If your patients with type 1 diabetes have vowed to exercise more this year, you can help them meet their goal by sharing a few key tips to stay safe. Many with type 1 diabetes don’t get enough exercise, and aside from the usual grumblings that keep people from physical activity, research suggests that a fear of hypoglycemia could be a particular issue for patients with type 1 diabetes.
Exercise, food, insulin, and blood glucose can become a crazy balancing act in a matter of minutes, especially for a patient new to physical activity. Complicating matters: A workout can mask the signs of hypoglycemia, making it harder to spot.
“Exercise gives you false symptoms, like sweating, increased heart rate, and tiredness,” said Michael Riddell, PhD, a professor of kinesiology and health science at York University, Toronto, Ontario, and cochair of the Type 1 Diabetes Exercise Initiative, the largest observational exercise study in adults with type 1 diabetes.
Riddell also lives with type 1 diabetes and exercises regularly and is a vocal advocate for helping patients move more.
“Physicians [who have patients with type 1 diabetes] really should encourage exercise because it has so many health benefits,” said Riddell.
Among them are better glycemic control and reduced insulin requirements, Riddell said. In a review led by Riddell, patients with type 1 diabetes who exercised at least twice a week had lower body mass index, better A1c concentrations, and fewer complications like retinopathy and microalbuminuria. They also were less likely to experience dyslipidemia and hypertension.
You can help motivate patients by emphasizing the role of exercise in mitigating these risks, Riddell said. Then, help your patient come up with a plan to enjoy those benefits while staying safe.
Talk About Timing
For many patients, the best time to exercise is simple: Whenever they can fit it in. Still, timing may help blood glucose control.
Consider mealtimes, for example. “Don’t exercise when you’ve taken a bolus of insulin for a meal,” Riddell said. “Your insulin is already working, and your blood sugar will start trending down. If you add exercise, it may go down too quickly.”
While exercise before a meal is best, post-meal exercise is okay too — just be sure patients reduce their mealtime insulin dose, as the exercise will intensify its effect, Riddell said.
Some research suggests that fasted morning exercise may reduce the risk for hypoglycemia. One randomized trial found that participants with type 1 diabetes who exercised before breakfast were 50% less likely to experience hypoglycemic events over the next 24 hours, compared with those who exercised after lunch. What’s more, on days following morning exercise, participants saw more normal-range blood glucose readings than on days prior.
Hormones may play a role. “Cortisol is produced in higher quantities in the morning, and it causes higher blood sugars,” said Sarah Kim, MD, an endocrinologist at UCLA Health, Los Angeles, California. So, “you may not have as much of a drop in blood sugar.”
Then there’s the dawn phenomenon, when hormones (like cortisol) signal the liver to produce extra glucose to wake you up. It happens in about half of patients with type 1 diabetes, and a morning workout may help counter its effects.
But regardless of when your patient chooses to exercise, staying consistent is key.
“Routine is really important,” said Jason Baker, MD, an assistant professor of medicine and endocrinologist at Weill Cornell Medicine, New York City. Always exercising at the same times, and for the same durations and intensities, can help patients learn how their body responds, so they know what to expect and how to prepare, Baker said.
Start Tracking at T-Minus 30
Patients should keep an eye on their glucose numbers starting about a half hour before the workout. Continuous glucose monitors (CGMs) are great tools for this, but keep in mind that there can be a 10- to 15-minute delay between the sensor and changes in blood glucose. “I always recommend patients still follow up with a finger stick,” said Baker, “to make sure they have good data and are making the right treatment decision.”
If the numbers are trending down, patients can have a snack without insulin immediately before starting the workout, Kim said. “If blood sugar is 150-200 mg/dL, they may still want to eat without any insulin because we expect the exercise itself to drop the blood sugar into a normal range.” If blood sugar is higher than that, they may skip the snack.
Stay Aware, Be Prepared
Exercise intensity matters, so it’s good for people to be aware of how hard they’re working out. However, a lot can affect one’s perceived exertion.
For example, a small randomized trial published last year suggests that immersive fitness video games can impair one’s ability to tell how hard they’re working. The game’s visuals, music, and interaction may distract the player from what their body is feeling, the researchers explained.
Instead of relying on feel alone, have patients peek at their CGM readings periodically during the workout, Riddell said.
Patients with insulin pumps may be able to connect the pump to the CGM, so it can adjust insulin based on CGM data.
If that’s not an option, the pump may still have an activity or exercise mode. “That will reduce the amount of basal insulin the pump is providing,” Kim said. “The patient can turn it on for the duration of the exercise” — and keep it on, even after the workout, until blood glucose returns to a stable range.
Just in case, patients should always keep a sugar source in their pocket, Baker said. “Don’t plan to run to the store across the street or back to your gym locker for some sugar,” Baker said. “When blood sugar drops, you may feel out of it and won’t be thinking clearly.”
A source with 15 g of carbohydrate, like three to four glucose tablets or six Lifesaver candies, can raise blood sugar quickly.
How to Choose the Best Type of Exercise
In general, aerobic exercise (steady state, moderate intensity) lowers blood glucose, while anaerobic exercise (shorter bursts, higher intensity) raises it.
Riddell’s suggestion: Do interval-style workouts with a mix of both. The combo may help blood glucose stay in range.
Try 30 minutes of aerobic exercise with anaerobic activities mixed in, like sprints, push-ups, sit-ups, burpees, or squats.
For beginners, “don’t exercise for more than 30 minutes,” Riddell added. Going longer than that may reduce blood sugar too much.
Change Your Habits, Change Your Insulin
“As physicians, we need to remind [patients] that when they change their behavior, they also need to change their insulin,” Riddell said. The more physically active a patient is, the less insulin they’ll probably need.
“You can take 20% less basal insulin throughout the day, and up to 50% less mealtime insulin if you’re physically active after the meal,” said Riddell. “Then you’ll have weight loss, you won’t have to treat with as much carbohydrate, and you won’t have as much hypoglycemia.”