Agreed. Folks are just running calculated tradeoffs too. It takes some input of personal time and energy to fuel well. If you've got a spouse who wants to spend time with you or a job/business that is pulling at you, and you CAN run your long run with just a bit more fatigue without carbs... well, I do that all the time! Not optimal at all, but optimal for life happiness and financial well-being given the time-cost for sure. ;)

The performance improvement and RPE and HR reduction is quantifiable, even within-session. Just small effect within session. Almost certainly would be quantifiable in a more meaningful performance way if studied long-term. Feasibility of long-term study for something like this is.... challenging, to say the least, from a poor researcher's perspective.

NIH doesn't give grants to optimize the pointy end of endurance performance. They give grants to research prevent diabetes... which just exercising more is fine for! Sport nutrition research grants' dollar figures are <<1% of common NIH grants. I'll be impressed with the resolve of any researcher who chooses to study the even medium-term training adaptation effects of higher carb fueling.




You're very welcome. I'd love to spur some change.

There have been other areas where a certain piece of info becomes "common sense" before it's actually been well-tested. Low-rest hypertrophy training was touted as the gold standard in muscle building for a long time because of a (meaninglessly transient) bump in testosterone after performing such a lifting strategy. The testosterone bump does indeed exist. Just not sufficiently to merit low rest intervals in the weight room all the time for maximizing muscle growth. When weighing all thing tradeoffs it becomes infinitely clear that longer rest between weight room sets is better for strength and muscularity, long-term. But that took almost 15 years of a few sport scientists like me shouting from the rooftops to overcome because the low-rest recommendation had made it to the textbook level... primarily because the leader of the low-rest movement had written a book on it, and was also head of the NSCA at the time, the publisher of the main strength and conditioning textbook used in all college courses on the topic.

The current sticking points in exercise fueling nutrition dogma vs. science and press, as I see it:

1. A few leading researchers who first discovered that 90g carbs of multiple sugar sources was better than 60g/hr, got their work into every nutrition journal's position stand, subsequently into all the textbooks, and then amplified by every nutrition certifying agency and supplement company who seized the opportunity to sell more sugar when "90" became the new "60." Now 60 & 90g/hr are cited, rote, with no further thought.
   
   
2. Primary reasons researchers don't question the 90g/hr:


1. There was a single study that found that 30g/hr of fructose was the limit for fructose absorption during exercise. Turns out, fructose by itself is not absorbed well. When it's consumed with a glucose source, fructose absorption can far exceed 30g/hr, and I suspect may approach 80-90g/hr in a very well-trained gut.
2. 60g/hr glucose, in isolation also appears to be a bit of a hard limit before GI distress results. I think this may bump up closer to 70-75g/hr in well-trained guts, of regular exercisers, when consumed with fructose
3. The above two facts are probably recent to within the last 10 years or so, and most of my colleagues who I would consider experts in general sport nutrition, but not endurance nutrition, are surprised to learn of it when I point it out to them.
4. Most sport science researchers are young. They are within 10 yrs of having graduated with MS or PhD. Folks gravitate towards more complex and more clinical questions as they age as researchers. 60 & 90g/hr is the dogma taught in virtually all undergraduate and masters nutrition, dietetics, and exercise science programs, even some leading sport science programs. I don't blame them. Endurance nutrition is a bit of a niche and unless you've experienced suffering during long
5. Most studies only examine 1.0-2.5-hour exercise tests with maybe 3 hours being as long as any research has time to study. The difference between 90 and 130 grams of carbs per hour is likely amplified only beyond about 3 hours. It's very hard to carry out studies that involve 4-hr time or 5-hr time trials. No one has time or interest in killing themselves for 4 hrs multiple times for science because it interrupts their training process. Even fewer (none) researchers want to carry that out because of the time-cost involved!
   
   
3. Primary reasons lay-people and athletes don't question the 90g/hr:


1. Most folks can't even figure out how to do 90g/hr because they're messing up osmolality and hydration needs. Gotta have hydration, and with fluid you gotta have sodium. Miss out on sodium and you're going to get sweet aversion and performance-relevant hyponatremia and avoid the 90g/hr. Miss out on fluid and you're going to get gut cramps or worse downstream GI effects, from even 90g/hr. Lots of folks report "a gel doesn't sit well with me" because they don't drink water with it. Most folks could take 3 gels at a time with 16-20oz water on an empty stomach in the middle of a hard session and fair okay. They fail to do the water with it. When there are so many hurdles that are lost on the average person, it's easy to believe that 90 is the top when there appears to be mountainous social proof that corroborates.
2. The fat adaptation movement which I hope has been quashed has intensified any subconscious thought that maybe less carbs is better and so I don't always need to train with them because there may be a benefit. There is not. See my other recent posts for more there.
3. Most folks don't train more than 2-3-hr sessions where you CAN get by on less. If you're routinely doing 4-6-hr sessions or racing 4+ hrs, there will be noticeable difference in performance. This makes basically ultra-runners, P/1/2 cyclists, and 70.3 & 140.6 triathletes the only folks who are ever likely to investigate enough personally, to notice a difference.

---

Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
-------------------------------------------------------------------------------------------------------------------------------------------------
📱 Check out our app → Saturday: Pro Fuel & Hydration, a performance nutrition coach in your pocket.
Join us on YouTube → Saturday Morning | Ride & Run Faster and our growing Saturday User Hub