Back muscles are commonly strained when lifting a heavy weight incorrectly. Strains of thigh, arm and forearm muscles are also fairly common, especially in athletes.
In case of a sore, bruised, beaten-up feeling in the affected muscles, Arnica 30 is the remedy of choice. A dose of this remedy should be given every hour or two till relief is obtained.
On the other hand, if the pain and stiffness are worse after a period of rest Rhus tox 30 will be more helpful. Rhus tox can also be tried if Arnica seems to have helped only partially.