The major muscles in the human upper leg are in two groups: the hamstrings and the quadriceps. The semitendinosus, semimembranosus and biceps femoris muscles comprise the hamstrings muscle group, while the rectus femoris... More »

According to AZ Central, seated leg extensions work the four muscle heads of the quadriceps, which are in the upper thighs. Standing leg extensions also work the quadriceps and other abdominal muscles. AZ Central explain... More » Health Fitness & Exercise Exercise

When viewed anatomically, the leg muscles are seen as overlapping layers of striated muscle fibers that range in color from pale to dark red, depending on myoglobin content. These striated muscle fibers give the leg musc... More » Science Human Anatomy Muscles

The Clermont College Biology Department lists examples of flexor muscles as the biceps brachii and the hamstrings, and some examples of extensor muscles are the triceps brachii, the quadriceps femoris and the gastrocnemi... More »

The muscles that control the knees include the quadriceps, hamstrings and calf muscles. These muscles all work together to allow the knee to move freely in order to walk, run, kick and jump. More »

A person's thigh is composed of three major muscles: the quadriceps, hamstrings and adductors. Typically, when someone refers to the thigh muscle, the person is speaking about the quadriceps. More »

According to, the quadriceps are the primary muscles used in leg extensions. The quadriceps are located on the front of the thighs and include the rectus femoris, vastus intermedius, vastus lateralis and vastus... More »