OK, I see where you got 2.5L. But once again you go to such extremes.
I just gave you this example. It had me taking in just 1.3L of fluid (2 x 23oz bottles). Even if I pushed that to 100g carbs, that’s still just 7.4% w/out any additional water. Although real world testing for myself (n=1) has told me that when I push 100g, I do need to add a little more water. So I’d say 7% is probably a good limit for me on max multi-hour efforts.
Per skratch’s blog that I posted (not sure if you are actually reading):
Depending on one’s hydration state, blood osmolality can range anywhere from 275 to 295 mOsmol per kg of water. Our Sport Hydration Drink Mix has an osmolality of 160 mOsmol per kg of water, primarily because of the lower concentration of carbohydrate
Skratch themselves say they made the concentration lower than that of the blood concentration to create a gradient of passive fluid travel into the blood. If you look at those numbers it’s about half. So they give you room to add other sources of fuel like gels and food without creating too high of a concentration. In my example I had a gel and ended up at a 6% solution, which per your posted study is around the best concentration to be.
The literature that studies the 90g/hr limit is only looking at fueling. Fueling transporters are active 1 way transporters. Except for the little bit of water hitching a ride with the fuel across those active transporters, the main method for fluid transfer is passive and is 2 way. Basically you can’t F up the fuel transfer, but you can F up your fluid transfer.
“Any decrease in absorption and emptying is minimal”. The study you posted, not posted by me, disagrees with that
Great thread with tons of useful info. However, in terms of actually making you’re own mix for someone who never has, can you pls post your “recipes” with links to the powders / products you put in them? Thanks!
I use 1:1 Dextrose:Fructose powders in my bottles with a constant rate of hydration mix (skratch clone, no calories or flavor) and a variable amount citric acid to taste (this amount goes up proportionally with the amount of carbs in the bottle). I just eyeball it. You could get fancy with all sorts of flavorings but I don’t suffer from “palate fatigue” in terms of flavors (sweet/salty, yes).
I can handle around ~120g carbs/hr split between two 26oz bottles with this “recipe” however based on the workout intensity, what’s happened before and after the workout, etc. I’ll adjust that number down all the way to 10-20 g/hr.
Making your own mix will save you a shit ton of money. And, I acknowledge that these carb sources are all corn derivatives. The rest of my diet is so micro-nutrient dense that I don’t really worry about that fact. I also try to limit the use of this mix (maybe only on 40% of rides), using the Feed Zone portables rice cake recipe(s) more often than not. They’re great from a sweet/salty fatigue standpoint, are wicked quick, easy, and cheap, and are a little more real than the powder mix.
Sure, I use 66% MaltoDextrin - buy in on Amazon in like a 10lb+ in the US.
33% Fructose - smaller bags available on Amazon and you might find this at a grocery store.
400g of Malto to 140g of Fructuse plus 2packets of WHO rehydration packets (Oral Rehydration Salts - current WHO formula) ]
I mix this all in a mixer and then use a old protein scooper that I weighed to figured out how many scoops I need in bottles.
I usually make about 300cal bottles and add a Nuune tablet for flavor or add Lemon/Lime squirts for flavor.
Most of this is waaay over my head. My one small contribution (n=1) would be that I’ve been quite happy using 3 scoops of the Skratch Sport Hydration Mix (Lemon) per 750ml bottle and drinking 1 bottle/hour. I like the fuller flavor, and that gives me ~63g/hour (240 kcal) of carbs + electrolytes. No GI issues.
One question, though: For a two- to four-hour outdoor ride, is there a guideline (or a maximum) for the percentage of calories burned that one is trying to replace? I’m still a beginner… don’t want to either underfuel or overeat, and what many of the racers on this forum use to fuel may be too much for me.
For me it all depends on the intensity of the workout. I don’t really have a formula but based on this graph (and the way I feel during hard rides where I spend a lot of time above threshold) I consume a higher percentage of the calories expended during a workout as time spent above threshold increases. For many endurance and recovery rides I will only consume 50 calories just to trick myself into thinking I’m taking in carbs to lower the RPE. It also depends on how you structure the rest of your diet/calorie deficit (if any).
In general yes. If you want a simple formula that doesn’t require much thinking, then simply aiming to replace half of what you burn will always have you in a good place.
Sure, higher intensity burns more carbs. But that can’t be maintained for very long. And once you subtract out your onboard carb stores, eating half what you burn will put you in the right place.
For longer endurance work (3hrs+), you will be riding at an intensity that will utilize fat stores for anywhere around 50% of burned calories. So the eat half what you burn works here too. Your basically aiming to replenish your carb tank as you have 50k+ calories of fat onboard and will never run out of it.
I believe you are right, but I’m curious how you arrived at the numbers. First two ingredients in skratch are cane sugar (sucrose, one glucose+one fructose) and dextrose (glucose). If those are in a 2:1 ratio then that’s the same as a 2:1 ratio of malto to fructose. I’ve been assuming it is 2:1 when I mix my drinks, just wondering if you’re also assuming or you analyzed it somehow.
From everything I’ve read, I’d agree with this (Sodium being the only thing to care about). When I did my own mix, I copied some commercial electrolyte mixes, but I think that made things way more complicated than they need to be.
I think adding the others isn’t bad, but I doubt that any benefit could be demonstrated. At a large scale, the cost of adding the other ingredients is trivial, so I think it is largely done to seem ‘better’ or more complete than alternatives.