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Is hot or cold better for sore muscles?

CNET 9/1/2019 Amanda Capritto

a person sitting on the floor: Getty Images

You hit a new squat PR yesterday and now your legs are killing you -- that "can barely walk up the stairs, would rather eat lunch standing up" kind of sore. Do you ice down your quads after work or snuggle up on the couch with a heating pad?

While people often use cold and heat interchangeably (which is different than using them intermittently -- more on that below), these two types of therapy do exactly the opposite of each other: Heat promotes blood flow and cold restricts blood flow.

Here's when to use heat and cold for the best relief from muscle pain.

When to use cold therapy

Cold therapy, also called cryotherapy, reduces blood flow to an injury site. That's why people historically use ice packs after, say, banging a shin on the coffee table. The ice pack directs blood away from the injured area, reducing the severity of the inevitable bruise. But how does this affect muscle pain?

Well, by reducing blood flow, cold therapy also reduces inflammation, swelling and tissue damage. When you work out, your muscles experience microtraumas, which lead to inflammation, fluid accumulation and a bunch of other things that result in muscle soreness.

If you apply cold right after a workout, you can slow the inflammation process and reduce soreness. Cold therapy seems to be particularly effective at treating swollen or inflamed joints.

No matter the injury type -- muscle microtrauma or otherwise -- cold therapy is best applied within 48 hours of an injury.

Try it: Wrap an ice pack or cold compress in a thin cloth (to avoid localized frostbite, don't apply ice directly to your skin); take an ice bath; try out whole-body cryotherapy.

a close up of a towel: Something as simple as a heated blanket can help you recovery quickly from your workouts. Sleep Number

When to use heat therapy

Heat therapy (which actually should just be warm, not overly hot) dilates blood vessels and promotes blood flow. This helps to "open up" sore muscles and relaxes them. Improved circulation delivers more oxygen and nutrients to your muscles and simultaneously removes lactic acid, which is essential for muscle healing.

Research has shown that heat therapy can reduce delayed-onset muscle soreness (DOMS) by up to 47% just 24 hours post-exercise.

Like cold therapy, heat therapy is best applied immediately after a workout.

Be wary of heat in some cases, thought: Heat seems to be the best option for treating exercise-related muscle pain, but heat is usually not good for treating injuries. Applying heat to a fresh injury can expedite the inflammation process and lead to even more pain.

Try it: Treat yourself to a hot bath; use an electric low-level heating pad; sit in a sauna or steam room; get a hot stone massage.

Alternating cold and heat

Many athletes use contrasting therapy -- applying cold and heat intermittently -- to reduce muscle soreness. Contrasting therapy works by first constricting blood flow with cold, and immediately promoting blood flow to the same area with heat. Research has shown contrasting therapy to be effective at reducing muscle soreness, but no more effective than other recovery techniques.

This cycle works in a similar way to that of pulsing compression therapy, which repeatedly constricts and releases your muscles via an inflatable suit.

Keep in mind that though science supports both heat and cold for muscle pain, neither treatment is really potent, so don't look at these as cure-alls for soreness. Instead, heat and cold should be one part of a multifaceted recovery regimen.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.

Related video: Kelsey Wells' how to fix your squats [via Health]