Hot and cold: Oxford Brookes expert explores the health benefits of cold water immersion and saunas

Have you ever started your morning with a plunge into icy water, or ended a busy day with the soothing warmth of a sauna? These contrasting therapies—cold water immersion and heat exposure—are gaining popularity for their potential health benefits.

With the rise of affordable portable ice baths, the viral influence of Dutch motivational speaker Wim Hof, and the increasing trend of open-water swimming, cold exposure has become a growing wellness trend. Meanwhile, saunas, hot tubs, and warm baths remain a time-honoured method for relaxation and recovery. Advocates suggest these therapies may enhance physical and mental well-being and even contribute to longevity.

But what does the science say? Ben Wright, Lecturer in Exercise Physiology at Oxford Brookes University, examines the evidence behind these popular practices, explaining how they can benefit both elite athletes and everyday individuals. He provides insights into their effects on recovery, stress relief, and resilience, along with expert guidance on how to use them safely and effectively.

What key safety tips should beginners follow when adding cold plunges or saunas to their wellness routine?

Ben says: "If you're new to cold plunges or saunas, it's important to ease into these practices gradually. Jumping straight into extreme temperatures can be overwhelming for the body, so it's best to start with short durations and build up tolerance over time."

Cold water immersion guidelines

• Ideal temperature: A range of 10 to 15 degrees Celsius works well for most people, with 11 degrees Celsius commonly used in recovery protocols.
• Duration: A 10 to15 minute immersion is a good target, though even shorter exposures of under five minutes can be beneficial.
• Safety warning: Going below 10 degrees Celsius increases risks without clear additional benefits, so it's important to be cautious.

Ben says: "An easy way to get started is with cold showers. Reducing the water temperature for the last 10 seconds of your shower and gradually increasing that duration over time can help your body adapt. This also allows you to gauge whether cold exposure is something you find beneficial and can commit to.

"The cold shock response is something to be aware of, you can expect rapid breathing, increased heart rate, and higher blood pressure. Your body will also activate heat production through shivering and non-shivering thermogenesis, so it's key to listen to how you're feeling and avoid pushing too hard."

Sauna guidelines

• Beginners: Start with 10-minute sessions and build up to 15 minutes, two to three times per week.
• Progression: You can increase session lengths in five-minute increments, but I wouldn’t recommend going beyond 45 minutes, as there’s little extra benefit.
• Optimal temperature: A range of 70 to77 degreesCelsius is ideal for cardiovascular and metabolic benefits.
• Stronger effects: If you're looking for a more intense effect, sessions at around 80 degreesCelsius for 20 minutes can boost circulation, mood, and stress reduction.

Ben says: "Hydration is key when using saunas. People often underestimate how much fluid they lose in the heat. Also, if you have low blood pressure, heart disease, or issues regulating sweat, it's best to consult a medical professional before starting regular sauna sessions."

What are the benefits of exposure to both the cold and heat?

Cold water immersion benefits

Ben says: "Cold exposure is often linked to reduced inflammation, enhanced immune function, improved mood and reduced stress and increased blood flow. There’s some solid research backing these claims, but it's worth noting that individual responses can vary.

"One study in 2023 found that a five-minute immersion at about 19.93 degreesCelsius improved mood, while another reported that 20 minutes in cold sea water at around 13.6 degreesCelsius reduced negative emotions like anger and depression while boosting self-esteem. However, since these effects are self-reported, motivation and the willingness to endure discomfort could be influencing factors.

"There's also evidence that cold immersion can lower cortisol levels, which helps with stress. A single 15-minute session at 10 degreesCelsius reduced negative feelings for up to three hours. However, no significant changes were seen in positive emotions or endorphin release.

“A lot of the research is on cold water swimming rather than cold immersion alone, so it’s hard to separate whether the benefits come from the cold or from the exercise itself. More studies are needed to clarify this."

Heat exposure benefits (Saunas and hot water immersion)

Ben says: "Heat exposure has some great cardiovascular benefits. It increases heart rate and blood circulation, endorphin release for mood and pain relief,  and the activation of heat shock proteins which protect cells and aid recovery, which is why people often feel more energized after a sauna.

"A 2022 study found that heat shock proteins, which are produced in response to heat stress, could lower the risk of neurodegenerative and cardiovascular diseases. There's also research from 2016 showing that young adults who did hot water immersions (40.5 degreesCelsius) for an hour, four to five times a week, had significantly improved vascular function.

"Interestingly, research on Finnish sauna users found that regular sauna bathers were 40% less likely to die prematurely, regardless of other lifestyle factors. It’s a fascinating area of study."

Do the health benefits of using portable saunas or cold plunges at home differ significantly from those in high-end sports spas?

Ben says: "Portable ice baths or home saunas can be just as effective as high-end sports facilities if they maintain the correct temperatures. Cold water swimming is another great option if you have access to a safe body of water.

"The physiological response to heat and cold doesn’t depend on whether you’re in a spa or your back garden. However, professional facilities offer precise control over temperature and consistency, which can make them more reliable. Home setups, while effective, may have more variability."

How do the benefits of cold water plunges and saunas for the average person differ from their impact on elite athletes?

Ben says: "Elite athletes primarily use cold immersion to help with recovery—reducing muscle soreness, inflammation, and fluid buildup after intense training. For them, it's about optimising performance and reducing downtime between sessions.

"Cryotherapy chambers, which expose the body to extreme cold (as low as -180 degreesCelsius), are also used for recovery, but they’re not widely accessible.

"For most people, cold exposure is more about general wellness—mood improvement, stress relief, and circulation benefits. It can still help with muscle soreness after exercise, but the response will be different compared to elite athletes.

"Similarly, saunas play a different role depending on the user. Athletes may use them to improve cardiovascular health and recovery, whereas the general public might use them for relaxation and heart health benefits. Even if you’re not training at a high level, regular sauna use can help with circulation and long-term cardiovascular well-being.

“Whether you're an athlete or just someone looking to improve your health, both cold and heat therapies have valuable benefits. The key is to approach them safely and find what works best for you."