# Cycling



## Helios (Sep 16, 2022)

Hi everyone,

Your thoughts please on cycling and diabetes. Does this exercise bring down blood sugar levels, and if so do I need to cycle everyday and over how many miles?

Thank you.


----------



## Chris Hobson (Sep 16, 2022)

My approach was not to worry when doing rides of around 12 miles or so. On long bike rides I would take cereal bars and have a small amount of sugar in my drinks. Because every one is different you need to experiment and see what works for you. It is definitely worth searching Matt Cycle who has done lots of posts about cycling and nutrition.


----------



## Helios (Sep 16, 2022)

Chris Hobson said:


> My approach was not to worry when doing rides of around 12 miles or so. On long bike rides I would take cereal bars and have a small amount of sugar in my drinks. Because every one is different you need to experiment and see what works for you. It is definitely worth searching Matt Cycle who has done lots of posts about cycling and nutrition.


Thank you Chris


----------



## void (Sep 17, 2022)

Helios said:


> Hi everyone,
> 
> Your thoughts please on cycling and diabetes. Does this exercise bring down blood sugar levels, and if so do I need to cycle everyday and over how many miles?
> 
> Thank you.


Any exercise potentially brings down blood sugar, cycling being one type. Rather than how many miles, it'll really be about how strenuous and how long. For example, you'll expend more energy over a couple of miles with a 200 metre vertical ascent than you will 10 miles on the flat.

In general, you may find exercise more onerous if you do it "for your health" rather than incidental to something else. I cycle everywhere and get my exercise incidental to errands, shopping, a nice day out.


----------



## Chris Hobson (Sep 19, 2022)

After I was diagnosed I returned to cycle commuting after a long lay off. My commute was about 12 miles one way so I had to get myself a little bit bike fit before getting back into it. Initially I was using insulin so I used to carry glucose tabs in case of emergency. When I started doing triathlons I gradually worked up to longer and longer training rides. I did enjoy them, especially the early morning rides, although getting out of bed at 4 am was a challenge.


----------



## Helios (Sep 20, 2022)

void said:


> Any exercise potentially brings down blood sugar, cycling being one type. Rather than how many miles, it'll really be about how strenuous and how long. For example, you'll expend more energy over a couple of miles with a 200 metre vertical ascent than you will 10 miles on the flat.
> 
> In general, you may find exercise more onerous if you do it "for your health" rather than incidental to something else. I cycle everywhere and get my exercise incidental to errands, shopping, a nice day out.


An important difference .. thank you Void.


----------



## PhoebeC (Sep 22, 2022)

Yes just be prepared for hypos, other than that cycling is great for you health wise so definitely worth doing


----------



## helli (Sep 22, 2022)

void said:


> Rather than how many miles, it'll really be about how strenuous and how long. For example, you'll expend more energy over a couple of miles with a 200 metre vertical ascent than you will 10 miles on the flat.


In my experience, it is not just about how strenuous. Or, at least, too strenuous and my levels will rise.
For example,
- pootling along the flat cycle path whilst nattering to my mates will have no effect on my levels.
- a speedy road cycle for at least 20 minutes will cause my levels to fall
- a short ride or stop start (interval training type) ride will cause my levels to rise (easier on an exercise bike)
- a couple of miles with a 200 meter vertical ascent on a wet day with the wind against me will be unpleasant and stressful. Thus causing my levels to rise.

As you say, it will take some experimenting and, as you get fitter, the effects may change: if I could bring myself to get used to those uphill slogs, my levels would probably fall as it would feel less strenuous.



PhoebeC said:


> Yes just be prepared for hypos, other than that cycling is great for you health wise so definitely worth doing


Hypos are only a problem if your diabetes is treated with insulin.


----------



## SimonP (Oct 17, 2022)

My experience of starting to cycle during lockdown, having not done it since I was a child, was quite interesting (I was previously active and played sport, etc. so it wasn't completely different, but just much longer duration/less easy to fix things if going low).

I prefer to leave home with no short-acting insulin on board, if it's a short ride (1-2h) I can live with having some still remaining, but will then also make sure I have ~2x my usual carbs for whatever remains in my system before I leave - I don't think about it quite this hard at the time, but this is basically what I'm doing. For a 1h ride I might just wing it but I do have probably 100g of mixed carbs in a framebag even for short rides (more for longer ones) and I'm not going to get far from home in that time, so that's fine.

My blood sugar will normally rise gradually over the first hour anyway (high anaerobic-type effort raises my blood sugar at any point in a ride too) but I will generally then need to start eating food from 1h30 onwards.

For longish rides (100km+) I will usually knock my basal down to ~3/5 of the normal dosage and have an uncovered snack/small breakfast before I leave. This means I tend to run a bit higher initially, but by 2h30 into the ride I'll need to start eating. I always take ample food (I started riding during lockdown, and made a few mistakes early on - not reducing basal being the main problem, but thankfully close to home). 

Interestingly I did a 6h ride earlier in the year having halved my basal and my blood sugar stayed stubbornly above 10 for the whole duration. I was reluctant to take any short acting as I expected to eventually start running lower. While it's nice to not need to eat (unusual for a diabetic doing sport), on this occasion I really did quite fancy something by the end of the ride!

I note that I need to eat earlier when riding than I would when not, as I assume digestion speed is reduced (I try to eat normal-ish food rather than dextrose tablets and gels), this can result in running temporarily high when you stop. Equally when stopping for lunch/cake, I have to be careful to not take much (or indeed any) insulin (depending on how long I'll be stopped for and what my BG is) because, if I'm already a couple of hours in, as soon as I start riding again it will drop my blood sugar if there's any short acting insulin left on board.


----------



## void (Oct 18, 2022)

It makes sense for your bg to climb a bit when actually cycling, otherwise you'd hypo. I'm p sure it's your muscles and liver breaking down stored glycogen which liberates glucose.

yeah https://pubmed.ncbi.nlm.nih.gov/2745344/ 





						Glycogenesis - an overview | ScienceDirect Topics
					






					www.sciencedirect.com
				




The glucose-lowering effects I can measure a short while *after* exercise.


----------



## SimonP (Oct 18, 2022)

Depends how long you cycle for and how hard, as others have mentioned. I agree it's the initial hit of glucose from the liver that generates the rise, and after than point, afaiu it depends on your effort level as to whether you solely use glucose or a mixture of fatty acids and glucose (and hence how quickly the liver/muscles' supplies are exhausted and therefore blood glucose starts to drop later in the ride unless you eat).

I'm not sure how to explain the 6h ride without food, other than just being "lucky" to get the balance spot on - presumably I wasn't going very hard so was also burning a mixture of glucose and fatty acids so didn't manage to use up all the available glycogen stores. If it had been insufficient insulin I'd expect to have gone higher, if I'd been riding harder I'd expect the muscles to be able to process the glucose even with very low insulin levels (afaiu), but perhaps this is just an edge case of insufficient insulin anyway. I must request a ketone test kit, it would be interesting to see what it says after riding.

I tend to trend low immediately after riding (assuming I've not eaten in the preceding 30min or so, otherwise I go high then come straight back down and need to eat). E.g. I would halve my bolus insulin for my supper after a long ride, though it does depend to a great extent on how much basal I take - if I've knocked that back, aside from an initial need to eat something when I get back, I can then dose fairly normally. If I've not adjusted basal and perhaps gone a bit further/longer than expected, I'll have to be careful for the rest of the afternoon and reduce bolus.

When I first started riding longer distances (100km or so) without adjusting basal I used to run low at night after a ride, so obviously overall insulin sensitivity is higher (which is also reflected in the fact that now that I do adjust basal, I can still eat and dose normally when I get back without going high despite the lack of the background insulin). The running low at night is also partly because I used to take my full basal dose in the evening, I have since split this to avoid lows at night and make it easier to skip the morning dose if I'll be out.

This is of course just me, it's different for everyone, and it's doubtless also different for me from the start through till now as my body has adjusted and I've tweaked (never a straight-forward and clear answer) but I would certainly recommend adjusting your basal if you're riding reasonably long distances.


----------



## Rob Oldfield (Oct 18, 2022)

Interesting - but very complicated - paper here....  https://link.springer.com/article/10.1007/s00125-020-05263-9

I keep meaning to dive into it to see what it means for me but haven't round to it yet.


----------

