Nutrition, Podcast, Science and Physiology

The science of hydrogels in endurance sports with Andy King, PhD | EP#333

 April 11, 2022

By  Bernardo Gonçalves


That Triathlon Show - Andy King

Andy King, PhD, is an exercise physiologist at the Australian Catholic University. Andy joins us to discuss the science and application of hydrogel products like Maurten and SiS Beta Fuel. Do they work, how do they work, and is it worth paying the premium compared to regular sports nutrition products?

In this Episode you'll learn about:

  • What are hydrogels, and how are they different from regular gels?
  • The theory behind how hydrogels could work to improve endurance performance
  • What does the science say? Do hydrogels improve endurance performance, metabolic markers, or gastrointestinal symptoms compared to regular gels?
  • Practical recommendations: is it worth it to use hydrogels?
  • Glucose and fructose - is there an ideal ratio for sports nutrition products?
  • How to maximise carbohydrate intake (e.g. taking in 120 g/h of CHO)

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Andy's Background

03:10 -

  • I am Andy King and a researcher in exercise physiology and human metabolism. I currently work at the Australian Catholic University, having moved from Leeds, UK, a few years ago.
  • Most of my interest lies in endurance sports and how we can optimise performance through physiology and nutrition.

What are hydrogels?

04:00 -

  • It is a new product that has appeared in the last 4-5 years. It initially gained popularity due to good marketing and relationships with many world-class athletes.
  • The product is the same in any carbohydrate drink or gel, as it is sugar delivered in a solution to take during exercise.
  • However, hydrogels have a couple of extra ingredients. Those ingredients are alginate, a product derived from seaweed and peptide, a similar biopolymer polysaccharide. These two allow the ingested solution to form a gel-like substance once it enters contact with a low PH environment.
  • The idea is that this will move with no problems to the intestine, where enzymes in the gut can access it to facilitate the transport of carbohydrates that you would not have with a standard carbohydrate solution or gel.
  • When you drink a solution that contains carbohydrates, gastro-emptiness will slow down. This process happens to the point of osmolarity, where the total carbohydrate content starts to slow down.
  • The hydrogel allows the carbohydrate to move through the stomach without slowing down the gastric emptiness. Once you go over that osmolarity threshold, hydrogels will "hide" the carbohydrate content and allow that not to delay gastric emptiness.
  • There is a balance between the fluid amount someone can drink and the gastric emptiness rate that will allow delivering that content and the amount of carbohydrate we want to get through the gut.
  • We can deliver more carbohydrate content even if gastric emptiness slows down.
  • Maurten is the primary driver of hydrogels. Beta Fuel is an alternative product. 
  • Maurten was fundamental to bringing this to the market, and their marketing strategy and support were a success.

State of evidence on the use of hydrogels to enhance endurance performance

09:23 -

  • The literature review we did in 2020 did not have many studies on hydrogels, and I would not even call it a meta-analysis. (not even a systematic review)
  • We looked at studies published at that time, and we wanted to see if there were similarities between those studies.
  • Typically, what we see in exercise nutrition studies is a range of protocols, study designs, and participants that we use in studies.
  • And that makes the initial comparison quite tricky. Therefore, we found that on the six studies we addressed in the review we published in March 2020.
  • I am not saying that each study was poor because reputable labs conducted those studies. However, one was in cross country skiing, the other was in the running, and the other was in cycling, making comparisons harder.
  • Moreover, we had different intensities, test duration, and training statuses.
  • Specific features make it challenging to analyse this topic with such few studies. 
  • However, it has not changed since then. Lab studies have been something complicated to do in the last two years.

Results of the studies

11:49 - 

  • In summary, the hydrogel does not work. 
  • None of the studies showed significant performance benefits over typical carbohydrate drinks.
  • We can make comparisons with controlled solutions (water) or sweeten placebo without any carbohydrate content. For those situations, hydrogels were beneficial.
  • However, hydrogels were only matching traditional sports drinks.
  • Metabolically, we looked at the carbohydrate amount that the body can use that came from the drink (exogenous carbohydrate).
  • When compared to typical sports drinks, this amount did not change. 
  • Of the six studies, only one measured this, and there was no difference.
  • We also looked at the body's endogenous carbohydrates, plasma glucose, and lactate, and we did not see any differences.
  • Maurten products claimed reduced gastric distress, and there were minor differences between the hydrogel and the traditional drink.
  • However, the variability between the participants was too significant to lead to any specific conclusions.

Andy's study on comparing hydrogels vs sports drinks vs placebo

Reasons to perform the study

15:58 -

  • We wanted to cover some gaps in the literature. Last year, we published this study, and it came out to full access in early 2022.
  • Josh Rowe, a PhD student, was the study's lead researcher. He did a fantastic work in assembling this study that brought a few extra challenges into the mix. (challenges in sample collection and test duration)
  • Josh spent much time in the lab formulating his hydrogel solution and tried different prototypes.
  • We did not use any commercial products.
  • It also looked at issues like gastro-intestinal comfort across different intensities to find a sweet spot for what intensity might be more beneficial.
  • We settle at 70 % of VO2max due to GI issues. (marathon pace - sustainable effort for 2-3h)
  • We had well-trained amateur athletes with a VO2max around 60.
  • This study came from some research on specific responses to typical carbohydrate ingestion. 
  • We targeted 90 g/h of carbohydrates because this was the value other researchers had found would be the ideal dose of exogenous carbohydrate to take.
  • Hitting 90 g/h with a mixture of fructose and glucose is now considered the ideal nutrition practice.
  • Moreover, we did this on runners because they often suffer more from GI problems. The running mechanics makes the gut mobile, while cycling tends to be more stable.
  • The mechanic dislocation of the gut might cause some issues, and there are some potential changes in blood flow.
  • Therefore, we thought we were giving a suitable environment for the hydrogen to work by increasing the exercise intensity slightly compared to previous studies.
  • Only one study reached that intensity from the ones accessed in the literature review. (cross country ski study)
  • And we also wanted to test duration, so avoid doing only a one-hour protocol.
  • We combined the study with a performance test, a challenge for athletes who came into a lab to do these tests.
  • We can do a protocol where we fix an exercise intensity or perform a test.
  • We add success doing both ways. Regularly, we add a performance test after a fixed intensity test. (2h running followed by a 5 km TT)

Methods, protocols and results

21:35 -

  • We met the energy requirements through the carbohydrate intake for the carbohydrate and hydrogel drinks. We also had a control group for a non-carbohydrate drink for comparison.
  • We found that having carbohydrates in the drink improved performance as expected. 
  • The hydrogel drink was about 2 % quicker than the carbohydrate drink in the 5 km TT.
  • Almost all athletes improved their performance by moving from the carbohydrate to the hydrogel drink.
  • It is too complex to point out what made the difference in the results compared with other studies. We have to gather more information on this topic before giving recommendations.
  • I think the difference was in increasing the exercise intensity slightly. With higher intensity, blood flow around the gut reduces.
  • We know that it is hard to ingest something comfortably in a shorter race. Moreover, the running element might also help explain this performance improvement.
  • By slightly reducing GI distress, athletes could handle more carbohydrate intake. 
  • This study also showed a slight increase in exogenous carbohydrate oxidation. (statistically significant)
  • Every participant did each of the protocols (carbohydrate drink, hydrogel drink or control drink).

Other studies developed after the literature review

25:25 -

  • There is a study from 2021 which looked at the exogenous oxidation in well-trained runners.
  • The participants drank about 70g/h of carbohydrates.
  • The study did not see any differences between different drinks.
  • However, they also gave a single dose of hydrogel, which increased exogenous oxidation.
  • The only problem is that they did not have a comparison group for the higher single dose of carbohydrates, so we expect exogenous oxidation to increase because carbohydrate intake was high. (and not necessarily from the hydrogel)

Takeaways from hydrogels

27:01 -

  • There is no point in doing these lab studies if it does not translate into helping endurance athletes improve their performance.
  • I still believe there is potential for the use of hydrogels. There is some research so that people use them properly.
  • It is not something I would rush to buy tomorrow because it will not change your race day performance.
  • Many other factors will overlap any benefit of having hydrogels. (many factors relate to nutrition)
  • Nevertheless, use it if it works for you and your gut, and you feel you benefit from using them.
  • We have to experiment ourselves and not rely only on what labs are doing.
  • If you are prone to having GI issues, you should try hydrogels. In my experience, 5-10 % of people will have some fructose intolerance. (not hereditary fructose intolerance)
  • If you know you struggle with fructose (bloating, stomach cramps when eating a lot of fruit), it might signify a slight intolerance.
  • And that hydrogel can be a way of having that carbohydrate delivered through the stomach quicker.
  • If your carb ingestion during exercise is low (e.g., one gel per hour), you probably do not need fructose.
  • Therefore, going for a Maurten hydrogel is not necessarily what you need. Maybe, address the composition of the sugars you intake.

Fructose:glucose ratio

32:38 -

  • Similar to the advice on hydrogels, go out and see what works.
  • No product, study, or article will always work for everyone.
  • When it comes to glucose, it is straightforward. The intestine's maximum absorption rate per hour is around 1-1.2 g/min. (60-72 g/h)
  • Fructose is trickier, partially because of the individual difference in tolerability. It seems to be the cause of many GI issues.
  • If you add fructose to your intake, start at a low amount and progress.
  • The evidence behind the ratio between glucose and fructose is mixed. There are excellent studies published between 2005 and 2015 that concluded a ratio of 0.8:1 was best.
  • The recommendations from those studies are in the range of 0.5:1 ratios. However, I think we see an effect of different studies on the recommendations (different protocols, intensities and feeding patterns)
  • However, I do not feel the exact percentage is not crucial. We will not produce significantly higher amounts of ATP if we vary that ratio from 0.5:1 to 0.8:1.
  • When your carb intake is already above 60 g/h, add some fructose and play around with it.
  • There is also research looking at sucrose (table sugar), and it works even though it is a 1:1 glucose/fructose ratio.
  • You might not get the optimum exogenous carb oxidation, but the differences are minute.

Higher carbohydrate intakes

37:52 -

  • There is some knowledge coming from the field. Aitor is a fantastic practitioner, and I had some communications with him.
  • Pro cyclists are consuming staggering amounts of carbohydrates. It is incredible to see how much they eat on the bike and their everyday diets.
  • I think we have to moderate the advice for the world-class cyclists and the rest of us.
  • We should try to push the limit on how much people can intake. The studies analysing consumption amounts like 120 g/h were on ultrarunners, focusing on parameters like recovery and muscle damage.
  • They showed that 120 g/h was beneficial. The researchers admitted that that could be potentially harmful in a training context. (less adaptive response)
  • My take is that people that could tolerate that consumption had previous exposure.
  • And Athletes now "train the gut" to push that 90 g/h recommendation to higher levels. They will not only consume those levels on race day.

Other carbohydrate sources

42:51 -

  • Graeme Obree (former cyclist hour record) used to eat jam sandwiches. 
  • People have to find foods that work for them. 
  • From a nutritional point of view, food is a reward system for your brain. Mood and satisfaction relate to food consumption.
  • If taking gels that might be sticky and hard to handle is not for you, find alternatives and consume them as you wish.
  • Most carb sources blend fructose and glucose, and even regular sugar is good. 
  • I have not seen any study where there was any difference in performance between regular sugar and sports nutrition products.
  • If a bag of sweets works for you, go for it. You might find that chewing them and their plasticity might increase GI issues, so it comes down to trial and error. (practice during training sessions, and not on race day)
  • For long sessions, you might want something that is whole food like jam sandwiches or carb bars, or rice cakes.
  • If you have food with protein and fat content in it, it will slow down digestion. It will take longer to chew it and for the stomach acid to break it down, and for the intestine to break it down and absorb it.
  • All of that delay could lead to GI distress. But if you have something that is much more simple to eat, you will not get those problems.
  • If you stop for a massive sandwich or a pizza, do not be surprised by how you feel when you start riding.
  • You want to get the best performance out of yourself on race day, so probably you will want to go on the more accessible digestible products. So go for the maximum fuel you can intake if that is your strategy.

Tips for athletes that have high training volumes

48:25 -

  • You can make your sports drinks. If you are into home cooking or baking, you will have sugar at home.
  • So, add sugar to your bottle and add water. Bear in mind that table sugar is sucrose, a 1:1 ratio of fructose and glucose.
  • You can also get glucose powder from a pharmacy and the same for fructose. (People make jams from fructose, and so you can buy it in a shop)
  • You can experiment with making it more concentrated by using less water.
  • The challenge with drinks is that you have to carry them. Therefore, it is easier for cycling than for running. (unless you have a back bag)
  • Moreover, you can buy sweets in bags ready to eat or put a jam sandwich in your back pocket.
  • Also, your diet should have high-quality food to support your training and fuel the training block you are doing.
  • Therefore, think of the training period and what you want your diet to do. Potatoes and rice are fantastic sources of carbohydrates.
  • You can use all that for regular training and supplement with sports products for when you need them.

Projects Andy is working on at the moment

51:55 -

  • The group here is looking at supplements that might enhance performance. (Louise Burke's group)
  • There are projects where we will evaluate the hydrogel further.
  • There is a study coming out on the topic.
  • So, we are looking to study nutritional strategies to enhance performance. We published something on ketone ingestion during exercise.
  • I have a project running at the moment looking at ketone ingestion during simulated triathlon, so we are playing around with the ketones and carb intakes.
  • We develop a demanding protocol on the bike. I have done it, and it was awful. Then, straight off the bike to a 10 km run.
  • So, that is a study in progress as well, and hopefully, we will finish it this year.

Rapid fire questions

53:50 -

What is your favourite book, blog or resource?

Mad, Bad & Dangerous to Know: The Autobiography of Ranulph Fiennes

What is an important habit that benefited athletically, professionally or personally?

Sorting out my sleep and getting a good sleep going.

Who is someone you have looked up to or who has inspired you?

Both of my granddads. They fought in WWII, and they represent the sacrifice of a generation that never asked for anything, and that is a thing I try and fail to do.


Bernardo Gonçalves

Bernardo is a Portuguese elite cyclist and co-founder of SpeedEdge Performance, a company focused on optimising cycling and triathlon performance. He writes the shownotes for That Triathlon Show, and also produces social media content for each new episode.

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