Help With Cycling & Long Acting Insulin

Hi Julian, runsweet.com offers advice on cycling. I cycle but only 20km a time and mainly flats, I reduce my bolus before I cycle, so if I ride in the morning I take 50% less bolus with my breakfast. I try to be above 7/8 mmol/l before I head out and test half way and if below 6 then I have 3 jelly babies. I find my burn comes about an hour afterwards when my glutes are still draining glucose.

Julian_Hands said:

Juicyj you may have resolved my issue, this morning I cycled to work and the halfway point is ironically at the top of the mountains so no more real climbing after this point.
I left home this morning after taking my Novorapid and eating my breakfast, with a BG of 11.6mmol/l. I stopped halfway 15.3km to take a BG test and was really shocked when I saw the result of 2.8mmol/l.
Thankfully I always carry my home made flapjacks on me and ate one then rode gently to remaining 15km.
Got to work and tested with a BG of 4.8mmol/l.
Does anyone have any experience of doing exercise first thing then having their breakfast and insulin after the workout?

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Are you normally hypo aware? That could be an issue for you if not?

On your second question, I used to cycle to work and eat once I got in. The issue becomes that it really depends on your ride. Mine is a stop start procession of traffic lights, so I am effectively doing multiple sprints. This is similar to HIIT training and results in me getting bg spikes as I am going Anerobic a lot. To keep a constant blood glucose over that period I have to have an increased basal rate prior setting off and then take less bolus with food once arriving at work.

It all gets very confusing and the best thing you can do is get hold of a Libre or CGM to track what really happens.

I had been cycling and trying to figure out what's best for me. I did some hunting around on these forums and tried a few things out.

I'd usually bolus for breakfast taking 50% of my insulin. Can see me starting around 9-13mmol and I checked frequently every 30 mins. The cycle was steadily up hill but enough to feel your legs working and get your heart working. Small packs of Haribo or a Banana worked perfectly to keep my blood sugar in check. I keep an eye on it for a number of hours later as your body replenishes it's stores (I think that right?) so I don't go low. Being on a pump I usually lower my basal to around 40% whilst on the bike and for 30-60 mins after.

Julian_Hands said:

This is why I need a pump, today has been a nightmare but also lessons learnt.

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A pump would be ideal as you can use a TBR (temporary basal rate) prior, during and after exercise to reduce the hypo's.

You might want to try reducing your bolus dose before the commute (if you don't do this already).

Hi @Julian_Hands another alternative apart from reducing bolus by 50% is to have a small banana before heading out, which should carry you through your ride. I appreciate that when cycling it's difficult to feel a hypo with the effort being put in but stopping to test at half way is a must. As mentioned above its an investment but get yourself a Libre so you can test whilst moving, it's easy to scan this and could prevent a hypo, personally I wouldn't touch your basal but maybe eat more effective carbs that will stop the low. What do you eat for breakfast ? So are you eating something substantial like porridge/weetabix ? It's a bit of trial and error I know but it will improve with knowledge and experience.

@Julian_Hands , following the discussion in your thread about cycling, I think you need to do two things. The first is that you need to basal test: https://mysugr.com/basal-rate-testing/ Given what you are seeing, I think you may have your basal level set incorrectly, and this might help you find out where it is at. This may help with understanding why getting your food and exercise levels right is proving hard.

Secondly, I've just looked at the timing of your doses. You say:

Julian_Hands said:

woken this morning at 5:40hrs with a glood glucose of 3.2mmol/L.
I've cycled in again today and reduced my NovoRapid (short acting) by 4 units, then ate my cereal (All Bran (75g) and Semi Skimmed milk(250ml) 46g carb in total, This allowed me toleave the house at 6:25hrs with a blood glucose of 6.0mmol/L but after getting to the top of the climbs on my ride, at the halfway point 15km in, I tested my sugar and had a reading of 2.8mmol/L, therefore eat a bit of homemade flapjack to give a boost and got to work with a BG of 5.1mmol/L at 7:45hrs. (perfect)
I've now seen a trend over the last 5 days, gained by closely monitoring my BG sugars with an average of 15 tests a day and to see the effects of the cycling, but really baffled by a definite trend i'm now seeing. My BG levels have spiked consistently an hour after I've got to work and today at 8:45hrs my sugar again rose 11.4mmol/L?

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I've attached a picture of what you've described. It's quite interesting. YOur Novorpaid seems to be kicking in between 6.25 and 7am and sinking you fast. Are you injecting this into your legs at all, as that would accelerate the use and potentially cause problems. I suspect that, while the all-bran does contain about 15g of sugar, it also contains about 30 of other carbs that can take some time to release due to the high levels of fibre. I think what you may see happening is the sugars from the all-bran kicking in soon after eating, then your novorapid kicking in whilst on your way up that hill but the remainder of the all-bran carbs becoming available a little later. When you eat the flapjack at the halfway point, not only are you replenishing missing glucose, but you are also adding to the additional release from the all-bran. This will be on top of your liver reacting to the hypo while cycling, causing the following spike, which is pretty typical of a hypo induced liver dump.

I think you're going to need a bit of trial and error on this one. I suspect that the insulin immediately before cycling is not helping, but also the breakfast you are eating is adding to the complicated picture. Have you tried doing this without breakfast and seeing what the results are? I suspect that will be better.

Julian_Hands said:

Can anyone advise if this maybe the cereal carb kicking in and should I eat my cereal nad take no NovoRapid, then administer my Novorapid once I've arrived at work after the cycle ride to help flat line these spikes?

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Rather than take no insulin could you not just reduce the bolus dose again to see if it prevents the commute hypo?

I'm think that your spike later on was because your liver responded to your hypo before you ate the snack, plus oats are not fast-acting carbs and eating glucose tabs/jelly babies or liquid glucose would have been a better option to get you out of the hypo quickly.

Julian_Hands said:

Wow, thank you Tim2000s for the time you have put into the considered and fantastic response.
I've not tried the ride without breakfast and will give this a go tomorrow.
I was always led to believe that I need insulin in my system to allow the storage of the glucose on your muscles, should I completely drop the breakfast and Novorapid tomorrow?

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It's physiologically more complex than that Julian. Exercise increase the action of Glut4 Receptors within the muscles, so if your blood glucose level is in the normal range, your muscles can use glucose, and often your basal insulin will be enough of a catalyst for this to work.

This is why, when exercising 3 to 4 hours after eating, we are advised, if it is aerobic exercise, to eat carbs. Anaerobic exercise is a different kettle of fish, and usually causes a liver dump that drives up blood glucose levels, in spite of Glut4 activation.

My experience of cycling without taking fast acting or breakfast is that I was fine, but I was travelling 13-14km rather than 30. I think I'd stop and test every 15 minutes if it was my first time doing it without breakfast, especially as you don't seem to notice going low when exercising.

Julian_Hands said:

Love to get hold of a Libre Freestyle or some CGM system, but unfortunately I cant afford £160 to get going.

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If you've an Android phone with NFC, all you need to pay is £50 for a sensor and you can download the free official LibreLink app.