Contrast Therapy Explained: Can Alternating Hot & Cold Soothe Your Nervous System?
In a time when mental health difficulties, chronic stress, and physical burnout are becoming alarmingly common, holistic therapies are reemerging. Among them, contrast therapy—the practice of moving between hot and cold—has received significant interest. Historically the province of athletes recovering from intense training, contrast therapy is beginning to be understood in terms of the changes it may induce in the nervous system. But can we move between temperatures and actually calm our nerves and contribute positively to our health?
This article examines, in depth, the science, processes, benefits, and its potential role in healing and regulation of the nervous system.
What Is Contrast Therapy
Contrast therapy, or contrast bath therapy or hot-cold immersion therapy, is a therapeutic technique that alternates the body (or a body part) in temperatures of warmth and coolness.
Contrast therapy can be delivered in several ways, including immersing in baths of hot and cold water, using hot and cold packs, alternating between hot and cold, or using a sauna and ice bath, or using cryotherapy and thermal wraps. In most cycles of a hot-cold treatment you would
spend 3 to 5 minutes in the hot water (generally from 38°C to 43°C) followed by a short immersion of 30 seconds to 2 minutes (10°C to 15°C) in the cold water.
This hot-cold cycle is typically repeated 3 to 6 times depending on individual tolerance and therapeutic aims. Contrast therapy has typically been used for muscle recovery in athletes and injured people, but this therapeutic approach is now seeing renewed interest because of possibilities of neurological and psychological benefits, such as mood improvements, fatigue reductions, and nervous system regulation.
Understanding The Nervous System
Before considering how contrast therapy might impact the nervous system, It should review the autonomic nervous system (ANS), which oversees involuntary body functions like heart rate, digestion, and respiration. The ANS consists of two primary components: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The SNS is responsible for your “fight or flight” response, engaging during times of stress or danger to prepare the body to respond to immediate threat. The PNS is responsible for your “rest and digest” state.
It promotes those sensations of relaxation to promote healing by slowing the heart rate and allowing for recovery. With the proper balance in the SNS and PNS, we feel energized, calm, and able to respond to challenges. But chronic stress, trauma, sleep deprivation, and sedentary lifestyles can pull these two systems out of balance and cause nervous system dysregulation.
Contrast Therapy Affects the Nervous System
1. Stimulating the Vagus Nerve
The vagus nerve has a function in activating the parasympathetic nervous system that relaxes you and helps you heal. One of the ways to stimulate the vagus nerve is to experience cold exposure to the face, neck, or chest. Cold exposure stimulates the vagus nerve and helps to reduce heart rate, decrease inflammation, and instill calm. Results have shown that cold water immersion will bring about stimulation of the vagus nerve that enhances vagal tone and increases the ability of the body to initiate recovery and return to a relaxed state after a stressor. This type of vagal nerve stimulation not only helps regulate stress response but enhances health and well-being through a balanced autonomic nervous system.
2. Thermoreceptor Stimulation
Thermoreceptor stimulation occurs when hot and cold stimuli are detected in the skin via thermoreceptors. These thermoreceptors signal the hypothalamus (the brain’s center for temperature regulation). The hypothalamus not only controls temperature regulation, but it
also activates the limbic system, which is the emotional regulation center of the brain (linked to the mood and stress response, among other functions).
Thus, by applying hot and cold stimuli via contrast therapy, we are engaging both the hypothalamus and the limbic system of the brain, which influences physical temperature regulation, as well as the emotional state/response and balancing stressors – with a possibility of improving mood outcomes. The connection between physical body temperature and emotional well-being points to the potential therapeutic outcomes of exposure to hot and cold stimuli.
3. Neurotransmitter Release
Cold exposure acts as a controlled stressor that momentarily activates the sympathetic nervous system, releasing norepinephrine and endorphins. This chemical response creates better engagement, and well-being with a feeling of immediacy and invigoration. Exposure is controlled and short lived allows for the body to have a manageable adaptation to stress. This is known as hormesis: a small and controlled exposure to stress can create “adaptation” that allows for more resilience for the body to manage real-life stressors. With continuous use, the body’s regulatory systems might continue to adapt to cope with the larger loads of stress and better manage stress overall.
4. Reducing Cortisol Levels
When people are under constant stress, their cortisol levels are often elevated. Cortisol is a hormone associated with signs of anxiety, feelings of depression, and suppression of the immune system. Chronic elevation of cortisol levels causes alterations in many hormonal systems and can adversely affect mind and body health. But research shows that a cold water swim, or regularly practicing contrast therapy, can lead to lower cortisol levels over time. Making cold water immersion a routine practice may support the body’s ability to manage stress more readily, which could support homeostasis and improve emotional flexibility. Therefore, contrast therapy may be a useful approach to help mitigate the stress hormone imbalances created by chronic stress.
Physical Health and Recovery Benefits
Although contrast therapy is primarily considered for its effects on the nervous system, its physical health benefits are just as important and connected.
- Contrast therapy can help reduce muscle soreness and fatigue, bring blood circulation, decrease inflammation, and increase recovery from strenuous physical activity. It can also help with chronic pain limitations.
- When physical discomfort is lessened and the body can recover more efficiently, the physical perceptions of stress are at minimum limits allowing for less load on the nervous system and ultimately contributing to improved mental and emotional health through increased physiological state resilience.
Mental Health Benefits of Contrast Therapy
Along with the physical advantages, contrast therapy can have powerful positive effects for mental health.
- This is primarily achieved by stimulating the parasympathetic nervous system and assisting in cortisol regulation to effectively diminish stress and anxiety. Stress and anxiety inhibition allows the body and mind to more easily become relaxed—both physically and mentally. For example, finding safe and comfortable places in a hot and then cold phase creates a great feeling of relief, relaxation, and calm.
- Moreover, as we have witnessed, with cold exposure initiation of a natural core body temperature drop begins, which can mimic the body's natural pre-sleep drop—when combined with heat, this can improve sleep and help produce a healthier circadian function.
- Finally, the cold-and-heat exposure cycle also releases dopamine, serotonin, and beta-endorphins which can improve one mood and these positive emotions are all crucial for a positive emotional experience.
- Through habitual cool/heat and heat/cool cycles in contrast therapy, repeated exposure in the short term can help one develop resilience towards the future stresses of both body and mind which would all help support long-term psychological balance and emotional resilience.
Contrast Therapy and Polyvagal Theory
The Polyvagal Theory developed by Dr. Stephen Porges highlights the vagus nerve as playing a critical role in emotional regulation and social affiliation. According to this theory, the function of the vagus nerve dictates how we respond to the world around us—either experiencing calm connection or defensively reacting to others.
Contrast therapy, especially with the cold exposure, activates the vagal pathways in the body, allowing it to move from a defensive, sympathetic-dominant state to a calm, connected parasympathetic state. This shift is essential for healing trauma, processing emotional experiences, and repairing the nervous system.
Final Thought
Contrast therapy provides a different way to support nervous system health, grounding physical practices in ancient practices combined with modern science. The alternating aspects of heat and cold provide stimulation to the vagus nerve supporting the balance of autonomic function and regulation of hormones. The benefits of contrast therapy don’t stop with physical recovery, they can support emotional resilience, the reduction of stress, and mental health benefits. While research continues to support the benefits of contrast therapy, it is shaping up to be a viable and holistic approach to support both body and mind – especially for those who suffer from and want natural solutions for: stress, trauma and nervous system dysregulation.
Reference
- What is a contrast bath? (2023e, July 7). WebMD. https://www.webmd.com/pain- management/what-is-a-contrast-bath
- Waxenbaum, J. A., Reddy, V., & Varacallo, M. A. (2023, July 24). Anatomy, autonomic nervous system. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK539845/
- Hing, W. A., White, S. G., Bouaaphone, A., & Lee, P. (2008). Contrast therapy—A systematic review. Physical Therapy in Sport, 9(3), 148-161. https://doi.org/10.1016/j.ptsp.2008.06.001
- Porges, S. W. (2022). Polyvagal Theory: A Science of Safety. Frontiers in Integrative Neuroscience, 16, 871227. https://doi.org/10.3389/fnint.2022.871227
- Bieuzen, F., Bleakley, C. M., & Costello, J. T. (2013). Contrast Water Therapy and Exercise Induced Muscle Damage: A Systematic Review and Meta-Analysis. PLoS ONE, 8(4), e62356. https://doi.org/10.1371/journal.pone.0062356
