The effects of EMG, HR, RPE and low back pain to legs in different exercise bikes riding positions were studied. In the condition of sixty RPM (revolutions per minute), the subjects are sixteen healthy graduates riding exercise bikes three minutes in five different seat positions (Standard, Forward, Backward, Up, Down), and use BioPacMP150, POLAR watch and VAS to record the changes of legs EMG, HR, RPE and Low back pain. When riding, turning the seat position upward, EMG signals is larger, HR, RPE and low back pain are also higher. In different riding seat positions really can bring out different muscular contraction, HR, RPE, and low back pain. The differences will provide references to exercise bike riders.