lying, standing and stepping, and transitions between postures. Accuracy in classifying posture and transitions between postures has been reported to be 100% in older adults and those with the disability.Two primary sedentary behaviour outcomes will be reported, including breaks per day (transitions from sit to stand), and the total volume of sitting time per day. Measurement of breaks is important as they are analogous to the functional task of sitting to standing, and breaking up long bouts of sitting has been identified as a particularly important behavioural target. Total daily sitting time is the volume variable historically measured in sedentary behaviour research and has been repeatedly shown in research with non-disabled populations to be associated with health risk factors.Steps per day is the primary physical activity outcome. Information about clinically important step per day are available for people with MS. Participants are asked to record their bed-time and sleep-time in a log book during ActivPAL3 measurement time periods, and throughout the intervention. They also record information in their log about falls. The primary outcomes from ActivPAL3(breaks per day, total sedentary time and steps per day) will be generated using the R package (PAactivpal). Outcomes are reported with respect to waking time, determined using the methods of Chastin and colleagues63 and the participant logs, prior to analysis in R.