Our conscious level of pain or discomfort during a cryotherapy treatment is not a benchmark to the efficiency of the treatment.
Clinical studies show that cryotherapy works efficiently under temperatures of -166 degrees Ferhenight (-110°C).
On the other hand, the more even cold distribution around the body the more pleasant the session is. Nonetheless, the physiological response that we seek is triggered when our body’s receptor feels endangering temperatures. Here is why…
How Do React to Change in Temperature?
We have a built-in sensory system for perceiving temperature.
Being a warm-blooded (or homeothermic) animal, we humans have a built-in sensory process (called thermo-reception) by which we detect different levels of temperatures in the environment and the body. This process helps us to maintain considerable inner physiological stability (e.g., body temperature and metabolism) under changing environmental conditions.
Thermal Body Sensors
Different sensors perceive different temperatures.
We perceive external temperature via thermo-receptors in our skin, which, in response to temperature stimuli, fires a specific neural pathway that carries a representation of thermo-sensory activity to the cerebral cortex in our forebrain. These receptors come in different types, some being warm spots and other being cold spots. These are, as you guessed, specific places in our skin that are selectively sensitive to warm or cold stimuli.
We sense a reasonably wide range of temperatures
The cold spots on our skin fire when temperatures go below the neutral skin temperature (~34 °C [93 °F]). The warm spots have increased activity at temperatures warmer than neutral skin temperature. The sensitivity of these receptors extends across a continuum of thresholds and response maxima. The static activity of many cold receptors reaches a peak at temperatures around 20–30 °C (68–86 °F). Some receptors have lower thresholds (i.e., less than 30 °C [86 °F]) and maximal activity at colder temperatures (i.e., less than 20 °C [68 °F]).
Warm receptors are continuously active at constant temperatures above neutral skin temperature and have response maxima around 41–46 °C (106–115 °F), although, in many cases, warm receptors are inactive at temperatures above 45 °C (113 °F). When the temperature is over 45 °C, and less than 5 °C (these values change slightly depending on the source), pain receptors called thermal nociceptors fire signals. These signals are what we experience as pain.
What about our temperature receptors?
The sensory system involved in perceiving the changes in skin temperature begins with free nerve endings found in the dermal and epidermal layers of skin that can be functionally classified as cold and warm thermo-receptors. Warm and cold receptors respond similarly to radiant and conducted thermal energy and are involved in the perception of innocuous (harmless) temperatures.
The molecular mechanisms underlying temperature sensation have been extensively studied over the past decade with the result that several temperature-sensitive ion channels of the transient receptor potential (TRP) family have been identified as candidate temperature sensors. These thermos TRP channels are expressed in sensory nerve endings and are active at specific temperatures ranging from noxious cold to burning heat (Dhaka et al., 2006).
In Cryotherapy, Pain Does Not Equal Gain!
Thermal shock type of conscious sensations of pain or other discomfort has no impact on the treatment results.
Our cold receptors are more profound in our skin than out heat receptors, and they stop registering temperatures few degrees before sub-zero levels are reached. As temperatures decreases bellow +4C° cold receptors stop recording temperature and our pain receptors take over.
E.g., if a person is submerged into +4 degrees Celsius water, the feeling of pain & thermal shock are imminent. However, this does not result in similar therapeutic effect as WBC, partly because the length of exposure is usually very short.
The efficiency of cryotherapy treatment depends on the exposure to extremely cold temperatures at the cellular level. The more substantial number of cells exposed to low temperatures the better. More receptors triggered means more “SOS” signals to our brain, signaling our body to produce the maximum output of life-supporting enzymes and hormones.
Simultaneously, the more even the distribution of supercooled air is, the less discomfort we experience. However, the receptors exposed to « life-threatening » temperature levels will signal the brain via our central nervous system, that all available life support is needed. This is the essence of successful cryotherapy session, not the level of discomfort in our conscious mind.
In other terms, the best equipment allows for longer exposure at a temperature around -166°F (-110°C) to benefit the body. Simultaneously, the more even the distribution of supercooled air is, the less discomfort we experience — Meaning better cold distribution equals better customer experience.
Going lower in temperature does not enhance the treatment results, and can cause frostbites to people with weaker blood circulation. Compare hot steam to cold air. The more pinpointed and concentrated the delivery of the cold or hot energy is, the more painful it feels on our skin.