It can be hard enough for anyone to muster the motivation and momentum to exercise. But for people with type 1 diabetes, real risks and potential threats loom. Even just the idea of safely undertaking any kind of athletic activity can be quite daunting.
With that in mind, we’re setting out to set the record straight.
The truth is that exercise is both safe and highly beneficial to those with T1D. Also true is that there are important precautions to consider.
But take heart — the experts and resources we tapped confirm that taking those precautions doesn’t have to be as strenuous as, say, bench pressing your body weight or trying to run a 5-minute mile.
The impact and benefits of exercise with T1D
Christel Oerum has been living with type 1 diabetes since she was 19. She’s an LA-based personal trainer, author, and co-founder of Diabetes Strong, a site dedicated to fitness and healthy living for those with diabetes.
According to Oerum, the main benefits of exercise go far beyond just balanced blood sugar levels.
“Exercise can help your body use insulin more effectively, which means that your body will need less insulin to lower blood sugars,” she says. “When we exercise, we use our muscles, and when your muscles contract, it helps move glucose from the blood into the active muscles. And the benefit doesn’t end when we stop exercising. The increased insulin sensitivity can last from 2 to 72 hours, depending on the type and intensity of the activity you do.”
A 2016 position statement published by the American Diabetes Association noted that “the adoption and maintenance of physical activity are critical for blood glucose management and overall health in individuals with diabetes and pre-diabetes.”
We also need to look beyond just the main physiological benefit of more effective insulin use to control blood sugar levels, Oerum says. “Other benefits of exercise include reduced risk of cardiovascular disease, stress management, and weight management.”
Being active increases your good cholesterol (HDL) and decreases unhealthy fats (triglycerides) in your bloodstream. This combination means you’re less likely to see fat build up in your arteries, thereby reducing the risk of cardiovascular diseases.
Exercise can also help release endorphins, which reduce the perception of pain and make you feel good, reducing anxiety and stress.
Finally, exercise can be critical in maintaining a healthy weight. While these benefits are important to everyone, they can be particularly beneficial to PWDs (people with diabetes), who may suffer increased complications weight fluctuations, and increased levels of stress, distress, anxiety, depression, and diabetes burnout.
It’s important to note that, despite all the benefits of exercise, type 1 diabetes cannot be controlled or treated with diet and exercise (lifestyle methods) alone.
T1D exercise guidelines go official
In 2017, the first-ever medical consensus guidelines for safe exercise with type 1 diabetes were released. These guidelines contained several disclaimers, including the all-important truth that there is no such thing as a one-size-for-all recommendation around exercise.
Exercise goals and approaches should be built around types of activity and individual aims, while taking into account "various factors including glucose trends, insulin concentrations, patient safety, and individual patient preferences based on experience."
But the guidelines do provide specific tips on glucose levels while exercising and insulin dosing strategies. For example, if you’re beginning an exercise session with your BG (blood glucose) at target levels (125–180 mg/dL), the guidelines advise that: 1) aerobic exercise can be started and 2) anaerobic exercise and high-intensity interval training sessions can be started, but beware that BG levels could rise.
Aerobic exercise is any type of cardiovascular conditioning or “cardio.”
Anaerobic exercise is activity that involves quick bursts of energy, performed at maximum effort for a short time.
Learn more here: AEROBIC VS. ANAEROBIC EXERCISE
Here are a few other key takeaways from the guidelines:
- Exercise can increase glucose uptake into muscle by up to 50 times.
- Hypoglycemia (low blood sugar) develops in most patients within about 45 minutes of starting aerobic exercise.
- Individuals who are aerobically conditioned have lower glucose variability than those who are unconditioned.
- The risk of hypoglycemia is elevated for at least 24 hours in recovery from exercise, with the greatest risk of nocturnal hypoglycemia occurring after afternoon activity.
- Weight lifting, sprinting, and intense aerobic exercise can promote an increase in BG that can last for hours. Although a conservative insulin correction after exercise might be prudent in some situations, over-correction with insulin can cause severe nocturnal hypoglycemia and lead to death.
- High-intensity interval training has been associated with a higher risk of nocturnal hypoglycemia than continuous aerobic exercise in some cases
How much exercise is recommended?
General exercise guidelines from the
Specific to people with diabetes, the American Diabetes Association also recommends 150 minutes (2.5 hours) or more of moderate-to-vigorous intensity activity weekly, spread over at least 3 days per week. It states that shorter durations (a minimum of 75 minutes per week) of vigorous-intensity or interval training may be sufficient for younger and more physically fit individuals. Furthermore, the ADA advises no more than two consecutive days without activity.
The ADA also recommends that people with diabetes should “interrupt long periods of sitting every half hour with light activity, such as walking, leg extensions, or overhead arm movement.” Prior recommendations were to get up and move around only every 90 minutes.
Choosing your best exercise type and getting started
While any exercise is good, and you will feel its benefits, different types of exercise will affect your blood sugars differently. The main differentiator is how aerobic the activity is. For example, depending on if you do yoga or dance, or if you walk rather than run, you’ll see a different effect.
In addition to what your body can handle, it’s crucial to find the right exercise regimen that you’ll enjoy and stick with, says Zippora Karz, a former soloist ballerina with the New York Ballet Company and author of “The Sugarless Plum,” a memoir about her journey to get a proper diagnosis and maintain her ballet career.
“What motivates and inspires you?” she says. “Sometimes it's finding a good teacher, and people in the class who inspire you. Sometimes, it's the form of exercise itself, and sometimes it's a combo of it all. Find what motivates and inspires you.”
Consistency is crucial to sustaining a healthy lifestyle. And it’s okay to be honest: sometimes starting is the hardest part. “Maybe you need a buddy system, someone to help get you to the class,” says Karz. “Or a walking partner. Maybe it's a time management issue, where you need to make sure you allow time to fit exercise in. If you don't have time to get to a class, there are many videos you can follow at home.”
Whatever your planned exercise routine looks like — whether it’s moderate walking, running, intensive cardiovascular interval training, or a combination of aerobic exercise, yoga, and strength training -- discuss your goals and capabilities with your healthcare team before launching into anything new. Always be sure to ask about insulin adjustments that may be necessary.
Trainer Oerum says to start slow and pay attention to how your body reacts to the new type of exercise. “Know that you most likely will see a more extreme response the first 7 to 14 days when you start something new,” she says. “The easiest and fastest way to figure out how to manage your diabetes during and after a new type of exercise is to take detailed notes, analyze the data every 4 to 5 days, and make small adjustments.”
Exercise precautions with diabetes
Too high and too low blood sugar are of course the main threats of exercise for PWDs, according to experts. So how does one both prevent and prepare for those risks?
The highest risk of exercise-induced low blood sugar comes when you do steady-state cardiovascular (cardio) exercise — the type of exercise where your heart rate increases and stays elevated during the duration of the exercise. Examples of steady-state cardio are brisk walking, jogging, swimming, dancing, and biking.
“There are two ways of reducing the risk of having a low blood sugar during exercise,” says Oerum. “You can either adjust your insulin or consume carbohydrates. How much you’ll need to adjust your insulin will depend on your body, time of day, how much insulin you already have on board, what kind of exercise you’ll be doing, and for how long. Generally, I recommend spending time to document how your body reacts to certain types of activities and adjust your insulin accordingly. When I work with my coaching clients I generally have them track their exercise and blood sugar patterns for a minimum of four (similar) workouts for us to be able to see trends and have enough data to discuss strategies for blood sugar management.”
If you don’t have time to adjust your insulin pre-workout, you’ll have to rely on consuming carbohydrates. Anyone taking insulin should routinely carry at least 15 grams of fast-acting carbohydrates during physical activity and have them easily accessible, in case of a low.
Oerum adds that if you are not taking insulin, but rather manage your blood sugar with oral medication or diet and exercise, you probably don’t have to worry too much about low blood sugars during exercise. However, should it happen, contact your doctor to discuss adjusting your medication dosing.
If you are too high, it might be best to wait until your sugars come down before you exercise. Exercise can also cause highs in some circumstances.
Anaerobic exercise can for some people result in high blood sugars rather than low. This type of exercise is characterized by the heart rate coming up very high for short spurts of time. Examples of anaerobic training are sprints, boot camps, CrossFit, and resistance training.
Some folks will benefit from adjusting their insulin upwards in order to avoid high blood sugars during their anaerobic workouts, but Oerum cautions thatthis type of exercise can significantly increase insulin sensitivity after the workout, increasing the risk of a low blood sugar after one is done exercising.
According to Joslin Diabetes Center, follow these guidelines to know when it’s safe to exercise:
- Don’t exercise if your blood sugar is over 250 mg/dL and you have ketones (the substance in your body that can cause ketoacidosis).
- If you live with type 1 diabetes and your blood sugar is over 300 mg/dL, but you don’t have ketones, you can start exercising once your blood sugar starts to drop.
CGM and other diabetes technology can help
Thankfully advances in diabetes technology have made tracking blood sugar and making needed adjustments much simpler. Most CGM (continuous glucose monitoring) systems can help you keep track of BG levels in real time, meaning that you can easily track your levels before, during, and immediately after an exercise session. Then you can adjust your activity, insulin intake, or carbohydrate intake accordingly.
Always check your BG prior to starting your activity. If it is lower than you want, consume some carbs — or if you use an insulin pump, consider adjusting your basal insulin using a temp basal setting.
You’ll need to recognize that prolonged activities (90 minutes or longer) are likely to reduce BGs, necessitating temporary basal insulin adjustments even if your pre-activity BG level seems ideal.
Short-duration exercises (sprints, intervals, or weight lifting) can raise BG by triggering adrenal hormones that release stored glucose from your liver. So those exercises may not require adjustments to basal insulin.
Finally, don’t forget the usefulness of apps to exercise. MyFitnessPal has become the go-to app for tracking exercise, activity, and food intake, and it works well. Apple Health offers a wide array of exercise tracking options that can be synced to show diabetes-specific data as well. Finally, GlucoseZone couches itself as an exercise app specifically geared towards PWDs, taking a data-driven approach to address the complexity of exercising with diabetes.
Life with type 1 diabetes as an athlete
For ballerina Karz, exercise and diabetes wellness have shared a complex role in her life as she’s worked to better understand what being an athlete with diabetes means and what a healthy level and approach to exercise looks like.
“My biggest challenge proved to be my own psyche, the perfectionist part of me that wanted and needed to have a perfect performance and perfect blood sugar levels,” she says. “Not to mention the pressure I felt to perform well for my directors so I would continue to learn soloist roles...
“In time I learned it was more important not to risk dangerous lows, by having blood sugar levels a little on the higher side before the performance. And if the performance wasn't as ‘perfect’ as my expectations, I had to learn that it was good enough.”
Karz’s narrative is similar to other elite-level athletes living with type 1 diabetes. Athletes with type 1 have excelled and are continuing to do so in numerous sports, including marathon running, triathlons, mountain climbing, cycling, football, baseball, basketball, yoga, swimming, skiing, and snowboarding. There have been NFL heroes, Olympians, and international sports champions all living with T1D.
Those who succeed do so safely, by working with an awareness of their individual bodies, blood sugar trends, and insulin needs in relationship to activity levels.
“All the systems of the body thrive on oxygen,” Karz says. “As you exercise, you’re bringing oxygen and better circulation to your cells and systems. You’re improving your balance and strength, and keeping your weight down. Exercise increases insulin sensitivity, lowers blood pressure, reduces stress, and elevates mood.
“As a dancer, the inspiration I get from dancing not only gives me all the benefits of exercise. I also get inspired and I am motivated to do everything I can to be healthy, to closely monitor my sugar levels and eat right because dancing makes me feel alive. I don't dance to exercise. I dance because it makes me feel alive and connects me to myself and my passions. All the benefits of exercise are the added bonus. I think for persons with diabetes, we need to find ways of exercising that inspires us.”
Want to dig in further on exercise with type 1 diabetes? Here are some useful resources to learn more:
- Diabetes Sports Project
- EndocrineWeb: T1D & Exercise
- Diabetes Strong
- JDRF: Don’t Sweat It!
- Dr. Sheri Colberg, Diabetes Motion Expert
Diabetes Exercise Guidelines Report
This article has been medically reviewed by Maria S. Prelipcean, MD, on 9/4/2019.