Ice and heat get used almost interchangeably by members dealing with soreness or minor injury, when the right choice actually depends on timing and what's being treated.
Ice suits acute, recent issues
For a fresh strain or acute swelling, ice helps reduce inflammation in the immediate aftermath — generally the first day or two.
Heat suits ongoing tightness and stiffness
For chronic tightness or stiffness without acute swelling, heat increases blood flow and can loosen the area more effectively than ice would at that stage.