Not All Activities Affect Blood Sugar the Same Way

One of the most confusing things about T1D and exercise is that your child's blood sugar doesn't always go in the same direction. A 30-minute bike ride might drop BG steadily, while a competitive game of tag might cause a temporary spike. Understanding why helps you plan better.

The Three Types of Activity

Aerobic activities use oxygen steadily and burn glucose as fuel. They cause a steady BG drop during activity and can continue lowering BG for up to 12 hours afterward.

Examples for young children: cycling, swimming laps, jogging, dancing, walking the dog, skating.

Anaerobic activities are short, intense bursts. They trigger adrenaline, which tells the liver to release stored glucose. This can cause a temporary BG spike that usually comes back down on its own.

Examples for young children: sprinting, climbing, jumping on a trampoline, wrestling, tug-of-war.

Mixed activities — and this is key — are what young children do most of the time. Playing at the park, soccer, swimming with friends, playground games — these combine running (aerobic) with bursts of intensity (anaerobic). The net result is usually a BG drop, but it can be unpredictable.

The Snack Guide: What to Give and When

This is the table you'll want to keep on your phone. It combines starting BG level and activity duration to guide your snack decisions.

Practical Snack Guide for Young Children

Scenario: Hugo at the Pool

Hugo is 8. On Wednesday afternoons, he swims for 75 minutes at the community pool. His dad, Marc, has learned through experience that swimming (mostly aerobic) drops Hugo's BG faster than anything else.

Before swimming, Hugo's BG is 160 mg/dL (8.9 mmol/L) — in the green zone. Marc gives Hugo half a granola bar (15g carbs) at the 30-minute break. At the 60-minute mark, Hugo eats a banana (25g carbs). After swimming, Marc rechecks: 134 mg/dL (7.4 mmol/L). Perfect landing.

Marc also reduces Hugo's basal rate by 20% starting 1 hour before swimming (they use a pump), which he figured out after three sessions of post-swim lows.

Choosing the Right Activity Snacks

Not all snacks are created equal. For during activity, you want things that are:

• Easy to eat quickly (no complex preparation)
• Portable (survives a backpack or pocket)
• Appealing to a child (they need to actually eat it)
• Predictable in carb content (you know what you're giving)

Best Activity Snacks for Young Children

A Word About Insulin Adjustments

For activities lasting more than 60 minutes, snacking alone may not be enough. Talk to your diabetes team about:

• Pump users: Reducing basal rate by 20-50% starting 30-60 minutes before activity
• MDI (injections): Reducing the meal bolus before activity by 25-50%
• Timing: The earlier you reduce, the smoother the BG curve

These adjustments take practice. Start conservative (smaller reductions) and adjust based on patterns you observe.