Carb deficit and cycling

[jimboalee]

As was mine... this could run and run But I am glad it's teased more out of you. Seriously.



I'd agree. That's a personal choice in many respects. The study only suggests it is possible, and that is what interested me.



I go further. I'd say the historical aspect laid out is anecdotal and can't really be used as the basis for a conclusion. The lab test is, despite it's short term nature, interesting; the observation of a drop in performance and a recovery. I'd agree, it'd be interesting to see how the cyclists performed over a longer time frame.



I think the latter bold bit is you're own interpretation. In fairness, I don't think the study concludes that. The study does add caveats about it not simply being a carb restricted diet but careful attention to other factors is also required. Note that the report also concludes...



Note the context, "therapeutic use", AND the direct advice regarding such diets and anaerobic performance.

Let me lay out some back story here. I was taken by a claim I read that there was no dietary requirement for carbohydrate to sustain life. Given that we, as cyclists, are given info about carbo loading and are sold energy bars, drinks and gels etc etc etc, I was interested as to how cycling (or any level of activity generally) featured in a 'sustained life'.

Jimbo, of this very forum, has addressed this point specifically. He has, in the past, posted quite detailed info on how he calculates his carb requirement for particular expenditures of effort. Whether he factors in a base level daily requirement, I can't remember.

But this study seems to indicate that, indeed and as I had read, that there is no base level requirement and one can (if so desired) perform "most forms of... recreational activity" on a low carb diet.

I have already stated that I personally would not do it, nor would I necessarily recommend anyone else to, but it is interesting none-the-less that seemingly it can be done, and safely. I don't know specifically what "therapeutic" reasons one might have (something perhaps to do with controlling blood sugars, diabetes like things, etc) but that's neither here nor there.

Yes I do.

Basal metabolic rate is calculated from the individual's Body Surface Area and will change with increases and decreases in ambient fluid ( gas or liquid ) temperature around the body.
The figures you read on web-sites assume the fluid surrounding the body is at Neutral Skin Temperature, or 33 deg C.
When a person is fully clothed, that is close to the truth.

As for carbohydrate requirement, it is true the human being can survive without it. The differences between Cellulose C6H12O6 and Animal C6H12O6 are subtle, but the human system can successfully assimilate both into usable fuel.

At high rates of energy expenditure, piling sugar into the stomach by-passes the process of changing fat into fuel. As for adrenaline, it is the body's mechanism for keeping the muscles working when the fuel supply is not rapid enough to cope with demand.
On a treadmill or gym bike, a novice might get the 'rush' after 20 - 30 minutes. A better trained person might go for over an hour before the 'adrenaline rush' starts.

A well trained person will be able to survive several days with only water. Many stories from desert and shipwreck survivors detail how they only had a few bottles of water and no food.

To ease the 'bonk' in an event, it is a good idea to force into it within a training session. ie, wake up the body's systems to expect another episode.

 

[rsvdaz]

I always seem to be on and off diets...and yes I have lost weight on a protein rich (atkins) type diet...but now i'm into cycling I am concerned with the lack of energy reserves on this type of regime..I am aware Slimming world have two types of regimes..a red - protein rich diet and a original green diet which has more emphasis on carbs..i have noticed losses on this type of diet before...i am planning to adopt this type of eating and coupled with the cycling hoping to see some improvement

 

[yello]

I'm sitting here in the St Pancras Eurostar terminal, killing time before catching the train back to Paris. So I bought a C+ for the first time in maybe 2 years and, low and behold, in their 'Know How' section, they state "Piling on the carbohydrates is the key to your recipe for cycling success".

I'm wondering, generally speaking, at what point do people query the perceived wisdom, and why? (Btw, to make it clear , I'm NOT saying C+'s advice is wrong nor that 'piling on the carbs' isn't right, just musing generally!)

 

[jimboalee]

I'm sitting here in the St Pancras Eurostar terminal, killing time before catching the train back to Paris. So I bought a C+ for the first time in maybe 2 years and, low and behold, in their 'Know How' section, they state "Piling on the carbohydrates is the key to your recipe for cycling success".

I'm wondering, generally speaking, at what point do people query the perceived wisdom, and why? (Btw, to make it clear , I'm NOT saying C+'s advice is wrong nor that 'piling on the carbs' isn't right, just musing generally!)

Its not disinformation, its misinformation.

They don't want you to drop down dead and they don't want you to finish Sportives ahead of their staff riders.

 

[Fiona N]

...
I'm wondering, generally speaking, at what point do people query the perceived wisdom, and why? (Btw, to make it clear , I'm NOT saying C+'s advice is wrong nor that 'piling on the carbs' isn't right, just musing generally!)

I have this thought every time I read about isotonic/salt replacement drinks (not the same, I realise, but part of the sports drink fraternity). I have misgivings about telling all and sundry to add salt to what they drink when they're only out for a couple of hours or so - partly this is because I know I can cycle (literally) all day without adding any salt to my water or energy drinks.

The 'Science in Sport' blogsite had a really good look at this issue as part of a series on cramps. The key point - sweat is less salty that body fluid thus sweating increases salt concentration in the body. For a short period -2 hours, say - there is no reason to replace salt even for very high rate/salt sweaters, keeping hydrated is more important - then eat some soup for recovery. Only in the longer term, does it become an issue as the amount of water needed to replace lost fluid becomes large. But here again some people go overboard - loss of performance usually is measured in top end athletes where 5% is a big loss whereas for weekend warriors, would they notice the difference?

There's yet another piece on hydration in CW this week, and once again salt replacement using commercial drinks is being pushed.

 

[Hont]

"The adrenaline was flowing. One can go for quite a while on that. That and water".

This is a quote by the CO of 1st Paras, referring to the taking of Arnhem bridge in September 1944.

But maybe the Germans were using isotonic drinks, which is why we lost it again?

 

[Crankarm]

I have this thought every time I read about isotonic/salt replacement drinks (not the same, I realise, but part of the sports drink fraternity). I have misgivings about telling all and sundry to add salt to what they drink when they're only out for a couple of hours or so - partly this is because I know I can cycle (literally) all day without adding any salt to my water or energy drinks.

The 'Science in Sport' blogsite had a really good look at this issue as part of a series on cramps. The key point - sweat is less salty that body fluid thus sweating increases salt concentration in the body. For a short period -2 hours, say - there is no reason to replace salt even for very high rate/salt sweaters, keeping hydrated is more important - then eat some soup for recovery. Only in the longer term, does it become an issue as the amount of water needed to replace lost fluid becomes large. But here again some people go overboard - loss of performance usually is measured in top end athletes where 5% is a big loss whereas for weekend warriors, would they notice the difference?

There's yet another piece on hydration in CW this week, and once again salt replacement using commercial drinks is being pushed.

Again there is much sense in your posts.

 

[jimboalee]

I have this thought every time I read about isotonic/salt replacement drinks (not the same, I realise, but part of the sports drink fraternity). I have misgivings about telling all and sundry to add salt to what they drink when they're only out for a couple of hours or so - partly this is because I know I can cycle (literally) all day without adding any salt to my water or energy drinks.

The 'Science in Sport' blogsite had a really good look at this issue as part of a series on cramps. The key point - sweat is less salty that body fluid thus sweating increases salt concentration in the body. For a short period -2 hours, say - there is no reason to replace salt even for very high rate/salt sweaters, keeping hydrated is more important - then eat some soup for recovery. Only in the longer term, does it become an issue as the amount of water needed to replace lost fluid becomes large. But here again some people go overboard - loss of performance usually is measured in top end athletes where 5% is a big loss whereas for weekend warriors, would they notice the difference?

There's yet another piece on hydration in CW this week, and once again salt replacement using commercial drinks is being pushed.

Yup, good post.

Salt supplementation is a personal thing. People are individuals and it's a game of 'trial and error' until salt replacement quanities are established to avoid cramps etc.

You would be surprised how much I pour on my tongue after a 200km Audax.

 

[yello]

In fairness to C+ (though they are quoting Ron Maughan, a Prof of sports science) they do state, in an article on electrolytes,

"The variation in sweat rate and sweat sodium content between individuals is so large that average values are largely meaningless"

Strange then that they then go and suggest one looks for a sports drink containing between 400 and 1100mg of sodium per litre.

As an example, at the top end of that scale, drinking a modest 1/2 litre per hour, I'd consume around 3000mg of sodium for a 100km ride. I don't class myself as an endurance athlete, that's a steady but gentle pace for me without knocking myself out. I'm not pouring sweat.

They state in the same article that 2300mg of sodium is the "upper level" of the daily intake, and that 1500mg a day is the amount that the Institute of Medicine recommends to replace lost sodium. So whilst acknowledging the vast differences in individuals sweat rates and sodium content, they actually advise a consumption that, for me, could exceed the recommended daily intake.

I accept that those figures could well hold true for performance athletes but for pootlers like me.... I think C+ really ought make that distinction more obvious. For the record, I have only water in my bidons!

 

[jimboalee]

It's not as simple as 1cm^3 H2O per 4 kCals usage. There is a frig-factor which involves the temperature of the surrounding fluid ( a thin layer of sweat beneath the clothing ) compared with the body's Neutral Skin Temperature.

In the wintertime, windchill is greater and the body sends blood to the skin to keep it warm instead of sweating to keep it cool. Not a lot of H2O is required.
In the summertime however, the thin layer of sweat stays closer to NST and vapourises more readily. Latent heat of evaporation is insufficient to keep the skin cool, so the body produces more sweat.

MY CALCS FOR ME. Note, for ME, no-one else.

100 km Audax in 5 hours.

10 deg C ambient, regular jersey and shorts – 2.2 litres requirement.

30 deg C ambient, same clothing – 10.3 litres requirement.

I haven't measured the salinity of my sweat. I work on 1000mg per litre.

This has turned into Na deficiency.