Hamstring Injury - Anatomy, injury mechanisms and prevention exercises

The hamstrings are composed of 4 main muscle bellies; the biceps femoris long head, biceps femoris short head, semimembranosus and semitendinosus muscles. The 2 biceps muscles make up the lateral hamstrings whereas the other 2 sit medially.

What is a hamstring strain, why does it occur and what are the different grades?

A muscle strain is a partial or complete tear to a muscle that typically occurs in muscles crossing 2 joints during explosive activity. Muscle strains occur when the force on a muscle is so great that the tissue can’t handle the load and begins to tear. A tear to the lateral hamstring muscles typically occurs during sprinting whereas a medial hamstring injury typically occurs due to a rapid stretching mechanism. Sports that require high speed running & kicking typically have a high incidence of hamstring injuries. The different grades of injury are:

• Grade 1: Mild damage to individual muscle fibers that causes minimal loss of strength or range of motion

• Grade 2: Moderate damage with more muscle fibers involved. This results in a significant loss of strength and range of motion

• Grade 3: Complete rupture of a muscle or tendon which can require surgery

Risk Factors for a Hamstring Injury

• Age

• Previous hamstring injury

• Weakness of the hamstrings

• Hamstring fascicle length

• Poor flexibility and core stability

• Fatigue

Prevalence in Sport

A study into elite football players (soccer) found that 40% of elite athletes over the age of 20 had a history of hamstring injury and there was an 18% incidence for the under 20’s. In the 2019 AFL season there was an average of 5.1 new hamstring injuries per club with an average of 18.5 games missed!