When it comes to relieving sore muscles, tackling joint inflammation, and treating a fitness injury, ice therapy is often one of the first remedies suggested by athletes and medical professionals alike.

While slapping a bag of frozen peas on an aching ankle might seem like second nature at this point, do you know what the cold sensation actually does for your body and why it helps? Don’t miss this essential guide to ice therapy:

Reduces Inflammation – following an intense workout or fitness injury like an ankle sprain, the body’s immune system triggers an inflammatory response wherein damaged cells release a flood of chemicals (including prostaglandins, histamine, and bradykinin). These chemicals cue blood vessels to leak fluid into the tissue (which causes swelling) and attract white blood cells to start the healing process.

While heat makes blood vessels contract or widen, application of something cold makes them do the opposite, or constrict. The cold shock of an ice pack applied to swollen tissues narrows the blood vessels enough to slow circulation and prevent more blood and fluids from inflaming the area. Icing an injury quickly can help prevent excessive damage to blood vessels and also limit potential bruising.

Relieves Pain – the analgesic effect of ice therapy comes in the form of a numbing sensation that only cold can provide. Sensitive nerve impulses go haywire in the days following intense exercise or right after an acute injury and ice serves as a way to diminish their conductivity and numb spasming nerve endings.

Icing has also been shown to aid pain and discomfort associated with overuse injuries (like carpal tunnel syndrome and plantar fasciitis) as well as wear-and-tear conditions like back pain and some forms of arthritis.

Speeds Recovery – you may have seen some of your favorite athletes taking ice therapy to the next level with immersive cryotherapy (ice baths) or full limb ice packs that wrap around an entire leg, for example. One school of thought believes that when you ice inflamed tissue and then remove the ice, the blood vessels rapidly rewiden and help to flush out built-up toxins and waste by-products in the damaged tissue.

Research on the efficacy of cold therapy for muscle recovery still goes back and forth however. For example, a 2015 study in The Journal of Physiology found that cold water immersion following intense exercise actually resulted in less muscle growth when compared to an active cooldown (like stationary cycling). Whatever you choose to do, experts do warn that anyone utilizing cold therapy should adhere to best practices to prevent unwanted injuries like frostbite.

Ice Therapy Best Practices

Want to make sure you’re getting the most out of your ice therapy? Whether tending to sore muscles or treating a fresh injury, keep these guidelines in mind:

Practice safety. You can actually incur ice burn simply by holding an ice pack against your skin for too long so practice safety when utilizing ice therapy. Always have some material between you and the ice pack whether it’s a towel, piece of clothing, pillowcase, or cloth wrap around the ice pack. And never ice for more than 15 to 20 minutes (every 4 to 6 hours).

Ice first, heat second. Applying a cold pack will always be the first thing you want to do, whether it’s for a sore back, tender knee, or aching neck. In the 2 to 3 days following the icing, if the pain persists, you can use a heating pad to help relax and soothe the injured tissues but only after swelling has subsided.

Try other cold therapy measures. You may want to consider alternative cold therapy measures like ice baths or ice massage as well depending on your athletic needs and degree of injury. Talk with your doctor or sports medicine specialist about how cold therapy could work for you.

Need to ice an injury right away but don’t have an ice pack? Get creative with handy solutions like using a frozen bag of vegetables, filling a resealable bag with ice cubes, freezing a wet towel or sponge, or even filling a resealable bag with dish detergent and freezing it until it forms a cold gel pack.