supply during the race. Depending on the weather conditions, these aspects are even more crucial than endurance or speed. And because a long-distance triathlon lasts three to four times as long as a marathon, the impact of these factors is even greater.
When talking about hydration, the primary focus is on electrolytes; specifically, sodium intake during competition. Those who underestimate this will face relatively mild consequences. The result is cramps, which in the worst-case scenario can force you to drop out. I experienced this firsthand during my first marathon.
Photo: Marcel Hilger
What happens when the energy deficit becomes too great for the desired pace was evident at the 2014 Frankfurt Marathon, when Philipp Pflieger had to drop out after 35km, completely exhausted. His experience was even more dramatic at the 2017 Berlin Marathon, when he collapsed, almost unconscious, into the arms of a passerby. He recounts his perspective on this in his recently published book.
The most dangerous factor, however, is heat. Everyone probably still remembers the images of Sarah True at Ironman Frankfurt. Marathon runner Callum Hawkins, also in the lead and not far from the finish line at last year's Commonwealth Games, clung to the course barriers before collapsing unconscious and being taken to the hospital. When he awoke, the last few kilometers before his collapse were completely erased from his memory.
None of the aforementioned protagonists lacked willpower, toughness, or training. Of course, the stories mentioned are extreme examples where professional athletes pushed themselves to their limits. It doesn't always have to come to that, however. Nevertheless, the deficiencies mentioned can have a performance-reducing effect much earlier, which is why every athlete should carefully consider their competition nutrition. In the following series, I will share my experience and knowledge on the topics of hydration, cooling, and energy supply.
Part 1: Fluid intake
Photo: Ina Rohden
Every endurance athlete participating in competitions lasting longer than an hour should be mindful of their hydration. In extreme heat, depending on the intensity, fluid intake becomes relevant even earlier. Since we're talking about a competitive scenario, I assume it always involves exertion to the point of exhaustion. That's why you've often seen athletes reaching for a water cup in 10,000m finals. Most triathlons or marathons last longer than two hours anyway, making hydration absolutely essential.
Even when not battling extreme heat, sodium (salt) loss through sweat remains a problem. The composition of sweat varies considerably from person to person and is genetically determined. Combined with individually varying sweat rates, this quickly leads to a guessing game about how much and what to drink.
Cramps got in the way
Although I was convinced I'd taken all the necessary precautions beforehand, I struggled with cramps in my calves and sometimes even in my arms during every marathon I ran. It started at kilometer 18 of my debut marathon, which ended in a DNF after 37 kilometers. To make matters worse, Franz Löschke, a triathlete who was just there for fun as a season finale, ran past me. Naturally, I reflected on the situation afterward and added more salt to my water bottles the next time. This allowed me to make it to kilometer 31 without any problems and ultimately reach the finish line. "Third time's the charm," I thought, and added even more salt. I made it 34 kilometers before the first twinge, which I managed to control by slightly reducing my pace, until I had a full-blown cramp at kilometer 40. The reward was a personal best time of 2:15:27.
Nevertheless, the situation remained unsatisfactory for me. The fact that I had to slow down at the end of every marathon due to cramps, despite consuming 150-250ml of fluids and salt every 5km, was frustrating. Through the PushingLimits podcast, I eventually became aware of Mario Schmidt-Wendling as an expert who analyzes the individual sweat composition, which was previously unknown to me, and who also conducted a corresponding measurement on Anne Haug, among others.
Belief is good, knowledge is better.
So, off I went to Frankfurt, and lo and behold: the sodium content in my sweat was 1105 mg/l at the start, right at the upper end of the reference range. As a second step, I measured my sweat rate at race pace by running a half marathon at marathon race pace. This is quite simple: you weigh yourself before and after and subtract any fluids consumed. The result: 1.9 liters of sweat per hour. Quite a lot. Combining both values with my marathon running time, this results in a sodium loss of 4700 mg (1105 mg/l * 1.9l * 2.25h), which is contained in 11,800 mg of table salt. Conversely, this means that I actually have to mix almost 12 g of salt into my drinks to prevent cramps. The rule of thumb of apple spritzer and 2-3 g of salt per liter won't get you very far.
Even those who don't experience cramps should be mindful of their sodium levels, as uncontrolled fluid intake, especially during long races in hot weather, can lead to hyponatremia (low sodium). In the worst-case scenario, this can be fatal, as tragically happened at the 2015 Ironman Frankfurt.
Conclusion: Test, analyze, react
At least measure your sweat rate during training, specifically at race pace and under comparable climatic conditions. If you're prone to cramps, I recommend a sweat analysis. These test kits are now available to order online.
Sodium and fluid balance is crucial for competition. I will discuss specific heat adaptation and cooling options in the next post.