Tired Legs - Sugar?

General cycling advice ( NOT technical ! )
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Sweep
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Joined: 20 Oct 2011, 4:57pm
Location: London

Re: Tired Legs - Sugar?

Post by Sweep »

Hypocacculus wrote:I suspect the two may not really have been closely related.

Until you stopped, your muscles were working and warm and you were in full energy output mode. Your blood vessels would have been dilated, supplying lots of oxygen and energy, your heart working hard to keep the turnover going.

Then you stopped dead and stood still for 20 minutes. Your muscles would have cooled down and started going into recovery mode, starting to deal with rebuilding damaged fibres, getting rid of accumulations of metabolites and so on. Your heart rate would have dropped, your blood vessels contracted, the oxygen supply reduced and possibly fluids would have built up in your muscles. Add to it the fact that you were probably still low on carbs at the point you moved off again (until your snack kicked in), it's not entirely surprising that your system complained - I think 20 minutes to get back up to speed is amazing really, given the physiological complexity of the situation. Many sports physiologists recommend a cool down to try and avoid some of the after effects of exercise, so perhaps if you came to a halt by gradually slowing your pace for 5 minutes or so, it might help, or try eating on the move.

Your blood sugar levels are much more stable than you might think (as long as you are healthy) and the rise and dip after eating a sugary snack is pretty transitory and your response has a psychological component, unless you are actually on the way to diabetes. At other times when people like to think they have low blood sugar, what they are really experiencing is a stress signal generated by the body telling them to eat because the total carb reserve (glycogen) is running low, not the blood sugar level per se. This prompting will become more insistent the worse the situation becomes.

Blood glucose level however, will be maintained at optimum to the bitter end because your brain can't function without it. You can tell (or more likely someone else can) if you actually have low blood sugar because you will probably behave as if you are drunk, then keel over. Having worked for some years with a diabetic and having to spoon feet him honey now and then when he went 'low', I learnt the difference between the notion and the actuality quite quickly. If he was a typical example, a spoon of glucose will start to revive a flagging diabetic within a couple of minutes, with a full recovery in about 15 (and will do the same up to a point for a flagging cyclist). This is a world away from a tedious afternoon at your desk fighting off the urge to eat the second half of that Twix and blaming a dip in your blood sugar when you do. It takes about 2 hours hard exercise to deplete a full glycogen store, but longer if you are working less hard because you will be burning fat to some extent instead.

So, if you are healthy and undertaking a 50 mile, hilly cycle ride, glucose is the thing to pick you up quickly, assuming you've been drinking enough and replacing lost salt. Other sugars are less quick. Fructose is not efficient for muscles as very little escapes the liver and it has to go through metabolic gymnastics to be converted to glucose before it can be released. Sucrose is 50% fructose and glucose. A sugary snack bar or a banana or a glucose tablet or some dates (my favourite) etc will do the job quite nicely. We all develop personal preferences.

Complex carbs take much longer to digest and kick in later so will keep you going without further eating being required. They work by breaking down, releasing, either directly or indirectly .... glucose. Eating a mixed meal will also help to slow down digestion to drip feed into your system; alternatively, you could just eat a few grams of glucose every 15 minutes. For normal cycling, it doesn't really matter too much what you eat, as long as there is some glucose involved somewhere, either in the form of neat glucose, or a glucose containing disaccharide (eg sucrose), or starch which is just a string of glucose molecules. Your body isn't actually that fussy unless you are at the extreme end of sporting endeavor where different eating regimes may make a difference. Anything else you eat is just tweaking the rate at which glucose hits your system, the desired rate being rather dependent on the rate the glucose is leaving your system - only you will know when you've got it right. Of course the sponsors will be encouraging their victims to down some weird gel or potion so they can flog it to the masses. Wannabe sporting heros seem to career from one nutrient fad to the next. But ultimately, the energy for those few hours during a ride comes down to glucose. So find it in a form you personally like, preferably with a smattering of salt, and a glug of water because we all know electrolyte balance matters too.

Sorry if I've gone on too much. In case you wonder where I'm coming from, I have a biology degree, specialising in physiology and have maintained an active interest in such things since doing a triathlon a couple of years ago.

Just found this via a link from another thread.
Many thanks.
Sweep
wirral_cyclist
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Joined: 17 May 2010, 9:25pm
Location: Wirral Merseyside

Re: Tired Legs - Sugar?

Post by wirral_cyclist »

To avoid the worst of 'cafe legs' I stop for only a few minutes be that for a swig/wee/banana, or I stop for more than 45 minutes at lunch.
It could be the short stop means repair mode doesn't start, and that the 40min stop means a pie and a pint and therefore caring less about restarting...
iandusud
Posts: 1577
Joined: 26 Mar 2018, 1:35pm

Re: Tired Legs - Sugar?

Post by iandusud »

I rode the World Champs Sportive last year and noted that the first feed stop was at Pateley Bridge at the foot of Greenhow Hill. Not a hill you want to ride up after stopping for more than a few minutes. Needless to say I stopped just long enough to grab some snacks at got going straight away, but I couldn't help wondering how many riders suffered more than they would have otherwise had they not stopped.

BTW I can ride all day on bananas and flapjack. However I do enjoy proper food (and drink) so on day rides will often enjoy a nice pub lunch but the first hour afterwards is hard work as body gets on with digestion!
pwa
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Joined: 2 Oct 2011, 8:55pm

Re: Tired Legs - Sugar?

Post by pwa »

A sugar boost is okay if you don't have far to go and you only have half an hour of riding to do. I have done that at the end of a long ride and it kind of works. But sugar is a rubbish way of fuelling otherwise. Complex carbs are much better.
Jamesh
Posts: 2963
Joined: 2 Jan 2017, 5:56pm

Re: Tired Legs - Sugar?

Post by Jamesh »

Interesting my last long ride 100mioes I did it with little food supplies due to CV.

But I studiously avoided going into the red is not chasing other cyclists / going full bore over hills. I didn't get the bonk and I didn't feel particularly tired afterwards.

However the scales revealed I had lost best park of a 1kg in weight!

Must have been a steady fat burning ride!!!

Cheers James
Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Tired Legs - Sugar?

Post by Jdsk »

Are you sure that didn't include some loss of water?

Jonathan
Jamesh
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Joined: 2 Jan 2017, 5:56pm

Re: Tired Legs - Sugar?

Post by Jamesh »

Of course lose of water but I weigh myself most mornings whilst I make the morning cuppa tea.

So it was a 24h difference and I drank plenty the evening of my ride....

Cheers James
philvantwo
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Joined: 8 Dec 2012, 6:08pm

Re: Tired Legs - Sugar?

Post by philvantwo »

Weigh yourself every morning? What's the reason for that Jim?
LittleGreyCat
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Joined: 7 Aug 2013, 8:31pm

Re: Tired Legs - Sugar?

Post by LittleGreyCat »

For an alternative:
https://www.amazon.co.uk/Art-Science-Low-Carbohydrate-Performance/dp/0983490716
The excellent post above explains how you go if you are fuelled by glucose.
It is possible to switch to being in ketosis long term, when you burn ketones not glucose for energy and just eat/make a small amount of glucose to stop your brain complaining.

I keep falling off the wagon, but when done properly you can ride 50 miles just on fats with proper hydration.
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