Recovery has turned into its own industry. Plunge tubs fill up our feeds, red light panels hang on bathroom doors, and cryotherapy studios keep opening next to the coffee shop. All of them promise the same thing: you will bounce back faster. Some of these tools hold up well in the research. One holds up for one goal and quietly works against another. One rests mostly on marketing. Here is what the studies actually show, and how we would use each one if you trained with Sonder.
First, decide what recovery means for you
Two different goals hide inside the word. The first is feeling ready for tomorrow: less soreness, more spring in your legs, a better mood. The second is getting more out of your training over months: more muscle, more strength, better fitness. Most recovery tools are tested on the first goal. The trouble starts when a tool that helps the first one gets in the way of the second, and the cold plunge is the clearest example.
Cold plunge (cold water immersion)
What it does well
A 2022 meta-analysis in Sports Medicine pooled 52 studies of cold water versus simply resting after hard exercise. After high-intensity sessions, people who got in the cold had more muscular power, less soreness and felt more recovered 24 hours later. It did not help strength bounce back, and shorter, colder dips tended to do the most for some outcomes. A follow-up analysis from the same group found cold water beat active recovery, contrast baths and warm water for most recovery measures. All of this is short term recovery: how you feel and perform over the next day or so.
So if your goal is to feel and perform better tomorrow, the plunge earns its reputation. Building muscle and strength over months is a different process, and that is where the story changes.
Where it backfires for lifters
The catch shows up when you look past tomorrow, and it applies mainly to lifting. In a 2015 study in The Journal of Physiology, 21 active men lifted twice a week for 12 weeks. After each session, half sat in 10°C (50°F) water for 10 minutes and the other half did an easy spin on a bike. The bike group gained more strength and more muscle. Their fast-twitch muscle fibers grew about 17 percent, while the cold group saw no meaningful change. Muscle biopsies showed the cold had dulled the signals that build muscle for up to two days after a workout.
A 2021 meta-analysis, also in Sports Medicine, pulled the training studies together and found the same pattern: regular cold water after training reduced gains in max strength, strength endurance and power, but had no measurable effect on endurance gains. Runners and cyclists have more room to plunge. Lifters chasing muscle have less.
Why both can be true
It sounds contradictory that the same plunge can help you recover and also slow your progress, but the two findings measure different things. The recovery studies looked at how people felt and performed a day later. The training studies looked at what they built over weeks and months. The biopsies in the 2015 study showed cold dulling the signals that turn a lifting session into new muscle. Quieting those signals can leave you feeling fresher tomorrow, yet add up to smaller strength and muscle gains over a training block. The research has not found the same cost for endurance training, which is why runners and cyclists have more freedom with it.
Beyond the gym
Plenty of people plunge for their head, not their legs. A 2025 review in PLOS One looked at 11 trials with 3,177 healthy adults. Stress dropped about 12 hours after cold exposure, and some trials reported better sleep and quality of life. Inflammation actually rose right after getting out, and the authors found very little support for the popular claims about immunity and mood.
The largest trial in that review is worth knowing. Researchers in the Netherlands asked 3,018 working adults to end their usual warm shower with 30, 60 or 90 seconds of cold water. Over the study, the cold groups called in sick 29 percent less often than the control group. They did not report fewer days of actually feeling ill, though. They seemed to push through it better.
Sauna
The sauna research reads less like sports science and more like cardiology. The best-known study, published in JAMA Internal Medicine in 2015, followed 2,315 Finnish men aged 42 to 60 for about two decades. Compared with men who used a sauna once a week, those who went four to seven times a week had a 63 percent lower risk of sudden cardiac death and a 40 percent lower risk of dying from any cause. Sessions longer than 19 minutes were also tied to fewer fatal heart events.
Two honest caveats. This is observational data from middle-aged Finnish men, so it shows an association, not proof that the sauna caused the benefit. And a 2018 review in Mayo Clinic Proceedings by the same research group notes that sauna use may lower blood pressure, but solid long-term trials are still missing. That review also looked only at traditional Finnish saunas, so infrared saunas cannot be assumed to deliver the same results.
Sauna and performance
There is also early evidence that sauna can help endurance athletes. In a small 2007 study, six competitive runners and triathletes used a sauna for about 30 minutes after training, roughly four times a week, for three weeks. They ran about 30 percent longer before exhaustion, and their blood volume rose, the same heat adaptation athletes chase before racing in hot weather.
The bigger picture is less settled. A 2025 review in Sports Medicine Open looked at 14 small trials and concluded that firm conclusions are not possible yet. Heat seemed to help endurance most, especially in hot conditions, but it did not raise VO2 max, and results for next day recovery were split. For lifters and team sport athletes, the research is just getting started. One recent Finnish study found that an infrared sauna after training eased soreness and, with regular use over six weeks, improved jump and early sprint performance, likely because athletes recovered well enough to keep training hard.
So the sauna is a solid heart habit with a possible edge for endurance athletes. For everyone else, it may help, but the evidence is still small.
Red light therapy
Red and near-infrared light therapy, called photobiomodulation in the research, has a surprisingly large body of studies behind it. A 2015 meta-analysis in Lasers in Medical Science reviewed 16 randomized trials. Light applied before exercise added about five and a half reps before fatigue and about four seconds to time to exhaustion compared with a placebo light, and the authors concluded the benefit shows up mainly when it is used before training rather than after. Worth noting: the lead author has received research support from a laser device maker.
A larger 2018 review of 39 trials and 861 people found effects that leaned in favor of the light, but rated the quality of evidence very low to moderate, with small samples and wildly different devices and doses.
There is a practical gap too. Many of these trials used lasers or LED clusters held against one specific muscle at carefully measured doses. A consumer panel across the room is a different tool, and the results do not automatically transfer.
Whole-body cryotherapy
Cryo chambers expose you to air colder than minus 100°C (about minus 150°F) for two to four minutes. A 2015 Cochrane review went looking for evidence that this reduces soreness or speeds recovery and found only four small trials with 64 participants, nearly all young men. Its conclusion was that there is not enough evidence to say whether it works compared with simply resting, no evidence at all in women, and very little reporting on safety.
One newer comparison found cold air edged out cold water for bringing strength back after hard exercise, so the door is not fully closed. For now, though, a cryo session costs a lot more than a bath of cold water and has far less research behind it.
What quietly beats all of them
A 2018 meta-analysis in Frontiers in Physiology compared recovery techniques across 99 studies. Massage came out as the most effective option for reducing soreness and the feeling of fatigue. Compression garments and water immersion also helped with fatigue, and active recovery, cold exposure, contrast baths and cryotherapy all trimmed soreness to some degree.
Then there is sleep, which no one sells as a recovery modality because you cannot put it in a tub. In a small Stanford study, 11 varsity basketball players aimed for 10 hours in bed each night and ended up sleeping almost two hours more per night than usual. Their sprint times dropped from 16.2 to 15.5 seconds, and their free throw and three-point accuracy each improved by about 9 percent. It is one small study, but nothing else on this list has a result like that.
The digestible version
Here is how we would put this research to work.
Protect your sleep before you buy anything. It is free, it helps everything, and every other tool on this list works better on a rested body.
If you lift to build muscle or strength, keep the plunge away from your lifting days. The studies that found blunted gains put people in the cold right after training. Save it for rest days, cardio days or a week when you simply need to feel fresh.
Use cold when tomorrow matters more than next month. Tournament weekends, two sessions in one day, race week, or a brutal conditioning day. That is where the plunge shines.
Endurance athletes have more freedom. Regular cold water did not hold back endurance gains in the research, so runners and cyclists can be less strict about timing.
Treat the sauna as a heart habit with a possible endurance edge. The strongest evidence links frequent sessions to heart health and longevity. Early, small studies also show endurance gains, especially for events in the heat.
Red light is optional and small. If you use it, use it before training, and do not expect it to make up for a short night.
Skip cryotherapy for soreness. The research is thin, the price is high, and cold water does a similar job.
Book the massage. If you are going to spend money on recovery, the evidence points here first.
If you want help fitting recovery around your training week, book a free consult and we will build it into your plan.
A few safety notes
Cold water. The first minute brings a gasp reflex and a jump in heart rate and blood pressure. Never plunge alone, especially in open water, and get in slowly. Check with your doctor first if you have a heart condition, high blood pressure, Raynaud's or are pregnant.
Sauna. Drink water, skip the alcohol, and get out if you feel dizzy or unwell. The Finnish researchers consider sauna use safe for most people, including many with stable heart disease, but talk to your doctor if that applies to you.
Cryotherapy. Extreme cold should only ever be used with trained staff present.
Red light. Protect your eyes and follow the device's guidance on distance and time.
For most people, the best recovery plan is a little boring: sleep, eat enough protein, train with a plan, and add the fun tools where they actually fit your goal.
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Sources
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Moore E, Fuller JT, Bellenger CR, et al. Effects of cold-water immersion compared with other recovery modalities on athletic performance following acute strenuous exercise in physically active participants: a systematic review, meta-analysis, and meta-regression. Sports Medicine, 2023. doi.org/10.1007/s40279-022-01800-1
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