How long can I go before refuelling with carbs?

[John D]

An interesting piece from the Globe:

http://www.theglobeandmail.com/life/hea ... le1878842/

Although I do need to re-fuel on Sunday rides, especially if we "go long", I've often wondered about my need for fuel on our weekday ride. I think bring food/water along more out of habit than need.

Particularly interesting (to me, anyhow) was the finding that the "performance boost" from a sports drink was the same whether the drink was actually swallowed or just swished around and then spit out.

J.

[Lister Farrar]

Interesting John. But I think the 'which carb' discussion is a bit like 'which aero wheels', when your jersey is baggy, or your hamstrings are so tight you can't get low. The difference is less than other related, but commonly overlooked factors. Dehydration is a bigger problem. It's also easy to prevent. If you weigh yourself before and after a ride, and you have lost anything, it means you're dehydrated. Any loss means you're operating at sub-standard conditions. I'll bet performance losses from dehydration in most of us are far greater than from the wrong carb.

[sylvan]

You need to buy my new book: 10 Ways to Eat, Eat, Eat (and drink) Your Way to Better Cycling Performance. It's full of crap and myths and methods to gain weight and get slower while spending all of your disposable cycling income on fake food from the companies that sponsored the book.

Although I do need to re-fuel on Sunday rides, especially if we "go long"...

This might be partly temporary.

I've often wondered about my need for fuel on our weekday ride. I think bring food/water along more out of habit than need.

This is probably right. We're not doing more than about 50 km or 90 minutes total on a weekday ride and it's easy to restore fluid balance by drinking some water before and after, depending on your sweat rate. I bring a bottle and usually don't touch it much, sometimes not at all. The theory of glycogen replenishment in the half hour following athletic endeavours is probably legit, but again, the morning rides aren't going to totally deplete you to the extent that you're not going to be topped up by the next day, anyway, so I don't think it's a big deal. Half a bottle of chocolate milk in one of your cages to chug before coffee would work well, especially this time of year where it'll stay cold and appetizing. Pre-ride meals? Personal preference and reaction. I don't have a problem with a quickie breakfast of oatmeal or toast and egg, so I try to do that before a long ride, like a Saturday double. So much is just training and fitness at our level. We don't do too many rides where we'll have a real glycogen bonk. I had one on a Saturday morning after only 60 km when I got back from travelling in late summer, after two weeks off the bike. After a decent autumn of training I did 150 km this past Saturday, lots of it really hard, on a toast and egg breakfast, one Clif Bar (didn't even finish it 'til I got home) and two bidons of sugar-spiked green tea on the bike. Not a ton of calories, probably less than 1,000 for a ~3,500 kcal ride. I finally got shelled late in the ride when the pace picked up for the Interurban sprint, but there wasn't any bonk involved - it was just fatigue. Food's not going to help with that or with playing better with others on the Beacon Hill laps on Tues/Fri. That's just training more and getting stronger.

[sylvan]

Particularly interesting (to me, anyhow) was the finding that the "performance boost" from a sports drink was the same whether the drink was actually swallowed or just swished around and then spit out.

In that case it's a placebo effect and the rider needs to put down the bottle and HTFU.

[sylvan]

Dehydration is a bigger problem. It's also easy to prevent. If you weigh yourself before and after a ride, and you have lost anything, it means you're dehydrated. Any loss means you're operating at sub-standard conditions.

Even a couple of pounds? Not sure I buy this. I tend to think that "any loss is bad" is the cousin of "drink before you're thirsty" - drummed up by the sports drink marketers. For pros, they're going to need to stay on top of it more, since they're frequently riding 1000+ km a week, sometimes in hot conditions, so they're not going to want to get into any kind of imbalance, but for us, it's pretty rare to have back to back long, hard rides. I don't worry too much if I'm 4-5 pounds down after a ride. I take comfort in knowing that a mere 2 litres of beer will compensate for that. Bliss. There was that sportsscientists.com piece awhile ago showing massive mass loss from dehydration in world-record setting and challenging marathon performances. If they're setting world records while highly dehydrated, it can't be that bad.

[Brian S]

I'll bet performance losses from dehydration in most of us are far greater than from the wrong carb.

And fitness counts even more (says he who is doing mystery miles). I agree totally that the week day <50 km/60-90 minute efforts require only water/sports drink if you like. Once you extend out beyond that time line, sports drink-->gels/bars/real food etc become more significant, with the usual argument about amount and personal preference. Lots of theory out there, but the real practical piece is experiment in training to find what works on race day.

[Lister Farrar]

I'll bet performance losses from dehydration in most of us are far greater than from the wrong carb.

And fitness counts even more (says he who is doing mystery miles).

And heredity even more so. But the thread was about drinking and eating. I know you're a triathlete, but try to keep up Brian.

[Lister Farrar]

Dehydration is a bigger problem. It's also easy to prevent. If you weigh yourself before and after a ride, and you have lost anything, it means you're dehydrated. Any loss means you're operating at sub-standard conditions.

Even a couple of pounds? Not sure I buy this. I tend to think that "any loss is bad" is the cousin of "drink before you're thirsty" - drummed up by the sports drink marketers. For pros, they're going to need to stay on top of it more, since they're frequently riding 1000+ km a week, sometimes in hot conditions, so they're not going to want to get into any kind of imbalance, but for us, it's pretty rare to have back to back long, hard rides. I don't worry too much if I'm 4-5 pounds down after a ride. I take comfort in knowing that a mere 2 litres of beer will compensate for that. Bliss. There was that sportsscientists.com piece awhile ago showing massive mass loss from dehydration in world-record setting and challenging marathon performances. If they're setting world records while highly dehydrated, it can't be that bad.

it is recommended that fluid intake be sufficient to minimize dehydration to less than 2% of body weight loss.

http://journals.lww.com/acsm-csmr/Abstr ... nce.6.aspx

In a 150 lb person that's less than 3 pounds, so we may be splitting hairs. I'm sure there are limits, stomach emptying rates for example, diuretics lke coffee, that would prevent maintaining 100% hydration. I'll look for more info.

[Brian S]

[quote="Lister Farrar But the thread was about drinking and eating. [/quote]
I think we will hear a lot more about "eating" from Alberto.

[Josh.E]

What percentage of weight loss is actually due to dehydration during hard exercise? You are also burning fuel food to produce mechanical work, your body is heating itself up, etc. There is definitely energy going out. How much mass is associated with that energy?

pretty sure it's not E=mc^2 in our body systems

[Lister Farrar]

This one is a bit lower:

In exercise tests lasting more than a few minutes, reductions in performance are apparent at modest levels of body water loss amounting to 1–2% of the pre-exercise body mass (Armstrong et al, 1985).

http://www.nature.com/ejcn/journal/v57/ ... .html#bib2

That's 1.5 to 3 pounds in a 150 pound rider.

[Lister Farrar]

What percentage of weight loss is actually due to dehydration during hard exercise? You are also burning fuel food to produce mechanical work, your body is heating itself up, etc. There is definitely energy going out. How much mass is associated with that energy?

pretty sure it's not E=mc^2 in our body systems

If I recall correctly, most of it is water. There's 3500 calories in a pound of fat. That's a lot of calories to use in a single workout. There's a bit of glycogen too, but that's stored in a ratio of 2 to 1 with water.

I must not have the right search terms tho'; Google Scholar isn't coming up with a tidy answer for me!