Both heat and ice can be effective in relieving a sore back, but it depends on the type of pain you are experiencing. Ice is typically recommended for acute injuries, such as a muscle strain or sprain, as it can reduce swelling and inflammation. Heat is typically recommended for chronic injuries, such as arthritis or muscle tightness, as it can improve blood flow and promote relaxation. If you are unsure which to use, you can try alternating between heat and ice therapy to see which provides the most relief.