Applications and Controversies of LF, HF and LF/HF in Heart Rate Variability Analysis* DONG Xue1,XU Xiao-Dan1,TAN Jing-Yi1,HE Zhen2,WANG Ting-Huai1,3,△ (1School of Health Science, Guangzhou Xinhua University, Guangzhou 510520, China; 2School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212000, China; 3Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510880, China)