Physical Activity Basics

If activity was a prescription medication, it would be the highest prescribed medication ever! Being physically active has so many benefits:

• Reduces your risk of heart disease
• Strengthens your bones and muscles
• Improves your sleep
• Helps you control your weight
• Increases your energy levels
• Improves your brain health
• Lowers blood pressure
• Decreases stress levels
• Prevents falls
• Increases life expectancy

Whether you are at the gym, taking a stroll at a park or actively doing household chores, movement affects your blood glucose. 

Physical activity can raise or lower your blood glucose so frequent monitoring and adjustments will be necessary to maintain a safe level. This is especially important if you start or change your activity routine.

Blood Glucose Effects of Different Types of Activity

Aerobic activity 

Continuous, light-to moderate intensity movement and includes activities like running, walking, long-distance swimming, biking or tennis

Aerobic activity typically tends to lower BGs

Anaerobic activity 

Shorter in duration, of maximal to super max intensity and includes activities like sprinting, gymnastic, ice hockey, or weight training

Anaerobic activity typically tends to raise BGs

Mixed activity 

Combination of the aerobic and anaerobic activity such as basketball or soccer

Time of Day

The time of day which you are physically active can affect how your blood sugars respond. For some, the hormones our bodies produce early in the morning will cause insulin to be less effective, so you may have a very different response in the morning compared to the exact same activity done later in the day. Physical activity performed at night may increase your sensitivity to insulin. For those who take insulin, this may put you at risk for hypoglycemia in the middle of the night.

Intensity of Activity

You may also notice the type of activity you perform will affect you differently. Intense physical activity (weight lifting/sprinting) can cause your BG to rise, and it may stay elevated for 1-2 hours afterward. This is due to hormones, like adrenaline, being released which work against insulin action. If you take insulin, you may need a bit more insulin prior to, or after, activity to compensate for this.

Mild to moderate activities generally drop your BG during the activity. Depending on how long you plan to be active, you may need a small snack prior or, if you take insulin, you may need to decrease your insulin dose prior to/during activity.

Delayed Hypoglycemia 

If you are taking a diabetes medication that puts you at risk for hypoglycemia (such as insulin or sulfonylureas), the more intense and longer you physical activity, the greater your risk for delayed hypoglycemia. Your body will re-stock spent glycogen (stored carbohydrate in liver & muscles) over the next few hours (for extreme activity, this can take up to 3 days!) by pulling it from the bloodstream, potentially causing a delayed onset of hypoglycemia. 

Strategies to avoid Hypoglycemia

• Use of temporary basal rates on an insulin pump (start 1hr prior to, and through the duration of, the activity)
• Reduction of meal/correction bolus w/in 1-2 hr of activity
• Try to be active in the morning or afternoon to avoid overnight lows. If active in the evening, you may need 15-30g carb at bedtime as a precautionary measure. 
• Have a carbohydrate source available at all times, 30-60 grams carbohydrate for every 30-60 minutes of activity & adjust as needed
• Check blood glucose before, during (for longer bouts of exercise) and after activity

Strategies to avoid Hyperglycemia

• Easy to moderate paced walk for 15-20 minutes
• Avoid high intensity activity if your BG is above your target
• Stay well hydrated

Reference

https://www.jdrf.org/t1d-resources/living-with-t1d/exercise/

https://www.healthline.com/diabetesmine/first-ever-guidelines-safe-exercising-type-1-diabetes#4 

Palo Alto Medical Foundation: Pre Pump Education Packet