Yes for many folks. Any meaningful consumption 30-75min pre-training opens the door to rebound hypoglycemia for a lot of folks.
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Rebound hypoglycemia is not a fun time.
Necessary ≠ Optimal.
False. It is likely to enhance, if done well.
This has nothing to do with glycogen and more to do with blood glucose maintenance for cognitive drive.
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Thanks for clarifying… I was picturing regular workouts of more than 2 hours fasted and died a little inside. Glad you can make an early workout work for you!
And feeling better for the rest of the day and subsequent workouts. I spent too many workouts feeling wasted afterwards.
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I haven’t seen any study showing that. What evidence do you have that it leads to superior adaptions and improvements in vo2 max?
Could you share the evidence for this please?
Maybe off topic (sorry OP), but what determines whether a person is susceptible to this? Is it something that happens to everyone but in different degrees and maybe not significant enough for most? Or should we all try to follow this type of timing for optimal performance?
I’m going to try it out (15 min before vs 30-45 min for morning sessions) and see if I feel a difference.
I usually do my morning workouts without eating breakfast before work, then eat at work. I’ve gotten used to early workouts fasted, it only took a few weeks. Getting a solid dinner the day before usually helps alot.
For me, learning how to ride fasted have enabled me to endure longer periods of time without risking bonking.
I really struggle with eating before sport (have been sick quite a few times from this before I got the hang of it 
) BUT through much trial and error I’ve found (weirdly!) Greek yoghurt I can eat and then go workout straight afterwards!
So if I’m doing something in the morning before work (which will be up at 6:30, start workout at 7) I’ll have a carby dinner the night before and I’ll have a big bowl of Greek yoghurt and seeds / raspberries / whatever in the morning before the workout, then some toast after I’m done.
Edit: Seen some comments about working out fasted, which is great if it works for you, but if you’re female be careful and research before you try this; not always a great idea for us.
Fueling is anecdotal and comes down to each person. So to me it makes no sense to push fasted riding if someone is asking about fueling morning workouts.
From my own personal perspective, I spent a year and a half doing fasted interval workouts early morning. Sure I was able to hit all my targets but looking back I noticed I was binge eating/ eating a shit ton Either later in the day or on a day off.
Since I have been fueling all my morning workouts for the past year now. No matter how long or how intense, I notice my eating is a lot more controlled and my appetite isn’t crazy on my days off or later in the day. Like I said this is all personal preference but that is my experience with fasted training.
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The only thing I would add (which isn’t just in relation to fueling but all variables) is to try it occasionally so you know what fasted feels like.
We all try to train in a perfectly controlled environment (fuelling, temp, etc), however the reality is that sometimes outside it goes wrong and you likely run out of food. It’s good to know what it feels like and you can indeed keep going.
To add to all the good and varied responses I have consistently done morning work outs during the week for the last 4-5 years. Most TR workouts are 60-90 mins during week, though those intense workouts feel a lot longer!
I can’t jump right on the bike when I wake up, but rather have coffee and mill about for a bit. On days of intense rides I may eat a piece of toast with jam or similar - something that digests quickly <30 min before the ride. I may also take a drink besides water, like a Tailwind or Skratch. I am not sure of the physiological benefits but I know there are psychological benefits/signals. The ability to take a drink between intervals and to get a taste in your mouth I think provides a boost. I will say that my RPE on rides with this approach is lower than fasted (which I did for a long time).
As to the night before, I generally try to stop eating before 7 or 8 and usually in bed before 10 and up between 5-6. During the week I don’t stress about carb loading given the morning ride durations. I DO try to focus on hydration though, as I think that makes a difference for me. For weekend long rides - and where I have more time in the morning I absolutely think about eating more the night before, and have time to eat a more hearty oatmeal+ breakfast 2 hours before. Riding sooner than that with oatmeal makes for an unpleasant first hour ride for me…
another n=1!
Quite simply it’s diversion of the body’s blood supply and resources. If the body needs to divert blood flow and resources to digest food, it’s blood / oxygen and resources that can’t go to the legs.
Vegan pancake with Nutella and a maltodextrin mix in my bottle. Nuun caffeine tab if I feel like I need it.
I get up at 4:30am 7 days a week for the years and years now. After the warmup I stop pedaling and drink a cup of coffee then I start pedaling again. I typically eat about 150 calories while on the bike. I start around the 30 min mark or whenever the next interval is over. Lately I have been eating a honey stinger waffle. I always do a run afterwards and I feel this helps set me up for the run, otherwise I probably wouldn’t eat anything. If I do more than an hour on the bike than I’ll split the waffle and eat half at 45 min and the other half at 1:15.
You’re right.
But VO2max training adaptations do not happen at the legs. They happen in the CV system. Your CV system’s adaptations don’t care whether oxygen was being used at legs or some small percent at gut additionally.
Just playing devils advocate.
Higher cumulative higher training intensity is generally agreed upon to cause greater adaptations.
I have no PDF’s at my fingertips for carb fueling enhancing VO2max performance specifically.
Loads of other ranges of performance from sub-threshold to all-out sprint performance are enhanced by higher blood glucose.
I have not compiled a repository of “carbs enhance X” articles though perhaps I should.
Susceptible to hypoglycemia and susceptibility to the sensation of hypoglycemia are two different things.
In my consulting and coaching experience: athletes who generally fuel better with carbs all the time are more susceptible to sensing it. Those who go without carbs during training are less susceptible to the sensation of it.
I have not used a CGM to see what was happening.
All should follow that timing recommendation regardless of susceptibility to sensation of rebound hypoglycemia because elevated blood glucose is optimal for exercise performance.
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So that’s assuming ingesting carbs during a VO2 max session allows more intervals to be completed during a session. Which is implying for most of us, the amount of time accumulated at vo2 max intensities, is limited if we don’t ingest carbs. The most time I accumulate at VO2 max a session is around 27 mins. That certainly isn’t limited by carb intake, I just don’t try and accumulate more minutes a session. Just how many minutes are being accumulated during carb ingesting VO2 max sessions?
Or higher intensity. As in, 1% greater power output.
Or ability to do more VO2max sessions without greater cumulative fatigue.