Step-ups can serve as an effective substitute or alternate for squats. You may struggle to do squats because of the pressure placed on your knees or because of the significant amount of strength you need in your quadriceps muscles in the front of your thigh. Understanding how each exercise is safely performed and which muscles each strengthens will guide you in creating an effective workout routine.
Both a squat and a step up work many of the same muscles. In a squat you will mostly use your knee extensors, or quadriceps, muscles with your hip extensors, which include your gluteus muscles and to some extent your hamstring muscles. These muscles have the primary role because they are resisting gravity as you move toward the floor, and then contract concentrically as you raise up. Similarly, during the power phase of the step-up as you raise your body onto the platform, these same muscles are predominant.
Eccentric vs. Concentric Contractions
Because of the forward movement of the step-up, you will target your hip extensors over your knee extensors, which is the opposite of a squat movement during the power phase. In the eccentric phase of both exercises, you will be lowering your body toward the floor. In the squat, you will use your knee extensors more than your hip extensors, with the step-up being the opposite. To target the hip extensors, a step-up may be more effective than a squat. A step-up, however, will not target your knee extensors on the front of your thigh as effectively as a squat.
One of the most common complaints during a squat is knee pain. Often this is at least partially related to poor form and bringing the knee in front of the foot as you lower to the ground. Even with proper form, this exercise can be very challenging as your entire body weight is being lowered and raised with the knee as the primary hinge point. Conversely, step-ups spread the impact and strain across all three major joints of your leg, namely the hip, knee and ankle. Also, during the power phase of the step-up, you must lift almost all of your body weight with one leg -- this can help you strengthen your muscles quicker. Although the step-up can still place impact on your knee joint, moving slowly and precisely and placing your foot gently on the platform will reduce some of this impact and can be more tolerable if you have weak, arthritic or injured knees.
Step-ups and Squats
Step-ups can be a valuable tool to help you work toward a squat if it is difficult for you. Because you can spread the movement more evenly over your entire leg with a step-up, you will likely have less pain. Cross training is an effective tool in any workout regimen and you may receive the best benefits from alternating between squats and step-ups in separate workouts to reduce strain and help you target the entire length of the muscle fibers.