Three Minute Step test

This page from Great Ormond Street Hospital (GOSH) describes what to expect when your child is booked for a 3MST test. The three minute step test (3MST) is performed in the lung function unit, and can be used to assess your child’s exercise tolerance.

What to bring

A letter or a MyGosh message will be sent in advance to give you the relevant information prior to the day of testing. Please ensure your child wears suitable clothing and shoes for performing the exercise test. If your child uses supplemental oxygen (continuously or sometimes during the day), please bring this with you. Patients should continue the use of regular medication.

Important information

The person bringing your child for the test should have ‘Parental Responsibility’ for them.

Parental Responsibility refers to the individual who has legal rights, responsibilities, duties, power and authority to make decisions for a child. If the person bringing your child does not have Parental Responsibility, we may have to cancel the test.

What happens on the day

On the day the physiologist will describe what will happen during the test and you will have the opportunity to ask questions. For monitoring during the test a pulse oximeter is placed on their finger or forehead to measure oxygen saturations and heart rate. We will ask a couple of questions about your child's breathing and leg tiredness using a visual analogue scoring system – this is simply a scale to assess your child's breathing and leg tiredness.

The physiologist will ask your child to step on and off a step to a metronome beat. The test is timed at three minutes but if your child is unable to complete this or keep with the rhythm of the metronome, the test may be stopped early. This test can be challenging for some so lots of encouragement will be given throughout.

Please note, children of a younger age (around six years and under) may not be able to perform the test due to co-ordination of stepping to the beat.

Once the test has stopped, your child will be asked to complete the visual analogue score again. They will also repeat the 15 second breath count.

Your child will be allowed to rest for as long as they need to after the test.

Are there any risks?

3MSTs carried out in hospital are very safe – the physiologists are experienced in carrying out the test and and safety equipment is available and will be used if necessary.

Your child’s baseline oxygen saturations and heart rate will be assessed and, in some circumstances checked with a respiratory consultant prior to the 3MST. If your child uses supplemental oxygen, the decision to perform on or off oxygen will be made by their consultant beforehand.

Your child will be monitored throughout the test and for a while afterwards.

Sometimes, children find the stepping hard to co-ordinate and in these circumstances, the test may not go ahead due to risk of falling.

Getting the results

The test results will be uploaded onto our electronic patient record system for your doctor to view. If you are seeing your doctor in clinic or later that day, they will go through the results with you.

If you are not seeing the doctor that day, they will still be able to view your test results and contact you if there is anything your child needs to do before their next appointment.

Compiled by:
The Lung Function Unit in collaboration with the Child and Family Information Group
Last review date:
February 2024