This might have been asked already, but did you jump straight to 80g carbs/hour or build up slowly? If you have a sensitive stomach you might need to build up to that intake more gradually. I’m a similar weight to you, and I have to be a little cautious with higher intakes. I’m at about 70-80g an hour right now, but getting there was a pretty slow process.
Also re the necessity of fueling on 1hr rides- if my intention was to start doing some longer rides, I’d rather make sure I’m not going to shit my pants in the first hour. Seems like pretty solid reasoning to me. Also if the OP sees improvement in RPE and recovery I hardly think that qualifies as “no benefit.”
With all due respect, this probably isn’t true. Especially if training first thing in the morning when blood sugar is lowest. Some sugar consumption right before and during exercise is VERY likely to enhance performance.
Starting fueling roughly 5-10min before training, and probably as much as 15min before training is likely to have your body respond virtually identically to had you waited until 15-30minutes after training-start, except with less initial blood sugar drop at onset of exercise, and probably improved performance.
What is needed / critical is not a good proxy of what is optimal.
Far too many folks get deterred from optimal fueling by a few attempts gone wrong, followed subsequently by the “it isn’t necessary” argument.
Necessary ≠ Optimal. And I think it’s both an important, and valuable distinction to make, especially for folks newer to endurance exercise, because when fitness is lower folks tend to burn carbs at a higher rate, are more likely to get symptomatic hypoglycemia, and are more likely to feel discouragement and cease or reduce their future training efforts in response to the negative early outcomes. Yes, my population sample = those that have sought professional nutrition advice… but I’d posit that the primary reason most do seek pro nutrition advice is precisely this line of thinking.
I do apologize to you personally for using your specific comments as an “example” here. I mean no disrespect personally. Just attempting to highlight a pattern I see among endurance athletes who are still troubleshooting how to manage it all.
Intra-workout fueling is primarily limited by gut tolerances which are largely independent of body weight.
I agree, slightly less may be necessary and optimal, especially if GI distress is present.
60-80g per hour? For intra-workout? or 60g-80g target for something else? Intra-workout targets apply for virtually anyone. Table of Intra-workout Carb Needs Per Hour of Training from The RP Diet for Endurance I profit from sales. Disclosing because other authors should get credit for table-sharing. Apologies for clutter)
It absolutely happens. Exercise exacerbates it if there is a bolus of carbs consumed 30-75min prior to exercise, and then slow/minimal consumption during exercise, or if gut clearance of what is consumed is slow. Thanks GLUT4!
Yup! Timing, composition, and hydration are meaningful.
Maybe not. If she errs on side of less during training, while still doing same pre-workout, symptoms of hypoglycemia are likely to worsen.
If she errs on the side of less pre-training and more or same during training, hypoglycemia may resolve but GI issues may remain.
If she just moves the timing and ensures optimal hydration, sugar & sodium concentration, issues may vanish with no reduction in consumption whatsoever.
You may also be right. But I posit that it’s worth seeking optimality before throwing in the towel on fueling.
Tolerance is same or better during short duration. Need is lower.
Unless it’s just a concentration issue, in which case more preemptive and intra-workout fluid consumption may solve it completely.
Seriously impressive! I just about died riding 9 hrs last week… but that might have been because that’s more hours than I typically ride in a week
You could do 57g an hour in the first 4 hrs and still do 57g an hour for the next 5. I did ~100g per hour for my ride with no issues. My wife did something like 75g/hr for 21 hrs straight. Could have done more had I not screwed up her sodium early-on. Sorry @michelleihowe!
GOLD.
Thank you! That’s one good reason. Another is that she’s fasted pre-ride, and in fasted states, in folks who generally consume a carb-inclusive diet (ie. not LCHF), performance will certainly be enhanced by the provision of elevated blood sugar via pre- and intra-workout sugar consumption.
Surprisingly, not THAT much. Probably not so variable that anyone EVER needs to consume <60g/hr, and I haven’t found anyone that can’t tolerate 75g/hr during cycling efforts >2hrs, with some coaching. Including women in the 50kg range. I have found folks who enjoy 150/hr and seem to tolerate more… though I never prescribe it. (men, high muscle mass, high-output, long fueling history)
Surprisingly, it’s not THAT weight dependent either. My wife weighs ~60kg and can easily tolerate 130g/hr for 2-5hr rides.
You are probably one of the lucky few for whom hypoglycemia is minimally noticed with physical symptoms. There appears to be a very wide inter-individual response. For me, it literally feels like I AM dying. The body is doing an excellent job shutting down my desire to continue exercising at whatever power I currently am. I have a similar faith in the body’s regulatory mechanisms.
Interestingly, you’re right… that the regulatory mechanisms in place do keep me alive, as I have actually TRIED to cause a fainting event by pushing harder. Feels utterly terrible. Sweating, shaky, angry, tingling, lightheaded, did I mention sweating profusely, even if cold, and generally, quite honestly, feeling like I might drop dead, but after a few minutes (sometimes an agonizing 30 minutes) my blood sugar will stabilize and symptoms slowly disappear.
I’m generally not prone to making recommendations that would get me sued, but I’d be pretty surprised if someone could cause fainting via exercise-induced reactive hypoglycemia. I think that the symptoms that would precede fainting would be too powerful in convincing the person that they ought to stop long before it gets there. I’ve even tried increasing motivational factors with high dose caffeine. No luck
A huge amount of increased fat-burning ability (the primary effect of “fat-adaptation”) comes from
Training age and general fitness.
Training occasionally, or regularly, with limited intra-workout carb consumption.
ie… you don’t have to have a low-carb or high-fat diet, to be reasonably fat adapted.
150g carb load in 67kg subjects.
75% VO2 max effort after 3 min warmup.
Improvement in plasma glucose after the 15 min nadir.
I still look at that and think, okay this is something you can evoke in a lab setting. This seems unnatural.
With people taking in less carbs/body weight for a more natural insulin spike and warming up more before an effort, there’s a good chance this is not relevant for general practice.
The parameters from that study. I don’t think people are taking in 2g/kg of glucose before doing an effort equivalent to 75% VO2 max without a legit warmup. Just because the authors could elicit a sub 4 mmol/L blood glucose under these parameters doesn’t convince me that everyone needs to worry about eating before riding their bike. If there is another study that has parameters more relevant to real life, I promise to look at it.
As I pointed out before, there are at least a dozen such studies - did you read them?
That said, and to repeat the point, although rebound hypoglycemia is well documented, it usually isn’t severe enough to cause neuroglucopenia. (However, that actually makes it potentially more insidious, as your performance could be impaired without you realizing it.)
ETA. The subjects in this study " reported to the laboratory 2,4,6,8, or 12 h after consuming a carbohydrate meal consisting of bagels, jelly, and orange juice (2 g/kg carbohydrate, 0.3 g/kg
protein, and negligible fat)."
I looked at this one, I didn’t do an exhaustive lit search and review. The concept didn’t have enough face validity to warrant significant time.
My personal takeaway after seeing this data and the other linked study is that you should warm up before jumping into a near threshold time trial effort. The group that ate the carb load 4 hours before their effort still reached sub 4 mmol/L. Should we always go into workouts fasted for at least 6 hours so that the pancreas is pumping out glucagon and all of the gluconeogenesis pathways are primed?
I guess if survival requires running for 5-10 minutes without prior warning, some of us might be in trouble.
I still see a lab scenario that wouldn’t be encountered in regular activity. I’ll continue to consume carbs prior to exercise and warm up for now.
My take is that rebound hypoglycemia probably happens a lot more often than you seem think, but since most folks don’t seem to become overtly neuroglucopenic, it goes unnoticed, and in fact may not matter, except when it actually does
That’s different, though, than simply denying it happens entirely, just because it doesn’t fit with one’s belief system.
I’m currently trying:
I’m starting with 75 g of carbs per hour of riding, 500 mL of water. Riding before breakfast.
1.) 50g of sucrose+25g of glucose.
I consumed all of it 10 min before exercise.
I had to stop because I started sweating so much, my vision got blurry and I felt so sick that I threw up. It felt like someone cut my legs in half. Thank God I wasn’t too far away from my house. Fail.
2.) 50g of sucrose+25g of glucose.
I again consumed all of it 10 min before exercise.
I brought a gel with me (25g of carbs-1:1 malto+fructose). I again started sweating, vision got blurry etc, but I took a gel and felt fine. Success?
TMI My stomach started gurgling, I came back home and found out a surprise in my pants.
3.) 50 g of sucrose+25g of glucose.
I started consuming it 5-10 min before, during my warm up and continued during riding. Everything went great. No hypo, no GI issues. Success.
Also, I feel like 500 mL of water is too much.
I think that now I know how to avoid hypo. My hypo seems like a textbook example.
Next is experimenting with carb sources. I also read other threads, seems like malto is superior to glucose?
I also went through my dairy and I was making a lot of mistakes with the intake of carbs, specifically fructose. I would consume 2:1 ratio of fructose to glucose! No hypo, no energy, but I would get a GI distress.
This thread is super interesting. I have some weird stuff going on to. I generally train in the morning about 6/7am for 1-2 hours. I have been following advice and simple carbs 20-40g pre and i always don’t feel great and slow and i always get a crash.
Today and a couple of other time did it fasted on just coffee and no such issues. Good power no crash not staving feeling.
The reactive hypoglycemia makes so much sense as when it is longer if i fuel on the bike no such issues it seem the pre to be the issue. I always have a large carb dinner too.
I wonder if there is anything in how fat adapted you are / body fat levels / glycogen depleted? When i have simple carbs (say a stroopwaffel) i go up like a rocket then crash like a bitch 20-30 mins later.
Same for me. I used to train fasted, on just a coffee. Even 2-3 hour rides. But I found out my heart was pounding too fast and I would sweat like nothing. I have a caffeine sensitivity.
Then I started consuming carbs pre/during and I felt so so much better, except for other issues (GI distress and hypo), but my recovery is so much better. And I don’t feel like dying anymore on a bike (except when I go hypo).
Thats interesting, i don’t get the pounding heart and generally just feel stable energy.
For example yesterday with 40g carb pre i felt low and lethargic and could get my HR above 155 and or put any efforts in no matter how hard i tried. Today fasted i could push, put power down and get the HR to around 173 in efforts.
“My take is that rebound hypoglycemia probably happens a lot more often than you seem think, but since most folks don’t seem to become overtly neuroglucopenic, it goes unnoticed, and in fact may not matter, except when it actually does”
Yes, minimally. But most important when gut distress is present.
Try 60g sucrose, 15g malto.
Yup. That’ll happen without sufficient intra-workout consumption.
Yep, no-carb is better for hypoglycemia-sensitive folks than screwed-up-carb approach. Hence: the fat adaptation movement exists… in my opinion. Hypoglycemia sucks. Avoiding carbs entirely fixes that.
Pre-carb in absence of intra-carb = hypoglycemia on bike.
Pre-carb + instra-carb, in absence of post-carb = probable hypoglycemia 15-20min post-training.
Yes.
Fitter = more fat adapted = lower risk of hypoglycemia.
More time spent training no- or low-carb = more fat adapted = lower risk of hypoglycemia.
Low-carb high-fat diet (mostly low-carb is what matters) = more fat adapted = lower hypo risk.
Higher body fat … maybe lower hypo risk.
Current hypercaloric status (ie… currently gaining fat tissue) = probable lower hypo risk.
I’m not sure glycogen depletion status has as much to do with it, ironically, but I haven’t investigated, primarily because glycogen depletion is never advisable.
Yup. Intra-carb consumption followed by absence of intra-workout carb consumption = hypoglycemia.
FYI: I only say the following as one giant ‘FYI’ and academic discussion, rather than trying to convince you to change anything!
I have found that my nausea and jitteriness following higher caffeine doses came as a result of delayed eating and increased physical activity and energy, caused by caffeine (appetite suppression, mood enhancement, and increased physical vigorousness are all caused by caffeine consumption)… all of which caused a rebound hypoglycemia which I could only achieve in the presence of higher caffeine dosing because I would inadvertently delay intra-workout fueling. Since mandating more regular intra-workout fueling strategies as standard practice for myself, I have experienced zero of those formerly caffeine-associated symptoms. I remember them well however! Not fun.
You have multiple people within this thread reporting symptoms of hypoglycemia. One of which is a PhD in Sport Physiology (me). Serious question… how much face validity do you need?
Maybe, maybe not. The symptoms folks experience aren’t tightly linked to performance outcomes, as the second study you linked by Dr. J, pointed out.
That breakfast study I posted suggests that fitter subjects are more susceptible to rebound hypoglycemia.
That would make sense, since the problem is excessive insulin-stimulated glucose uptake combined with muscle contractions, and training increases insulin sensitivity.
Yes, fitter suggests greater ability to burn glucose at higher rates too. Which would also support your case.
Higher fitness is also generally associated with greater glucose uptake increases via GLUT4, which would further support your case.
In my experience, in practice (no research to substantiate this claim), my fitter clients also tend to have greater resistance to hypoglycemia but now that I think about it, that probably stems from the fact that they’re less likely to “accidentally” be training at very higher percentages of their threshold or VO2max, whereas lesser trained folks are more likely to stumble into the “oops, I just went very hard, relative to my fitness, and now I’m hypoglycemic in response” type scenario.
I should have also clarified the following: One aspect of increased fitness is greater fat burning ability. And with regard to that one aspect, increased fat burning ability, there will be a reduced risk of hypoglycemia, if such attribute didn’t exist. (ie high fitness sans increased fat burning ability in the same person.)
