Liquid vs. solid carbohydrates: what ratio should you aim for during training and racing?

Gels, drink powders, bars, fruit, sandwiches... endurance athletes have no shortage of options to meet their carbohydrate needs. But does the format (liquid or solid) really change the outcome for performance? Here is what research says, and how to adjust your ratio according to your sport and the duration of your effort.

What science says: the dose matters more than the format

Several studies on cyclists show that a glucose:fructose mixture ingested in the form of a solid bar is just as well oxidized (and thus just as well used as fuel) as an identical mixture taken as a drink, provided the same amount of carbohydrates is ingested per hour. The same observation applies to semi-solid gels versus liquid drinks: oxidation rates are similar. In other words, it is not the format that primarily determines performance, but the total amount of carbohydrates absorbed per hour.

But intensity and the sport change the game

This finding holds true primarily for cycling, a low-impact sport where the stomach remains relatively stable. As soon as you move to running, the picture changes: a Dutch study of 32 triathletes compared the ingestion of liquid and solid carbohydrates during an intense effort of over 3 hours combining cycling and running. The result: half of the athletes completed the effort with liquid nutrition only, compared to only 9 out of 32 when solids were introduced. The movement of running (the "sloshing" effect in the stomach) makes the digestion of solids much more difficult at high intensity.

The role of duration: managing fatigue during very long efforts

For efforts lasting several hours (ultra-trail, Ironman), 100% liquid or gel nutrition becomes difficult to tolerate in terms of taste and digestive comfort—this is known as "palate fatigue." This is why ultra-endurance athletes often integrate a portion of solid, real food (bananas, potatoes, sandwiches) at aid stations, supplementing a liquid base. As intensity is generally lower during these very long efforts, the stomach tolerates these occasional solid inputs better.

The practical ratio to target based on your activity

By combining these elements, here is a realistic starting point to adjust according to your personal tolerance (always tested in training, never improvised on race day):

• Short and intense efforts (less than 90 minutes, running or racing): aim for 100% liquid or gel. The body does not need solids for this duration, and the digestive risk outweighs the benefit.
• Moderate efforts (1.5 to 3 hours, running or cycling): a liquid base of 70 to 100% remains the safest bet for running; on a bike, you can integrate 20 to 30% solids (bar, fruit) without major digestive issues.
• Ultra-distance (over 4 hours): a more balanced distribution, around 50-60% liquid and 40-50% solid at aid stations, helps maintain appetite and caloric intake over time—while prioritizing liquids whenever intensity increases (a climb, a final sprint).

And what about gut training?

Regardless of the target ratio, the key remains "gut training": gradually increasing, in training, the amount of carbohydrates ingested per hour to accustom the gut to absorbing more, regardless of the format. A trained gut tolerates both solids and concentrated liquids better.

This is exactly why a reliable liquid base like the ELIXYR Endurance Fuel is an excellent foundation: easy to dose, to dilute in your ELIXYR soft flask, and designed for optimal absorption even at high intensity. You can then add occasional solids on your longest outings, once your liquid base is well tolerated.