Is polymyositis related with poliomyelitis?

No. Polymyosotis is an autoimmune disease where a person's own white blood cells are attacking their muscles causing inflammation, pain, and weakness. Poliomyelitis is the disease caused by the polio virus which attacks the nerves and can leave a person with permanent weakness due to nerve damage. Very different in that it can be prevented in most people who are vaccinated against polio.
No. Polymyositis is a nonspecific term describing inflammation of "many muscles" at the same time. It implys pain & swelling in the muscle itself and microscopic exam of a biopsy may show inflammatory cells. In polio the nerves are the target of the inflamation not muscle, and changes in strength and muscle function are due to nerve damage.