Per info on the Magenta website:
"Graded Exercise Therapy
Participants in this group will receive a detailed physical assessment including how far they can walk in 2 minutes and how many times they can move from sitting to standing in one minute. This will help us set a safe exercise programme. Participants will be asked about the exercise they do each day and will be helped to find their exercise baseline. The baseline is the average amount of exercise they do each day. It will be less than they do on a good day. When they have found their baseline, we will ask participants to slowly increase their exercise. When they are able to do 30 minutes each day, we will increase the intensity of exercise. participants will be asked to record exercise using either charts or the iPhone app ActiveME. They will not be asked to record other activities, only exercise. To make sure participants do not over do their exercise, we will ask them to use a heart rate monitor."
So,
@Amw66:
The participants can use the (Bristol devised) "iphone app Active ME"
http://www.bristol.ac.uk/ccah/research/childdevelopmentdisability/chronic-fatigue/magenta-trial/