Hamstring Strain Injuries

Oh, the hammies. Such a fascinating collection of muscles. The hamstring muscle group refers to the three muscles on the back of the thigh- biceps femoris, semitendinosus, and semimembranosus. All three extend the hip, tilt the pelvis, and flex the knee. Also, they all attach (except for the short head of the biceps femoris) to a small boney part on the bottom of the pelvis called the ischial tuberosity, aka sits bones. The other (distal) end of the muscles each connect to different sites, either on the tibia or fibula.

A hamstring strain is a tear in the muscle fiber. You may have heard it referred to as a pulled hamstring. It occurs mostly to runners and those involved in any sport that involves some sort of kicking motion. While strains can occur anywhere along the body of the muscle, most hamstring strains occur at the musculotendinous site, which is where the muscle fibers join the tendon fibers.

How it Happens

To understand how a hamstring strain occurs is to explore the biomechanical factors at play during movement, in particular, running. There are several phases of the gait cycle. One phase is the swing-through phase. The swing-through phase is broken down into more phases, but the one we’re looking at here is the terminal swing phase. This is when the foot is mid-air and approaching the ground. It is also the time most likely for the hamstrings to be injured. It is at this point the hamstrings are contracted and stretched at the same time and the muscles are preparing to decelerate. The biceps femoris is the hamstring that receives the greatest stretch, which may explain why it is the most commonly injured hamstring muscle. Sports that involve kicking or dance put the hamstrings in an extreme stretch and most often involve the other hamstring muscles, the semimembranosus and semitendinosus. While the general understanding is that hamstring strains are an acute injury, there is thought that accumulated damage to the muscle due to overuse can be a cause.

Risk Factors

Current research cites lack of flexibility, muscle fatigue, muscle weakness, insufficient warm-ups, and strength imbalances between the hamstrings and quads as contributing factors. Have you had a previous hamstring injury? Well, that may factor in as well.

Something…Just…Happened

Say you’re out running fartleks and you feel a sudden pain. This pain can range from mild to severe, depending on the severity of the injury. You may also hear a loud popping sound at the time of the injury. So, you slow your roll and find yourself limping. The pain may be located somewhere along the posterior thigh or, if the tendon is involved, the pain may be at or near the ischial tuberosity. After the initial injury, you may notice the pain more when you are sitting. Around the time of injury, and depending on the location of the injury, you may see bruising. Strains range in severity from grade 1, with few fibers torn and minimal loss of function, to grade 3, which is a full rupture of the muscle fibers and a total loss of function.

Back in the Saddle, er, on the Asphalt

The location and severity of the injury affect healing time. A grade 3 strain can take months to heal while a grade 1 strain heals faster. An injury within the muscle belly will heal faster than one within the muscle-tendon unit. If you experience sudden pain during an activity that keeps you from continuing, your best bet is to get it checked out by a medical doctor. While you may suspect a strain, there are other possibilities to be considered. Your doctor may prescribe physical therapy, which may involve work such as eccentric strength training, trunk stabilization and agility exercises, or neuromuscular control exercises for the legs and lumbopelvic region.

Save the Best for Last

Massage helps recovery by reducing the hypertonicity of the hip and leg muscles. Just find your favorite massage therapist (ahem) and ask for a relaxing massage.  

References

Heiderscheit, Bryan C; Sherry Marc A; Silder, Amy; Chumanov, Elizabeth S; Thelen G. Hamstring Strain Injuries: Recommendations for Diagnosis, Rehabilitation, and Injury Prevention.

Journal of Orthopaedic & Sports Physical Therapy. 2010;40(2):67-81Opar, David A; Williams, Morgan D; Shield, Anthony J.

Hamstring Strain Injuries: Factors that Lead to Injury and re-injury. Sports Med. 2012 Mar 1;42(3):209-26Lowe, Whitney. Orthopedic Assessment in Massage Therapy. Daviau Scott Publishers, 2006