Background and PurposeBackward walking exercise is being recommended for increasing lower extremity strength, especially vastus medialis strength. But little research has been conducted backward walking training to clarifying vastus medialis strength. The purpose of this study is to verify the effectiveness of backward walking training on knee muscle strength especially vastus medialis strength. Subjects and MethodsFourteen healthy male adults were randomly divided into backward walking (BW, n=7) and forward walking (FW, n=7) training groups. Each group took part in muscle strength tests of knee extension and flexion isokinetic peak torque (PT), total work (TW). Vastus medialis (VM) and vastus lateralis (VL) root mean square (RMS) of electromyographic (EMG) also measured during maximal voluntary isometric contraction. Each group took one week resting period and then, performed BW and FW training program for 6 weeks, consisting of 3 sessions per week for a total of 18 sessions. The training intensities applied to individual subjects were at 65% of their VO2max respectively. ResultsThe BW training group showed a significant increases in knee extension and flexion isokinetic PT (4.6%, 13.9%), isokinetic TW (17.34%), and isometric VM EMG RMS (48.5%). But FW training group did not show a significant increase in any of the items. ConclusionBW training has positive effectiveness on knee muscle strength, especially vastus medialis strength, which is acting as medial stabilizer of the patella.