From marathon runners and elite athletes to TikTok wellness influencers and celebrities, ice baths have become one of the biggest health trends of recent years. With marathon season and training cycles ramping up, more long-distance runners are turning to ice baths as a key recovery tool. But beyond the viral videos and social media challenges, what actually happens inside your body when you plunge into ice-cold water?
Cold plunges or ice baths are also known as cold-water immersion, which involves submerging the body in water around 5°C for several minutes. This is why they are increasingly being used by marathon runners post-training and post-race. The benefits of improve wellbeing, performance and resilience.
Dale Atkinson, owner of Peak Health and Fitness, explains the real physiological changes that occur when your body hits icy water from the immediate shock response to long-term recovery benefits.
The Immediate “Cold Shock” Response
The moment your body hits ice-cold water, it triggers what scientists call the cold shock response. Your breathing rate quickly increases, your heart rate peaks, and stress hormones like adrenaline pump through the body. This response is part of the body’s natural survival response. For marathon runners, this effect can feel even more intense after a long-distance run when the body is already under physical strain.
Your nervous system rapidly goes into alert mode. The body thinks it needs to protect itself from the cold, so it floods the system with adrenaline and increases circulation.
That rapid rise in adrenaline is one reason many people report feeling energised, mentally clear and alert straight after a cold plunge. This is why some runners use ice baths to feel re-energised after long runs.
Your Blood Circulation Changes
One of the most dramatic physical effects of an ice bath happens inside your skin. Cold temporarily triggers vasoconstriction, meaning blood vessels shrink to conserve heat back up again and protect key organs. When you leave the water and heat back up, the vessels will begin to expand again, helping to flush oxygen-rich blood through tissues and muscles.
This process acts like a pump for your circulation. It pushes fresh blood through the body which is one of the reasons many athletes use ice baths after extreme training sessions. Cold water plunges have been linked to lowering swelling, inflammation and muscle tenderness. This is particularly beneficial for marathon runners dealing with muscle fatigue and inflammation after long-distance mileage.
Your Muscles Start Recovering Faster
Recovery is one of biggest reasons why ice baths are still popular, particularly in athletes. When muscles are exposed to cold water, inflammation near muscle fibres can reduce and help to lower soreness after intense training.
Studies show cold exposure can reduce muscle pain and help recovery after workouts, especially in endurance athletes. This is why ice baths are essential for sports professionals. After a hard session, an ice bath can help calm down muscle inflammation. This is why you see footballers or rugby players using them post-match. Marathon runners are now adopting the same approach after long runs and races.
But the timing matters. Using ice baths too often after strength training can actually prevent muscle growth, so it’s recommended that they are used after endurance training or competitions. This makes them especially suited to marathon training rather than gym-based sessions.
Your Stress Levels Can Drop
Although ice baths feel stressful in the moment, they can actually reduce stress levels later in the day. Cold-water immersion can lower stress levels for up to 12 hours after exposure and improve overall wellbeing. This can be particularly helpful for runners managing the mental pressure of marathon training.
The reason is down to how the body adapts to controlled stress. Cold exposure helps the nervous system learn how to handle discomfort. Over time, it can help build resilience both physically and mentally. A key trait needed when pushing through long-distance runs.
Some studies have also linked cold-water immersion with increased endorphins and mood improvements, which explains why many people feel alive after a cold plunge.
Your Sleep May Improve
Surprisingly another benefit from ice baths is sleep. Some research has linked cold exposure with better sleep quality, mostly due to the drop in internal body temperature and changes in the nervous system.
Cooling the body naturally signals the brain that it is time to rest and relax. You can notice the difference quickly as people usually say they sleep deeper after a cold plunge, particularly if they do them early in the day after exercise. This can be especially beneficial after long marathon training sessions where recovery sleep is essential.
It May Boost Resilience and Energy
Cold exposure can also help build the body’s tolerance to stress better. Scientists call this as a ‘hormetic stress’ effect, small doses of stress that help the body become more adaptable and stronger. Something marathon runners rely on during intense training blocks.
Cold water can also trigger hormones like dopamine and norepinephrine, which can link to motivation, mood and energy. This is why most people say ice baths leave them feeling refreshed, rejuvenated, awake and mentally stronger.
But Ice Baths Aren’t Risk-Free
Despite the benefits of ice baths, they’re not suitable for everyone. Cold water immersion can cause rapid breathing changes and raise heart rate, which can be dangerous for people with heart conditions.
Also, prolonged exposure can cause hypothermia. For beginners, it’s important to start slow. You don’t need to sit in freezing water for 10 minutes. Just 1-3 minutes can be enough to trigger these benefits. Even for marathon runners, shorter sessions are often more effective and safer.
How to Try Ice Baths Safely
Dale suggests for new starters follow these simple guidelines. These apply whether you’re new to cold exposure or adding it into a marathon recovery routine.
Start with cool water rather than ice: This helps your body alter to the cold more gradually.
Limit sessions to 1-3 minutes initially: You can slowly build up the time as your tolerance improves.
Focus on slow breathing to control the shock signal: Steady breathing helps calm the body and deal with the initial cold shock.
Never plunge alone or in open water without experience: Having someone nearby makes sure help is there if you feel unwell.
Avoid if you have heart or circulatory conditions: Cold water plunges can suddenly put sudden strain on the heart.
