At FTP, everybody’s going to be oxidizing mostly carbohydrates, with habitual diet being the primary determinant of any remaining interindividual variation. Fat oxidation will be less than maximal, and you’re not going to run out of even IMTG in just an hour or so. I therefore don’t see fat oxidation as having anything to do with TTE (FTP itself, obviously yes - but even there, the primary effect of training is to reduce CHO flux, with the increase in fat oxidation being primarily a passive phenomenon).
You are, however, likely to run out of glycogen in at least some muscle fibers, which is why I would put it at #1. There can be considerable variation in how much glycogen you start with as well, which would explain variation in TTE both between and within individuals.
As for the study, I’m not buying it. There is simply far too much other data demonstrating the importance of adequate glycogen stores during exercising lasting far longer than just 1 hour to accept their conclusions as being correct.
Presumably the size of your FTP matters. Me, with a puny 230W wouldn’t have a problem but someone with 450W might if they weren’t fully loaded up beforehand. Does the body start to limit your output as your glycogen stores deplete below a certain level?
First of all - I do not know a thing so if my reasoning is flawed, sorry.
There is no doubt about glycogen depletion as the main contributor to fatigue - this is logical. But at FTP there is some contribution of fatty acids in the energy system (?) so if you improve fat oxidation ability you basically have a little bit more of energy? (I mean if you can process it, not only to produce it but your ability to convert into energy is impaired). Sorry for my layman language as I am as far as I can be trained in biochem and physiology
The maximal rate of fat oxidation isn’t the limiting factor, either in terms of power (FTP) or duration (TTE). Rather, the primary effects of training are to 1) slow the rate of CHO utilization (thus allowing fat to provide more energy), and 2) increase the amount of CHO that is stored. If you then ask different individuals (or the same individual on different occasions) to exercise as long as possible at a high but tolerable rate of CHO flux, it is largely the of your CHO reserves that dictate how long you last.
What exactly do you mean by CHO flux and the reduction of it / slowing the rate of CHO utilization?
(In my mind I want to connect your statements to Cori and Krebs cycle but I assume you are a step before and mean sparing/reducing Glycolysis in the first place…? Sorry no native speaker here which makes all this metabolism talk a bit harder to understand for me.)
The primary effect of endurance training is to slow the rate of hydrolysis of the glucosyl units of glycogen. Other metabolic changes largely flow from this fact.
So, then would you agree that the proper amount of base training via SST is more effective way to achieve 1 and 2 noted above, verse threshold / VO2 efforts (those have a place in training given specificity and 6 weeks out from an A event). If so, then how you fuel SST should be different than how you fuel Threshold and VO2 efforts. Which is the core of my original questions… how to fuel SST work without overdoing your carb in-take (relying more on nutritional carb intake during normal meals rather than sugar-dosing each ride (not all carbs are created equal). Yes, at hour 4, 5 and 6 once you’ve depleted your ~2500 cal of onboard carbs then simple sugars are your only option.
2x20 is much different that 40 minutes straight at FTP… not to mention the extra 20 minutes… The 10 minute between interval allows your body to clear lactate. If you reach max heart-heart 40 minutes into your effort and can’t clear lactate, your done.
Not necessarily, and B) carbohydrates are always an endurance athlete’s best friend, but especially during longer SST workouts. Shorter threshold and VO2max workouts will be fueled even more by muscle glycogen, which can really only be replaced post-exercise.
Not really. Most people could only go about 5% harder during a single maximum 20 minute effort - if you’re doing two of them back-to-back the difference is generally going to be less than that, even with 10 minutes of rest. (Who rests that long anyway?)
Yes. At one point I put a lot of value into FTP. I’ve since learned it not everything. I spent all my effort trying to pull FTP up by doing threshold and above efforts. I’ve since focused on pushing my FTP up with Tempo and SST work because I get the added bonus of training my body to ensure longer efforts, plus I can get more TSS each week.
There is much more to cycling performance that FTP. And… I would argue lactate threshold (power and heart rate) is a much better measurement and provides more information on how your training is progressing.
Will need to learn more about this. Would be nice if you could give more detail or point me to a good paper / starting point for that part of metabolism.
The classic 2 x 20 has only 5 minutes in between. Anything more than that is just cooling down for no real reason, requiring you to work harder to get going again during the 2nd effort.
Even during VO2max training lots of rest is unnecessary, if not counterproductive.
Probably should target more like 90-130g/hr or higher, if you can muster it. Cooler temps required for higher than that.
Yes, you can, and more importantly, should. Limiting fat and fiber ensures max carb absorption and hydration is possible. Limiting protein helps too. This is very strongly evident in the scientific literature.
As a fun anecdote, my wife recently rode 310 miles and 20k elevation in 25 hrs, and consumed roughly ~1700g carbs, no fat, no fiber, and no protein, throughout. She’d have consumed closer to 2000-2400g carbs but we assumed she’d be done in 20 hrs. Mechanical issues ensued.
