The physiology behind electrolyte and energy intake during long and hot efforts
Introduction
Let us start with something that may sound a little controversial: If you are running a 5K, this article — and the product it is about — is probably not written for you.
Not because Hypertonic Gel 30 is not a good product. But because it is built for a completely different reality than a quick run: for the hours when the body truly starts leaking salt, and where simple energy intake is no longer the whole story.
Stay with us — because if you cycle long distances, do triathlon, or run marathons and ultras, there is a good chance you will recognize yourself in what we cover here.
Hypertonic Gel 30 is not built to replace anything in the PurePower range — it is built to fill a gap that arises in a very specific situation: when the effort extends beyond two hours, or when the heat seriously makes the body sweat heavily.
In that situation, the question stops being "do I have enough energy" and instead becomes "do I have enough sodium to keep my fluid balance intact".
This document reviews the physiology the product is designed around, with reference to the underlying research — and gives you concrete suggestions for how to integrate it into your specific sport.
1. What happens in the body when you sweat for hours?
Sweat is not pure water — it contains sodium, among other things, and the amount varies greatly from person to person. Research into exercise-associated hyponatremia (EAH) shows that sodium loss through sweat is highly individual, and that endurance athletes generally have a lower sodium concentration in their sweat than the general population (1).
In practice, this means that some athletes — the so-called "salty sweaters" — lose significantly more sodium than others under the same load, and that the need for electrolyte intake is therefore highly individual.
At the same time, it is important to be precise about causality: the consensus reports on EAH indicate that the main cause of dangerously low blood sodium is typically excessive intake of hypotonic fluids (plain water) rather than insufficient salt intake alone (2).
Sodium loss through sweat is one contributing factor among several — not the only one — but for athletes with a high sweat rate and high sodium loss, sodium intake during long efforts can help support performance and marginally reduce risk (1).
The point: Hypertonic Gel 30 is a tool to support sodium balance in athletes who know from experience that they lose a lot of salt — not a general necessity for everyone, and always in combination with sensible, non-excessive fluid intake.
2. Osmolarity: why "hypertonic" is a physical property, not just a name
Blood osmolality is normally around 280-300 mOsm/kg. An "isotonic" solution matches this concentration and can be absorbed without extra fluid.
A hypertonic solution is significantly higher — and this is where energy gels typically belong: classic gels contain approx. 60-70 g carbohydrate per 100 g and are therefore, as a starting point, hypertonic, not isotonic, which is why you should generally drink water together with an energy gel (3).
The physiological mechanism is well documented: when a hypertonic solution reaches the intestine without sufficient dilution, fluid is osmotically drawn from the bloodstream into the intestinal lumen to equalize the concentration difference.
This results in a negative net contribution to fluid absorption and plasma volume, in contrast to hypotonic and isotonic fluids (4). A randomized study of hyperosmotic saline in the intestine confirms the same mechanism: increased osmolarity markedly increases fluid volume in the intestine via secretion of water into the intestinal lumen (5).
That is why we recommend taking Hypertonic Gel 30 together with water.
Without water, the concentrated solution physiologically works against hydration; with sufficient fluid alongside it, it delivers both energy and a significant sodium contribution without the osmotic disadvantage.
3. The glucose:fructose ratio — why 1:0.6 is still a good deal for absorption
Intestinal carbohydrate absorption is limited by the transport capacity of the intestinal wall. Glucose is primarily absorbed via the SGLT1 transporter, which becomes saturated at intakes above approx. 60 g/hour — after this, oxidation does not increase further, regardless of how much more glucose is consumed (6).
Fructose, on the other hand, is absorbed via another transporter, GLUT5. By combining the two — so-called "multiple transportable carbohydrates" — both transport pathways can be utilized at the same time.
The effect is well documented in a series of studies from Jeukendrup and colleagues at the University of Birmingham: a mixture of glucose and fructose has shown up to 65% higher exogenous carbohydrate oxidation compared with glucose alone, and oxidation rates have been observed as high as 1.75 g/minute with a glucose-fructose mixture, compared with a previously assumed ceiling of 1 g/minute for pure glucose (7).
In one of the most cited studies in the field, total exogenous oxidation rose to 76 g/hour with combined intake, compared with significantly lower levels with glucose alone at the same total amount (8).
Our 1:0.6 ratio (glucose:fructose) sits in the broad, well-documented middle of this research field — it utilizes both transport pathways without being so fructose-heavy that it requires specific gut training to be well tolerated.
This is an important point: newer research indicates that a ratio closer to 1:1 (such as 1:0.8) only really shows its advantage at very high intake rates around or above 120 g/hour (9) — a level above what Hypertonic Gel 30 is designed for.
4. Sodium and electrolyte intake — what it actually contributes
With 169 mg sodium per sachet, Hypertonic Gel 30 provides a concrete contribution to electrolyte balance during long efforts.
Sodium plays several physiological roles during endurance sport: it is the primary electrolyte lost through sweat, it helps maintain the osmotic pressure that retains fluid in the bloodstream, and it stimulates thirst, which in practice makes athletes more likely to drink sufficiently along the way.
Consensus reports on EAH conclude that recommendations for low salt intake in the general population are not necessarily appropriate for endurance athletes — especially those training in heat, and that replacing sodium lost through sweat can contribute to performance and marginally reduce the risk of hyponatremia (1).
It is this target group — long, hot efforts with high sweat and salt loss — that Hypertonic Gel 30 has been developed to support.
5. How Hypertonic Gel 30 is designed based on this physiology
| Design choice | Physiological rationale |
|---|---|
| 30 g carbohydrate per sachet | Practical dose that fits into a combined fueling program without having to cover the entire hour’s energy requirement on its own. |
| 1:0.6 glucose:fructose | Utilizes two separate intestinal transporters (SGLT1 + GLUT5) for higher total oxidation than pure glucose, without the need for specific gut training. |
| 169 mg sodium | Targeted electrolyte contribution for athletes with high sweat and salt loss during long or hot efforts. |
| Very fluid consistency | Easy to consume late in a hard effort. Does not change the fact that the product is still hypertonic — it should always be taken with water. |
6. How to integrate it — sport by sport
The physiology behind Hypertonic Gel 30 is the same whether you are on a bike or running on asphalt. But the practical use — when, how often, and with what — differs from sport to sport.
Here are our recommendations for four of the most common situations where the product really makes sense.
Road cycling and long rides
On the bike, you have an advantage that runners do not: you are seated, and your stomach does not have to absorb impact from every contact with the ground. This generally makes it easier to consume a more concentrated gel along the way.
Cyclists often reach high sweat rates on long, hot rides or during hilly stages where intensity fluctuates — and it is precisely the combination of duration and heat that makes electrolyte balance relevant.
Practical recommendation: Build your carb strategy as usual with Energy Gel or Elite Gel, and add a Hypertonic Gel 30 every 60-90 minutes once the ride passes two hours, or as soon as you feel the heat really start to set in. Take it with a sip of water from your bottle — it is easy to combine when you are already drinking regularly.
Triathlon
Triathlon is particularly interesting physiologically because the load is cumulative across three disciplines.
The swim typically does not cause major sweat losses, but the bike leg — often the longest part of the race in terms of time — is where the actual salt loss truly begins to build. If you go into the run leg with a deficit, that is often where cramps and stomach problems really appear, because the body is already under pressure.
Practical recommendation: Use the bike leg actively to build an electrolyte foundation, especially in the second half — it is easier to consume and digest on the bike than later on foot. Use T2 (the transition to running) as a natural checkpoint: if you have sweated a lot on the bike, or it is a hot day, take another Hypertonic Gel 30 here before the run leg seriously stresses the system.
Marathon
Here, the relevance depends very much on how long you are out there and how hot it is. A marathon run in under three hours in cool conditions largely resembles shorter distances, where your regular gels cover the need well.
But the longer you are out there — and the warmer the weather is — the more the situation resembles one where sodium balance truly comes into play. Runners who spend longer on the course are also exposed to heat and sun for longer, which increases total sweat loss.
Practical recommendation: If you expect a finish time over three hours, or you are running in hot weather, add a Hypertonic Gel 30 around halfway and again in the final third, alongside your regular energy strategy. Combine it with water from the aid stations rather than sports drink at those same moments, so you do not double-dose carbohydrate.
Ultrarunning
Ultradistance is where the product truly finds its home. During efforts of six, twelve, or more hours, sodium balance is no longer a side issue — it becomes a central part of whether you can keep going.
It is also worth knowing an important detail from the research: a large proportion of the cases of dangerously low blood sodium seen in ultrarunners are caused by excessive intake of plain water at aid stations, not only by too little salt (2).
This makes a conscious, planned salt strategy — rather than random "drink when you are thirsty" behavior — especially important.
Practical recommendation: Make Hypertonic Gel 30 a fixed, scheduled part of your hourly plan rather than something you only take when you feel like it — the body’s thirst and salt signals become less reliable the longer you are out there.
Combine it with real food and possibly salty snacks in the later phases of the race, which is common practice in ultradistance, and always use water alongside it.
If you have an A race on the program, it is a good idea to test the rhythm on long training runs first — the gut, like the rest of the body, performs best when it is used to it.
7. Who is the product for?
Hypertonic Gel 30 is a specialist product. It is designed for athletes who are committed to their sport and consciously plan their nutrition around efforts that last a long time or take place in hot conditions — and who already know their own sweat and salt profile from experience.
Used correctly, together with water and as a supplement to the rest of your gel strategy, the product provides a documented physiological contribution that none of the other PurePower gels deliver to the same degree.
Recommendation for recreational athletes
If you are a recreational athlete, or you typically run/cycle for under two hours at a time without extreme heat, Hypertonic Gel 30 is probably not the right place to start.
Here, we recommend that you begin with Energy Gel 25 — it has been widely tested, requires no prior gut training, and covers the needs of the vast majority of training sessions and competitions without the extra complexity that electrolyte-focused fueling involves.
For longer sessions where a bottle-based carbohydrate plan makes more sense, energy powder can also be used as part of a structured endurance fueling strategy.
References
- Hew-Butler, T. et al. (2017). Exercise-Associated Hyponatremia: 2017 Update. Frontiers in Medicine. Read the study
- Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference, as reproduced in (1) and in Considering exercise-associated hyponatraemia as a continuum, PMC. Read the study
- Squeezy Sports Nutrition. The importance of osmolarity for endurance athletes and sports nutrition. Read more
- The Hydrating Effects of Hypertonic, Isotonic and Hypotonic Sports Drinks and Waters on Central Hydration During Continuous Exercise: A Systematic Meta-Analysis and Perspective. PMC. Read the study
- Influence of osmolality on gastrointestinal fluid volume and drug absorption: potential impact on oral salt supplementation. PMC. Read the study
- Jeukendrup, A.E. (2010). Carbohydrate and exercise performance: the role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition and Metabolic Care.
- Gatorade Sports Science Institute. Multiple Transportable Carbohydrates And Their Benefits, by Asker E. Jeukendrup. Read more
- Jeukendrup, A.E. (2008). Carbohydrate feeding during exercise. European Journal of Sport Science. Read the study
- Jentjens, R.L.P.G. & Jeukendrup, A.E. (2005). High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise. British Journal of Nutrition.