By Stephen E. Alway, Ph.D., FACSM
The biceps femoris muscle of the hamstrings is a two-headed muscle. The long head of the biceps femoris attaches to the ischial tuberosity,2 which are the bony parts of your posterior pelvis that you sit on when you are in a chair. The fibers of the short head of biceps femoris begin on the lower one-third of the femur bone just above the knee. Because they do not attach to the ischial tuberosity, the short head is not considered to be a “hamstring” muscle. Both heads of the biceps femoris muscle fuse into a thick tendon, which crosses the lateral side of the knee joint to attach to the fibula bone (and some ligaments) near the knee.2
The semitendinosus muscle fibers attach to the ischial tuberosity and insert into a cord-like tendon that crosses the knee joint posteriorly to anchor on the medial side of the superior part of the tibia bone2. The adductor magnus muscle primarily acts as a thigh adductor and it pulls the thigh close to the mid-line of the body. However, a vertical portion of the adductor magnus is called the “hamstring part” because it connects to the ischial tuberosities and runs to the adductor tubercle on the femur. The adductor tubercle is a small prominence of bone just above the knee joint on the medial side of the femur bone.2
“True” hamstring muscles cross the knee and the hip joints posteriorly2 and they can both extend the thigh at the hip joint (i.e., it helps to draw the thigh posteriorly as when running) and flex the leg at the knee joint (bringing the heel towards the buttock). The short head of the biceps femoris only flexes the knee and the hamstring part of the adductor magnus only extends the thigh at the hip joint.2
Dumbbell Leg Curls
1. Choose a bench that has an incline to it. This will help to maintain tension on the hamstrings throughout the exercise. A perfectly flat bench (parallel to the floor) generates rather large torques through the lower back, which increases the risk for back injury.
2. Although you can use a training partner to place the weight on your feet, you can also do this without one. If you train alone or at home, place a dumbbell on the floor, standing on end. Place your feet on either side of the dumbbell and then lie on your stomach and grip the end of the incline bench for stability. The flat part of the dumbbell should sit on the soles of your shoes. The top of your knees should be just beyond the edge of the bench pad upon which you are lying.
3. Pull your heels towards your buttocks. Keep your hips on the bench and do not let them lift upwards during the exercise.
4. After moving your heels a few inches, plantarflex your feet by pointing your toes away from your head (as if you were standing on your toes). Plantarflexion decreases the effectiveness of the gastrocnemius (calf) muscles to contribute to knee flexion. This will make the exercise much harder and pinpoint the activation of your posterior thigh.
5. Continue to flex your knees with the intent of bringing the dumbbell up to your buttocks. This should be done under full control and not with a ballistic momentum-stealing repetition. You might not quite make it that far, but pull as far as you can. Hold the top position for a two- to three-second count.
6. Slowly lower the legs to the starting position but do not straighten your knee completely. Immediately after reaching the end of the repetition begin the next repetition. Aim for 12-15 repetitions before resting.
Spend your time between sets stretching your hamstrings3 and hold each stretch for 20 seconds before switching to the other leg. Stretching the hamstrings is a very important preventative measure that should minimize the chances of obtaining back injures or pain that results from having hamstrings that are too tight.4Try to avoid lifting your hips, or moving your ankles from plantarflexion into dorsiflexion as both of these modifications will reduce the effectiveness of the exercise on firming your posterior thigh.
1. Ebben WP: Hamstring activation during lower body resistance training exercises. Int J Sports Physiol Perform 2009;4:84-96.
2. Moore K.L , and A.F. Dalley. Clinical Oriented Anatomy 4th Lippinot Williams Williams Philadelphia, 1999, pp. 563-571.
3. Laur DJ, Anderson T, Geddes G et al: The effects of acute stretching on hamstring muscle fatigue and perceived exertion. J Sports Sci 2003;21:163-170.
4. Bedard RJ, Kim KM, Grindstaff TL et al: Increased active hamstring stiffness after exercise in women with a history of low back pain. J Sport Rehabil 2013;22:47-52.
5. Wild CY, Steele JR, Munro BJ: Insufficient hamstring strength compromises landing technique in adolescent girls. Med Sci Sports Exerc 2013;45:497-505.
6. Kong PW, Burns SF: Bilateral difference in hamstrings to quadriceps ratio in healthy males and females. Phys Ther Sport 2010;11:12-17.
7. Koutedakis Y, Frischknecht R, Murthy M: Knee flexion to extension peak torque ratios and low-back injuries in highly active individuals. Int J Sports Med 1997;18:290-295.
8. Koutedakis Y, Sharp NC: Thigh-muscles strength training, dance exercise, dynamometry, and anthropometry in professional ballerinas. J Strength Cond Res 2004;18:714-718.