Exercise Guide — Part 2

Mixed and Team Sports with Type 1 Diabetes

Mixed exercise can raise glucose, lower glucose, or do both in the same session — and the outcome is dominated by insulin on board, not the sport.

Overview

This page explores how to build 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 mechanism here is that the outcome is dominated by starting conditions — especially insulin on board.

This page follows the GNL approach: 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.

A quick recap from the Exercise Guide introduction: mixed exercise appears unpredictable only when insulin on board and starting conditions are not accounted for.

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.

Meal and bolus timing before mixed exercise tends to matter more than the sport itself.

Chart showing how bolus timing relative to exercise affects insulin on board and glucose risk

Many people find that observing the Three-Hour Rule makes mixed exercise much easier to interpret — because when insulin on board is lower, the aerobic and anaerobic swings become smaller and more predictable.

Diagram of the Three-Hour Rule applied to mixed exercise — insulin on board diminishing before the session

Major 2: Starting glucose value

Starting glucose determines how much room there is to tolerate aerobic drops and anaerobic rises. Starting higher may provide more buffer during 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, many people check the CGM before exercise and then every 20–30 minutes during activity. Combining glucose value with trend arrow helps inform whether carbohydrate is likely to be needed.

Why does mixed exercise behave this way?

During the aerobic phases of mixed exercise, muscles take up glucose through insulin-independent pathways — the same “side door” mechanism as steady-state aerobic exercise.

Diagram of the insulin-independent glucose uptake pathway active during aerobic phases of mixed exercise

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

Diagram showing stress hormone release during intense exercise driving hepatic glucose output

The balance between these phases — combined with insulin on board — determines whether glucose tends to fall, rise, or oscillate across a session. This is why the same sport can produce very different CGM traces on different days.

After exercise: the delayed risk

Mixed exercise depletes muscle and liver glycogen stores that may be replaced over the following 6–11 hours. Delayed hypoglycaemia risk is common after longer sessions and is worth monitoring through the remainder of the day.

CGM trace illustrating delayed hypoglycaemia risk after a longer mixed exercise session

Building a starting plan

The algorithm below provides a starting plan and two adjustment rows. The approach is to begin with the “Starting plan”, then use the outcome as data. Adjust only after reviewing what actually happened.

The glucose never lies — use outcomes as feedback, not judgement.

Mixed exercise starting plan algorithm with adjustment rows for high and low glucose outcomes

Generic worked example

Breakfast, then a 60-minute team sport session mid-morning, followed by lunch. Building a plan using the algorithm and reviewing 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 plus trend arrow to inform carbohydrate intake
After exercise: consider whether bolus and/or basal warrants reducing if exercise lasted longer or glucose fell later
Review: repeat the starting plan if it worked; use the adjustment rows if glucose ran high or low

Carbohydrate charts and calculators

Personalised PDF calculators — choose the device you use:

Carbohydrate charts covering body weights from 10–60+ kg — available in both mmol/L and mg/dL:

mmol/L device — carbohydrate charts for 20 minutes of mixed exercise

Carbohydrate chart for mixed exercise using a mmol/L CGM device, lower body weight range

Carbohydrate chart for mixed exercise using a mmol/L CGM device, higher body weight range

mg/dL device — carbohydrate charts for 20 minutes of mixed exercise

Carbohydrate chart for mixed exercise using a mg/dL CGM device, lower body weight range

Carbohydrate chart for mixed exercise using a mg/dL CGM device, higher body weight range

Optional deep-dive video

This video explains how glucose behaves during mixed exercise in more depth. Skip it if you just want the practical steps above.

Watch: glucose behaviour during mixed exercise (YouTube)

Key principles for mixed and team sports

Mixed exercise can raise glucose, lower glucose, or do both — insulin on board determines which dominates
Aerobic phases activate insulin-independent glucose uptake; anaerobic phases trigger stress hormone release
The Three-Hour Rule tends to reduce the amplitude of swings by removing bolus insulin from the equation
Trend arrows are especially important because intensity — and therefore glucose direction — can shift rapidly
Delayed hypoglycaemia risk after longer sessions is common and worth monitoring through the rest of the day
Use CGM outcomes as feedback to refine the next plan — the glucose never lies

This content is for educational exploration only. It describes average responses and general principles. It is not medical advice and cannot replace individual clinical guidance from your diabetes care team.

Continue the guide

← Part 1: Aerobic Exercise Part 3: Anaerobic Exercise →

Back to the Exercise Guide overview