Movement
- Semitendinosus and semimembranosus extend the hip when the trunk is fixed; they also flex the knee and medially rotate the leg when the knee is flexed
- The long head of the biceps femoris extends the hip
- Both short and long heads flex the knee and laterally rotate the leg when the knee is flexed
Mechanisms of Development of a Hamstring injury
Strain is the typical mechanism of injury, and of all such injuries, the hamstring muscle complex is by far the most commonly involved (1)
- it is poorly understood at which phase of gait hamstring injuries occur. However some studies have demonstrated that biceps femoris has a tendancy to tear during the terminal swing phase of the running gait (2)
- the most common site for hamstring injury is in thebiceps femoris at the myotendinous junction. At the microscopic level the injury disrupts the myotendinous junction at the Z line between adjacent thin filaments
Hamstring injuries can also be considered in term of direct and indirect trauma:
- musculotendinous injuries usually occur as a result of either direct or indirect trauma
- direct trauma such as from a blow results in muscle contusion (bruising)
- indirect trauma can occur as a result of alteration in the intensity or synergy of contraction, resulting in a single powerful muscle contraction
- indirect trauma can also result from an overstretch of the musculotendinous unit leading to a strain, tear or avulsion
- hamstring muscles are most vulnerable to injury during the rapid change from eccentric to concentric function, such as where the leg decelerates to strike the ground during running (2)
- concentric function is where a muscle actively shortens in order to produce movement. For example, concentric action of the quadriceps, the muscle at the front of the thigh, straightens the knee to produce a kicking action
- eccentric function is where a muscle generates active tension as it lengthens, braking a movement. For example, the hamstrings, situated at the back of the thigh, would function eccentrically to brake the kicking action.)
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Reference:
- 1) Koulouris and Connell Evaluation of the hamstring muscle complex following acute injury Skeletal Radiology (2003) 32:582-589 DOI 10.1007/s00256-003-0674-5
- 2) Bryan C. Heiderscheit a, Dina M. Hoerth a, Elizabeth S. Chumanov a,Stephen C. Swanson c, Brian J. Thelen b, Darryl G. Thelen. Identifying the time of occurrence of a hamstring strain injury during treadmill running: A case study. Clinical Biomechanics 20 (2005) 1072-1078.