Back in April 2008, I wrote a post on this blog asking a pretty simple question: is using ice and cold water after resistance exercise actually a good idea? At the time, the evidence pointing against routine cryotherapy was already there if you looked for it — but challenging the ice bath orthodoxy was not exactly a popular position. Athletes were plunging into ice baths after every hard session. Physios were recommending it. Teams were investing in cold tubs like they were mandatory kit.

My argument back then was straightforward: the inflammatory response triggered by training is not the enemy. It is the signal. It tells your muscles to rebuild stronger. Blunting it with ice might feel like recovery, but you may actually be interfering with the very process you are trying to support. The data at the time suggested cold water immersion did little to reduce DOMS, and there were real reasons to think it was getting in the way of training adaptations.

That post got some pushback, a few spirited comments, and then the world largely carried on icing things anyway.

Fast forward to 2025–2026, and I have been part of two research studies that, I think, put this debate on much firmer ground — particularly when it comes to actual muscle injury rather than just post-training soreness. And the bottom line is the same as it was in 2008, only sharper: if you have a muscle injury and you want it to heal well, heat is more likely to help you than cold.

“The inflammatory response is not the enemy. It is the signal.”

What we actually studied

The first study, published in The Journal of Physiology, looked at what happens to injured muscle tissue when you apply different thermal treatments every day for 10 days. We induced real muscle damage in 34 participants using electrically stimulated eccentric contractions — this is not just the kind of soreness you get from a hard leg session, but a protocol that causes genuine myofibre necrosis and triggers the full regenerative cascade, similar to what happens in a meaningful sports injury. We then assigned participants to daily lower body water immersion: cold (12°C for 15 minutes), thermoneutral (32°C for 30 minutes), or hot (42°C for 60 minutes). We took muscle biopsies before, and at 5 and 11 days post-damage, so we could see what was actually happening at the cellular level — not just what participants were reporting on a pain scale.

The second study, just published in Experimental Physiology, took a step back and asked a more practical question: if we want to apply heat before exercise — as part of a warm-up or return-to-play protocol — which of the commercially available heating devices actually gets the job done in terms of raising deep muscle temperature? We compared a water-perfused suit, short-wave diathermy, and hot water immersion.

What we found

In the injury study, hot water immersion came out clearly on top. Participants in the hot group reported less pain than those in the thermoneutral group. Their levels of circulating creatine kinase and myoglobin — two blood markers of ongoing muscle damage — were significantly lower than in both the cold and thermoneutral groups. At the molecular level, the picture was even more telling.

Hot water immersion significantly increased the expression of heat shock proteins (HSP27 and HSP70) — chaperone proteins that are known to play a key role in repairing damaged cells. NF-κB, a signalling molecule involved in inflammation, rose in all groups except the hot immersion group, while interleukin-10 — an anti-inflammatory cytokine — was upregulated only in the hot immersion group at day 11. This suggests that heat therapy may be actively modulating the inflammatory environment in a way that supports rather than suppresses the regenerative process.

Notably, cold water immersion — despite its popularity — did not improve chronic perceived pain, failed to reduce circulating markers of muscle damage, and appeared to blunt the very cellular recovery signals that the body relies on to rebuild damaged tissue.

Now, one important nuance: we did not see differences between groups in the recovery of force-generating capacity. So the case for heat is not that it gets you back on the pitch faster in terms of raw strength — it is that it appears to drive better biological repair of the tissue itself. Whether that translates to better long-term outcomes, reduced re-injury risk, or more complete structural restoration is a question that deserves further study.

Honestly — it is time to rethink the ice applications in professional sport

I am not going to pretend this is a radical finding that nobody has ever considered. The cracks in the cold therapy consensus have been visible for years, and several colleagues have been pushing back on routine cryotherapy for a while. But what I do think is that in professional sports, the default response to a muscle injury — reach for the ice, apply it immediately and repeatedly — deserves much more scrutiny than it typically gets.

Every season, in football, rugby, athletics, basketball and pretty much every sport you can name, athletes suffer muscle injuries that keep them out for weeks or months. The pressure to speed up return-to-play is enormous. And yet the treatments applied in those first critical days after injury often haven’t moved much beyond what was standard practice 30 years ago. Ice is convenient. It feels like you are doing something. It reduces pain, which looks like progress. But if it is also blunting the cellular signals your muscle needs to regenerate properly, the short-term comfort may come at a cost to the quality of repair.

“Ice is convenient. It feels like you are doing something. But feeling like recovery and being recovery are not always the same thing.”

The data from our study — taken at biopsy level, not just blood markers or self-reported pain — suggest that hot water immersion is doing something genuinely positive inside the injured muscle. That is a different and more meaningful finding than most of the cryotherapy literature, which has largely relied on subjective outcomes or superficial measures.

I am not saying ban the ice bath. For certain situations — acute swelling management, thermal comfort, sleep quality? — cold might have its uses. But reflexively applying it to every muscle injury in professional sport, as if it were evidence-based best practice, is increasingly hard to justify. I said something similar in 2008 with far less data. Seventeen years and two studies later, I feel more confident saying it.

A word on the practicalities

One question that comes up immediately when I talk about hot water immersion as a therapeutic tool is: how do you actually implement it? Forty-two degrees Celsius for sixty minutes, daily for ten days, is a specific and quite demanding protocol. It is not a warm bath at home. The second study we published addresses the adjacent question of heating before exercise — specifically which devices are most effective at raising deep muscle temperature — and the answer matters because getting heat into the target tissue, rather than just warming the skin, is the actual physiological objective. Not all devices achieve this equally well, and practitioners investing in heat therapy equipment should have access to comparative data rather than just marketing claims.

I will write more about the practical implementation side of all this in a future post. For now, the headline message is simple: the science on thermal therapy is moving fast, and heat is looking increasingly like the underused tool in the sports medicine toolkit. Critical thinking is key.

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References:

1. Dablainville V, et al. Muscle regeneration is improved by hot water immersion but unchanged by cold following a simulated musculoskeletal injury in humans. J Physiol. 2025 Dec;603(23):7603–7625. PMID: 40437768

2. Nasir N, Townsend N, Cardinale M, Labidi M, Racinais S. Applying thermal therapy: Comparison of different commercially available heating devices to increase muscle temperature. Exp Physiol. 2026 Jan 18. PMID: 41548103