Which muscle is mainly strengthened by sitting posture and leg flexion and extension

Sitting posture leg flexion and extension mainly strengthens the quadriceps, including the rectus femoris, lateral femoris, medial femoris, and medial femoris muscles. This action stimulates the anterior thigh muscles through knee joint extension, and may slightly activate the hamstring and gluteal muscles as coordinating muscles.

Sitting posture leg flexion and extension is a classic instrument movement for isolated training of the quadriceps. When the knee joint moves from the flexed position to the extended position, the quadriceps femoris muscle acts as the active muscle to complete centripetal contraction, with the rectus femoris muscle participating more in exerting force in the flexed hip state as it crosses the hip and knee joints. The backrest design of the instrument reduces the compensation of other muscle groups, making the load more concentrated on the target muscle group. During training, it is important to align the axis of the equipment with the knee joint to avoid excessive pressure on the patella.

Some trainers may experience slight exertion in the hamstring or gluteal muscles behind the thigh, which is usually due to excessive range of motion or compensatory tilting of the trunk. The standard movement requires the back to be tightly pressed against the cushion, and only the knee joint flexion and extension are used to complete the movement. If there is a significant separation of the buttocks from the cushion or a back bow in the waist, the load may be transferred to the hip joint extensor muscle group. For individuals with a history of knee joint injuries, it is recommended to switch to closed chain movements such as squats to reduce shear forces. When performing sitting posture leg flexion and extension training, it is recommended to choose a moderate weight to ensure the quality of the movement, and repeat 12-15 times per group until exhausted. The quadriceps femoris should be fully stretched before and after training, and the iliotibial band should be relaxed with the foam axis. Schedule 2-3 training sessions per week, combined with compound movements such as squats and lunges, to enhance overall lower limb strength. People with knee joint discomfort should reduce their range of motion or switch to static contraction training. For those who sit for a long time, it is necessary to strengthen the balance training of the hamstring and gluteal muscles to avoid muscle imbalance.