By, Sean Light CSCS
The first thing we need to realize when discussing the Biceps Femoris is that it is not in your arms, but anatomically we have to note that there are two heads to this muscle, hence “Bi.” One can then safely assume that any triceps muscle will have three heads.
The Biceps Femoris is located on the posterior thigh (the hamstring area) and is responsible, although not solely responsible, for knee flexion (heel to butt), hip extension (moving leg backwards), the lateral rotation of the knee when flexed, and flexing the calf from the knee.
The origin of the long head of the Biceps Femoris is on the pelvis at the Ischial Tuberosity. The short head originates at the linea aspera of the femur (thigh bone). Because these are the points of origin, all Biceps Femoris muscle contractions will move towards this point.
The insertion point of the BF’s long head is on the head of the fibula which is the smaller of your two shin bones. The small head inserts at the lateral tibial condyle.
It’s important to know that no muscle can actually push. All motion is derived from shortening, pulling muscles. Thus, if the insertion always moves towards the origin, the action of this muscle will always be pulling upwards.
SOURCE: Hosford DPT, Darryl,”Posterior Thigh Musculature,” http://www.PTCentral.com/muscles