Subjects will be randomized to receive firstly either one of the treatment arms, and then crossed over to receive another arm after 30 days washing out period. It is expected that Gua sha is 1) effective in reducing the intensity of chronic low back pain in the elderly; 2) effective in helping one or more outcome measures in this study and 3) more effective on relieving the low back pain than hot pack in terms of the outcome measures in this study.