Ice or Heat — When to Use Which
Ice constricts blood vessels, which reduces swelling and inflammation, making it the right first response to a fresh sprain or acute injury. Heat, on the other hand, dilates blood vessels to boost circulation and relax muscles, making it better suited to ordinary post-workout soreness or stiffness that isn't an injury. This calculator uses your workout intensity and injury status to recommend the right method and duration for your situation.
Acute injuries call for ice first. For the first 48 hours after a sprain, bump, or swelling, ice should come before heat — applying heat during this window can widen blood vessels and worsen inflammation and swelling. Apply for 15-20 minutes every 2-3 hours, and always wrap ice in a towel rather than placing it directly on skin.
Plain soreness responds better to heat or alternating therapy. If you're not injured but simply sore after a hard session, heat improves blood flow and aids recovery. Alternating between ice and heat can also work well when soreness lingers after high-intensity training.
Frequently Asked Questions
Yes — applying heat within the first 48 hours of an acute injury can dilate blood vessels and worsen swelling and inflammation. Ice should be applied first for acute injuries.
For ordinary post-workout soreness without injury, heat or alternating ice-and-heat therapy to improve blood flow is often more effective for recovery.