Infra-red rays can be useful for:

Infra-red rays are primarily known for their ability to penetrate the skin and warm deeper tissues. This warming effect can be particularly beneficial in preparing the muscles and tissues for massage. When tissues are warmed, it increases blood circulation and enhances the flexibility of muscles, making them more pliable and receptive to manipulation during massage therapy. This pre-conditioning of tissues helps to prevent injury and allows for a more effective massage experience.

While infra-red rays may have some potential effects on muscle pain relief and circulation, their specific application for warming tissues significantly prepares the body for therapeutic treatments like massage. Therefore, the emphasis on this function aligns closely with the intended use of infra-red rays in a therapeutic context.