The subjects stand on the vibration platform for 10 minutes for 7 days on 2 occasions. The vibration is delivered as 4 "blocks" of 2.5 minutes each, with 30 seconds rest in between each block. The initial Whole Body Vibration (WBV) on day 1 will be undertaken in the Sheffield Children's Hospital Clinical Research Facility (SCHCRF) under supervision. Subsequent WBVs D2-D7 and D85-91 will be done in the participants' homes. Participants will be asked to record the administration and timing of WBV in a diary.