Magnesium oil is to increase magnesium content in the underlying muscles from transdermal absorption. This may enable healing of strained tissues, inflammation or reduce muscular spasms such as 'restless legs'.
Alternative products to assist muscle tissue repair include Arnica gel or Comfrey oil. There is also Magnesium gel (or Magnesium and MSM gel). There is also Herbal Horse balsam-a mixture of herbal components in a gel.