Getting fitter

Hi
Have you lost or gained any weight?

Tony

Could also be seasonal. My total insulin requirements change fairly significantly between summer and winter, even aside from any weight changes.

Are you eating more? Alternatively as you were previously exercising but not as much, you might have been experiencing almost continuous post-exercise insulin sensitivity previously and adjusted basal down accordingly to avoid going low. As you get more used to the level of exercise (by doing it more regularly) this response is reduced or eliminated (or at least it is for me) - e.g. in the summer when I'm riding a lot of miles (say >800km/month), a 100km ride will do nothing to my overnight basal requirements nor will I reduce morning basal for the ride, nor does it make much of a dent in my foot-on-the-floor fwiw.

If not been riding much for a few weeks (e.g. winter indoor only, illness, work, etc.) then a 100km ride would require a bedtime snack/slight reduction in overnight basal and I'd probably reduce morning (pre-ride) basal a bit too otherwise I'd trend downwards during the ride (though for that distance I can live with the required level of carbs I'd need to eat so don't always bother adjusting as it's more of a spontaneous distance).

I've never really thought too hard about why this happens, though I assume there's some habituation to the level of exercise such that there's less hepatic glucose production as exercise stress hormones are lower (so less requirement for it to replenish over the following 24-48h) and in addition one assumes that the muscles become more efficient, but I can't really explain why my basal stays pretty much the same as usual despite more exercise. Answers on a postcard, ideally with a link to a journal paper!

Actually, having thought a bit more about it while picking the kids up from school (sat in the car and waiting with the rain drumming on the roof!) if my muscle insulin sensitivity is always reasonably high due to exercise (whether doing lots or not quite much - but still fairly regular - I must see if there are any papers about how long it lasts) then this factor could perhaps be eliminated for the most-part, and then it's just hepatic and muscle glycogen recharge that cause the lows one would usually see post-exercise. So if habituation means less glycogen is used from the liver that would mean less running low afterwards.

I doubtless eat more food and don't require more bolus (I eat unbolused when riding, do normal bolus the rest of the time unless it's been a mammoth day), which probably handles the bulk of the muscle replenishment too.

So that sort of makes some sense, however, while it might explain what I see, it doesn't really explain what @Zinadane was asking about. So sorry, I don't think I've helped!

Hi
I remember reading somewhere that's lots of cardio releases the stress hormone, cortisol, into your body. Not sure how accurate this is but I've noticed that my blood glucose goes shooting up when I am under stress which seems to make sense to me. This would increase your insulin requirements. I've had T1 since I was a teenager, almost 40 years and when I was first diagnosed, I used to run long distance for the cadets, ATC. It used to play havoc with my glucose levels and I just thought at the time that I would need extra sugar to stop going hypo. I also used to climb mountains in my 30s and used to not take insulin for my breakfast (very bad idea but I didn't know back then) then as I climbed the mountain my bg would come down and back to normal.
My advice would be to speak to an expert about it (preferably someone who knows you as personally, I've found them very hit and miss) but it might be the cortisol release increasing your need for more insulin.

Zinadane said:

Ah, good point. I have suprisingly gained weight, up from 74 to 78kg. Muscle gain maybe, not sure though.

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Muscle weighs more than fat so not unusual to gain weight while getting fitter.

JenHarvey said:

Hi
I remember reading somewhere that's lots of cardio releases the stress hormone, cortisol, into your body. Not sure how accurate this is but I've noticed that my blood glucose goes shooting up when I am under stress which seems to make sense to me. This would increase your insulin requirements. I've had T1 since I was a teenager, almost 40 years and when I was first diagnosed, I used to run long distance for the cadets, ATC. It used to play havoc with my glucose levels and I just thought at the time that I would need extra sugar to stop going hypo. I also used to climb mountains in my 30s and used to not take insulin for my breakfast (very bad idea but I didn't know back then) then as I climbed the mountain my bg would come down and back to normal.
My advice would be to speak to an expert about it (preferably someone who knows you as personally, I've found them very hit and miss) but it might be the cortisol release increasing your need for more insulin.

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You're correct that stress hormones are released for intense exercise and these then cause the liver to convert stored glycogen into glucose for help in "fight or flight". It may be that long term stress hormone exposure raises insulin resistance (I don't know, I've not looked), however, I don't think exercise will produce such a long term rise. I certainly find that my liver stops producing additional glucose after a couple of hours of exercise (or at least I then start dropping back down and need to start eating), so I don't think that the longer term requirement for higher basal could be down to hepatic production due to stress hormones.

I also find that if I do lots of exercise I get a smaller hepatic contribution (either because there are fewer stress hormones with habituation or the liver requires a higher level to start conversion, or the liver has not fully replenished itself.) Apparently this hepatic glycogen/glucose sparing is a real "thing" - I read a paper about it, though I'd have to do some digging to find it again, so probably not just something that happens to me.

Second hand info, but a good T1 friend of mine was advised that short sprinting style of exercise would increase blood glucose where repetitive endurance style would lower it.

The difference of course, is stress hormones, as you say.

If you find that paper, please pass on the link, the big thing I'm trying to focus on right now, is "what causes the liver to produce glucose, from glycogen, from new, or to produce ketones" - it's got to be a question of competition between hormones and enzymes, but I feel like its a major puzzle piece for me.. I mean on the face it's relatively simple, but dig just a little, and it gets complicated fast...

I have exactly the same problem. In fact even without the exercise I still have issues trying to control foot-on-the-floor when driving my kids to school (so a similar desire to not go low while also not being high!)

I really don't know what the answer is, though as I'm cycle-commuting to work first thing at least twice a week now due to a road closure making driving a massive pain, I will be experimenting more (in the past I've often done some admin, etc., at home before heading in on the bike, which means the FotF and most of the active insulin was gone, which made life much easier.)

What I'm trying is taking enough bolus to reduce the FotF rise, and then depending on BG level perhaps eat some breakfast uncovered (or go without if high to avoid adding more bolus to the mix). If I then don't have a massive effort riding in it seems to be ok and I also don't go low (1h commute) but I need to see how repeatable this is. OTOH if it's very busy on the roads, which means I tend to go faster to be exposed for less time, I do end up going high.

Perhaps I should take up drinking on the evenings before I commute in (or do some late night exercise), as this seems to reduce FotF which would make the whole situation easier to deal with! Or, probably better all round is to find a quieter route to ride in, which would mean a much gentler ride and less/hepatic helpfulness!

Zinadane said:

When I cycle to work (15mile) I tend to go without food and usually also take 2-4 units to battle the fotf depending on how it's looking.
This usually works well. Food and adjustments then at work.

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My main issue with commuting to work is trying to eat lunch (at work) early enough that I can do a proper bolus and not have too much left floating around for the ride home - it's not too bad for my usual ~1h commute, where I can snack before leaving to overcome any small amount of remaining IoB, but sometimes I ride to our other site which is getting on for 2h each way, which means I'll definitely need an uncovered snack before I leave and something else on the way. Not a major problem once you realise what you need to do though.

Interestingly the ride to the alternative site usually works quite well, even if I misjudge bolus I tend to be back where I want to be by the time I arrive (and I probably give slightly more bolus than I would for a longer ride because I know it's only 2h and I can stop and eat at the other end.)

Zinadane said:

But if going on a 50miler etc. I need the breakfast first.

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I would prefer to eat first, but sometimes I just go and then start eating some of the food I've taken with me. For long rides (200km) I really do need to eat something before I leave unless I've got a stop planned with guaranteed food. These are the rides where I can go really high if I misjudge how much basal cover to do before I leave (doubtless also some pre-ride nerves as these are always self-planned and not previously ridden routes).

If I then do a correction after a couple of hours it only needs to be 1U to bring me crashing back down from the high teens/20s into single figures over the course of an hour or so (which is ok if a proper stop is coming fairly soon so I can start cramming in lots of food on my way to the stop to counter any low and then have a bit of a break from both riding and eating when I stop - otherwise it's unpleasant eating enough carbs to continue with an already full stomach.)

The last one I did in August actually wasn't too bad - I peaked in the low teens iirc. This was perhaps as I had a quick ride to the train station then sat on a train for an hour to get to my start point, so I was willing to give some extra bolus as I knew there would be less IoB by the time I was actually riding properly.

It's all a continuous experiment though!

Zinadane said:

I try and eat a couple of hours prior in order to get some level of stabilisation and trend prediction, but so far it usually always tends to go high during fotf. I

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Rides that start mid-morning onwards are much easier to deal with!

Zinadane said:

never have the courage to take that little bit more insulin prior to a bike ride, even though I tend to carry way more carbs than I evere use.

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Lol, same here, I both carry vast quantities of food and don't want to have to start eating it too early (and generally don't need to eat very much of it either, though on some occasions I have had to so was glad it was there).

What I'm finding on long rides is that if I don't start eating reasonably early in the ride I loose my appetite and don't really fancy anything when I need to start eating a bit later on (e.g if that is 4h into the ride), so I think perhaps erring on the side of a bit too much insulin so that I can actually start snacking around say 2h30 might work better even if I do end up needing to eat a bit more overall.

If I stop and get off the bike for say 45min for some food it's fine, my appetite will return, and I'll also get enough of a BG rise from the uncovered food to not need to eat for another ~1h30+ which takes some of the pressure off/acts as a reset for my stomach.

Zinadane said:

Agree, drink (night before and 2-3 to put me in a slight hangover state) can give a bonkers no insulin requirement next morning scenario!

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But cycling through a hangover isn't all that much fun!

Is this on the shorter rides to work, or the longer ones?

You said you were taking some bolus to counteract DP, is this not working any more? Could you take more? I know the fear is that suddenly you'll drop like a stone. I take my DP bolus and then have perhaps 10g of carbs to take the edge off any drop, though if I'm still heading up when I'm leaving the house I don't eat anything more.

I don't think there's any issue with exercise at elevated BG levels. There is some hazy guidance that you shouldn't because high BG levels can be associated with ketones (due to illness or lack of insulin) and exercising can increase ketones. I don't think this is an issue if you have basal insulin on board, and especially not with bolus to counteract DP.

If you do decide to treat, I'd make it a small dose, though it does depend on how long you've been riding for - if it's been a couple of hours then insulin sensitivity is starting to increase (for me anyway) and a 1U bolus will drop me something along the lines of 10mmol/l over the next hour and a bit. If you're only riding for an hour or so to work I'd just not bother until you arrive there rather than needing to stop and faff around as it won't have a chance to do very much.

Zinadane said:

It can happen on commutes or longer weekend group rides.
The commute I tend to bolus slightly higher and if needs be just stop and top up.
The problem for me is on the longer weekend rides, where I don't want to be the person who needs to stop (although a no-drop type of ride). Plus a bit more competitive so always airing on the cautious side of bolusing (thinking I can burn any highs away).

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Riding harder tends to raise my BG (on the way to/from work, I've not been on a group ride for ages now.) I know what you mean though, terrible to be going hypo and slowing people down - if I do ride with others I make sure I have fact acting snacks to hand so I can treat early, though this won't help here.

I really don't know what the answer is, but...

Zinadane said:

Like I say, if I get into mid teens is it ok to carry on for an hour say before dosing.

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I really don't think this is a problem (aside from the usual not wanting to run high due to long term damage.) I've certainly not read anything indicating that exercise while high is any worse than not exercising. The guidance actually says to exercise to reduce BG, with the caveat about not above a certain BG level due to the concerns about ketones which I addressed above.

Zinadane said:

Be great to be able to take while riding (on the move) if needed .

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I guess a pump is the answer there - I can't see myself finding a straight and clear enough piece of road to faff around with pens and lids riding no-handed unfortunately!

Zinadane said:

I've never had the big plummit at the start, so I think I need to be braver with my breakfast bolusing.

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I tend to not get a plummet even I don't exercise, so I think I should also be braver. Interestingly if I drive my BG does reduce by the time I get home from the 1h school drop-off loop so this is probably why I'm a bit cautious about DP doses in general. If I'm riding straight to work then it tends to sit wherever it was when I left the house, then fall once I arrive (probably a combination of ~1h duration producing a bit of muscle insulin sensitivity, and the abrupt drop-off in hepatic glucose - it's not a very nice trip these days with lots of traffic due to road closures so I'm riding pretty hard, and it's hilly too (Bath in the UK))

Zinadane said:

I usually carry anywhere between 120 and 150 carbs and generally I always return with it all

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For my commute I don't take vast amounts - though I guess I probably do have at least 100g simply because it's the standard bag of stuff I take everywhere (I never need to eat anything on my commute to work, sometimes I do on the way back depending on whether there's any lunchtime IoB.)

So I don't know, sorry, I am also open to ideas and suggestions.