Background : In recent studies on back pain control, various exercises for strengthening the gluteus maximus have been suggested, however most of them imply load bearing exercise or giving resistance. Small knee bending is a movement evaluation that is frequently used in clinical practice and provides basic data for therapeutic intervention. It is also introduced as a safe way to exercise without applying a large load. Objectives : This study was conducted to investigate how the hip squeeze exercise using a tension sensor affects the muscle activity of the hip joint extension muscle during small knee bending. Methods : In this study, 30 subjects without back pain conducted to two conditions, with and without real-time visual biofeedback for small knee flexion. The hip squeeze force was measured using a tension sensor, and this was confirmed by real-time visual biofeedback. The muscle activities of hip extensors acting on the extension of the hip joint were measured by superficial EMG. To compare the difference in muscle activity under the two conditions, it was analyzed using a paired t-test. Results : As a result, the hip extensor muscle (gluteus maximus, both erector spinae) activity (maximum voluntary isometric contraction, %MVIC) significantly increased (p < 0.05) when real-time visual biofeedback using a tension sensor was applied compared to when it was not applied. Conclusions : Our study confirms that even a low-intensity exercise, such as a small knee flexion, can increase selective muscle activity if appropriate visual biofeedback is applied. In addition, the proposed hip squeezing method using a tension sensor induces selective muscle activity in a low-intensity exercise, which renders this method appropriate for subjects who do not exercise with great force, such as the elderly or women.