HPRC staff get many Ask the Expert questions from Military Service Members, and the answers often include important information that can help you stay mission-ready, so you can perform well.
Asked & Answered
If I’m going to promote exercise to my diabetic patients, how often and for how long should I tell them to work out?
Diabetics can exercise following the Department of Health and Human Services recommendation of 150 minutes of moderate-intensity physical activity—about 30 minutes 5 times—per week.
The body’s hormonal response to exercise can vary based on the type (aerobic vs. resistance training), duration (short, medium, or long), and effort (moderate vs. intense).
Aerobic exercise, such as distance running, can actually lead to blood sugar uptake by the muscles without insulin. In a normal person, the body can generate glucose to maintain blood sugar levels. Type 1 diabetics don’t have this ability because their insulin levels are determined by the amount they take in via injection or pump. In type 1 diabetics, aerobic activity can lead to hypoglycemia, so it’s important to take precautions.
- Have a sugar source available to maintain blood sugar levels during aerobic training. Type 1 diabetics should plan exercise around meals and insulin injections to prevent eating and injecting to maintain normal blood sugar, and then burning through the sugar quickly because the exercise and insulin act together at the same time.
- Regularly monitor blood sugar during exercise to help track levels and prevent hypoglycemia.
- Eat a bedtime snack.
- Wake up every few hours to conduct overnight glucose checks. Or perform continuous glucose monitoring with alarms.
Intense exercise, such as high-intensity interval or circuit training, and resistance training (that is, weight training) can lead to the opposite blood sugar response in type 1 diabetics compared to aerobic exercise. It leads to an increase in blood sugar to provide the necessary energy to the muscles, but the specific hormones that control this blood sugar increase can take a while to go back down to normal levels.
Intense activity can lead to hyperglycemia, even in well-controlled type 1 diabetics. Patients can try these tips to reduce their risk of spikes in blood sugar:
- Perform resistance or intense exercise before aerobic exercise to help keep blood sugar levels stable.
- As a precaution, have a source of insulin readily available while performing intense exercise.
Normal fasting blood sugar levels are 60 to 100 mg/dL (3.3 to 5.5 mmol/L), but blood sugar can go up to 140 mg/dL after eating. Some experts recommend achieving a blood sugar level of about 120 mg/dL before aerobic activity, so that when the level does go down due to exercise, it’s still within the normal range and gives a buffer before blood sugar gets dangerously low.
- Foods with a high glycemic index, such as glucose and fructose, are fast acting and can be used in times of hypoglycemia. However, if a diabetic is severely low and at risk of diabetic coma, an intramuscular glucagon injection is recommended. Simple carbohydrates (honey, juice, crackers, etc.) can be used to bring low blood sugar levels up quickly, although this isn’t recommended as a general method to maintain adequate blood sugar in type 1 diabetics.
- Foods with a low glycemic load—such as whole grains, beans, and vegetables—are more slow acting. Before aerobic exercise, type 1 diabetics should eat foods with a glycemic load lower than that of simple carbohydrates to sustain blood sugar longer and avoid a quick spike from a simple sugar that will go away quickly.
- Both type 1 and type 2 diabetics should carry an emergency treatment kit with them while exercising. The kit should contain a glucometer and test strips to measure blood sugar, a source of fast-acting carbohydrates (for example, simple sugar packets, juice, or a sports drink) and/or glucagon injection kit, a source of insulin, and relevant emergency medical information and contacts.
- For those who don’t exercise regularly, it’s important to ease into a routine, and not immediately ramp up to 150 minutes of activity. This will reduce the risk of developing overuse injuries and allow for a more gradual adjustment to eating and insulin bolus scheduling to prevent blood sugar levels from getting either too low or too high due to exercise.
- Specific precautions for exercise will vary for patients based on their own personal medical histories. For example, for diabetics who have had a heart attack or stroke, exercise should initially be supervised in a cardiac rehabilitation program, and progress in intensity as they’re able to. Those with a peripheral neuropathy or foot ulcers should take care to keep their feet clean and dry, consider limiting weight-bearing activities such as jogging, and substitute for other types of aerobic exercise. Before starting an exercise program, diabetics should be cleared by a physician because certain conditions will limit particular types of exercise that can be performed.
To learn more about nutrition during exercise or ask an HPRC expert about other issues that affect performance, visit the HPRC website.
Tim Gribbin, of the Henry M. Jackson Foundation, is a Senior Scientist for the Consortium for Health and Military Performance (CHAMP) at the Uniformed Services University of the Health Sciences.
* The views expressed are those of the author and do not reflect the official position of the Uniformed Services University of the Health Sciences or the United States Department of Defense.
