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There are two main possibilities which could be responsible foe your
symptoms.
This could be intermittent claudication which is pain in the calves with
exercise which is relieved by rest.
It is associated with poor blood supply to the muscles and is relatively
easy to diagnose by doing ultrasound examinations of the blood vesels to
the legs.
Another possibility would be lumbar stenosis which is caused by pinching
of the spinal cord in the lower back due to disc degeneration.
Since the possibilities are quite varied, the only way to clarify this is
by means of a complete history, physical examination and appropriate tests
as directed by the initial consultation.
I would suggest that you see a physicain soon to have all of this worked
out.