Running

I'll state first that I'm a T2, so what I say may not be entirely relevant to T1.

However, my experience based on fingerprick tests is that my BG readings increase due to stress, be that the physical stress of exercise, or psychological stress. It causes your liver to dump glucose into your system, which is a physiological response to give you the additional energy needed to handle the situation.

The liver's response is unavoidable for all of us. Some T2s are on medications that can reduce the liver's output of glucose, but it still happens. For a T1, I would assume you'd need to somehow dose with insulin, but I have no idea how you'd go about that, or how to calculate based on an unknown carb load from a liver glucose dump.

@Antje77 has done some testing and experimentation with exercise, how it affects BG levels, and has experience dosing insulin for it, so will be able to offer better insight than T2s on the matter.

Hi @Fern Hopper , welcome to the forum.

Paul_ said:

I'll state first that I'm a T2, so what I say may not be entirely relevant to T1.

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As a T1, I can confirm that everything @Paul_ has said is true for me.

Fern Hopper said:

I have my usual long amount of long acting and at least 1 unit of short acting and no food.
I like to start Parkrun with a BG of less than 5. But I know by the finish (about 24 minutes as an average) I will have spiked at about 12. A slow warm down of at least another mile and a half helps a bit but usually I require more insulin to bring BG down.

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There are some things I know make me rise every time (apart from food, obviously). My liver likes to dump glucose upon waking, when I visit the gym, as soon as I walk into the dentists practice, and at my annual endo appointment.

To my thinking, glucose from my liver isn't any different than glucose from food. I take insulin before eating because I know the food will raise me, this way I prevent going high.
For those few things I know my liver will add glucose to my bloodstream, I also take insulin before it does. My endo thinks it's pretty hilarious and somewhat unnerving I dose for seeing her just like I would for lunch.
But it's much easier for me to prevent those highs than to correct them afterwards, and it saves me from feeling rubbish and frustrated.

Mind, there are situations where I rise without food in an unpredictable way, and of course I can't dose for them, but I can for things that have proven to cause a predictable rise for me.
I only wish my liver dumps came with a carb count, the amount of insulin I need varies a bit, like Paul_ suspected. Trial, error, and gut feeling are my guides on this. Especially the gut feeling part, if it tells me to take a bit more or less insulin than logic tells me, I tend to go with the gut feeling, it's often correct.

I don't run, but I'm still trying to find a way to go to the gym (rise), followed by a short cold swim (steep drop). I'd want to dose for the gym, but this means the insulin will be most active during my swim, so a bad idea.

How often do you do those runs and for how long have you been doing them?
When I started going to the gym last summer, my spikes were much higher, apparently my body is getting used to this weekly torture.
And equally, when I started open water swimming in October, the drop was much more spectacular than it is now I'm used to going in at least twice a week.
So things may improve all by itself if you're lucky!

And well done on doing those park runs, I couldn't do them if my life depended on it, and I'm twenty years your junior!
I'm with you on the tight control and the hba1c range though, if not on the BMI at 35.
One of the downsides of tight control is feeling rubbish at relatively low numbers, starting at below 10 for me.

How soon before the run are you taking your bolus?

For a Type 1 runner, you might be interested in Dr Ian Lake, who is also a UK GP. His website is: https://type1keto.com/

Ian has done lots of distance and extreme distance, on a keto diet.

To be clear, I'm not suggesting you adopt a keto lifestyle (you don't say anything about your fuelling style), just being clear.

Fern Hopper said:

I start Parkrun with a BG of less than 5 - can't really go any lower.

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I understand that you cannot start much lower than 5 mmol/l.
However, as the rise is predictable and you do it every week, you can take insulin to counteract the high before it happens.

Different exercise has different affects for me - cardio will lower my BG. However, resistance training will raise my BG.
One of my weekly activities is climbing (and the local indoor climbing wall) and it used to cause my BG to soar.
Then I started to pre-empt the rise. I would begin my climbing with a bolus which, under normal circumstances would lower my BG to 3 mmol/l. This would, obviously, be too low, except I know my liver will dump glucose which will ensure I never go so low.

It will take some trial and error to find out what works for you and as you get fitter and run for longer, you may find the effects change.

Bear in mind the route a weather could have an affect as well. I rarely run but, as well as climbing, I also cycle and I can predict what will happen to my BG depending upon the type of ride:
- a slow amble along the flat canal tow path whilst chatting to my mates, will have little impact
- a zoom around the gently undulating country roads (or an indoor Spin class) will lower my BG
- a strenuous slog up a steep hill against the wind on an uncomfortable wet day, will raise my BG

Fern Hopper said:

I am not too sure when I can inject myself to counteract BG rise.
Thanks very much for your reply. It's all very interesting and informative.

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Fern Hopper said:

But, I start Parkrun with a BG of less than 5 - can't really go any lower. I, of course, can't inject myself half way round to correct BG.

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Do you know how long it usually takes for a correction to start dropping you?
For most of us, this isn't instantly, so if you start at 5 and inject right before it shouldn't drop you further before the rise from the run starts.

If you do this parkrun every week, you might want to consider sacrificing your excellent running time once or twice to do a fingerprick test halfway through if you want to do some experimenting with insulin and timing.

How is your hypo awareness?

Had the same issue with exercise until I realised that balancing the burn with carbs can eliminate the hormone rebound spike.

My burn is about 500 kcal, which for me equates to a smallish banana. The carbs take about 15 mins to really kick in so I start my exercise about 15 min after eating. Last time out my BG was 5.2-5.7 from start to finish (one hour from banana to shower!) and no spike in the following 2 hours.

Fern Hopper said:

I'm not sure I could run half an hour after a banana but I will give that a try. And what sort of exercise do you do?
I even ran half marathon without any food. I ate 6 hours after finishing.
My hypo awareness is very good even after 57 years. I am quicker than sensor. Reluctant to sacrifice quick time but I will also try finger prick test.
Many thanks for your replies. Food for thought (if you pardon the pun).
Riding the bike is far different - less insulin and more food!

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I run, cycle or use an exercise bike - and you're right a banana is not the best prep for a run! Instead I have a protein bar (which are famously full of carbs).

I can't imagine running a half-marathon without any carbs - I'd need at least 100g to get through that. But the downside is the rebound effect, even if you don't feel hypo, the corticosteroids and catecholamines will kick in and spike your BG not long after. I guess it's different for different people but I get these spikes from a steady 5-6 mmol/L long after exercise pretty much as @Antje77 described, and if left "untreated" they can go up to 11 mmol/L.

Btw do you or anyone on here notice any insulin resistance when trying to reduce those hormone driven spikes? I've had to inject 6-10 units fast-acting just to get the spike to flatten let alone go down.

I'd rather have the cake!

The spike after your Park-run is caused by catecholamines & Co. (cortisol, somatotropin, epinephrine, glucagon and others) - they cause the rebound effect. In fact almost any BG rise not caused by carbs or illness is due to these guys.

EllieM said:

Can you recommend any good links that explain this? I must admit to not knowing a lot about this subject.

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When discussing exercise induced counter-regulatory BG spikes, i.e. hormone responses caused by physical activity, it's important to distinguish these from similar BG spikes caused by periods of low-blood glucose without exercise, or by stress or the dawn phenomenon, because the way to deal with each may be different.

Exercise: The article from Sunsweet referenced by @lovinglife, http://www.runsweet.com/diabetes-and-sport/ is a good start. This lists the counter-regulatory effects you may see when taking exercise. A fuller description of the hormones involved is here, https://www.type1familycentre.org.au/post/clinic-chat-counterregulatory-hormones.

Low-BG and Stress: The reason for the counter-regulatory effect is often cited as a response to periods of low BG (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3755377/), but I get them after BGs of 5-6, so maybe it's stress (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9360912/).

Dealing with these BG spikes: I can prevent the dawn phenomenon (the spike that most people get at 3-4 am) with 2 units of fast acting insulin, but this doesn't work with the exercise exercise induced and stress-induced BG spikes.

For these there is also the problem of counter-regulatory transient insulin resistance - and when the hormones have subsided the insulin injected to get the BG down will come back to bite you. This is discussed here, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7609903/. I've only found one way of getting BG down when faced with a stress-induced spike and that's to burn it with exercise... and yes, I get an initial exercise-induced spike too to add to the burn.

If all of that scientific blurb is a bit overwhelming - this old article covers most of it and has some easily understandable graphics (https://diabetesjournals.org/diabet...7/Glucose-Counterregulation-and-Its-Impact-on).

Jasmin2000 said:

Dealing with these BG spikes: I can prevent the dawn phenomenon (the spike that most people get at 3-4 am) with 2 units of fast acting insulin, but this doesn't work with the exercise exercise induced and stress-induced BG spikes.

For these there is also the problem of counter-regulatory transient insulin resistance - and when the hormones have subsided the insulin injected to get the BG down will come back to bite you.

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We're all different, what works or doesn't work for you doesn't have to be the same for everyone.

I can and do inject for both exercise and stress (dentist, endo visit) without issue, and mostly manage to keep a straightish line.