Most anatomy classes teach that the hamstrings flex the knee.  Based on this many people train and strengthen the hamstrings using a leg curl machine either sitting or laying on their stomach.  If we stop and look at the body function in various activity you will see that rarely ever are people sitting or laying prone and flexing their knees.  Even in walking or running when you see the knee flexing it is a passive event caused by momentum.

Lets first look at the anatomy.  In general. the hamstring attaches proximally to the ischial tuberosity (the bone you sit on) and runs down the back of your leg to attach distally to the medial and lateral tibiia (lower leg bone).  Next lets consider the “true” function of this muscle.  Using gait or a lunge as an example, knowing what the bones are doing (in all 3 planes) and knowing where a muscle attaches prox. and distally will allow you to see and figure out function of any muscle.  Remember that in the loading phase (eccentric muscle activity) the tibia advances forward and internally rotates and the pelvis/hip flexes, adducts and internally rotates (see when the foot hits ground and “barking hip posts for review).  So with that in mind, as the foot swings forward the hamstring muscle eccentrically contract to decellerate the leg to prepare it for heel strike.  When the foot hits the ground and begins to load the hamstrings eccentrically contract to control hip flexion in the sagittal plane (so we dont fall on our face).  They eccentrically control tibial internal rotation in the transverse plane and help control hip adduction (in single limb stance with the glut med / min) in the frontal plane.  Distally, think of the hamstrings like reigns of a horse controlling and acellerating tibial rotation.  Once the foot gets to late midstance we have completed the loading phase and the muscles now concentrically contract to propel us forward. The hamstring concentrically contracts to extend the hip and externally rotate the tibia.  How well the hamstring (or any muscle) concentrically unloads or explodes contracts depends on how efficiently it eccentrically loads.  Based on the biomechanics and “functional” anatomy one can see how doing leg curls will not prepare you to walk, run or lunge.  When considering exercise for function or performance it is important to consider how the muscle or joints respond to gravity, ground reaction force (GRF) and momentum.  Gary Gray refers to this as training in the context in which you will actually utilize the muscle and joints in relation to GRF, gravity and momentum.

                                                

Some examples (above) of functional hamstring exercise consist of single leg (SL) squats w/ reaches, lunges with reaches, isom. SL squat w/ alternating cross reaches modified deadlifts, and SL mod. deadlifts.

Get Strong! Stay Strong!

Chris

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