Last reviewed: 7 October 2026 · Sources are numbered and listed at the end.
The short answer: use cold for a fresh knock, sprain or strain, especially in the first two to three days. Use heat for muscles that feel tight, stiff or sore after training. If something is swelling, skip the heat.
That's the rule of thumb most of us grew up with, and it holds up. Here's why, how long to use each one, and when it's time to stop guessing and see someone.
What does cold actually do?
Cold narrows the small blood vessels near the skin and slows the nerves that carry pain signals, which is why an iced area goes numb. It's the "I" in RICE (rest, ice, compression, elevation), the first aid Australian health services recommend for sprains and strains in the first 48–72 hours.[1][2]
Reach for cold when you have:
- a knock, a corky or a rolled ankle
- a fresh sprain or strain
- a joint that's swelling or puffy
- a hot, achy area straight after a big session, if cold feels good
One honest note: for muscle soreness in the days after exercise, the research on cold packs is mixed.[3] Where cold really earns its place is first aid for fresh knocks and swelling, and short-term comfort.
What does heat actually do?
Heat widens blood vessels and increases blood flow to the area, and most people find it eases tightness and stiffness. A 2021 review of 32 trials found that heat applied soon after exercise was linked with less muscle soreness over the following days, the clearest result of the hot and cold methods it compared.[3]
Reach for heat when you have:
- tight or stiff muscles
- sore legs a day or two after a hard session
- morning stiffness
- muscles you want to loosen before light activity
Don't use heat on a fresh injury that's swelling, or in the first 72 hours after a sprain or strain. Australian first-aid guidance says to avoid HARM in that window: Heat, Alcohol, Running (or re-injury) and Massage.[1]
Ice or heat? A quick guide
| Situation | Use |
|---|---|
| Rolled ankle or a knock, first 2–3 days | Cold |
| A joint that's swollen or puffy | Cold, never heat |
| Tight, stiff muscles | Heat |
| Sore legs a day or two after a big session | Heat has the stronger research; cold can feel good short-term |
| Morning stiffness | Heat |
| Not sure what's going on | Ask your doctor or physio |
How long should I use ice or heat, and how often?
- Cold: about 15–20 minutes at a time. For a fresh sprain or strain, first-aid guidance is up to every 2 hours while you're awake, for the first 48–72 hours.[1] More detail in how long to ice a sore or injured knee.
- Heat: about 15–20 minutes at a time. It should feel warm and comfortable, never hot.
- Check your skin every 5 minutes. Stop if it turns red, numb or discoloured, or if it hurts.
- Wrap ice in a damp cloth rather than putting it straight on skin, and never fall asleep with ice or heat on.[1]
- Don't use either on open or broken skin, or on an area where you have reduced feeling.
Can I alternate hot and cold?
Plenty of athletes swap between the two, often called contrast therapy. Most of the research is on hot and cold water immersion, where alternating beat simply resting for soreness, but wasn't clearly better than cold or heat on its own.[4] If you like it, there's little downside once any swelling has settled. Keep each turn short and keep checking your skin.
When should I see a doctor or physio?
- You can't put weight on the leg, or a joint looks out of shape
- There's a lot of swelling or bruising
- The pain is severe, or getting worse rather than better
- It hasn't improved after a week
- You heard a pop, or the joint locks or gives way
- You have a circulation or sensation condition, such as diabetes, before you use hot or cold at all
Get urgent help for severe muscle pain together with dark, cola-coloured urine.[5]
Where CompressiveX fits
Most of us reach for frozen peas one day and a hot-water bottle the next. We designed our gear so one setup does both, and stays put while you use it.
- Hot or cold from the same pack. Freeze a Dual Thermo™ Pack for cold, or microwave it for heat.
- Hands-free. The wrap holds the pack in place, so you're not balancing a bag of ice on your knee.
- Recovery Flex Pack: a compression wrap with hot or cold therapy for the knee, leg or arm, designed to help manage pain and swelling after a knock.
- Recovery Knee Brace – Spring Support: compression and spring side supports for the knee, with the pack in a pocket behind the kneecap.
See the Recovery Flex Pack → · See the Recovery Knee Brace →
The hot & cold therapy guide has the freezing and heating steps.
General information only, not a substitute for advice from your doctor or physiotherapist.
Sources
- Safer Care Victoria: soft tissue injuries (RICE and HARM)
- Healthy WA: first aid for sprains and strains
- Wang et al. 2021: heat and cold therapy for delayed onset muscle soreness (32 trials)
- Bieuzen et al. 2013: contrast water therapy and exercise-induced muscle damage
- Cleveland Clinic: delayed onset muscle soreness
