The muscles in the back of your body are what physiologists call the "Posterior Chain." These muscles start at the ERECTOR SPINAE go to the GLUTES, HAMSTRINGS and down to the CALVES.
The erector spinae are a muscle that alighns the back of y our spine and go from the base of your skull down. Their structure is similar to that of a cable.
Your Glutes are usually referred to as your butt haha...but it should be known that the gluteus maximus is the largest muscle in your body. There are two other muscles underlying the minimus and the medius glutes. The gluteus maximus generates the power to sit, stand and run, while the minimus and the medius keep you balanced and from going to the left or right i.e tipping over.
The hamstrings consists of three muscles the semitendonoisis, semimembranosis and the biceps femoris. These muscles run along the back of your legs and go from the inside of your sit bones to the outsides of your knees. The Hamstrings stabalize the hip and knee joints.
The calves are made up of the outer muscles and the inner muscles which is called the soleus. These muscles are used to lift your heels and to flex your knees which means they are very important for explosive power events...including sprints.
SOOOOOO KEEP the muscles of your POSTERIOR CHAIN in check! STRENGTHEN THEM AND WORK ON THEIR FLEXIBILITY!,,