February’s Muscle of the Month

Entry number two in the Muscle of the Month series will help you better understand the leg, how we sit, stand, walk and run.

Introducing the Hamstrings: Biceps Femoris, Semimembranosus, and Semitendinosus

That’s right, the Hamstrings are made of three different muscles, and one muscle (the Biceps Femoris) has two muscle bellies, hence the name Biceps (Bi = 2).  These three muscles work together, opposing the Quadriceps, to successfully do things like walk, stand up, and sit down.  The Hamstrings flex (bend) the knee, and extend the hip.  The back leg of a kneeling lunge puts the Hamstrings in their flexed position at both joints that they cross.

What do they do?  While doing a squat the Hamstrings bend the knee.  To stretch your Quadriceps you raise your lower leg toward your back side (the Gluteal muscles) which activates the Hamstrings.  When the Quadriceps stretch, the Hamstrings flex.  Therefore, these two muscle groups, with help from the Gluteal muscles and the Iliopsoas complete walking, running, and squatting motions.  This is why the Hamstrings are the second Muscle of the Month because they work so closely with the Quadriceps to perform what we think are such simple everyday movements.  I give you two guesses what muscle group we’re going to be learning about next month!

What can go wrong?  Most people say they have tight hamstrings.  I would beg to differ.  Although, just like any other muscle or muscle group, they can get tight, more often they suffer from being over stretched.  It might seem strange, but this is one reason why they are a common muscle to “pull”.  I’ll try to keep this as simple as possible.  Often what happens with the Hamstrings is that the entire muscle group spends a lot of the time lengthened, but sections of muscle fibers become contracted because of strain on the muscle.  These contracted sections are shorter in length than the entire muscle so when the Hamstrings are engaged in an activity such as running, the short fibers are more vulnerable to being torn.  Stay tuned for a special addition of “Muscle of the Month” for more on the inner workings of muscle fibers.

I hope you have enjoyed learning about the Hamstrings Group!