Philipp Gauckler from the Innsbruck University Department of Nephrology and Hypertensiology has got to the bottom of the phenomenon of water retention. He explains the background in an interview.
TOUR: Are you an ultra-cyclist and is that why you came up with the idea for the Ultracycling Study?
Gauckler: No. I've done a triathlon a few times, I like road cycling and gravel biking. But the idea for the study came from a podcast in which Transcontinental Race winner Fiona Kolbinger was interviewed. She said that she had often seen people with water retention at the finish line of the TCR (editor's note: Transcontinental Race). In other words, oedema-like swellings in the face, hands and feet. And she had noticed that. I listened to this and I already had a connection to the topic of fluid regulation in endurance sports. I had once reviewed a scientific paper on ultramarathon runners. Endurance runners in particular occasionally get hyponatraemia, i.e. a dilution of the blood. Probably due to drinking too much. And I found that exciting at the time because it went against my intuition that the risk of dehydration was the issue.
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The podcast that started it all...
Water retention
TOUR: For the ultracycling study, the women and men cycled 1,200 kilometres and 20,000 metres of altitude in one go. What did you observe?
Gauckler: We saw that the 13 participants showed signs of volume overload or overhydration. We saw that the total body water had increased significantly, that the plasma volume, i.e. the blood volume, had increased significantly. You can see that the circumferences of certain parts of the body have increased significantly.
TOUR: What is the risk from a medical point of view?
Gauckler: We cannot answer the potential health consequences of this with this study. The fact that water is deposited in the tissue and you get swelling is quite reversible and not dangerous. However, there will certainly be some consequences, depending on how many years you do it, how extreme, how often you do these races. Effects on the cardiovascular system. This is an issue that is already known among endurance athletes: that at a certain extreme they are more likely to suffer from heart disease. Something like atrial fibrillation, which is associated with intensive endurance sport, and I could imagine something like that. Because we also saw the signs of cardiac stress: that blood markers for cardiac stress increase and we also saw in the cardiac ultrasound that the ventricles were stretched, especially by the right heart. This stretching stress can cause micro-scars in the heart in the long term, but this is of course purely hypothetical.
TOUR: Micro-scars are familiar from the specialist literature on ultra-running ...
Gauckler: Yes, exactly. When you start to exert yourself, it's a mechanism of the body to get the water back so that you have enough blood volume. The vascular resistance becomes much lower when you start exercising, which means you need more blood overall. This circulates in the body and that's fine to a certain extent. The heart pumps faster and more volume per beat and this puts more strain on the heart. This means that it is stretched more and has to work harder.
Many questions arise from the study
TOUR: If I regulate the water balance perfectly, will the effects be less?
Gauckler: That's a great question and that's what we need to look at further. In this study, we only looked at what we could see. We didn't intervene, we didn't say this is how you should drink. But these are precisely the questions that arise from this. It's also interesting to look at these athletes again in five to ten years' time. To see if they have more micro-scars in the MRI of the heart compared to the average normal population. And the other question that arises is: if I drink less now or if I sleep more than three hours at night between days, will I manage to reduce this volume overload? And will this reduce the signs of cardiac stress? There are a lot of question marks and it is therefore difficult to draw conclusions for the individual athlete.
TOUR: Is there any feedback from the ultra-cycling scene on the subject of hydration?
Gauckler: Christoph Strasser had to abandon the Race Across America twice due to pulmonary oedema, i.e. water retention in the lungs. Since then, his team has taken extreme care to ensure that he doesn't drink too much. He also described this several times in interviews, saying that he only got through the races because he wasn't given so much water, even though he wanted to drink it.
TOUR: Even if it wasn't investigated in the Ultracycling study: are there other factors?
Gauckler: Even if we haven't investigated this now, I can imagine that recovery times are a relevant factor. The mere fact that you can Tour de France The fact that you don't see any swollen eyelids or legs is an indication. In our study, after 12 hours of regeneration, we saw that some things had already regressed quite well. For example, the whole-body water on the bioimpedance scale and also the signs of cardiac stress in the blood. Other things have not yet recovered, for example the blood volume was still at the same level as at the finish. The ultrasound also showed that the heart cavities were still slightly enlarged. It probably just needs enough regeneration. I have the impression that every day of ultracycling adds something extra. If you always take adequate breaks between the stages, then it doesn't get to the point where everything increases even further. But that's just how I imagine it.
TOUR: One tip that definitely wouldn't hurt would be to take longer breaks?
Gauckler: Yes, exactly. It's better to recover well between the stages, that won't hurt, but you don't need to tell someone who's in an ultra race that.
Background to the Ultracycling Study:
Study leaders Philipp Gauckler and Andreas Kronbichler - both renal specialists who conduct research at the Innsbruck University Clinic for Nephrology and Hypertensiology at the Medical University of Innsbruck and are amateur cyclists themselves - invited the two scientists together with Jana Kesenheimer and Fiona Kolbinger 13 ultra-cyclists from all over Europe to Innsbruck. The athletes were put through their paces during a multi-day road bike tour with a self-selected route length of 1,205 kilometres on average and almost 20,000 metres in altitude between 4 and 11 September 2021.
The five female and eight male test subjects in the Ultracycling study underwent an interim analysis on the fourth day after extensive basic diagnostics before the start and were examined during the recovery phase and at the end twelve to 24 hours after their arrival. Laboratory analyses of blood and urine, bioelectrical measurement of body composition and echocardiography (ECG) as well as continuously recorded logs of the athletes' fluid intake and the circumference of their extremities were used to collect data. "To this end, we cooperated with the Tyrolean start-up Ionsent Technologies Gmbh (formerly UriSalt GmbH), which provided the participants with mobile devices that allowed them to analyse their electrolyte balance themselves by taking a simple urine sample. The measured values were directly synchronised using the mobile app specially tailored for the study by the Innsbruck-based IT company web-crossing GmbH," says study director Gauckler, describing the innovative approach of the study. The province of Tyrol supported the cycling study with a technology grant of 130,000 euros.
The formation of peripheral oedema (swelling around the eyes, arms and legs) after above-average physical exertion is a phenomenon that has already been described in the literature in individual cases of ultra-runners. An interdisciplinary research team at the Medical University of Innsbruck has now systematically investigated this connection for the first time in ultra-distance cyclists. Further research is needed to provide concrete recommendations for action.
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