Exercise is a key pillar of diabetes management, and many people with type 1 commit to doing more exercise as one of their New Year’s resolutions. Decisions about exercise with insulin-dependent diabetes are never simple, so learning how to exercise safely is vital.
Consider the question: ‘Should I exercise now?’ People with type 1 really have to consider several questions: Is it safe for me to exercise right now? Are my glucose levels in a safe range? Is my glucose headed up or down? Am I at risk of low or high blood glucose when I exercise?
The process for answering the question ‘Should I exercise now?’ can end up looking something like this!
It takes time and attention to get through this decision tree to your answer. By the time you get to the end you haven’t even put on your sneakers! So let's break it down a little:
Exercise and blood glucose levels Different types of exercise impact your blood glucose levels differently. Aerobic exercise, such as walking, swimming or riding a bike will tend to make blood glucose levels drop. Anaerobic exercise, such as sprinting or lifting weights, often makes blood glucose levels rise, and mixed exercise, such as most team sports, can be challenging to manage because they combine sprinting and aerobic exercise. Check out the awesome JDRF Peak resources on the impact of exercise on blood glucose to get some tips and strategies for approaching different types of exercise.
Type 1 diabetic Ginger Vieira, former record-holding powerlifter, personal trainer, and author of Your Diabetes Science Experiment, lays out how to use testing-in-pairs to discover how exercise, food, medication, and stress affect your glucose levels and what you can do about it.
When it comes to learning how exercise impacts your diabetes Ginger suggests three steps:
First, ‘test your blood sugar before you start. Test it during [exercise] if you think you need to. And test it within 15 minutes of finishing. Take good notes on what happened. Did 30-minutes of cardio exercise before eating a meal drop your blood sugar? Yes or no? Then you can start to apply that logic to other types of exercise.
‘Secondly, learn the difference between cardio/aerobic exercise vs. strength-training/anaerobic exercise because they impact your blood sugar very differently. The more you understand which type of exercise you’re doing, the better you can plan for your blood sugar needs around that exercise.
‘Thirdly, when trying a new type of exercise, I always assume I could go low and I prepare for that potential [with] fast-acting carbohydrates - whatever is easiest for you to keep in your pocket or in your hand or within reach during your workout.'
Learn How Insulin Affects Your Exercise Sheri Colberg, PhD, is the founder of Diabetes Motion, a website providing resources to people with diabetes who want to be physically active, and author of The Athlete's Guide to Diabetes, the go-to reference on how to approach managing diabetes while participating in over 150 different sports. Interesting fact: three members of the Family Centre's community, our swimming CEO Bec Johnson, ultra-endurance cyclist Neil McLagan, and Jamie Read, also a cyclist, are quoted extensively in Sheri’s book on their approaches to exercise!
Sheri’s key tip is to be aware of how much insulin you have on board during activity – this includes both background insulin and meal/correction boluses. People on insulin pumps have the flexibility to change their basal rates before, during, and after activity, whereas those on injections have to think ahead if they want to change long-acting insulin, because once it’s onboard, you’re committed to that dose for up to 24 hours.
Ginger added the following: 'The easiest time of day to manage your blood sugar around exercise is before eating a meal, when it’s been at least three hours since your last bolus for food. By exercising before you eat, you don’t have to feed your exercise as much with carbohydrates because you don’t have active insulin in your bloodstream.'
Bec Johnson, our CEO, and Amy Rush, the Family Centre’s diabetes educator, have presented at AMSL Diabetes Sports Camps at the Australian Institute of Sport since 2014. Their approach, entitled ‘The Four Ts: Tucker, Timing, Training and Therapy’ outlines the four main variables in play when exercising with type 1 diabetes.
One of their favourite tips echoes Ginger’s – when you exercise on background/basal insulin only, with a system clear of food and rapid-acting insulin, you’ll clearly see the true effect of the exercise on your blood glucose. For example, if Bec exercises in the morning before breakfast, she knows that her blood glucose will stay steady with up to 90 minutes of swimming or cycling (aerobic exercise), but if she does weights or high-intensity exercise like a spin class, her levels spike. It's easy to run experiments and see the impact of the exercise when breakfast and a bolus aren't in the picture.
Experiment The lesson here is: experiment. Think about the variables in play – food (Tucker), time of day and duration of exercise (Timing), type of exercise (Training), and bolus or correction insulin and basal insulin (Therapy), and try to set up your experiments so that you’re managing only a few variables at a time. Build up your knowledge by logging your results, and learn how exercise impacts your body and your glucose levels. If you need support, check-in with your diabetes educator, check out the JDRF Peak resources, and consider using the Family Centre’s online communities for parents and adults to connect with active, knowledgeable people with type 1 from all around WA.
This article was adapted from Bigfoot Biomedical's blog post 'Exercising with Insulin-Requiring Diabetes', January 2020