Background: Neuromuscular electrical stimulation is currently being used for treatment in rehabilitation situations. Studies indicate that neuromuscular electrical stimulation increases muscle strength in weakened muscles; however few studies have examined the effect of neuromuscular electrical stimulation and muscle strength on healthy muscles or compared combinations of NMES and exercise. Objective: To compare the effectiveness of three methods in strengthening the vastus medialis muscle in healthy adults. Methods: Fifteen healthy male participants between the ages of 18-25 participated in this randomized repeated measures study. The participants were randomly assigned into three (neuromuscular electrical stimulation, neuromuscular electrical stimulation + exercise or exercise only) groups of five. They performed eccentric stepdowns for 5 minutes, 3 times a week for 4 weeks. The force of the vastus medialis muscle was measured with an isometric leg extension at 60 degrees, using the Biodex force dynamometer (Model 820-110). This test was performed a total of three times on each participant: pre-testing, mid-testing and final-testing. Results: A two-way analysis of variance and a post hoc Scheffe’s test revealed a significant test interaction difference between group and test time. In the neuromuscular electrical stimulation group the mean force from the pre-test (121.4Nm), to the final-test (165.8Nm) significantly increased compared to the pre and post-tests in the other groups. Conclusion: Neuromuscular electrical stimulation training was most effective in increasing muscle strength of the vastus medialis muscle in healthy participants after four weeks.