Mixed (Team Sports) Exercise with T1D: Understanding Dynamics

Overview

This page teaches you how to make reasonable starting plans for mixed exercise — activities that combine aerobic and anaerobic elements such as football, cricket, interval training, netball, hockey, basketball, and similar team sports.

Mixed exercise can raise glucose, lower glucose, or do both in the same session. The key point is that the outcome is dominated by your starting conditions — especially insulin on board.

This page follows the GNL rule: major in the majors. Start with insulin on board, then starting glucose, then trend arrows. Mixed-exercise physiology comes after — because it explains direction changes, not risk.

The detail

A quick recap from the exercise introduction page: mixed exercise is unpredictable only if you ignore insulin on board and starting conditions.

Major 1: Insulin on board (the main driver)

In mixed exercise, insulin on board is the dominant driver of risk. It determines whether aerobic phases cause rapid drops and whether anaerobic phases produce manageable or excessive rises.

Meals and bolus timing before mixed exercise matter more than the sport itself.

If you can observe the Three-Hour Rule, mixed exercise becomes much easier to interpret because insulin on board is no longer dominating every swing.

Major 2: Starting glucose value

Your starting glucose determines how much room you have to tolerate aerobic drops and anaerobic rises. Starting higher may buffer aerobic phases; starting lower increases risk during longer low-intensity periods.

Major 3: Trend arrows (direction and speed)

Trend arrows are especially important in mixed exercise because direction can change rapidly as intensity shifts. Numbers without direction are incomplete information.

As a starting heuristic, check CGM before exercise and then every 20–30 minutes during activity. Use glucose value plus trend arrow to decide whether carbohydrate is needed.

Why does mixed exercise behave this way?

During the aerobic phases of mixed exercise, muscles take up glucose through insulin-independent pathways.

During anaerobic or very intense phases, stress hormones push glucose out of the liver.

The balance between these phases — combined with insulin on board — determines whether glucose falls, rises, or oscillates.

After exercise: the delayed risk

Mixed exercise depletes muscle and liver glycogen that may be replaced over the next 6–11 hours. Delayed hypoglycaemia risk is common, especially after longer sessions.

Practical

The table below provides a starting plan and two adjustment rows. Always begin with the “Starting plan”. Adjust only after reviewing what actually happened.

The Glucose Never Lies — use outcomes as feedback, not judgement.

Generic worked example (template): Breakfast, then a 60-minute team sport session mid-morning, followed by lunch. Build a plan using the table and review the outcome.

Before exercise: reduce the meal bolus according to timing and insulin on board
During exercise: check CGM before and every 20–30 minutes; use glucose value + trend arrow to guide carbohydrate intake
After exercise: consider bolus and/or basal reductions if exercise lasted longer or glucose fell later
Review: repeat the starting plan if it worked; adjust using the yellow or red row if it didn’t

Personalised PDF calculators (choose the device you use):

Carbohydrate charts for 10–60+ kg and both mmol/L and mg/dL (if you cannot use PDFs):

Carbohydrate charts for 20 minutes of exercise with a mmol/L CGM device