It was during a second-year-university anatomy class when I was first introduced to a little anatomical tidbit that can contribute to reducing the chronic hamstring tightness plaguing many individuals. The lecturer mentioned – in passing – that we should avoid ankle dorsiflexion during hamstring curls in order to properly strengthen them. Dorsiflexion of the ankle? What’s that have to do with the hamstrings?
The Gastrocnemius muscle is a superficial bipennate muscle that spans from distal femur to form part of the calcaneal tendon (achilles tendon). Its main functions are plantarflexion of the foot (pointing toes away from the knee) and also has some knee flexion capabilities.
Hamstring (Biceps femoris, Semitendinosus and Semimembranosus)
The Hamstring muscle group primarily originate at the ischial tuberosity in the pelvis (with the exception of short head of biceps femoris which originates from the linea aspera on the femur). Biceps femoris attaches to the head of the fibula while semitendinosus and semimembranosus attach to the tibia.
With the exception of short head of biceps femoris, the hamstring muscles are responsible for both hip extension and knee flexion. They also combine to generate some lateral and medial rotation of the thigh.
Getting to the point
The traditional hamstring stretch we were all introduced to as tweens was to stretch your hamstring by grabbing your toe. Undoubtedly that will promote us to dorsiflex our toe to make it easier to reach (so we can show off our flexibility). However, dorsiflexing the toe with your knee straight also causes the gastrocnemius to be stretched. The issue that arises is that as we perform the “toe-grab hamstring stretch”, we feel a stretch in the back of the knee, we hold this “hamstring” stretch and switch sides and go about our business. The evident issue as a result of the dorsiflexion of the toe, we mistake the stretch felt for a hamstring stretch rather than what it primarily is – a gastrocnemius (calf) stretch.
Try it out
Sit on the floor with your knee straight and toe dorsiflexed (pointing back towards your body) and lean forward until you feel a stretch behind your knee.
Next, maintaing the stretch, relax your foot and plantar flex it (pointing your toe away from the knee).
Lean forward and feel the difference in the stretch.
That’s how a hamstring stretch should feel.
The Gastrocnemius muscle has a relatively short belly with a long taught tendon. The muscle can be stretched with only a few degrees of dorsiflexion. The issue with a dorsiflexed foot during a hamstring stretch is that the gastrocnemius is maximally stretched well before the hamstring muscles reach a stretched state. So we stretch the gastrocnemius maximally while the hamstring remains at a neutral length. Therefore there is no net stretch on the hamstring. Since the aim stretching usually to increase flexibility, the negation of the hamstring stretch can result in perpetually tightening hamstring which is associated with reduced range of motion, strength and lower back pain.
Impact on Hamstring Strengthening
Although hamstring curls are not the most efficient way to strengthen the hamstrings (we’ll save that discussion for another day), the information can be readily applied to hamstring strengthening as well. If you have performed or witnessed a prone hamstring curl on a cable machine at the gym, you will notice that most people have their toes severely dorsiflexed as they curl their hamstring. This indicates that they are recruiting gastrocnemius for a large part of the movement. In essence, it becomes more of a calf exercise than a hamstring exercise. This makes sense when you take into consideration the amount of pain and fatigue associated with a dorsiflexed hamstring curl, as the gastrocnemius has a lower endurance than the hamstring.
A workaround is to simply ensure your foot is neutral or plantar flexed when performing any exercise targeting the hamstring through knee flexion.
We have seen how an understanding of gastrocnemius/hamstring anatomy and physiology can affect how we go about stretching and strengthening the hamstring muscles. Being aware of the position of your feet can go a long way to ensuring better hamstring health and maximising the time we dedicate to the posterior compartment of our lower limb.