Muscle Strains Part 3: The Hamstrings
Hamstring strains are very frustrating for athletes and they are one of the most common muscle strains in sports. Recurrence rates of hamstring strains are estimated at 12-33% (Emlund and de Almeida Vieira, 2017). They take a long time to rehabilitate and usually require 16 weeks before returning to sport. Perhaps recurrence is high due to common mistakes made when rehabilitating the hamstring. But before we get into mistakes, let’s first understand how it happens in the first place. To understand that, we need to understand the anatomy.
The Anatomy of the Hamstrings:
The hamstrings are really a group of three muscles; from medial to lateral: semimembranosus, semitendinosus, and biceps femoris. This group of muscles are two joint muscles, meaning they cross over the hip and knee.
Two joint muscles have the ability to move two joints, as the name suggests. In the case of the hamstrings, they can perform hip extension and knee flexion (picture a donkey kick). As with all muscles, they are placed on stretch with the opposite motion. So that means hip flexion and knee extension (the motion that your lead leg does when walking or running). One of the advantages of two joint muscles is that they can store a lot of potential energy and become “spring loaded”. For example, when you are running and your lead leg comes in front of you, you are in hip flexion, partially winding up the tissues of the hamstring. As your foot lands, that stored energy becomes kinetic energy as your foot propels you forward to take your next stride.
This does not come without risk though. When your foot lands, the hamstring is undergoing a strong eccentric contraction (on stretch but still under tension). All muscles have a limit to their capacity and when the force placed on the tissue outweighs the capacity to tolerate the force, injury occurs. An under trained and weak hamstring, or overly tight hamstring will increase the risk for injury.
This brings me to my next point. The hamstring was just strained by being placed on too much stress with too much force. Despite this, the common (and in my opinion, wrong) thing to do is stretch the hamstring and push through the pain. Why would we stretch something that just got injured from too much stretch? It is appropriate to take the muscle through gentle range of motion, but when we feel pain, that is our body telling us that it is too much. Instead, you should be allowing the hamstring time to heal, and slowly begin to load the tissue within tolerance. This usually means isometrics to start, then progress to concentrics, then onto eccentrics, and finally progress to dynamic strengthening. Patience is crucial and the pressures to return to sport ASAP lends to the high recurrence rates.
(n.d.). Hamstring injuries: update article - NCBI. Retrieved May 30, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5582808/