The main effects of hot compresses of salt bags on the waist are to accelerate blood circulation, relieve fatigue and reduce swelling. 1. Accelerate blood circulation: because the heat of the salt bag can continue to release heat after heating, so the process of the salt bag can accelerate the blood circulation of the local muscles, promote the discharge of local inflammatory mediators, relieve the symptoms of pain. 2. Relieve fatigue: hot compresses can effectively relieve muscle spasm, relax local muscles, avoid the accumulation of lactic acid and other harmful metabolic products, relieve fatigue. 3. Reduce swelling: through the salt bag external application can also achieve the role of swelling, because the heat in the process of hot compresses will make the local microcirculation accelerate, while the local blood vessels are dilated, the permeability of the blood vessel wall increases, which is conducive to the faster and more precipitation of metabolites, reduce local edema, reduce pain.