The Quadricep - Rectus Femoris
Of the four muscles on the front of the thigh only the rectus femoris muscle crosses the hip. It functions to flex the hip and extend the leg at the knee joint. Research has found that the rectus femoris activation is significantly higher during a knee extension compared to multi-joint exercises.
Depending on which sport is being played muscle injuries represent approximately 9-54% of the total injuries. A muscular strain of the rectus femoris is more likely to occur in sports that require repetitive kicking and sprinting.
Adding the single joint movement of leg extensions to a workout regime is an excellent way to fully develop this muscle and help protect against the risk of a quadricep strain.
Pendulum Leg Extension
Training the Quadriceps with Knee Extensions