Diabetes & Aerobic Exercise – Managing Type 1 Diabetes DURING Aerobic Exercise

Diabetes & Aerobic Exercise – Paul Coker & Dr Rob Andrews discuss approaches to managing type 1 diabetes before, during and after aerobic exercise.

Introducing Dr Rob Andrews

In this short video Dr Rob Andrews, a world leading clinical expert on diabetes and exercise, shares some incredible insights and guidance on the latest research into Type 1 Diabetes & Aerobic Exercise.  The focus of this video is managing type 1 diabetes before aerobic exercise.

What is Aerobic Exercise?

Exercise that you can do for more than a minute or two is said to be aerobic.  Aerobic exercise includes sports like running for more than 400m, cycling, swimming.  Gardening, cleaning the car, or the house might be aerobic exercise and perhaps, like me, you have noticed that you have a low blood glucose level when you do some of these daily chores.  Dr Andrews says that during aerobic exercise it is common for blood glucose levels to drop quickly in people who have type 1 diabetes and in this video Dr Andrews shares some strategies on how to stop this from happening if you plan your exercise.

What will I learn?

Dr Andrews helps elite athletes and olympians who have type 1 diabetes to excel in sport, you may or may not be an elite athlete but you can be certain that you will get information that has helped people with diabetes to exercise safely at the highest levels on the planet.  With this video to learn some of the amazing secrets about diabetes and exercise that Dr Andrews shares with elite athletes.

Paul Coker was diagnosed with type 1 in 1977 and even with 40 years of experience of living with type 1 diabetes and he says that in this interview he learned new diabetes management tools.  If you or a loved one have type 1 diabetes that this video has lots of important tips and advice, even if you think that you do not exercise.

Be Part of the Research

Dr Andrews leads a team of researchers who define and explore exercise guidelines that other Doctors share with their patients around the world.  Dr Andrews is also a key member of the Exercise with Type One Diabetes (EXTOD) team.  EXTOD are looking for people, like you, who have type 1 diabetes who exercise or are thinking about exercising to take part in an important study.   Why not take part?  You can learn more about how you can take part in this study at the EXTOD website.


Hi. Paul Coker here from 1BloodyDrop.com. On the previous video, I was talking with Dr. Andrews about how you manage your diabetes before aerobic exercise. In this video, I’m with Dr. Andrews, and he’s going to be sharing with us how you manage your diabetes during aerobic exercise. Just for those that haven’t seen the first video, Dr. Andrews, could you just give us a quick introduction of your phenomenal expertise in diabetes and exercise?

I’m Dr. Rob Andrews. I’m a physician who works with people with diabetes in a district hospital, in Taunton. As well as taking care of people who’ve got type 1 diabetes, I see people who are coming up to do sporting events, such as marathons and things, or people who are doing sports at an elite level, and try and give them advice to help them manage their blood sugars before and during and after. To aid with that, we have a research programme that’s run through the University of Exeter that we try and answer questions to make that advice better with time.

Rob the work that you and your team are doing is just incredible, and I know that I’ve benefited from it. By us sharing some of your knowledge on this video, I’m hoping that we can get some of your fantastic knowledge out to a much wider community, so thank you for joining us today.

Preparing to do Aerobic Exercise with Type 1 Diabetes

The previous video, we were talking about how you manage your diabetes before you do aerobic exercise. In this video, I’d like to talk about what you should do to manage your diabetes during aerobic exercise, or rather what the research suggests is a useful strategy for managing diabetes during exercise. Because, of course, what works for me may not work for the next patient. I think there’s an element here where I can find a method that works for me, and somebody else could try that exact same method. It wouldn’t necessarily work for them, and they would need to refine it.

There may be a benefit to Exercising in a FASTING STATE

Dr. Rob Andrews:               Yeah. I think you’re right. Exactly what you said is is that it’s very personal what works for certain people. One way of changing the variance that some people see with … Sometimes people find if they do the same exercise, they get a different response each time they do the exercise … is to think about whether it’s worth doing it fasted. We know from research that if you do your exercise before breakfast in the morning, that actually the response you get with whatever exercise you do for you is pretty consistent.

Whereas, if you’re exercising at other times of the day, there’s lots of other things going on, stress of work, when you last ate, when you last took your bolus insulin. That means that you could have a very varied response even though you think you’ve cracked it one time, having done it before. That’s one tip that I would say if you want to try and decrease your variance is think about whether you do that fasted.

Paul Coker:                             Okay. That’s really interesting because if you look at all of the sports material out there, everybody tells you, “Oh, you should be loading with food before you exercise,” and so actually exercise fasting is not recommended in the mainstream literature. Now, how much science is based on the mainstream literature, I honestly don’t know. But I find it absolutely fascinating because my preferred strategy for going for a run is to get up first thing in the morning and run before breakfast.

For me, personally, I experience a severe amount of insulin resistance in the morning because of a variety of hormones that are flying around in my body. Actually, going for a 30-minute run, I actually manage to negate all of those insulin-resistant hormones without having a huge dose of insulin. That means that I am then going through the whole morning period and getting to lunchtime without going hypo. Whereas, if I try to manage those insulin-resistant episodes with increased insulin, by lunchtime, I am battling hypoglycemia. For me, I find it an essential part of my diabetes management tool kit.

We’re going on a slight tangent here, so I’d like to actually talk about what you actually do during an exercise session. Doing it in a fasted state is one strategy, but, of course, my own opinion would be you need to make sure that you’ve got fast-acting carbohydrates around in case you do go hypoglycemic. If you’ve not eaten for the last 12 hours, you may be at risk if you’re on the running machine for 20 minutes. I think that that, for me, would be one thing I would recognise from my own experiences. What other recommendations would you have?

Safety is Essential in Your Diabetes & Exercise Strategy

Dr. Rob Andrews:               Yeah. Starting with just what you were talking about with safety … It’s really important when people are thinking about doing exercise that they have the kit with them that they need. Part of that kit, as you already said, is that they should have some fast-acting carbohydrate. They should have some fluid. They should have an ability of actually testing their blood sugars. If you’re out doing events that you’re not around people, then we would suggest that, if possible, have a mobile phone so that you can do things. Of course, have something to identify that you’ve got diabetes for people.

It’s worth doing that. I think sometimes people get slightly upset that they say, “Well, with a type 1 diabetes, I have to really plan my event.” If you talk to most people who do exercise if they don’t have type 1 diabetes, they have to do all of those. They carry a phone around. They carry some food around. They carry fluid around, and they do have contact ability. It’s not actually that much that’s different, just that you are more reliant on having enough food around.

Paul Reflects on Carrying Diabetes Supplies When Running

I think in my own case, the additional things that I carry are my insulin pump and my blood glucose testing equipment. Now, I’m usually lucky enough to be running with a CGM, which actually connects to my phone. That means that it’s only really my insulin pump that’s in addition. I think that the frustration for me is, on a long run, it’s just the amount of equipment that I have to carry in terms of blood glucose, sorry, not blood glucose [inaudible 00:06:06] the amount of extra fuel that I have to carry. Because it’s not just about … I’m not one to eat a couple of Jelly Babies every half an hour to keep me going. It tends to be a little bit more complicated than that.

Dr. Rob Andrews:               Yeah, it certainly does. In the previous video, and it’s worth watching the previous video, we talked about what you can do, the strategies before you start. One of the strategies you might have done before was reduce your insulin. If you’ve done that during the event, you might find actually that you hardly need to take any carbohydrate or do anything with your exercise to help with your blood sugar.

If you do need to do something in the event, you’ve only got two choices. One of them is that you take some food because actually what’s happening is that your glucose is falling. Your body’s not able to keep up with the rate that it’s falling, so you’ve got take something in order to level that out so it doesn’t keep falling. That’s when you’re talking about fast-acting carbohydrates. Or, the other thing that you could do is you can fool the body into actually saying, “I’m doing a different event. I need to produce the hormones that will push up my blood sugar.”

What we know is if you’re doing an aerobic event that’s continuous, if you introduce little sprints in them … There used to be something called Fartleks, which is that you would run in a line. When you get to the back of the line, you had to sprint to the front of the line. That sprint is enough to raise your hormones and prop up your blood sugars. During an event, if you’re trying to lose weight during training and things, you can intermittently during an aerobic event do a little sprint. That will help prop up your blood sugar so it doesn’t fall.

Fartlek session can be repeated multiple times during an Exercise Session to Give Protection from Hypo’s

Paul Coker: Does that continue to work? If you do that once, it’ll make you … The other hormones will make you slightly insulin resistant. If you do it a second time, does it have the same level of effect? If you’re doing it once, twice, three times, four times over the course of an event, can you rely on it being as effective each time?

Dr. Rob Andrews:               We haven’t done as much research as we would like into that. The small amount of research suggests that there is a little diminishing effect but that it still is effective. Certainly, on kid holidays when we do kid holidays and things, just … If they’re doing activity holidays, what we do is just stop them and ask them to do a couple of sprints, and that’s protective through the day of actually keeping up their blood sugar.

Paul Coker:                             Protective through the day? Not just for the next five minutes or ten minutes, but for the entire day?

Dr. Rob Andrews:               It can last for two or three hours, the effect of the sprint. I think the things that people worry about, and we’re probably going to talk about that in another video, is what happens afterwards is that if you do sprints as part of your aerobic, you’re burning more of your muscle glucose stores. The thing that predicts whether you’re going to have a low blood sugar overnight is how much of your blood stores that you predict.

Burning Fuel on Exercise is like spending money on a Credit Card – there is a Debt to be Repaid

Rob Andrews: The way I kind of try to say it to people is a bit like a credit card, is that during the event, you are spending stuff that you have to give back. You’re using the fuels in your body. At some point, the body’s going to say, “Hey, mate, you owe me what I gave you,” and you have to replenish that. If you don’t replenish that, then there are penalties. Those penalties are the low blood sugars.

Paul Coker:   I love that analogy about the credit card. That makes so much sense. It just makes it suddenly so very simple to think about in terms of, I’ve been out for a run. I’ve burned all of these calories. Even though I may wish to lose some weight, I can’t just let that calorie deficit continue because my body requires more than the calories. Those muscles and my liver want to get the carbohydrate stores back, so that’s a really nice, simple way to think about it.


Key Principles for Aerobic Exercise

Paul Coker:                             Would there be any other tips that you would share that you can think of? Or would they be your key principles-

Dr. Rob Andrews:               The key principle of regular carbohydrates. I think people, sometimes what they want to do … It used to be the old adage is why it’s called a fun Mars bar is that people used to be told just have a fun-size Mars bars by four, and go off and have some fun. What we don’t like to do is to actually load you with carbohydrates at the start. I think people think if they start with a high blood sugar, it protects them from being … fall. It doesn’t. If it’s very high, it easily moves into the cells. It drops much quicker if it’s high. What we want you to do is take a small amount frequently. What appears to be the ideal thing is take something every 20 minutes, so take a small amount every 20 minutes.

Is there an Upper Blood Glucose Limit for Exercising Safely with Type 1 Diabetes?

Paul Coker:                             Something we didn’t really talk about on the previous video, and perhaps we should have, is there an upper limit of your blood glucose level when you should consider not performing exercise?

Dr. Rob Andrews:               Yes, there is. Luckily, we’ve finally got it agreed worldwide. There used to be different figures that were in different parts of the world. We now all agree that if your blood sugar’s above 15, that you should be checking for ketones. That’s blood ketones, not urine ketones, because urine ketones are too late. If you can’t check for blood ketones, lots of people don’t have blood ketone monitors, then what we would say what you need to do is, is to think about a correction.

Or, just wait and see whether it falls, but don’t exercise if it’s above 15. If you do have a tester, then what we want you to do is really not do anything if the ketone’s at above one, apart from low-grade exercise. There’s a lot of debate about that. We generally say don’t do anything if you’ve got any ketones at all to be safe.

The Dangers of Starting to Exercise if Your Blood Glucose Level is Too High

Paul Coker: Can you just share with us what the dangers are of us exercising if our blood glucose levels are too high or we do have ketones?

Dr. Rob Andrews: If the blood sugars are high, what that suggests is that you, at that point, are slightly under insulinized, so you’ve not got enough insulin around. Because if you have enough insulin around, you’d expect the glucose to be lower. It means that when you do exercise, there are two ways of getting the glucose into the cell. One is the exercise induced, but you still …

Everyone who exercises who hasn’t got type 1 diabetes still keeps a small amount of insulin around so that you can have insulin that takes the glucose into the cell. If you’re missing that then what can happen is you don’t take up as much of the glucose that is being produced by the liver, particularly if you’re doing anaerobic when you’re pouring out the glucose … What can happen is the glucose just keeps going up as you’re exercising, and then you can run into problems with ketosis and things.

Paul Coker:  If your blood glucose levels are really high, the last thing you want to do is to give them another excursion even higher.

Dr. Rob Andrews: When we talk to people who are trying to do things to the best that they can do, people always think about the low and that it doesn’t perform. But what we know is that there seems to be a perfect spot for each event. If you’re doing coordination events, and your blood sugar is about 12, the coordination will go off. Actually, the higher end is just as bad for doing a sport well as the lower end.

Paul Coker:  For us to perform at our best regardless of the sport, it seems that we actually need to manage our blood glucose levels within that tight bandwidth of between 7mmols/l and 12mmols/l.

Dr. Rob Andrews:               Yeah.

Paul Coker: That is absolutely consistent with my own findings of my own performance in different sporting events. I know for a fact that I’ve run half marathons with my blood glucose levels being very, very high because of adrenalin surges at the start line and a variety of effects. Actually, my performance on those particular events has been greatly reduced over my typical performance. I think that it’s really important that we actually get to a point where we can exercise safely with a good starting blood glucose level, and that we don’t carbohydrate load or reduce our insulin too much so that we get a high glucose level as you were talking about just now. I find that that is a world of pain, both physically and in terms of my performance.

Dr. Rob Andrews:               Yeah, and I think you’ve come across the same … I’m not sure if we’re going to talk about that, but the prime problem that people get really worried about is how to manage high blood sugar before an event. Doing an event is completely different from training.

The Difference between Training and an Event

Paul Coker:                             Yes, it really is. Actually, it’s a good point to be talking about that because I know that I did 40 half marathons in a year, and I did lots and lots of training before the very first one. In fact, I’d run a number of half marathons. On a training run, my blood glucose level and my diabetes would behave in one way, and I’d get to an event, and it behaves in an entirely different way. I think it’s really important for us to understand that there is a difference. What might be causing that to happen? Why is it different on the day when I go to a big race compared to the day when I go out and run 12 miles on my own?

Dr. Rob Andrews:               Well, there’s a number of reasons. The two main reasons are, one, that the people who organise events don’t think of the participants. They think about how they’re going to get it to do with the traffic and all those things. Sometimes the events aren’t ideally placed in terms of time. It can be a 9:00 start or sometimes an earlier start. That makes it very difficult to have the normal pattern that you would’ve had of having the breakfast at the normal time and the insulin, so there’s an added complexity that you’re adding into that. Then, the other thing is that you’re nervous. Being around people makes you nervous. You produce more of the nervous hormones that you were talking about, so the adrenalin, the noradrenalin. That stops the insulin working as well and makes you a bit insulin resistant and pushes the blood sugars up.

Dr. Rob Andrews:               What we try and say to people is if that you’re going to do an event like that, try and get exposed to that and see what that does. I’m not saying do a marathon before you do a marathon. What we’re really lucky about is that there are park runs. You can go to a park run, have a little go as to what happens in that first 20, 25 minutes. You can have a number of goes, and you will get the effect of lots of people being around you, getting slightly stressed that you’re doing a run.

Paul Coker:                             I think that’s really good, actually. I do regularly go to my local park run, and I run it. There’s a whole community out there of park run with diabetes, which I’m an advocate of and I support. A park run is absolutely brilliant because, as you say, it’s 25 to 30 minutes. Now, my only experience of running is that I can go out, and I can run. I know from my CGM trace results that for 24 minutes, my blood glucose levels are absolutely stable. I get to 24 minutes, and they start to drop. It happens like clockwork every single time.

I know that at 24 minutes of running, my blood glucose levels are going to start falling. If I run beyond 24 minutes, they’re going to continue falling. So, I know if I’m going to be running for more than about 30 minutes, I need to be thinking about carbohydrate loading at 20 minutes. That’s for me, personally. I’m not suggesting that’s the same for everybody out there, but if somebody out there is starting to participate in running or cycling, it might be a strategy they wish to try. I’m not suggesting it will work for everybody, but …

How to Use a Continuous Glucose Monitor / Flash Glucose System whilst Exercising

Dr. Rob Andrews:               Yeah. I think that’s probably an entirely different subject, but that brings up about how do you use your continuous glucose monitor when you’re exercising?

Continuous glucose monitors weren’t made for noticing very quick changes. The trouble is that, as you start to exercise, there’s a cooling of the skin and then an increase of the temperature of the skin. What we say to people is the first 20 minutes, actually, your CGMS is going to take time to find out where your blood sugars are. That’s when you’re running blind. What you need to do is if you’re doing an aerobic event, think that the blood sugars are likely to fall and take something.

Then, once you’ve got past the 20-minute point, then you can start looking at the continuous glucose monitor, but still remember there’s a delay. I always say to people if it’s saying six, then you need to be taking something because actually it’s four. It’s just a question of just learning that with that. There are some nice algorithms that are out there that say what to do with each blood sugar depending on what type of continuous glucose monitor you use.

Paul Coker:                             Okay. Well, perhaps we can put those algorithms … Are they on the internet?

Dr. Rob Andrews:               Yeah, yeah.

Paul Coker:                             Perhaps what we can do is find out what they are and put them on the footer of the video for people. I think we’ve covered an awful lot in that video about exercise and managing type 1 diabetes for aerobic exercise. We’ve probably gone a little bit off the track there, but once again, Dr. Andrews, thank you for sharing your incredible knowledge.

The Next Video: How To Manage Blood Glucose Levels After Aerobic Exercise

Paul Coker:                             We’re going to do another video where we will be talking about how to manage your diabetes after aerobic exercise. I think that this one is really, really important because when you go and exercise … You already made the analogy earlier of a credit card and a debt that needs to be repaid. If we don’t repay that debt, it’s going to lead almost certainly to hypoglycemia in the hours of recovery. I’m really excited to be shooting the next video with you where we’ll be talking about how to prevent that from happening.