The hip sled and leg press are very similar exercises that work many of the same muscles. Each exercise is generally performed from a decline position and involves extending the hips and knees upward against a high degree of resistance. However, while the hip sled remains fairly constant, you can perform a number of variations of the leg press.
Target Muscles
In a typical 45-degree hip sled or leg press setup, the primary target muscles are the quadriceps. The quadriceps refers to a four-headed muscle that runs down the front thigh and helps extend the knee while also flexing the hip. In one variation to the leg press, the lever 45-degree, plate-loaded leg press, the target muscle is the gluteus maximus. This muscle supports and mobilizes the hip joint.
Synergists
Synergists are muscles that help assist the target muscles in executing a particular movement. During both the hip sled and leg press, the gluteus maximus, adductor magnus and soleus assist the quadriceps in pushing the weight forward. The adductor magnus is located in the inner thigh and helps move the hip away from the body. The soleus runs down the back of the leg and supports the ankle. In the lever 45-degree, plate-loaded leg press, however, the quadriceps serve as a synergist to the gluteus maximus.
Dynamic Stabilizers
Dynamic stabilizers are muscles that shorten at the target joint while lengthening at the adjacent joint to stabilize and counter the force of a high degree of resistance. These muscles are important for preventing injury to susceptible joints. In both the hip sled and leg press, the hamstrings and gastrocnemius serve as dynamic stabilizers. The hamstrings are four muscles that run down the back of the thigh and help mobilize the hip and knee. The gastrocnemius, or calf muscle, helps mobilize the knee and ankle.
Recommendations
To improve muscular strength, perform three sets of three to five repetitions of the hip sled and leg press using moderate to heavy weight. To develop muscular atrophy or an increase in the size of the muscle fibers, perform three sets of six to 12 repetitions using moderate weight. To improve muscular endurance, select a light weight and perform three sets of 12 or more repetitions.