Physical activity has many benefits for both physical and mental health, and yet there are many people who are not meeting the recommended weekly amount of exercise. This could be due in part to the many common barriers to exercise: time, energy, accessibility, motivation, etc. People with type 1 diabetes may experience the same barriers plus the added challenge of managing blood glucose levels during and after exercising.
The recommendations from the Center for Disease Control (CDC) are:1
- Adults need 150 minutes of moderate-intensity physical activity and two days of muscle strengthening activity per week
- Children ages 6-17 should be active for 60 minutes per day
- Children ages 3-5 should be active throughout the day
Examples of moderate-intensity aerobic physical activity include brisk walking, playing tennis, pushing a lawn mower, or riding a bike on ground level. For strengthening exercises, these include things such as lifting weights, using resistance bands, push-ups, sit-ups, or strenuous yard work. Also, the number 150 may feel overwhelming, but every time that you can move your body instead of being still, it helps!
Aerobic exercise is what most people refer to as “cardio” because it increases your heart rate and breathing. Anaerobic is physical activity that strengthens the muscles and does not typically increase heart rate and breathing the way that aerobic activity does. The combination of these types of exercise is ideal, and for people with diabetes, there are some strategies to the timing of these exercises to help maintain glucose levels within target.
How Exercise Affects Blood Glucose Levels:
Without planning, and sometimes even with planning, aerobic exercise can cause low blood sugars.2. This can be particularly frustrating when you are trying to exercise to achieve body weight goals, with those low blood sugars forcing you to eat to exercise safely. For anaerobic exercise, it can cause an increase in blood glucose levels, and when you’re doing a combination of aerobic and anaerobic, the effects on blood glucose can vary.
Of course, all these circumstances depend on what your blood glucose level is to start, how much active insulin you have on board, what you ate that day, how much you’ve been active recently, what direction the wind is blowing…ok maybe we’re exaggerating a little with the wind comment, but sometimes it feels that way!
How to Plan Exercise with Diabetes:
The good news is, the more you exercise, the more your body will be conditioned to the activity, and you’ll experience less variability in glucose.3 Ideally, you will have a routine so that you know ahead of time if you’re going to engage in physical activity. If you do, or can think a couple hours ahead, you can do a few things to help prevent hypos related to exercise, depending on your diabetes regimen:
- Starting your exercise with resistance training (anaerobic) before doing aerobic exercise can help prevent lows.3
- If you’re on an insulin pump, lower the basal 90-120 minutes ahead of time by 50-80% (the amount will depend on the planned intensity of the exercise).3,4
- If you’re on a hybrid closed-loop system, set the “activity” or “exercise” target 90-120 minutes ahead of the exercise.
- You can eat carbohydrates to maintain a higher glucose target before aerobic exercise. For example – aim to stay between 140-180 mg/dl (7.8-10 mmol/l).4
- If you eat before you exercise, reduce the bolus for the meal by 25-75% depending on the intensity of the exercise.3
- If you eat after you exercise, you also may want to reduce the bolus by up to 50%.3
- Reduce nighttime basal by 20% or consume a snack without insulin if you exercise in the afternoon or evening.3
- Try exercising when you have not taken a bolus recently.
- Try exercising first thing in the morning when you’re experiencing the normal insulin resistance of the morning.
Other recommendations and considerations:
- Make sure you’re hydrated and replacing fluids after exercising.3,4
- Exercise increases the risk of low blood sugars overnight because the body replenishes the glucose stores in the liver, so adjusting insulin or food intake before bed is advised; higher protein or fat content snacks could be beneficial.3
- Do not exercise if you have ketones, as this can increase your risk of diabetic ketoacidosis (DKA), so if your blood glucose is elevated above the 180 mg/dl (10 mmol/l) target, check for ketones prior to exercising.3
There are several moving parts to exercising with diabetes, and as with many things, everyone is unique, and it may take some time to figure out what works best for you and your diabetes. We’d recommend meeting with your diabetes healthcare team to get advice on how to manage exercise for you.
We all need to move more, and finding something that you enjoy can really help you stay engaged in physical activity. Getting your friends and family involved can also help keep you motivated and on track. For me, my dog keeps me the most motivated to get out and enjoy the fresh air. I hope that you find what works for you!
- Physical Activity: Adults (CDC)
- Prediction of Hypoglycemia During Aerobic Exercise in Adults With Type 1 Diabetes
- Exercise management in type 1 diabetes: a consensus statement
- Effect of aerobic and resistance exercise on glycemic control in adults with type 1 diabetes
Written and clinically reviewed by Marissa Town, RN, BSN, CDCES