Weight Training and Exercise for Type 1 Diabetes

Working Out With Type 1 Diabetes

Woman stretching before a run

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Both type 1 and type 2 diabetes result in too much glucose in the blood, the health consequences of which can be serious if glucose (blood sugar) levels rise too high.

The good news: exercise can help, no matter your age at diagnosis for type 1 diabetes. Below, you'll find tips for developing an exercise and weight training plan specific to type 1 diabetes. (Type 2 diabetes workouts are slightly different.)

Exercising with Type 1 Diabetes

Type 1 diabetes usually occurs in childhood or the early teenage years, which is why it was once referred to as “juvenile diabetes.” However, it can also occur in older people. It’s then called latent autoimmune diabetes in adults, or LADA.

According to the most recent guidelines from the American Diabetes Association (ADA), most children, adolescents, and adults with type 1 diabetes should not be discouraged from physical activity, since its benefits for general health are well known.

For those with type 1 diabetes, exercise generally lowers blood sugar. As a result, insulin doses and food intake may need to be adjusted to match exercise time and intensity. But that shouldn’t mean avoiding exercise, which has significant benefits.

Many world-class athletes have type 1 diabetes. In the US, Olympian swimmer Gary Hall Jr, the NFL’s Jay Cutler, and the skier Kris Freeman are a few examples. The Australian rugby player Steve Renouf and cyclist Monique Hanley are others.

How to Stay Safe Exercising with Type 1 Diabetes

Before beginning an exercise regimen, be sure to consult with your doctor and other members of your health care team, such as a diabetes educator. Since insulin or other medication doses and food consumption will probably need modification, those who are insulin-dependent should be especially careful to seek advice.

Diabetic complications may also require special consideration. The following is a partial list of complications that may limit exercise type, duration, or intensity:

  • Uncontrolled blood glucose (high or low)
  • Uncontrolled high blood pressure
  • Unstable heart conditions
  • Retinopathy
  • Peripheral neuropathy (nerve damage to extremities, foot ulcers, etc.)
  • Autonomic neuropathy (nerve damage to internal organs)
  • Microalbuminuria and nephropathy (poor kidney function)

Even with these or other complications, however, exercise may still be possible with careful modification.

For example, individuals with retinopathy or high blood pressure should avoid the Valsalva maneuver, in which an exercise is performed by forcibly exhaling against a closed airway and straining to lift a weight. People with diabetic nerve damage should also learn how to care for their feet and look for foot ulcers or other injuries with physical activity.

If you’re not sure how to create an exercise plan that works for your diabetes, ask for a referral to a diabetes-knowledgeable physical therapist. He or she can help you establish a safe exercise regimen that suits your needs and interests.

Benefits of Exercise for Type 1 Diabetes

According to the American Diabetes Association, exercise for those with type 1 diabetes offers a number of important benefits.

  • Overall, exercise improves insulin sensitivity, muscle strength, and cardiovascular fitness.
  • Aerobic exercise at moderate to high intensity also lowers cardiovascular and mortality risks.
  • Weight training, in particular, can reduce the risk of exercise-induced low blood sugar (hypoglycemia) for those with type 1 diabetes. To reduce the risk of low blood sugar, perform weight training or resistance exercises first, then do aerobic exercise.
  • Flexibility and balance exercises, such as those in yoga and tai chi, can improve joint mobility, which naturally decreases as we age, and reduce the risk of falls. Although there’s less evidence about them, some clinical trials have shown even these gentler forms of exercise can improve insulin sensitivity, build muscle, and lower cholesterol (lipid) levels. They’re also great for stress relief and improving quality of life.
  • Exercise also benefits children and young adults with type 1 diabetes. One meta-analysis of exercise among kids under age 18 diagnosed with type 1 diabetes found significant reductions in HbA1c among the exercisers. Engaging in physical activity more than three times a week for more than an hour, and combining aerobic and resistance training, provided the most benefits.

Alternate Sitting with Short Exercise

Don’t sit for too long. For all people, and particularly those with type 2 diabetes, the American Diabetes Association suggests breaking up periods of sitting with light activity. For every 20 to 30 minutes of sitting, stand or walk around for about five minutes. You can also try simply body-weight exercises, such as leg lifts and squats, for 3 to 5 minutes. Doing so has been shown to improve glycemic control.

Planning for Exercise with Type 1 Diabetes

Blood sugar responses to exercise can vary widely from person to person, as well as according to timing and activity levels. You’ll need to frequently test your blood sugar levels as you train and adjust carbs and insulin accordingly.

The ADA suggests the following general guidelines:

  • Exercise before a meal (while fasting) is likely to produce a small increase or decrease in blood sugar.
  • Exercising immediately after a meal that’s preceded by your standard insulin dose will reduce your blood sugar. However, long periods of exercise under these conditions can produce significant drops in glucose.

In addition to testing before and after an exercise session, also test your blood sugar every half-hour when you’re beginning a new exercise regimen. Over time, you’ll learn your body’s response to different types and varying duration of exercise.

Exercise duration and intensity is also likely to affect blood sugar. The ADA reports the following based on its review of current research:

  • Short-duration exercise—less than 30 minutes—may not require a carb or insulin adjustment.
  • Short (less than 10 minutes), very high-intensity exercise, such as intervals, weight training, or HIIT, may not require adjusting insulin or carbs. However, short-duration, high-intensity may also raise blood sugar.
  • Longer-duration exercise—more than 30 minutes, and particularly when aerobic—will generally require reductions in insulin, carb supplementing, or both. Exercise that varies intensity, such as field sports, is more likely to result in better glucose stability than exercise that is solely aerobic.

Using a Continuous Glucose Monitor

The ADA notes that continuous glucose monitors can have issues: for example, sensors breaking, being unable to calibrate, or delayed or inaccurate glucose-level reporting. If you use a continuous monitor, speak with your health care providers about alternative options if needed.

Exercise and Pregnancy in Type 1 Diabetes

Exercise reduces the risk of complications during pregnancy, including the risk of developing gestational diabetes. If you’re planning to become pregnant, ideally you’ll already be exercising. For women with type 1 diabetes or who are at risk of developing gestational diabetes, the American College of Obstetrics and Gynecology recommends 20 to 30 minutes of exercise every day or on most days of the week.

If you develop gestational diabetes, it is generally very safe to begin exercising during pregnancy, even at high intensity, which can help prevent weight gain. Aerobic and resistance training improves glycemic control during pregnancy. Women who develop gestational diabetes should watch for low blood sugar after exercise and be sure to follow their doctors’ recommendations regarding insulin and carb regimens.

Balancing Carbs, Insulin, and Exercise

Testing blood sugar levels frequently as you train will help you adjust carbs and insulin according to your body's needs. To help you get started, the ADA offers these preliminary guidelines:

  • When circulating insulin is low, ingesting 10 to 15 grams of carbs before exercising at low to moderate intensity for 30 to 60 minutes may maintain blood sugar levels.
  • If you’ve recently taken insulin, you may need 30 to 60 grams for each hour you exercise to maintain performance and blood sugar—which is what most athletes need, the ADA points out, regardless of whether they have type 1 diabetes.

You may also need to adjust your insulin dose before or following exercise to account for the blood sugar changes likely to result. The ADA suggests starting with the following adjustments, then fine-tuning according to your testing results.

  • If you use injected insulin, try reducing your before-exercise and after-exercise doses by 20 percent.
  • If you use a continuous insulin pump, you can reduce or stop your dose when you start exercising. Alternatively, try stopping your dose 30 to 60 minutes before starting to exercise.
  • If you exercise within two to three hours of taking insulin (whether by pump or injection), you may need to lower your usual basal dose by 25 percent to 75 percent to prevent hypoglycemia.

It’s important to emphasize that your specific needs may vary—that’s why it’s essential to test glucose levels before, during, and after exercise.

Stop exercising and ingest about 15 grams of fast-acting carbs if you feel weak, shaky, or dizzy, or when your blood sugar drops below 90 mg/dL.

Before exercising, your blood glucose should be between 90 and 250 mg/dL. The ADA suggests the guidelines in the following table based on starting glucose levels.

Starting Glucose Levels and Exercise
Below 90 mg/dL If you plan to exercise for more than 30 minutes, have 15 to 30 grams of carbs before you start. Have more carbs as needed based on your testing results. For shorter and very high-intensity sessions, you may not need carbs.
90–150 mg/dL Have carbs when you start exercising, taking into account how long a session you’re planning and your existing insulin level. Continue with carbs as needed for longer sessions.
150–250 mg/dL Start exercising without carbs. When blood sugar drops to below 150 mg/dL, then supplement with carbs.
250–350 mg/dL Test for ketones, and don’t exercise if they’re moderate to high. If they’re low, exercising at mild to moderate intensity is fine, but don’t perform high-intensity exercise until blood sugar drops below 250 mg/dL, since high-intensity exercise may raise blood sugar. 
More than 350 mg/dL Test your ketones, and don’t exercise if they’re at moderate to high levels. If they’re negative or at trace levels, considering taking insulin at 50 percent of your usual dose. As with lower glucose levels, avoid high-intensity exercise until blood sugar reaches 250 mg/dL.

Preventing Low Blood Sugar Post-Exercise

Exercise’s ability to lower blood sugar is one of its benefits, but blood sugar may also drop too low after exercising. This can occur within six to 15 hours of exercise, but can occur as long as 48 hours after an exercise session.

Low blood sugar overnight is particularly important to watch for. If you use injections, the ADA suggests reducing your basal insulin dose by 20 percent on the days you exercise, eating a low-glycemic meal in the evening after you’ve exercised, and reducing your post-meal bolus insulin. If you use a continuous monitor, reduce your basal insulin rate by 20 percent for six hours after exercising.

For both groups, having a snack before going to sleep can help. You may also want to check your blood sugar levels at some point during the night or set your continuous monitor to alarm you if blood sugar drops too low.

You can also work these tips into your exercise routine. Each has been shown to reduce the risk of exercise-induced delayed low blood sugar:

  • Try beginning or ending a moderate-intensity session with 10 seconds of all-out effort, such as a sprint.
  • Incorporate short, high-intensity periods intermittently into an otherwise moderate exercise session.
  • Perform resistance exercise (weight training) before aerobic forms of exercise.

Weight Training and Workouts

Exercise falls into three primary types: aerobic, resistance (weight training), and flexibility. Ideally, you’ll do all three within a given week.

Aerobic exercise includes walking, jogging, running, and swimming—anything that gets your heart rate up to a higher level than what you’re accustomed to. Resistance and weight training can be as simple as a yoga session (your Plank and Down Dogs count!), or a session with weights at a gym.

Remember to start where you are, adjusting your expectations and activity for existing fitness, age, and goals.

If jogging is too much, for example, start with walking, then gradually increase your pace and distance over time. If walking is too much, start by increasing your daily activity—try a short walk around the block after a meal, or do chair yoga. Even gardening, cleaning, or playing with your kids are forms of activity that can improve blood sugar and glycemic control—start there if more feels like too much.

As your activity levels increase, you may be surprised to see how quickly you progress to feeling better and having more energy. That’s when to extend exercise duration or increase intensity. The ADA recommends 150 minutes of exercise per week that includes all three. When you reach this point, you’re receiving excellent health benefits from your effort.

A weekly program could look like the plan set out in the following table. Adjust to your individual needs.

A sample weekly aerobic and weight training plan
Day 1 Aerobic training: 30–45 minutes
Day 2 Weight training: 45–60 minutes
Day 3 Aerobic training: 30–45 minutes
Day 4 Aerobic training: 30–45 minutes
Day 5 Weight training: 45–60 minutes
Day 6 Aerobic training: 30–45 minutes
Day 7 Rest
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