Both hot and cold water can help sore muscles, but they work differently and suit different situations. Cold water reduces inflammation and numbs pain, making it ideal immediately after an injury or intense exercise when swelling is the main problem. Apply cold for 15–20 minutes within the first 48 hours. Hot water increases blood flow, relaxes tight muscles, and eases stiffness, working best for chronic soreness or muscle tension days after exercise. Many athletes use contrast therapy—alternating between hot and cold—to combine benefits. The best choice depends on timing (acute vs. delayed soreness), your injury type, and personal preference. If you have swelling, choose cold; if you have lingering stiffness without inflammation, choose heat. Some people find that gentle movement in warm water (like a warm bath or pool) combines pain relief with mobility improvement. Avoid extreme temperatures, and stop if you experience increased pain or skin irritation. For persistent or severe soreness, especially if accompanied by other symptoms, consult a healthcare provider to rule out injury requiring different treatment.