The Future Of Optimised Fuelling For Cycling Performance

Fuelling on the bike is undoubtedly one of the most important nutrition strategies for cyclists looking to optimise performance, particularly when cycling is prolonged or intense.

One of the big unanswered questions in sports nutrition in recent years has been what is the optimal dose of carbohydrates for cycling performance. For prolonged intense events, too little carbohydrate intake can potentially cause you to miss out on additional performance benefits of fuelling. Too much can potentially hinder performance due to stomach issues or even accelerated muscle glycogen use.

Currently, when it comes to how much to fuel on the bike, we have general guidelines to follow, which suggest that riders exercising for longer than 2.5 hours should aim for 90 grams of glucose: fructose per hour.

However, for a long time, we've known that individual differences exist in exogenous oxidation (the amount of a sports drink that is actually used), but we have not really known why. As we covered in a recent blog post, a recently published study has shown that smaller athletes may not be able to use as much carbohydrate from exogenous sources as heavier athletes. So, there is clearly a need to better individualise the feeding dose based on a rider’s body weight, at the very least. 

We also know many professional cyclists consume well in excess of the current 90g/hr guideline, and many amateur athletes may not even be able to get close to 90 grams of carbohydrates per hour. So, what is the best dose, and how do we determine it beyond just using trial and error? 

When it comes to fuelling, one of the key reasons why more isn't always better is because we have a limited capacity to utilise the carbohydrates that we take in during exercise. It is believed that this limit exists within the gut. As such, just because an athlete takes in 120 grams of carbs an hour, whilst they maybe able to tolerate it, it doesn't necessarily mean their gut can absorb it all, and the likelihood is that excess carbohydrates that aren't absorbed are accumulating in the gut over time, resulting in stomach upset, which may negatively influence performance. 

So, how do we determine an individual cyclist's absorption capacity and potentially the optimal dose of carbohydrates for fuelling? 

Fortunately, using clever scientific techniques, we can actually measure the amount of sports drink, gel, etc., that is oxidised (i.e. burned off) by the muscle, a process referred to as exogenous oxidation. 

A hot-off-the-press research study published yesterday has demonstrated a laboratory-based testing method through which a rider can establish the optimal dose for them. This study will no doubt pave the way for more athletes to get tested and determine the most effective dose of carbohydrate for their fuelling strategy based on their individual responses to carbohydrate feeding.   

The study, led by Dr Tim Podlogar, a researcher specialising in carbohydrate metabolism who also works as a nutrition consultant in professional cycling, involved a group of trained endurance athletes completing two trials. In the first trial, they consumed 90 grams an hour of glucose and in the second a dose that corresponded to their peak oxidation rate in the 90gram trial. 

Glucose is a carbohydrate that we typically see can be oxidised (i.e. utilised by the muscle as fuel) at a rate of around 60grams an hour; by feeding at 90grams an hour and measuring how much was used, they were able to determine the highest rate of feeding that was possible for glucose. 

After the 90gram glucose trial, participants then returned to the lab to be fed with a dose that was 20% higher than their peak rate of exogenous oxidation in the 90gram trial. The 20% above was to account for the around 70-90% oxidative efficiency (i.e. not all carbohydrates are 100% absorbed) that occurs when feeding carbohydrates. 

 Despite participants consuming a much lower dose of glucose in the second study, they saw the same rate of exogenous carbohydrate oxidation, oxidative effeciency went from 58% ± 9% to 83 ± 9%, which means that less carbs was left lingering in the stomach. This could have the benefit of reducing stomach upset, improving performance and optimising your intake of fuel on the bike.  

This method is now being offered as a way in which individuals can be tested to determine thei optimal fuelling strategy... https://sites.exeter.ac.uk/spet/ and is absolutely the future of determining the amount of carbs to consume on the bike. 

References

Ijaz, A., Collins, A. J., Moreno-Cabañas, A., Bradshaw, L., Hutchins, K., Betts, J. A., Podlogar, T., Wallis, G. A., & Gonzalez, J. T. (2024). Exogenous Glucose Oxidation During Exercise Is Positively Related to Body Size. International journal of sport nutrition and exercise metabolism, 35(1), 12–23. https://doi.org/10.1123/ijsnem.2024-0097

Podlogar, T., Cooper-Smith, N., Gonzalez, J.T. et al. Personalised carbohydrate feeding during exercise based on exogenous glucose oxidation: a proof-of-concept study.Perform. Nutr. 1, 2 (2025). https://doi.org/10.1186/s44410-025-00003-9