Since ancient times, cooling the body has been recognized for its positive effects on both mental and physical well-being. This practice, referenced by Hippocrates and preserved through the Middle Ages, is still popular today, especially in colder climates where research on cold-water swimming and cold showers (4-10°C) continues to evolve. The underlying idea of such practices is that cooling the body induces physiological responses that strengthen immunity and stimulate physical activity.
The Effect of Cryotherapy on Physical and Physiological Health
Circulatory Response:
When the body is exposed to cooling, the skin initially undergoes vasoconstriction to retain heat. This process cools the area, which is then followed by vasodilation and alternating periods of constriction and dilation. This pattern, known as “Lewis’s Hunting Reaction,” helps maintain circulation. During vasodilation, the arteriovenous anastomosis closes, increasing blood flow through the capillaries, which is particularly beneficial in reducing swelling and repairing tissue damage. Ice therapy is often used to relieve swelling and speed up tissue recovery, for example, by massaging with ice cubes to accelerate healing in pressure sores. Additionally, cooled muscles can contract more frequently before fatigue sets in, thanks to the lowered metabolic rate in cooled tissues.
Metabolic Rate:
The main effect of cooling living tissue is a decrease in metabolic rate, as outlined by Van’t Hoff’s Law, which suggests that chemical reaction rates decline as temperature falls. Metabolic processes, which are series of chemical reactions, slow down with each drop in temperature—decreasing to about one-eighth of the initial rate per 1°C.
Motor System:
Cooling a limb in water at 10-15°C can temporarily decrease muscle strength, likely due to changes in viscosity and metabolic rate. However, strength is observed to return, sometimes exceeding baseline levels about an hour after cooling ends.
Neural Response:
Skin contains receptors that respond primarily to temperature changes, with cold receptors more abundant than warm ones. These receptors increase in activity as temperature drops, sending a greater number of signals. Cooling mixed nerves (motor and sensory) reduces conduction rate, affecting myelinated A fibers first, followed by B and C fibers at lower temperatures. Synaptic transmission slows down as well, providing relief from pain and hypertonicity, which is beneficial for pain management.
Uses of Ice Therapy:
- Pain reduction
- Relief from spasticity and muscle spasms
- Reduction of swelling
- Support for tissue repair
- Stimulation of inhibited muscles
- Strength training support
The Effect of Cryotherapy on Mental Health
Cryotherapy triggers the nervous system to release beneficial biochemicals like endorphins, adrenaline, and oxytocin. These hormones help elevate mood and reduce anxiety and depression symptoms. Although not a cure, this biochemical response provides noticeable mental benefits, including mood improvement and enhanced sleep quality. After a session, many people report feeling highly alert and energized.
