Vastus intermedius: Nestled between the vastus lateralis and vastus medialis, it also aids in knee extension. Vastus medialis: Situated on the inner thigh, it's key for knee stability. 2.

The step-up with deliberate co-activation resulted in greater activation of the hamstrings, greater co-activation indices for semimembranosus-vastus medialis and biceps femoris-vastus lateralis ...