Once written informed consent from participants or proxies is given, subjects will be randomly assigned to 4 different program combinations based on a 2X2 factorial design: (1) low dose vitamin D / low intensity physiotherapy; or (2) low dose vitamin D / high intensity physiotherapy; or (3) high dose vitamin D / low intensity physiotherapy; or (4) high dose vitamin D / high intensity physiotherapy. Low dose Vitamin D is 800 IU cholecalciferol per day and high dose vitamin D is 2000 IU cholecalciferol per day.