Carbohydrates are your body’s primary fuel during endurance exercise, and most experts recommend taking in around 90g carbs per hour for optimal performance on the bike. But are these recommendations outdated? Is it possible to ingest and utilize more than 90g per hour, and if it is, would taking in more carbs improve your performance?
A new study by Dr. Tim Podlogar and colleagues explores these very questions. In this episode of the Science of Getting Faster Podcast we get all the details from Dr. Podlogar, and we consider the implications of this research for cyclists and endurance athletes.
Really interesting and surprising results from my initial read of the study. In my layman’s reading, it does not seem like the study showed any performance benefits from going to 120 instead of 90. But I’ll definitely tune into this podcast to see what the researcher’s POV is.
Based on what I understood from the talk he was more focused on carb uptake, and he concludes that a fit rider has the ability to take on and process 120g (Malto:Fructose @ 1 : 0.8) which means your body would have that energy on board to continue using.
The most interesting part for me was the pre-test onboarding process 500ml with 120g (1:0.8) or 90g (2:1). This is interesting since it means your body has the entire hour to process that first round. While what ever you consume during the first hour is just topping things up.
Great question! Prior to the recording, Dr. Podlogar and I were discussing this very thing. This is what he said:
Muscles are “super hungry” after exercise, and all the unabsorbed carbs will become available to [the rider] as soon as the exercise finishes, making the recovery process optimal. I had an athlete at the Tour ingesting 140 g/h, and he was feeling full for quite a while after the stage, so we skipped one of the recovery meals as the unabsorbed carbs probably provided him the fuel for glycogen replenishment.
He did mention that ingested fructose is not used by the muscles, but processed in the liver resulting in lactate and glucose production. According to the podcast with Peter Attia and Richard Johnson MD, is first metabolized by phosphofructokinase to phosphofructose. This is a constitutive enzyme, and will consume ATP to make ADP, and ADP to make AMP, and AMP to make plain adenine, which is then metabolized to uric acid, leading to deleterous effects on the mitochondria. I remain skeptical about consuming high amounts of fructose. I have not seen anyone adress this in the context of endurance athletics.
So for those of us who are not quite as science literate, can anyone with a good grasp of the pod and/or article confirm whether there is a benefit to taking in 120g of carbs per hour vs 90g? Also the article mentioned a 0.8:1 ratio instead of the traditional 1:2 ratio.
Watch @Dr_Alex_Harrison video in the other thread breaking down the paper and his hypothetical extrapolation of the results. In short if you can tolerate 120g/hr it can potentially help for events over 3 hours. The ratio needs to change when you exceed 90g/hr because glucose is essentially maxed out
From the recovery standpoint the 120 g/h definitely make sense! Or even higher! Because when you stop exercising, transporters for carbs are still present at the muscle’s membrane from during exercise. And if there is fuel available straight away, this will go in and the replenishment will start straight away! Very useful if limited in time until the next session!
There are studies looking at the effects of fructose on health. And yes - there could be some when you overflow the body with carbs! In the case of exercise, you can’t really ingest more than you expend. And no, uric acid levels don’t really go up after exercise because of a high fructose diet… Dehydration is a bigger problem when it comes to uric acid concentrations for instance.
@SarahLaverty great job asking questions, the only additional question I was hoping to hear - around what %FTP was VT1 / GET / boundary between moderate and heavy intensity domains?
@timpodlogar thank you so much for the very clear explanation on the decisions taken while designing the study, selection criteria, etc. Really appreciate it, along with your hypothesis and anecdotes around recovery.