Background: This study investigated quadriceps femoris muscle activity by comparing concentric and eccentric contractions with self-selective squat speed. Objectives: Study participants agreed in advance and included 30 male college students in their 20s without musculoskeletal system disease. Design: A randomized controlled trial. Methods: Participants who participated in this study agreed in advance and recruited 30 male college students in their 20s who had no disease with musculoskeletal system to conduct this study. When squatting at a self-selected speed, the subjects were evaluated using one-way ANOVA to compare concentric and eccentric contraction muscle activity. Results: There were significant differences between the rectus femoris, vastus medialis, and vastus lateralis regarding concentric contractions.contractions. There was a significant difference in vastus medialis but no significant difference between rectus femoris and vastus lateralis for eccentric contractions. Conclusion: During concentric contraction, all muscles and eccentric contractions indicated significant improvement in the vastus medialis. Therefore, to minimize knee joint injury and maximize efficient muscle activity, self-selected slow and moderate speeds based on self-selection speed when performing the sit-down motion during a squat and moderate speed with fast motions when performing the standing motion should be considered as high muscle activities.

INTRODUCTION
SUBJECTS AND METHODS
    Subjects
    Experimental Procedure
    Measurement Method
    Statistical Analysis
RESULTS
DISCUSSION
CONCLUSION
ACKNOWLEDGEMENT
REFERENCES

• Yeeun Lee(Student, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea)
• Jeehwan Bae(Student, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea) | Yeeun Lee
• Dongyeop Lee(PT, PhD, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea)
• Jaeho Yu(PT, PhD, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea)
• Jinseop Kim(PT, PhD, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea)
• Seonggil Kim(PT, PhD, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea)
• Jiheon Hong(PT, PhD, Department of Physical therapy, Sunmoon University, Asan, Republic of Korea, Digital Healthcare Institute, Sunmoon University, Asan, Republic of Korea) Corresponding author