Hamstring Injury

Hamstring consists of biceps femoris long head, biceps femoris short head, semitendinosus and semimembranosus. Its injury is probably the most common muscle injury of runners.  

It is commonly accepted that hamstring injury is usually caused by imbalance between hamstring and its antagonist - quadriceps.  Since the knee extension of the grounded leg carried out by the quadriceps is the major propelling phase of running, the quadriceps is strengthened by almost every workout, especially by hill and speed workouts. The hamstring brakes the extension of the knee extension of the leg off the ground.  When the quadriceps overpowers the hamstring, the hamstring is torn in the braking process (an eccentric contraction).

Since all hamstring muscles except the biceps femoris short head originate from ishial tuberosity in the hip, sometimes the injury of its upper part is confused with other hip muscle injuries.  As described in the injury page, specific hamstring stretching and exercise can be used to confirm whether the hamstring is injured. 

The book Lore of Running (Noakes, 1991)  has a very good treatment of hamstring injury with two succinct pages (p527-528).  According to Noakes, a hamstring injury can be completely healed in one or two weeks by intensive treatment of the muscle together with muscle stretching and strengthening. 

Strengthening and stretching are not only the means to heal the injury but also the effective way to prevent hamstring injury.  Hamstring stretching is one of the most common stretching exercises that everyone is familiar with and it is easy to do. If stretching is not properly done (e.g. over-stretching and ballistic stretching), it can exacerbate or even create hamstring injury. Injured hamstring muscles can be stretched only very gently and they are best relaxed actively by contracting the antagonist muscles during stretching. Speed work or down-hill running should be done extremely cautiously. If one is not sure about the appropriate stretching technique, stretching should be completely avoided.

The strengthening of hamstring is a bit tricky.  The most common hamstring strength work is leg curl that usually requires an equipment.  Theoretically this exercise strengthens all hamstring muscles because all of them participate in the knee flexion.  In reality, it is doubtful that the leg curl can give a complete evenhanded strengthening work to all the hamstring muscles.  Since the hamstring also participates in the hip extension especially when it is flexed, barbell straight leg deadlift should be included in the hamstring strengthening work.  There are other variants of this exercise.  The key of this type of exercise is to keep the leg straight while extending the hip.  Please note that there are other muscles (e.g. gluteus maximus) involved in the hip extension.

Increasing the flexibility and strength of the hamstrings will significantly enhance the running form by making it more efficient and pleasing (if you care).


To cure hamstring injury:

  1. Stop running for a few days to let the inflammation disappear judging by the pain. This usually takes 2-3 days.
  2. Deep tissue massage to help dissolve scars while doing some very light jogging to increase the perfusion of the injured spot. Do some very gentle hamstring stretching or completely avoid stretching. This usually takes 2-3 days.
  3. Gradually increase jogging distance but maintain an easy pace. Keep deep tissue massage and very gentle hamstring stretching or completely avoid stretching. This takes about one week.
  4. If the hamstring remains tenderness free (judging with the help of powerful fingers) after an easy jogging of at least 10 miles, uphill workout can be resumed starting with a relatively easy pace.
  5. If the hamstring remains tenderness free after a hard uphill workout, speed workout can be resumed beginning with a relatively easy pace.
  6. If the hamstring remains tenderness free after a hard speed workout, the hamstring injury is completely healed. Congratulations!

If the hamstring becomes painful or tender at any of the above step, go back one step and continue the process.




Noakes, T (1991) Lore of Running. Leisure Press, Champaign, Illinois.



(originally written on 5/4/2002)

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