Dan posted some myth busting on his blog:
https://www.endureiq.com/blog/beyond-the-hype-exploring-6-endurance-sport-myths
I was not aware #4 was a thing. I own a PH Sweat Testing rig, and I’ve never heard someone say that to me during one of their sessions, and I’ve test around 200 people over the last 5 years.
waits for Dr Harrison to chime in
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I am interested by Plews’ comments on using just enough carbohydrate to keep blood sugars steady.
As a type 1 diabetic who has had to use gels and carbs to do any exercise longer than 30 minutes for the last 30 plus years this strikes me as right. I have a fixed amount of insulin in my body and only try to consume enough carbohydrates to keep my blood sugars steady with the exercise I am doing and insulin which is present. Without those carbs I just wouldn’t be able to complete the exercise.
I have often wondered if Maurten’s claims are just an attempt to get people to buy more of their overpriced product. It is such a ripoff. Although I do like the flavourless aspect of it, it definitely did not ‘enhance’ my performance.
waits for Dr Harrison to chime in
Dr. Dan Plews: “However, this understanding of the metabolic response to carbohydrate ingestion during exercise – no effect on muscle glycogen breakdown, sparing of liver glycogen breakdown – doesn’t suggest to me that more carbs should be better.”
He’s right. That’s *not *what would suggest to someone that more carbs might be better.
Here’s what *would *suggest to someone that more carbs might be better:
The avoidance of hypoglycemia, especially later in long exercise bouts (>>3 hours)
The increased cognitive drive caused by consistently elevated blood glucose.
The fact that not everyone can train 10-20 hours per week for years on end and still may want to compete well, even with merely mortal fat oxidation ability, and mediocre fitness, and meager resistance to symptoms of neurogenic hypoglycemia, all due to the aforementioned lack of training volume, history, and fitness. (FYI: high training volume, high fitness and work capacity are the primary drivers of high fat ox ability).
I’m sure there are others but those are top of mind at this hour 
Finally a couple common red herrings.
Red herring # 1: “It doesn’t spare muscle glycogen.” That’s not the point, nor is it necessary for carb fueling to spare glycogen to improve performance
Red herring # 2: “Not much data on improved performance.” First, not true. Second, even if it were true, the absence of data does not indicate absence of effect, when the challenge of obtaining such data is obviously enormous.
(Read: it’s hard to ask someone to try a low-carb 5-hour time trial, let alone repeat trials of 5-hour all-out efforts with varying carb dosing strategies. It’s equivalently hard to cajole researchers and their graduate assistants to sign up for this sort of thing. Virtually all studies on efficacy of carb fueling strategies for enhancing performance use 3-hour sessions or less. It’s very likely the that the greatest differences in performance between high-carb fueling strategies and lower-carb strategies exist in 4-10-hour events. Maybe the even longer ones too, if fueling execution is good, but it’s probably easiest to tease out in the data and get fueling/hydration ‘correct enough’ in the 4-10-hour non-thermally challenged scenarios. Those have been virtually non-existent in the literature for the aforementioned reasons.)
I’d concur.
As coach to several individuals pushing 320 / 330 / 340w (males) and 220+ w (females) in an ironman, setting bike all of whom have set bike course records, one even putting 6mins into Cam Wurf on the bike and big fat ZERO of these folks are running well / to their potential off 90g CHO per hour (men) or 70g CHO per hour (women) even with well validated world class fat oxidation.
I understand the difference of optimal carbohydrate intake between men and women is most likely to be explained by the body size difference, right? If yes, have you observed any quantifiable differences within the same gender, e.g. man 55kg vs man 75kg?
(Read: it’s hard to ask someone to try a low-carb 5-hour time trial, let alone repeat trials of 5-hour all-out efforts with varying carb dosing strategies. It’s equivalently hard to cajole researchers and their graduate assistants to sign up for this sort of thing. Virtually all studies on efficacy of carb fueling strategies for enhancing performance use 3-hour sessions or less. It’s very likely the that the greatest differences in performance between high-carb fueling strategies and lower-carb strategies exist in 4-10-hour events. Maybe the even longer ones too, if fueling execution is good, but it’s probably easiest to tease out in the data and get fueling/hydration ‘correct enough’ in the 4-10-hour non-thermally challenged scenarios. Those have been virtually non-existent in the literature for the aforementioned reasons.)
This brings me back to the Dan Plews & Sam Long case.
Early 2023 Sam was doing well on the 70.3 distance, struggling to deliver on the 140.6 distance. He might not have fully know what he wanted to prioritise at that moment. He partnered together with Dan, who no doubt is an excellent coach, but has his style (as does Sam of course). Dan introduced the training & feeding interventions, to bring up the fat oxidation levels for Sam. Sam probably didn’t like it and/or didn’t see short term improvements, plus probably thought to himself “let’s maybe focus on 70.3 for the time being”, where he didn’t need massive fat oxidation. He (re-)started winning 70.3s and later the year was offered the T100 contract, suiting his energy system perfectly.
waits for Dr Harrison to chime in
Dr. Dan Plews: “However, this understanding of the metabolic response to carbohydrate ingestion during exercise – no effect on muscle glycogen breakdown, sparing of liver glycogen breakdown – doesn’t suggest to me that more carbs should be better.”
He’s right. That’s *not *what would suggest to someone that more carbs might be better.
Here’s what *would *suggest to someone that more carbs might be better:
The avoidance of hypoglycemia, especially later in long exercise bouts (>>3 hours)
The increased cognitive drive caused by consistently elevated blood glucose.
The fact that not everyone can train 10-20 hours per week for years on end and still may want to compete well, even with merely mortal fat oxidation ability, and mediocre fitness, and meager resistance to symptoms of neurogenic hypoglycemia, all due to the aforementioned lack of training volume, history, and fitness. (FYI: high training volume, high fitness and work capacity are the primary drivers of high fat ox ability).
I’m sure there are others but those are top of mind at this hour
Finally a couple common red herrings.
Red herring # 1: “It doesn’t spare muscle glycogen.” That’s not the point, nor is it necessary for carb fueling to spare glycogen to improve performance
Red herring # 2: “Not much data on improved performance.” First, not true. Second, even if it were true, the absence of data does not indicate absence of effect, when the challenge of obtaining such data is obviously enormous.
(Read: it’s hard to ask someone to try a low-carb 5-hour time trial, let alone repeat trials of 5-hour all-out efforts with varying carb dosing strategies. It’s equivalently hard to cajole researchers and their graduate assistants to sign up for this sort of thing. Virtually all studies on efficacy of carb fueling strategies for enhancing performance use 3-hour sessions or less. It’s very likely the that the greatest differences in performance between high-carb fueling strategies and lower-carb strategies exist in 4-10-hour events. Maybe the even longer ones too, if fueling execution is good, but it’s probably easiest to tease out in the data and get fueling/hydration ‘correct enough’ in the 4-10-hour non-thermally challenged scenarios. Those have been virtually non-existent in the literature for the aforementioned reasons.)
Plews actually talks about enough carbs to avoid low blood sugar/hypoglycaemia. To avoid hypoglycaemia you simply don’t need 90grams plus of carbs per hour. I have a fixed amount of insulin in my body and at race efforts have 25grams of carbs in gels every 45 mins for half Ironman and above, plus maybe around 30 to 40 grams per hour in sports drink. This has not changed with improvements in speed etc.
I’m not sure if this would necessarily change with elites unless they were doing stuff above threshold effort like in road cycling for example.
For 3 hours that is 190 to 220 grams of carbs. So between around 63 grams of carbs and 73 grams of carbs per hour averaged out. This is easily enough to keep my blood sugars topped up without any chance of a hypo. And the insulin in my body is fixed so a much great chance of going low in blood sugar.
There is no difference in my own cognitive drive if I am in a normal range of blood sugars (ie 5.0 to 9.0 mol/L). Where it is affected is when I get into the 4.0s and below. Not sure if a ‘normal’ person ever truly goes hypoglycaemic. Bodybuilders who use insulin as a PED have described it as a pretty scary experience.
Anyway, that’s just my own 20 years plus experience of using carbs to ensure I can do endurance sports. I’m no scientist but basically have needed carbs for the last 34 years or so to do sports I enjoy, so have a pretty good idea of how carbs can impact my blood sugars with exercise.
intra-gender at the same w/kg and assumming similar fat oxidation rates yes you’d expect slightly lower CHO needs, slightly. Since the “work” being done is less (say 280w vs 330w)
I agree that Dan does too much heavy lifting with his no evidence claims.
Especially when there is evidence of success athletes doing exactly that.
True, it might not be causation, but if he’s looking for a well designed study to validate the current trends, that would leave his athletes perpetually behind the curve.
And there’s at least one good reason for targeting higher carbs – you rarely end up consuming them all. Some get left in the bottle, wraper, spilled out etc. The reality is taking measured carbs in a controlle, relaxed environment is different than when these athletes are measuring them out days before, prone to make mistakes then, and then taking them while under stress.
All that said, I do appreciate how he’s relying on science, not trends. But as a scientist, it would be nice if he was willing to run his own tests with his athletes and report his findings.
Personally, I can’t explain the precise mechanism but I definitely experience a feeling of an increase in capacity to continue pushing shortly after taking carbs in during a race. I doubt it’s transported them to my muscles so quickly, but I wouldn’t be surprised if there’s some neuro function going on that signals my muscles, “it’s OK to keep pushing I just lined up a other fuel source”. Or even if the effect is entirely neurological and not linked to the metrics Plews is monitoring.
Have you actually tried doing 100+ g/h or did you just decide you don’t need that much? Nearly every top level endurance athlete is doing massive carb intake for every long event. I’m sure there’s an upper limit, but the current landscape suggests the optimal carb intake is as much as your stomach can handle.
The premise you’re starting from is that as long as you’re not hypoglycemic them your performance is stable. I don’t find this to be true. There’s a pretty clear performance decline as muscle glycogen depletes. Eat a large calorie deficit for a few days and go for a ride vs. eat a carb heavy loading diet for a few days and go for a ride. Not hypoglycemic on either, but one is surely going to be faster.
Personally, I can’t explain the precise mechanism but I definitely experience a feeling of an increase in capacity to continue pushing shortly after taking carbs in during a race. I doubt it’s transported them to my muscles so quickly, but I wouldn’t be surprised if there’s some neuro function going on that signals my muscles, “it’s OK to keep pushing I just lined up a other fuel source”. Or even if the effect is entirely neurological and not linked to the metrics Plews is monitoring.
This has actually been studied and proven. 2-3% for a “carbohydrate mouth rinse” for a few minutes, at least.
Nice! Thanks.
I think Plews finds himself in a tough spot. He’s staked out so much of his coaching reputation on his scientific background and how is he supposed to say, “looks like I got it wrong with how I built my training around the science.”
I suppose he can just flip the switch and say he’s happy to adjust based on new evidence, but that does admit he was arguing himself out of being on the cutting edge while he argued his position with old or incomplete studies.
It’s not like he’s entirely wrong. It’s just wrong in terms of degrees. So why not do a training block with higher carb doses with some athletes and at least get a feel for whether or not it works. Sure, it’s not a robust RCT, but some direct personal evidence might at least give some clues.
Your body doesn’t require insulin to uptake carbohydrate during exercise though.
I’ve noticed a massive increase in performance and durability using 100-120 g/hrs for everything from interval rides to 5 hour races. I only do that when there’s significant intensity on the ride though
Yeah, he’s certainly painted himself into a corner.
On one hand he can “follow the science” and get more consistent results but miss the cutting edge. As you said, he’s always going to be a step behind if waiting for studies to confirm what’s being done.
Ultimately I think the issue is that coaching athletes to consistently finish in the top percent is great, but 13th place 20 times doesn’t pay the bills. One big win is preferable even if the other 19 races are completely anonymous. Leaving just that fraction of a percent on the table is a disadvantage right off the bat.
It’s puzzling why he doesn’t at least test high carb with his athletes. It takes one long ride at a good effort to see if it works.
Besides going to a performance lab, how would you determine one of your athletes has a world class fat oxidation rate?
Let’s not forget that it’s not only his coaching philosophy, but also he has a brand to protect: sFuels. He built it around a low-carb, high-fat approach. A few years ago he was also selling some courses so one could apply his strategy, I know because I paid for two of them.
It’d be like Andy Blow saying that it turns out we don’t really need sodium supplementation, and coming out with his brand of bottled water: SIMPLE HYDRATION.
I don’t think Plews is ever coming back from the HFLC approach.
Besides going to a performance lab, how would you determine one of your athletes has a world class fat oxidation rate?
You can get a very rough approximation through lactate testing. Lactate is only produced through glycolysis so any fat burn that you have is lowering the glycolysis need. There’s a lot of confounding factors like lactate clearance rates. But very generally if you see an athlete with a high threshold power output and a low blood lactate value you can infer that a “world class” amount of output is generated through fat oxidation.
I feel like I am reading this wrong. You agree with 90/70g CHO/hr, correct? Also, do you lower the CHO for an old guy like me who rides 180w?
Thank you,
Let’s not forget that it’s not only his coaching philosophy, but also he has a brand to protect: sFuels. He built it around a low-carb, high-fat approach. A few years ago he was also selling some courses so one could apply his strategy, I know because I paid for two of them.
Bingo. No real room for objectivity here. In finance, we call it “talking your book”.