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This study aimed to compare the ratios of quadriceps muscle activity between the maximum voluntary isometric contraction and unloaded knee extension. A total of 28 healthy men and women in their 20s who agreed to participate in the study were tested. The Ratio was calculated by measuring the muscle activity of the subject's maximum voluntary isometric contraction and unloaded knee extension of rectus femoris, vastus lateralis, and vastus medialis oblique. The data analysis used a paired t-test for the ratio comparison between the two methods. There were statistically significant differences in the ratio of the rectus femoris and vastus medialis oblique during maximum voluntary Isometric contraction and unloaded knee extension (P<.05). However, there was no statistically significant difference in the ratio of the vastus lateralis during maximum voluntary Isometric contraction and unloaded knee extension. To strengthen the vastus medialis oblique, high-intensity exercises such as maximum voluntary isometric contraction can be used, and for the rectus femoris, low-intensity exercises such as unloaded knee extension can be used.