How Cryotherapy Affects the Brain, the Immune System, Metabolism, and Athletic Performance
Posted on February 12th 2016 (over 3 years)
Cryotherapy – a hormetic stressor
If you’ve ever popped outside on a cold winter’s day without your coat, you know that your body reacts quickly: You start to shiver, and your fingers, hands, and toes turn blue. Stay out a little longer, and your thinking might become a little muddled. Cold stresses the body. So why would anyone intentionally want to be exposed to extreme cold? Enter cryotherapy – the practice of exposing the body (or specific areas of the body) to extremely cold temperatures for defined time periods. Much like exercise, extreme heat (such as from sauna use), and fasting, cryotherapy stresses the body in a hormetic manner, triggering cellular responses in the body that exceed what is actually needed to compensate for the otherwise damaging insult.
Cryotherapy on the brain
Exposure to cold has profound effects on many parts and functions of the body, including the brain, immune system, and metabolism, among others. Perhaps the most clear-cut examples of cryotherapy’s beneficial effects are observed in the brain, where levels of the hormone and neurotransmitter norepinephrine – responsible for vigilance, attention, focus, and positive mood – increase markedly when the body is exposed to extreme cold.
Cryotherapy also switches on the activity of cold shock proteins, especially RNA binding motif 3, or RBM3, which is found in many of the body’s tissues, including the brain. RBM3 increases protein synthesis at the ends of dendrites – where synapses form – and protects the brain from cognitive and behavioral deficits associated with some neurodegenerative diseases.
Cryotherapy on inflammation and immune function
At the core of many chronic diseases and the aging process is one common feature: inflammation. Cryotherapy, however, appears to reduce inflammation. One way it does this is via its influence on norepinephrine, which decreases levels of tumor necrosis alpha, a proinflammatory cytokine instrumental in promoting systemic inflammation. Norepinephrine inhibits other proinflammatory processes and may reduce the pain and inflammation associated with arthritis, among other conditions.
Another critical factor in chronic disease is immune function. Cryotherapy promotes the development of a healthy immune cell population, including cytotoxic T lymphocytes, which play key roles in protecting the body from cancer.
Cryotherapy and metabolism
The metabolic responses to cryotherapy serve one purpose: to warm the body through a process known as thermogenesis. The shivering associated with exposure to cold is well-known: Your muscles start to contract in an involuntary effort to produce heat, a process called shivering thermogenesis. But the body also engages in a more efficient attempt to produce heat, called non-shivering thermogenesis, in which norepinephrine (again) acts on key proteins to uncouple the normal electrical processes within mitochondria. The body responds by producing more mitochondria, effectively converting the body’s white adipose tissue into its more metabolically active counterpart, brown adipose tissue. The greater the amount of brown adipose tissue the body has, the greater the amount of fat it will burn, potentially promoting weight loss.
Cryotherapy and athletic performance
Cold exposure improves athletic performance and recovery, but the benefits come with two caveats: the timing of the cold stressor and the type of the exercise performed.
Shortly after exercise the body initiates a cascade of pro-inflammatory responses. The body eventually counters with an anti-inflammatory response. These complementary, yet opposing forces are necessary for mitochondrial biogenesis and muscle repair and growth. Appropriate timing of cryotherapy, whether local (e.g., ice pack usage) or systemic (e.g., cold water immersion), is critical for optimal benefits. If the cryotherapy is administered too soon after exercise, the delicate balance of responses can be interrupted. The type of exercise matters, too, with greater benefits likely observed with endurance training versus strength training.
In choosing a cryotherapy modality – whole-body cryotherapy, cold-water immersion, or ice packs – a few factors should be considered, such as thermal conductivity, body surface area exposure, and temperature gradient. Whereas each modality has its pros and cons, the data are equivocal for whole-body and cold-water immersion, as long as the exposure is sufficiently long.
A growing body of evidence supports the use of cryotherapy for optimal health and human performance. The jury is still out on exactly how, when, and under what circumstances cryotherapy works best. This podcast takes an in-depth look at the scientific evidence surrounding the practice of cryotherapy.
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