I am new to TR and loving it. FTP up by 10% in just 6 weeks of structured training (260W / 3.4w/kg) and I feel so much stronger aerobically. Currently in SSB2 LV plan but generally ride 4x/week or 7-8 hours.
One big change I have implemented is fuelling my workouts with sugar water. I take in 60-120g sugar/hr depending on intensity. I don’t drink any on short recovery rides (i.e. less than endurance zone for under 60 mins). It definitely:
makes the workout feel easier; and
I feel a lot less tired after the workout and recover faster. It is a gamechanger for me in this respect. I can still have a productive day after the workout!
I am not overweight and generally eat nutritious and healthy foods. However, people around me are concerned about me consuming so much sugar e.g. 300g of sugar on a 3 hour ride - they say it doesn’t sound “healthy”.
Firstly, my understanding is that our muscles burn the sugar directly from the blood while exercising without needing much insulin. Is this correct?
Second, do you have regular check ups with a doctor or sports nutritionist to check sugar levels / blood values are still in a healthy range?
Third, might it be better to use sugar with less GI e.g. table sugar as compared to maltodextrin for endurance riding?
Like Dr Alex already explained. This is because people don’t understand that your body works differently when exercising. 300g of suger during a long ride is totally different then 300g of suger when sitting on the sofa for 3 hours.
When you brush after the enamel will have become soft from the acids formed from the sugars, whereas the fluoride from brushing with fluoride toothpaste somewhat protects your teeth from the acids
This seems like a good opportunity to ask the question I have: I’ve just recently started fueling appropriately (based on info I’ve read on TR, under the Nutrition section) on 90-minute indoor rides. So far it appears that my stress levels in Garmin Connect go off the chart, after these rides. This is a new phenomena. I’m still evaluating, but this type of stress is exactly what I would see after consuming moderate or above, amounts of sugar or alcohol. On the one hand it makes sense, but on the other - this kind of stress is exactly what I want to avoid. Has anyone else seen this kind of stress spike after fueling for rides?
I have heard all of the “sugar is fine” for years, but stuff about fructose has recently made me wonder about it.
The leap from ingested sugar to muscle power is a pretty big one. Does anyone know if that study has been done? Something like ingesting tagged glucose then seeing when/where it is metabolized. Without something like that, it’s all inference.
I have not looked at the studies myself, but this specific method has been mentioned in discussions of how they determine if ingested glucose is actually used in various studies.
Can you be more specific regarding ‘stuff about fructose’ and what your specific concerns are?
For a deep dive on the subject of fructose, check out Peter Attia’s podcast with Dr. Richard Johnson on the subject. Personally I’m using Maltodextrin in my bottles and have no problems with 100+ grams/hr. No fructose.
Peter Attia’s podcast mentioned above has me wondering. His guest’s financial interests made me skeptical of him, but that doesn’t mean he is wrong.
My wonderment is more academic than anything - the effect makes more sense to be central (brain) rather than peripheral (muscle) without some very specific studies that I don’t think have been done. It is tough for people to consider given the strong push to dismember the body into its parts and analyze. This leads to faulty logic and a “well it’s the best we have” rationale. Just because it’s the best we have doesn’t in any way make it right or even guarantee that it is pointing in the right direction.
I am not arguing in any way that sugar/carb ingestion helps performance. That argument has been put to bed. Just wondering about the mechanism, not that it matters in the end at all
Still kinda confused about your question, but maybe this paper is what you were looking for:
But from what I can understand these are the steps:
When exercising we are in a low insulin state due to the fact that muscles are taking in the blood sugar and keeping it low.
So when consuming glucose(maltodextrin) say 100g/hr, the glucose gets absorbed in the small intestine and put directly into the blood. That glucose is then moved to the muscles where it is consumed. If the muscles are burning more than you are consuming, which is true for most cycling, there will be no insulin response.
Glucose being absorbed into the small intestine is the rate-limiting step. So a combination of fructose and glucose is used to maximize the sugar absorbed. BUT fructose must be converted to glucose in the liver which puts an extra burden at high concentrations. There is also some evidence of fructose being converted to lactate.
So fructose has an extra step to get to the muscle and high amounts could be detrimental to the liver but again detrimental might be drinking a 32 oz coke with high fructose corn syrup and sitting on a couch all day. I think we are fine doing a sweet spot workout with an extra 30g of fructose.
I’ve seen similar stress after really hard workouts. Things like a 90min Vo2max or Threshold workout. When doing Z2 work for 90min i see a much lower stress response in GC. Fuel is the same for both rides (90g an hour, 30fructose, 60 malto).
One explanation that made sense to me was that as the glycogen storage starts to be depleted, protection mechanisms kick in to reduce power output and preventing you running out of fuel. This happens gradually and starts way before the “tank” is nearly empty. So one benefit of carb consumption during a workout is removing this biological brake.
The other day my wife rolled her eyes at something i was snacking on, post workout, saying “urrgh that’s got about 10 grams of sugar in it!” I explained that in the last 2 hours i’d just consumed over 200 grams of sugar so this wasn’t even touching the sides.
This is right along the “Endure” train of thought. Super interesting book. It goes the opposite direction of the common reductionist approach to training. Your brain is a razor-sharp feedback and management tool for your body. Disregard it’s signals are your own peril
I definitely agree with this. One thing pointing to this as a possibility is that it’s been shown that even a mouth rinse with sweet drinks can lower RPE and increase output. Also, it makes sense that it isn’t like a gas tank. You can’t just refill it if it is drained to empty. Glycogen stores at zero essentially means you go into rigor and die. So it makes sense that your body would have some pretty hard stops to prevent that from happening.
I will try to explain in easy terms. All carbohydrates eventually end-up being broken down to three monosaccharides: glucose, fructose and galactose. These are then absorbed from the intestines into the bloodstream.
Glucose can be used by pretty much all cells, whereas fructose and galactose first need to go to the liver as muscles and other tissues don’t really know what to do with them.
Let’s forget about galactose now and focus on fructose. Fructose gets taken up by the liver so that there is barely any fructose floating around in the bloodstream.
In the liver it gets converted to glucose, lactate, glycogen and a very tiny bit can go into triglycerides. The latter two pathways aren’t really active during exercise but rather in recovery. So, during exercise we get glucose and we get lactate. Both lactate and glucose are great energy sources for the muscles and other tissues, so this gets converted to ATP (i.e., energy) very quickly.
In studies when we compare glucose based carbohydrates only with a combination of glucose and fructose we tend to see the same kinetics of their oxidation, meaning that CO2 that gets produced from fructose appears at mouth pretty much as quickly as from glucose, meaning that this conversion is pretty rapid. So nothing to worry about.
I rally wouldn’t be concerned about fructose for as long as you exercise and you remain in energy balance (i.e., not gaining body mass).
