Data collection was performed at the Defence Medical Rehabilitation Centre (DMRC) at Headley Court. This research was a collaboration between the Academic Department of Military Rehabilitation (ADMR) and the Department for Health at the University of Bath  as part of a PhD programme. The PhD aimed to investigate the impact of exercise rehabilitation in a UK military rehabilitation centre of unilateral and bilateral amputees. Part of this process is to assess the energy expenditure of these amputee groups at home and during rehabilitation. As physical activity monitors have not been validation in amputees before, the aim of this study was to validate an accelerometer that could accurately predict physical activity energy expenditure during free living.