Brief Answer:
Can be due to injury.

Detailed Answer:
Hello,
Thanks for posting your query.
Repeated injuries of hamstrings are common and people who don't warm up and stretched properly before moving their muscles,have increased chances of injury.
Doing too much,too soon and too fast creates problem
Repeated injuries cause formation of scar tissue and subsequently complete healing doesn't take place .
Other factors are
Poor fitness levels and lack of regular exercises
Poor nutrition and obesity
Some times referred pain from bulging discs is the reason.

Treatment is done by
Rest
Icing of hamstrings
If pain,take anti inflammatory drugs and local gel
Stretching of hamstrings by pulling both legs towards chest with hands below knees
Full recovery takes 3 to 6 weeks.

Prevention
Take enough calcium,VIT D and B complex vitamins
Do stretching for 15 minutes before you exercise.
Use proper shoes
Strengthening your hamstrings.

I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
Wishing you good health.
Regards.
Dr. Praveen Tayal.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Praveen-Tayal

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Brief Answer:
Calf stretches will help.

Detailed Answer:
Hello.
Thanks for writing again.
You can learn proper calf muscle stretches from a physiotherapist who will guide you regarding the right amount of pressure you can put on the muscle without injuring it.
Hope my answer is helpful.
Do accept my answer in case there are no further queries.
Regards.

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